Article

Open-Label, Dose Escalation Phase I Study in Healthy Volunteers to Evaluate the Safety and Pharmacokinetics of a Human Monoclonal Antibody to Clostridium difficile Toxin A

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Abstract

Recent data suggest that Clostridium difficile-associated diarrhea is becoming more severe and difficult to treat. Antibody responses to C. difficile toxin A are protective against symptomatic disease and recurrence. We examined the safety and pharmacokinetics (pk) of a novel neutralizing human monoclonal antibody against C. difficile toxin A (CDA1) in healthy adults. Five cohorts with 6 subjects each received a single intravenous infusion of CDA1 at escalating doses of 0.3, 1, 5, 10, and 20 mg/kg. Safety evaluations took place on days 1, 2, 3, 7, 14, 28, and 56 post-infusion. Samples for pk analysis were obtained before and after infusion, and at each safety evaluation. Serum CDA1 antibody concentrations and human anti-human antibody (HAHA) titers were measured with enzyme-linked immunosorbent assays. A noncompartmental model was used for pk analysis. Thirty subjects were enrolled. The median age was 27.5 yrs. There were no serious adverse events (AE) related to CDA1. Twenty-one of the 48 reported non-serious adverse events were possibly related to CDA1, and included transient blood pressure changes requiring no treatment, nasal congestion, headache, abdominal cramps, nausea, and self-limited diarrhea. Serum CDA1 concentrations increased with escalating doses: mean C(max) ranged from 6.82 microg/ml for the 0.3 mg/kg cohort to 511 microg/ml for the 20 mg/kg cohort. The geometric mean values of the half-life of CDA1 ranged between 25.3 and 31.8 days, and the volume of distribution approximated serum. No subject formed detectable HAHA titers. Administration of CDA1 as a single intravenous infusion was safe and well tolerated. C(max) increased proportionally with increasing doses. A randomized study of CDA1 in patients with C. difficile associated diarrhea is underway.

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... The human monoclonal anti-TcdA (CDA1) and anti-TcdB (CDB1) antibodies used in this study were developed by Massachusetts Biologic Laboratories and Medarex, Inc. [6], and were provided for this study and currently licensed by Merck, Inc. These antibodies have already been used in the hamster model [6], the piglet model [7], and in clinical trials in humans [11,12]. Both CDA1 and CDB1 are IgG1k antibodies and bind the receptor-binding domain of TcdA and TcdB, respectively [6]. ...
... Both CDA1 and CDB1 are IgG1k antibodies and bind the receptor-binding domain of TcdA and TcdB, respectively [6]. CDA1 and CDB1 were administered to piglets at a dose of 10 mg/kg suspended in sterile PBS via intraperitoneal injection [11,12]. The dose used in piglets was based on that given to humans in clinical trials, as well as the protective dose in piglets in past experiments in our laboratory [7]. ...
... In this study we show an association between colonic injury due to CDI and the presence of IgG in the gut lumen, as compared with normal intestinal mucosa. The anti-toxin HMabs used in these experiments have been shown to be effective in modifying the clinical outcome of CDI in the hamster and gnotobiotic piglet models, and in clinical trials with human patients [5,6,11,12]. However, it is unclear how systemically administered IgG antibodies are able to provide protection against bacterial toxins liberated in the lumen of the large intestine. ...
Article
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The use of anti-toxin human monoclonal antibodies (HMab) as treatment for C. difficile infection has been investigated in animal models and human clinical trials as an alternative to or in combination with traditional antibiotic therapy. While HMab therapy appears to be a promising option, how systemically administered IgG antibodies protect the colonic mucosa during Clostridium difficile infection is unknown. Using the gnotobiotic piglet model of Clostridium difficile infection, we administered a mixture of anti-TcdA and anti-TcdB HMabs systemically to piglets infected with either pathogenic or non-pathogenic C. difficile strains. The HMabs were present throughout the small and large intestinal tissue of both groups, but significant HMabs were present in the lumen of the large intestines only in the pathogenic strain-infected group. Similarly, HMabs measured in the large intestine over a period of 2–4 days following antibody administration were not significantly different over time in the gut mucosa among the groups, but concentrations in the lumen of the large intestine were again consistently higher in the pathogenic strain-infected group. These results indicate that systemically administered HMab IgG reaches the gut mucosa during the course of CDI, protecting the host against systemic intoxication, and that leakage through the damaged colon likely protects the mucosa from further damage, allowing initiation of repair and recovery.
... The human monoclonal anti-TcdA (CDA1) and anti-TcdB (CDB1) antibodies used in this study were developed by Massachusetts Biologic Laboratories and Medarex, Inc. [10] and provided for this study and currently licensed by Merck, Inc. These antibodies have already been used in the hamster model [10] and in clinical trials in humans [16,17]. Both CDA1 and CDB1 are IgG1κ antibodies and bind the receptorbinding domain of TcdA and TcdB, respectively [10]. ...
... Both CDA1 and CDB1 are IgG1κ antibodies and bind the receptorbinding domain of TcdA and TcdB, respectively [10]. CDA1 and CDB1 were administered to piglets at a dose of 10 mg/kg, based on the dosing in human studies [16,17]. As a control, we used the irrelevant human monoclonal anti-shiga toxin 2 (anti-Stx2), developed by our institution [18], at a dose of 10 mg/kg. ...
... For this reason, the experiments with monoclonal antibodies were undertaken. We used monoclonal antibodies that had already been exhaustively examined for their toxin-neutralizing activity in vitro and in vivo in animals and humans, and these antibodies were not previously shown to have any toxin-enhancing effect [10,16,17]. In vitro cytotoxicity assay results from our laboratory have not shown either the polyclonal or monoclonal antibodies to have any toxin-enhancing capability at any concentration, and both types of antibodies are able to fully neutralize TcdA and TcdB in vitro. ...
Article
Background: A dramatic increase in morbidity and mortality from Clostridium difficile infection (CDI) due to the recent emergence of virulent, antibiotic-resistant strains has led to a search for alternatives to antibiotics, including vaccines and immune-based therapy that target the 2 key toxins-TcdA and TcdB. Methods: We investigated the efficacy of specific human monoclonal antibodies (HuMab) and alpaca polyclonal antibodies against each toxin separately and in combination in the gnotobiotic piglet model of CDI. Additionally, the HuMab and polyclonal antibodies were exploited to investigate the precise contribution of each toxin to systemic and/or gastrointestinal (GI) tract disease. Results: Our results indicate that TcdB is an important virulence factor associated with GI and systemic pathology. Administration of anti-TcdB antibody alone or with anti-TcdA protected 100% of piglets from development of systemic CDI and minimized GI lesions. Conversely, 100% of piglets administered only anti-TcdA developed severe GI and systemic disease, with 67%-83% fatality, faring worse than placebo-treated control animals. Conclusions: These results highlight the importance of TcdB in the pathogenesis of CDI and the effectiveness of TcdB-specific antibody in treating CDI. However, the results raise new questions regarding the nature of TcdA interaction with therapeutic antibodies.
... After successful assays in animal models, CDA1 and MDX1388 targeting TcdA and TcdB RBD respectively, were selected and tested in clinical trials ( Table 1). A phase I with CDA1 in healthy volunteers was completed ( Taylor et al. 2008). Single injection of CDA1 at different doses did not lead to serious adverse events nor anti-human antibodies production. ...
... gov Fully HuMAbs Phase I CDA1 Single i.v. injection different doses: 0.3, 1, 5, 10 and 20 mg/kg Safety No serious adverse effect Taylor et al. (2008) Healthy subjects PK No HAHA Half-life 25.3-31.8 days CDA1 (MK-3415, actoxumab): anti RBD of TcdA Phase II CDA1 Single i.v. ...
Chapter
C. difficile infection (CDI) is an important healthcare- but also community-associated disease. CDI is considered a public health threat and an economic burden. A major problem is the high rate of recurrences. Besides classical antibiotic treatments, new therapeutic strategies are needed to prevent infection, to treat patients and prevent recurrences. If fecal transplantation has been recommended to treat recurrences, another key approach is to restore immunity against C. difficile and its virulence factors. Here, after a summary concerning the virulence factors, the host immune response against C. difficile and its role in the outcome of disease, we review the different approaches of passive immunotherapies and vaccines developed against CDI. Passive immunization strategies are designed in function of the target antigen, the antibody-based product and its administration route. Similarly, for active immunization strategies, vaccine antigens can target toxins or surface proteins and immunization can be performed by parenteral or mucosal routes. For passive immunization and vaccination as well, we first present immunization assays performed in animal models and second in humans and associated clinical trials. The different studies are presented according to the mode of administration either parenteral or mucosal and the target antigens, either toxins or colonization factors.
... The plasma concentrationtime profiles after i.v. infusion of 5, 10 and 20 mg/kg CDA1 in healthy adults were taken from [60]. The data for the dosages 0.3 and 1 mg/kg were not used since the PK data could not be read with sufficient accuracy from the published figure. ...
... Comparison of experimental plasma concentration-time profiles for CDA1 in humans with simulation results. Experimental data are taken from[60] ...
Article
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Proteins are an increasingly important class of drugs used as therapeutic as well as diagnostic agents. A generic physiologically based pharmacokinetic (PBPK) model was developed in order to represent at whole body level the fundamental mechanisms driving the distribution and clearance of large molecules like therapeutic proteins. The model was built as an extension of the PK-Sim model for small molecules incorporating (i) the two-pore formalism for drug extravasation from blood plasma to interstitial space, (ii) lymph flow, (iii) endosomal clearance and (iv) protection from endosomal clearance by neonatal Fc receptor (FcRn) mediated recycling as especially relevant for antibodies. For model development and evaluation, PK data was used for compounds with a wide range of solute radii. The model supports the integration of knowledge gained during all development phases of therapeutic proteins, enables translation from pre-clinical species to human and allows predictions of tissue concentration profiles which are of relevance for the analysis of on-target pharmacodynamic effects as well as off-target toxicity. The current implementation of the model replaces the generic protein PBPK model available in PK-Sim since version 4.2 and becomes part of the Open Systems Pharmacology Suite. Electronic supplementary material The online version of this article (10.1007/s10928-017-9559-4) contains supplementary material, which is available to authorized users.
... BEZ was studied in 9 clinical trials as adjunctive therapy for the prevention of CDI recurrence. 4,13,16,17 Phase 1 ...
... A single 10-mg/kg dose was recommended for further studies. 16,17 Phase 2 ...
Article
Objective: To review the pharmacology, pharmacokinetics, efficacy, safety, and place in therapy of bezlotoxumab (BEZ), a novel monoclonal antibody against Clostridium difficile toxin B. Data sources: A PubMed search was conducted for data between 1946 and April 2017 using MeSH terms bezlotoxumab, MK-6072, or MDX-1388 alone and the terms Clostridium difficile combined with monoclonal antibody or antitoxin. Study selection and data extraction: The literature search was limited to English-language studies that described clinical efficacy, safety, and pharmacokinetics in humans and animals. Abstracts featuring prepublished data were also evaluated for inclusion. Data synthesis: BEZ is indicated for adult patients receiving standard-of-care (SoC) antibiotics for C difficile infection (CDI) to prevent future recurrence. Two phase III trials-MODIFY I (n = 1452) and MODIFY II (n = 1203)-demonstrated a 40% relative reduction in recurrent CDI (rCDI) with BEZ compared with placebo (16.5% vs 26.6%, P < 0.0001). The most common adverse drug events associated with BEZ were mild to moderate infusion-related reactions (10.3%). Conclusions: In patients treated with SoC antibiotics, BEZ is effective in decreasing rCDI. BEZ has no apparent effect on treatment of an initial CDI episode. In light of increasing rates of CDI, BEZ is a promising option for preventing recurrent episodes. The greatest benefit has been demonstrated in high-risk patients, though the targeted patient population is yet to be defined.
... A combination treatment with CDA1 and MDX-1388 in a hamster model for primary disease and relapse showed the best outcome. After safety and pharmacokinetics of CDA1 were assessed in healthy volunteers in a phase I clinical trial (Taylor et al., 2008), efficacy of combination treatment with CDA1 and MDX-1388 was examined in a randomized doubleblind, placebo-controlled phase II clinical trial (Lowy et al., 2010). The addition of both antibodies to either metronidazoleor vancomycin-treated patients with CDI significantly reduced recurrence rates. ...
Article
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Clostridium difficile causes antibiotic- and healthcare-associated diarrhea, which is characterized by a high mortality rate (5–15%) and high recurrence rate of 20% or more. Therapeutic alternatives to antibiotics are urgently needed to improve the overall cure rate. Among these, therapeutic antibodies have shown promising results in clinical studies. Herein, the authors review current monoclonal and polyclonal anti- C. difficile antibodies that have entered the clinical development stage, either for systemic administration or by the oral route. The antibodies can be applied as monotherapy or in combination with standard-of-care to treat an infection with C. difficile or to protect from a recurrence. Bezlotoxumab is the first antibody for secondary prevention of recurrence of C. difficile infection approved by the regulatory agencies in US and Europe. The human monoclonal antibody is administered systemically to patients receiving oral standard-of–care antibiotics. Other antibodies are currently in the clinical pipeline, and some are intended for oral use. They show a good safety profile, high efficacy and low production costs, and can be considered promising therapies of the future. The most promising orally administered drug candidate is a bovine antibody from hyperimmune colostral milk, which is in an advanced clinical development stage. Which antibody will enter the market is dependent on its bioavailability at the site of infection as well as its activity against C. difficile toxins, protection against colonization and possible action on spore formation. The antibody must demonstrate a clear benefit in comparison with other available treatment options to be considered for use by clinicians.
... Since then strategies using both passive and active immunization have been studied for the prevention and treatment of CDI. Human monoclonal antibodies CDA-1 and CDB-2 have been tested in CDI and demonstrated a decreased risk of recurrence from 25% to 7% when compared to placebo [22][23][24]. However considering the cost and inconvenience of this form of therapy, it is unlikely to be used as primary prophylaxis except in very high-risk patients [25]. On the other hand, vaccines against C. difficile, if and when they are available, will be a cost-effective method to limit the spread of CDI [26]. ...
... 8 Multiple animal studies reported toxin A as the major virulence factor associated with severe inflammatory response and intestinal damage in CDI. 9 Immunization against toxin A, not toxin B, in hamster models was protective against C. difficile colitis. Toxin B was reported to be functionally dependent on toxin A-related intestinal damage to produce cytotoxic effect on intestinal epithelial cells. ...
Article
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Clostridium difficile infection (CDI) is the most common health care-acquired infection associated with high hospital expenditures. The incidence of subsequent recurrent CDI increases with prior episodes of CDI, 15%–35% risk after primary CDI to 35%–65% risk after the first recurrent episode. Recurrent CDI is one of the most challenging and a very difficult to treat infections. Standard guidelines provide recommendations on treatment of primary CDI. However, treatment choices for recurrent CDI are limited. Recent research studies have focused on the discovery of newer alternatives for prevention of recurrent CDI targeting prime virulence factors involved in C. difficile pathogenesis. Bezlotoxumab is a human monoclonal antibody directed against C. difficile toxin B. Multiple in vitro and in vivo animal studies have demonstrated direct binding of bezlotoxumab to C. difficile toxin B preventing intestinal epithelial damage and colitis. Furthermore, this monoclonal antibody mediates early reconstitution of gut microbiota preventing risk of recurrent CDI. Randomized placebo-controlled trials showed concomitant administration of a single intravenous dose of 10 mg/kg of bezlotoxumab, in patients on standard-of-care therapy for CDI, had no substantial effect on clinical cure rates but significantly reduced the incidence of recurrent CDI (~40%). It shows efficacy against multiple strains, including the epidemic BI/NAP1/027 strain. Bezlotoxumab is a US Food and Drug administration-approved, safe and well-tolerated drug with low risk of serious adverse events and drug–drug interactions. Bezlotoxumab has emerged as a novel dynamic adjunctive therapy for prevention of recurrent CDI. Further studies on real-world experience with bezlotoxumab and its impact in reducing rates of recurrent CDI are needed.
... [13] Guery et al. (2017) 127 showed that a tapered treatment schedule with fidaxomicin (days 1-5: After analyzing the results of the phase I trials for bezlotoxumab and actoxumab, a combined 154 single dose of 10 mg/kg was recommended for further studies. [19,20] In the phase II, multi- (Table 4). [17] In the interim analysis of MODIFY 1, 161 the rate of rCDI was found to be significantly higher in the actoxumab group than in the 162 combined group. ...
Article
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Background: Clostridium difficile is the leading cause of antibiotic-associated diarrhea, both in healthcare facilities and the community. The recurrence rate of C. difficile infection (CDI) remains high, up to 20%. Since the publication of the ESCMID guidance document on CDI treatment in 2014, new therapeutic approaches have been developed and tested to achieve higher sustained clinical cure in CDI. Aim: To review novel treatments and approaches for CDI, except probiotics and vaccines. We focused on new antibiotics, antibiotic inactivators, monoclonal antibodies (mAbs), and gut microbiota modulating therapies. Sources: A literature review was performed for clinical trials published in Pubmed, Embase, or Cochrane library between January 2013 and November 2017. Content: We analyzed 28 clinical trials and identified 14 novel agents. Completed phase II studies were found for cadazolid, LFF571, ridinilazole, and non-toxigenic C. difficile strains. Four phase III active comparator studies comparing vancomycin with bezlotoxumab, surotomycin (n=2), and rifaximin have been published. Seven clinical trials for treatment of multiple recurrent CDI with fecal microbiota transplantation (FMT) were analyzed, describing FMT by upper or lower gastrointestinal route (n=5) or by capsules (n=2). Implications: Metronidazole is mentioned in the ESCMID guideline as first line therapy, but we propose that vancomycin orally will become the first choice when antibiotic treatment for CDI is necessary and the severity of the disease difficult to assess. Fidaxomicin is an good alternative, especially in patients at risk to develop a relapse. Vancomycin combined with FMT remains the primary therapy for multiple recurrent CDI . We anticipate that new medication that protects the gut microbiota will be further developed and tested to prevent CDI during antibiotic therapy.
... CDA1 and MDX1388 were selected for treatment of CDI in humans. First, a phase I clinical trial with CDA1 in healthy subjects was completed [54]. There were no serious adverse events after a single i.v. ...
Article
Introduction: Clostridium difficile infections are characterized by a high recurrence rate despite antibiotic treatments and there is an urgent need to develop new treatments such as fecal transplantation and immonotherapy. Besides active immunotherapy with vaccines, passive immunotherapy has shown promise, especially with monoclonal antibodies. Areas covered: Herein, the authors review the different assays performed with monoclonal antibodies against C. difficile toxins and surface proteins to treat or prevent primary or recurrent episodes of C. difficile infection in animal models and in clinical trials as well. Notably, the authors lay emphasis on the phase III clinical trial (MODIFY II), which allowed bezlotoxumab to be approved by the Food and Drug Administration and the European Medicines Agency. They also review new strategies for producing single domain antibodies and nanobodies against C. difficile and new approaches to deliver them in the digestive tract. Expert opinion: Only two human Mabs against TcdA and TcdB have been tested alone or in combination in clinical trials. However, many animal model studies have provided rationale for the use of Mabs and nanobodies in C. difficile infection and pave the way for further clinical investigation.
... 8 This long half-life suggests that a single infusion of IgG1 could offer protection of patients from CDI, or in the case of patients with CDI, this could reduce the chance of relapse. 8,33 While the development of mAbs as antitoxin and antimicrobial agents is well documented, concerns over their potential costs and widespread adoption are warranted. 24,34,35 sdAbs provide attractive therapeutic modalities against CDI. ...
Article
Full-text available
Greg Hussack,1 Jamshid Tanha1–3 1Human Health Therapeutics Portfolio, National Research Council Canada, Ottawa, 2School of Environmental Sciences, University of Guelph, Guelph, 3Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, ON, Canada Abstract: Clostridium difficile continues to be one of the most prevalent hospital-acquired bacterial infections in the developed world, despite the recent introduction of a novel and effective antibiotic agent (fidaxomicin). Alternative approaches under investigation to combat the anaerobic Gram-positive bacteria include fecal transplantation therapy, vaccines, and antibody-based immunotherapies. In this review, we catalog the recent advances in antibody-based approaches under development and in the clinic for the treatment of C. difficile infection. By and large, inhibitory antibodies that recognize the primary C. difficile virulence factors, toxin A and toxin B, are the most popular passive immunotherapies under investigation. We provide a detailed summary of the toxin epitopes recognized by various antitoxin antibodies and discuss general trends on toxin inhibition efficacy. In addition, antibodies to other C. difficile targets, such as surface-layer proteins, binary toxin, motility factors, and adherence and colonization factors, are introduced in this review. Keywords: antibody, Clostridium difficile, immunotherapy, toxin
... The product of F1 and CL up describes the rate of pinocytosis, and the product of F2 and (1-r V ) controls the fraction of mAb in plasma that was able to move via convection into the interstitial space. To obtain estimates for mean values of F1 and F2, and estimates of the variability of F1 and F2, data were digitized for 11 monoclonal antibodies administered to healthy subjects [29][30][31][32][33][34][35][36][37][38][39], with selection of mAbs at dose-levels associated with linear pharmacokinetics (Table 4). Values for F1 and F2 were then estimated for each mAb. ...
Article
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Accurate prediction of the clinical pharmacokinetics of new therapeutic entities facilitates decision making during drug discovery, and increases the probability of success for early clinical trials. Standard strategies employed for predicting the pharmacokinetics of small-molecule drugs (e.g., allometric scaling) are often not useful for predicting the disposition monoclonal antibodies (mAbs), as mAbs frequently demonstrate species-specific non-linear pharmacokinetics that is related to mAb-target binding (i.e., target-mediated drug disposition, TMDD). The saturable kinetics of TMDD are known to be influenced by a variety of factors, including the sites of target expression (which determines the accessibility of target to mAb), the extent of target expression, the rate of target turnover, and the fate of mAb-target complexes. In most cases, quantitative information on the determinants of TMDD is not available during early phases of drug discovery, and this has complicated attempts to employ mechanistic mathematical models to predict the clinical pharmacokinetics of mAbs. In this report, we introduce a simple strategy, employing physiologically-based modeling, to predict mAb disposition in humans. The approach employs estimates of inter-antibody variability in rate processes of extravasation in tissues and fluid-phase endocytosis, estimates for target concentrations in tissues derived through use of categorical immunohistochemical scores, and in vitro measures of the turnover of target and target-mAb complexes. Monte Carlo simulations were performed for four mAbs (cetuximab, figitumumab, dalotuzumab, trastuzumab) directed against three targets (epidermal growth factor receptor, insulin-like growth factor receptor 1, human epidermal growth factor receptor 2). The proposed modeling strategy was able to predict well the pharmacokinetics of cetuximab, dalotuzumab, and trastuzumab at a range of doses, but trended towards underprediction of figitumumab concentrations, particularly at high doses. The general agreement between model predictions and experimental observations suggests that PBPK modeling may be useful for the a priori prediction of the clinical pharmacokinetics of mAb therapeutics.
... At present, the use of probiotics is not recommended in the clinical community for the prevention of CDI [103,104]. Several other alternative therapies have been proposed such as the use of a novel neutralizing monoclonal antibody against C. difficile toxins, the anion-binding resins that neutralize clostridial toxins, vaccination against the pathogen and its toxins or immunoglobulin based therapies, but most of these treatments are in an early stage of development [109][110][111][112][113]. ...
Article
Full-text available
Antibiotics strongly disrupt the human gut microbiota, which in consequence loses its colonization resistance capacity, allowing infection by opportunistic pathogens such as Clostridium difficile. This bacterium is the main cause of antibiotic-associated diarrhea and a current problem in developed countries, since its incidence and severity have increased during the last years. Furthermore, the emergence of antibiotic resistance strains has reduced the efficiency of the standard treatment with antibiotics, leading to a higher rate of relapses. Here, we review recent efforts focused on the impact of antibiotics in the gut microbiome and their relationship with C. difficile colonization, as well as, in the identification of bacteria and mechanisms involved in the protection against C. difficile infection. Since a healthy gut microbiota is able to avoid pathogen colonization, restoration of the gut microbiota seems to be the most promising approach to face C. difficile infection, especially for recurrent cases. Therefore, it would be possible to design probiotics for patients undergoing antimicrobial therapies in order to prevent or fight the expansion of the pathogen in the gut ecosystem.
... The published literature has indicated that TcdA-specific antibodies in patient sera positively correlated with the prevention of CDAD recurrence [11][12][13][14][15]. Therefore, passive immunization with anti-toxin antibodies has been shown to confer protection against CDI in murine models, and TcdA-specific monoclonal antibodies are currently being tested in clinical trials [11,[16][17][18][19]. In addition, different C. difficile vaccine strategies are being evaluated; the most advanced strategy is vaccination with formalin-inactivated toxins [11,[20][21]. ...
Article
Full-text available
Clostridium difficile is an emerging pathogen responsible for opportunistic infections in hospitals worldwide and is the main cause of antibiotic-associated pseudo-membranous colitis and diarrhea in humans. Clostridial toxins A and B (TcdA and TcdB) specifically bind to unknown glycoprotein(s) on the surface of epithelial cells in the host intestine, disrupting the intestinal barrier and ultimately leading to acute inflammation and diarrhea. The C-terminal receptor-binding domain (RBD) of TcdA, which is responsible for the initial binding of the toxin to host glycoproteins, has been predicted to contain 7 potential oligosaccharide-binding sites. To study the specific roles and functions of these 7 putative lectin-like binding regions, a consensus sequence of TcdA RBD derived from different C. difficile strains deposited in the NCBI protein database and three truncated fragments corresponding to the N-terminal (residues 1-411), middle (residues 296-701), and C-terminal portions (residues 524-911) of the RBD (F1, F2 and F3, respectively) were designed and expressed in Escherichia coli. In this study, the recombinant RBD (rRBD) and its truncated fragments were purified, characterized biologically and found to have the following similar properties: (a) are capable of binding to the cell surface of both Vero and Caco-2 cells; (b) possess Toll-like receptor agonist-like adjuvant activities that can activate dendritic cell maturation and increase the secretion of pro-inflammatory cytokines; and (c) function as potent adjuvants in the intramuscular immunization route to enhance immune responses against weak immunogens. Although F1, F2 and F3 have similar repetitive amino acid sequences and putative oligosaccharide-binding domains, they do not possess the same biological and immunological properties: (i) TcdA rRBD and its fragments bind to the cell surface, but only TcdA rRBD and F3 internalize into Vero cells within 15 min; (ii) the fragments exhibit various levels of hemagglutinin (HA) activity, with the exception of the F1 fragment, which demonstrates no HA activity; and (iii) in the presence of alum, all fragments elicit various levels of anti-toxin A-neutralizing antibody responses, but those neutralizing antibodies elicited by F2 did not protect mice against a TcdA challenge. Because TcdA rRBD, F1 and F3 formulated with alum can elicit immune protective responses against the cytotoxicity of TcdA, they represent potential components of future candidate vaccines against C. difficile-associated diseases.
... Différentes voies d'administration ont également été étudiées. Les résultats découlant de ces essais sont plutôt encourageants et montrent, pour la plupart, l'acquisition d'une protection contre les infections à C. difficile et l'absence de risque pour l'homme [55][56][57][58][59][60][61][62]. Des essais de phase II et III sont en cours. ...
Article
Clostridium difficile is an enteropathogenic bacterium that causes post-antibiotic nosocomial diarrhea and pseudomembranous colitis. During the last decade, the incidence and the severity of C. difficile infections have significantly increased in America and Europe. This evolution seems to be related to the emergence and to the rapid dissemination of a particularly virulent clone of PCR-ribotype 027. The main virulence factors of C. difficile are the TcdA and TcdB cytotoxins which are responsible for intestinal lesions. However, the intestinal colonization by the bacterium is considered as an indispensible step for infection.To better understand the hypervirulence mechanisms of strain 027, we focused on the study of intestinal colonization process of this strain compared to the colonization process of the non-epidemic strain 630Δerm. First, we studied the role of the fibronectin binding protein FbpA. In vitro and in vivo characterization of a mutant FbpA showed the involvement of this protein in the colonization process of the non-epidemic strain 630Δerm. The difficulty of obtaining a mutant in the epidemic strain R20291 027 does not allow us to compare the adhesive properties of FbpA between the two strains.In a second step, we studied the characteristics of flagellar proteins FliC, FliD, FlgE and MotB. We showed that the flagella have a role in the adhesion and colonization of strain 027 and that this role is less important in strain 630Δerm. We also showed that flagella are involved in other cellular processes than adhesion and colonization. A transcriptomic study of a FliC mutant in 027 R20291 shows that flagellin is also involved in toxin production, sporulation and in the adaptation of bacteria to stress conditions. Further study should be performed to better understand the regulation system that governs these different cellular processes. Finally, we performed a transcriptomic analysis of the kinetic of in vivo colonization of the 027 R20291 strain. The study revealed a very early expression of toxin and sporulation genes during the first stages of the infection process. This analysis also allowed us to identify some genes, specific to 027 strains, which appeared regulated during the infection process. These genes could be involved in the virulence of C. difficile 027 strains and could provide new issues of study to better understand C. difficile virulence.
... Other treatment options currently in clinical development include toxin-absorbing polymer, new antibiotics (e.g. nitazoxanide, rifaximin, tigecycline and teicoplanin), and toxin-specific human monoclonal antibodies [14][15][16][17]. Furthermore, three vaccines, respectively from Sanofi, Valneva, and Pfizer, targetting C.difficile toxins are in different stages of clinical trials [18][19][20][21]. ...
Article
Full-text available
Clostridium difficile (C. difficile) is the most common cause of nosocomial antibiotic-associated diarrhea and the etiologic agent of pseudomembranous colitis. The clinical manifestation of C. difficile infection (CDI) is highly variable, from asymptomatic carriage, to mild self-limiting diarrhea, to the more severe pseudomembranous colitis. Furthermore, in extreme cases, colonic inflammation and tissue damage can lead to toxic megacolon, a condition requiring surgical intervention. C. difficile expresses two key virulence factors; the exotoxins, toxin A (TcdA) and toxin B (TcdB), which are glucosyltransferases that target host-cell monomeric GTPases. In addition, some hypervirulent strains produce a third toxin, binary toxin or C. difficile transferase (CDT), which may contribute to the pathogenesis of CDI. More recently, other factors such as surface layer proteins (SLPs) and flagellin have also been linked to the inflammatory responses observed in CDI. Although the adaptive immune response can influence the severity of CDI, the innate immune responses to C. difficile and its toxins play crucial roles in CDI onset, progression, and overall prognosis. Despite this, the innate immune responses in CDI have drawn relatively little attention from clinical researchers. Targeting these responses may prove useful clinically as adjuvant therapies, especially in refractory and/or recurrent CDI. This review will focus on recent advances in our understanding of how C. difficile and its toxins modulate innate immune responses that contribute to CDI pathogenesis.
... Two fully humanized monoclonal antibodies, CDA-1 and CDB-1, which target and neutralize TcdA and TcdB, respectively, in addition to standard antimicrobial therapy, were tested in 200 patients recovering from an initial episode of CDI in a phase 2 multicenter, randomized, double-blind, placebo-controlled trial. 103,104 Interestingly, in a phase 1 trial, the infusion of CDA-1 alone was not protective again emphasizing the importance of neutralizing both toxins. The performance of these antibodies for use as a prophylaxis still remains unclear. ...
Article
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Clostridium difficile is a spore-forming gram-positive bacillus, and the leading cause of antibiotic-associated nosocomial diarrhea and colitis in the industrialized world. With the emergence of a hypervirulent strain of C. difficile (BI/NAP1/027), the epidemiology of C. difficile infection has rapidly changed in the last decade. C. difficile infection, once thought to be an easy to treat bacterial infection, has evolved into an epidemic that is associated with a high rate of mortality, causing disease in patients thought to be low-risk. In this review, we discuss the changing face of C .difficile infection and the novel treatment and prevention strategies needed to halt this ever growing epidemic.
... Other options, such as anion-exchange resins, have limited efficacy and are potentially harmful [33]. Experimental treatments currently in clinical development include toxin-absorbing polymer, some antibiotics, and toxin-specific human monoclonal antibodies [34][35][36][37]. A toxoid vaccine inactivated by formaldehyde and administered intramuscularly is currently under clinical trial by Acambis [38,39]. ...
Chapter
Clostridium difficile is a spore-forming Gram-positive anaerobic bacillus, and is the leading cause of nosocomial diarrhea and colitis in the industrialized world. The incidence and mortality rates of C. difficile infection (CDI) have increased dramatically in the past decade. CDI is difficult to treat as antibiotic options are limited. Moreover, 15-35% of patients infected with C. difficile relapse following antibiotic treatment, which limits the ability of the colonic flora to inhibit C. difficile colonization. In an effort to improve outcomes and reduce recurrences of CDI, interest has been renewed in the development of nonantibiotic and adjunct approaches to therapy. Among these, probiotics have been investigated for primary and secondary prophylaxis against CDI, with varying success. This review discusses the mechanisms by which probiotics interact with C. difficile and its toxins, evaluates experimental models and clinical trials for probiotic use in the prevention or treatment of CDI and provides a framework for future research directions.
... Passive immunization or antibody administration has been well accepted in medical practice. Various types of antibodies against viral and bacterial infection were tested in vitro, in animal models and in clinical trials (Heijtink et al. 2001; Domanski et al. 2005; Taylor et al. 2008). More recently, humanized monoclonal antibody specific to E protein of West Nile virus (WNV) has been used in phase I clinical trial. ...
Article
Dengue virus (DENV) infection is an arthropod-borne disease with increasing prevalence worldwide. Attempts have been made to develop therapeutic molecules for treatment for DENV infection. However, most of potentially therapeutic DENV monoclonal antibody was originated from mouse, which could cause undesirable effects in human recipients. Thus, fully human antibody is preferable for therapeutic development. Human single-chain variable fragments (HuScFv) with inhibitory effect to DENV infection were generated in this study. HuScFv molecules were screened and selected from the human antibody phage display library by using purified recombinant DENV full-length envelope (FL-E) and its domain III (EDIII) proteins as target antigens for biopanning. HuScFv molecules were then tested for their bindings to DENV particles by indirect ELISA and immunofluorescent microscopy. EDIII-specific HuScFv exhibited neutralizing effect to DENV infection in Vero cells in a dose-dependent manner as determined by plaque formation and cell ELISA. Epitope mapping and molecular docking results concordantly revealed interaction of HuScFv to functional loop structure in EDIII of the DENV E protein. The neutralizing HuScFv molecule warrants further development as a therapeutic biomolecule for DENV infection. No approved vaccine and specific drug for dengue virus (DENV) infection are available; thus, their developments are urgently required. The human single-chain variable antibody fragments (HuScFv) specific to DENV envelope (E) protein are potential to be developed as therapeutic biomolecules. HuScFv that bound specifically to recombinant full-length DENV E (FL-E) and its domain III (EDIII) were generated and testified for its inhibitory effect in DENV infection. EDIII-specific HuScFv inhibited DENV infection in a dose-dependent manner and has potential to be further developed as a therapeutic biomolecule for DENV infection.
... 3 4 25-30 This additional treatment remains controversial up to now. Immunoglobulin therapy can be responsible for potential side effects: kidney failure and poor glycemic control in general; and headache, hypertension, digestive disorders specifically for human monoclonal antibody to C difficile toxin A. 31 Lowy et al 29 showed a significant reduction in recurrence of infections with C difficile treated with monoclonal antibodies against toxins A and B versus placebo. 29 However, this treatment did not reduce the time to resolution of diarrhoea, the duration of initial hospitalisation or the severity of the initial episode. ...
Article
Although rare, pseudomembranous colitis may be a cause of perineal necrotising fasciitis in a context of immunosuppression, as in the case we report. This origin must be quickly identified because the therapeutic management, especially surgery, is unlikely to be the same as usual. Similarly, antibiotic treatment is also a matter of discussion due to the potential deleterious role of antibiotics in pseudomembranous colitis.
... A number of indirect CDAD treatments are currently in clinical trials, including use of new antibiotics, toxin sequestration compounds, monoclonal antibodies to C. difficile toxins and active probiotics [3,4,6,34]. It is well known that recurrence of CDAD is associated with a lack of protective immunity to C. difficile toxins TA and TB. ...
Article
Clostridium difficile associated diarrhea (CDAD) is a critical public health problem worldwide with over 300,000 cases every year in the United States alone. Clearly, a potent vaccine preventing the morbidity and mortality caused by this detrimental pathogen is urgently required. However, vaccine efforts to combat C. difficile infections have been limited both in scope as well as to efficacy, as such there is not a vaccine approved for use against C. difficile to date. In this study, we have used a highly potent Adenovirus (Ad) based platform to create a vaccine against C. difficile. The Ad-based vaccine was able to generate rapid and robust humoral as well as cellular (T-cell) immune responses in mice that correlated with provision of 100% protection from lethal challenge with C. difficile toxin A. Most relevant to the clinical utility of this vaccine formulation was our result that toxin A specific IgGs were readily detected in plasma of Ad immunized mice as early as 3 days post vaccination. In addition, we found that several major immuno-dominant T cell epitopes were identified in toxin A, suggesting that the role of the cellular arm in protection from C. difficile infections may be more significant than previously appreciated. Therefore, our studies confirm that an Adenovirus based-C. difficile vaccine could be a promising candidate for prophylactic vaccination both for use in high risk patients and in high-risk environments.
... More importantly, an estimated 15–35% of those infected with C. difficile relapse following treatment [45,46]. Alternative experimental treatment options include the use of probiotics, fecal treansplant, toxin-absorbing polymer, new antibiotics, monoclonal antibodies, IVIG, and toxoid vaccines474849505152. C. difficile infection accounts for approximately 15–25% of cases of antibiotic-associated diarrhea, and the incidence of infection is rising steadily [53]. ...
Article
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The major virulence factors of Clostridium difficile infection (CDI) are two large exotoxins A (TcdA) and B (TcdB). However, our understanding of the specific roles of these toxins in CDI is still evolving. It is now accepted that both toxins are enterotoxic and proinflammatory in the human intestine. Both purified TcdA and TcdB are capable of inducing the pathophysiology of CDI, although most studies have focused on TcdA. C. difficile toxins exert a wide array of biological activities by acting directly on intestinal epithelial cells. Alternatively, the toxins may target immune cells and neurons once the intestinal epithelial barrier is disrupted. The toxins may also act indirectly by stimulating cells to produce chemokines, proinflammatory cytokines, neuropeptides and other neuroimmune signals. This review considers the mechanisms of TcdA- and TcdB-induced enterotoxicity, and recent developments in this field.
... 6 A study assessing the efficacy of CDA1, a human monoclonal antibody to toxin A, is underway. 38 ...
... We have shown that these antibodies can reduce mortality in acute and relapsing hamster models of C. difficile associated diarrhea [16]. In phase I clinical studies these antibodies are safe and well-tolerated when given as a single intravenous infusion to healthy adult volunteers [17,18]. A randomized, double-blind, placebo-controlled phase II study was undertaken in patients to examine the safety and efficacy of a human monoclonal antibody against toxin A of C. difficile (CDA1) with standard of care antibiotics to treat CDI. ...
Article
Previous studies have demonstrated a correlation between Clostridium difficile anti-toxin A serum antibodies and protection against symptomatic disease and recurrence. A neutralizing monoclonal antibody to C. difficile toxin A (CDA1) developed by MBL and Medarex, Inc. was studied in a phase II, randomized, double-blind, placebo-controlled trial in patients receiving standard of care treatment for C. difficile infection (CDI). Twenty-nine subjects received a single intravenous infusion of 10mg/kg CDA1 and 17 subjects received placebo and were evaluated for recurrence of CDI during the 56-day study period. Serum antibodies against C. difficile toxin A and B were measured by ELISA and cytotoxicity assay at various time points before and after infusion. CDI recurrence occurred in 5 of 29 (17%) in the CDA1 group and 3 of 17 (18%) (p=NS) in the placebo group with a trend toward delay in time to recurrence in the group treated with CDA1. The geometric mean concentration of antibody to an epitope of the receptor-binding domain of toxin B (0.300 and 1.20microg/ml, respectively; p=0.02) and geometric mean titer of neutralizing B antibody (8.00 and 100, respectively; p=0.02) at study day 28 were lower for those subjects with recurrence compared to those who did not recur. In addition, a significantly greater proportion of subjects who recurred were infected with the epidemic BI/NAP1/027 strain compared with those that did not recur (88% vs. 22%; p=0.002). Finally, in a multiple logistic regression analysis neutralizing anti-toxin B at day 14 (p<0.001), anti-toxin A at day 28 (p<0.001) and infection with the BI/NAP1/027 strain at enrollment (p=0.002) were all predictive of CDI recurrence. In this prospective study, lower concentrations of neutralizing anti-toxin B and anti-toxin A antibody and infection with the BI/NAP1/027 strain of C. difficile were significantly associated with recurrence of CDI.
... 82 A variety of novel strategies are at an early stage of development, but may be useful future developments in the treatment of CDI. These including bovine colostrum 143 and specific human monoclonal antibodies aimed at neutralizing toxin A. 144 A variety of proteins, including toxins A and B, have been targeted as potential candidates for a C. difficile vaccine 145 and a novel temperate bacteriophage has been identified that possesses an endolysin that is biologically active and capable of lysing cells of C. difficile, 146 offering possible alternatives for the prevention and treatment of CDI. ...
Article
Clostridium difficile is the commonest cause of nosocomial diarrhoea. The epidemiology and clinical phenotype of the disease has dramatically changed with the global emergence of a virulent strain of C. difficile. This review was compiled using data from individual studies and review articles identified from PubMed. The retrieved articles were also examined for additional references. Appropriate and timely infection control measures are required to control C. difficile infection (CDI) in the hospital environment, and either oral metronidazole or vancomycin remains the mainstay of treatment depending on the severity of infection. The optimal method for diagnosing CDI remains unclear, as does the best therapeutic strategy for the management of multiple relapses. GROWING POINTS/AREAS TIMELY FOR DEVELOPING RESEARCH: Studies of new antimicrobial agents with activity against C. difficile are required to improve the management of multiply relapsing disease. The use of novel therapeutic approaches that do not require antimicrobials requires urgent research, including the use of immunological or vaccine-based regimen, bacteriotherapy or C. difficile-specific bacteriophages.
... This report presents the first description of a DNA vaccine targeting C. difficile toxin A. Over the past decade, a variety of vaccines and immunotherapeutics intended to treat or prevent C. difficile disease have been tested in murine and hamster animal models [21,[25][26][27][28][38][39][40][41][42]. The inactivated toxoid and monoclonal antibody platforms are the furthest in clinical development [43,44]. In fact, recently released phase II results of a monoclonal antibody product has provided the first evidence of the efficacy of an immunotherapeutic product in preventing recurrent diarrhea in affected human subjects [45]. ...
Article
Clostridium difficile is a pathogen with increasing severity for which host antibody responses provide protection from disease. DNA vaccination has several advantages compared to traditional vaccine methods, however no study has examined this platform against C. difficile toxins. A synthetic gene was created encoding the receptor-binding domain (RBD) of C. difficile toxin A, optimized for expression in human cells. Gene expression was examined in vitro. Mice were inoculated and then challenged with parenteral toxin A. Vaccination provided high titer antibodies and protected mice from death. This represents the first report of DNA vaccine inducing neutralizing antibodies to C. difficile toxin A.
... Taylor et al [156] examined the safety and pharmacokinetics of a novel neutralizing human monoclonal antibody against C. difficile toxin A (CDA1) in 30 healthy adults whose median age was 27.5 years. While there were no serious adverse events related to its use, 21 of 30 reported non-serious adverse events were possibly related to CDA1. ...
Article
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A new, hypervirulent strain of Clostridium difficile, called NAP1/BI/027, has been implicated in C. difficile outbreaks associated with increased morbidity and mortality since the early 2000s. The epidemic strain is resistant to fluoroquinolones in vitro, which was infrequent prior to 2001. The name of this strain reflects its characteristics, demonstrated by different typing methods: pulsed-field gel electrophoresis (NAP1), restriction endonuclease analysis (BI) and polymerase chain reaction (027). In 2004 and 2005, the US Centers for Disease Control and Prevention (CDC) emphasized that the risk of C. difficile-associated diarrhea (CDAD) is increased, not only by the usual factors, including antibiotic exposure, but also gastrointestinal surgery/manipulation, prolonged length of stay in a healthcare setting, serious underlying illness, immune-compromising conditions, and aging. Patients on proton pump inhibitors (PPIs) have an elevated risk, as do peripartum women and heart transplant recipients. Before 2002, toxic megacolon in C. difficile-associated colitis (CDAC), was rare, but its incidence has increased dramatically. Up to two-thirds of hospitalized patients may be infected with C. difficile. Asymptomatic carriers admitted to healthcare facilities can transmit the organism to other susceptible patients, thereby becoming vectors. Fulminant colitis is reported more frequently during outbreaks of C. difficile infection in patients with inflammatory bowel disease (IBD). C. difficile infection with IBD carries a higher mortality than without underlying IBD. This article reviews the latest information on C. difficile infection, including presentation, vulnerable hosts and choice of antibiotics, alternative therapies, and probiotics and immunotherapy. We review contact precautions for patients with known or suspected C. difficile-associated disease. Healthcare institutions require accurate and rapid diagnosis for early detection of possible outbreaks, to initiate specific therapy and implement effective control measures. A comprehensive C. difficile infection control management rapid response team (RRT) is recommended for each health care facility. A communication network between RRTs is recommended, in coordination with each country's department of health. Our aim is to convey a comprehensive source of information and to guide healthcare professionals in the difficult decisions that they face when caring for these oftentimes very ill patients.
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Clostridioides difficile (C. difficile), known as the major cause of antibiotic-associated diarrhea, is regarded as one of the most common healthcare-associated bacterial infections worldwide. Due to the emergence of hypervirulent strains, development of new therapeutic methods for C. difficile infection (CDI) has become crucially important. In this context, antibodies have been introduced as valuable tools in the research and clinical environments, as far as the effectiveness of antibody therapy for CDI was reported in several clinical investigations. Hence, production of high-performance antibodies for treatment of CDI would be precious. Traditional approaches of antibody generation are based on hybridoma technology. Today, application of in vitro technologies for generating recombinant antibodies, like phage display, is considered as an appropriate alternative to hybridoma technology. These techniques can circumvent the limitations of the immune system and they can be exploited for production of antibodies against different types of biomolecules in particular active toxins. Additionally, DNA encoding antibodies is directly accessible in in vitro technologies, which enables the application of antibody engineering in order to increase their sensitivity and specificity. Here, we review the application of antibodies for CDI treatment with an emphasis on recombinant fragment antibodies. Also, this review highlights the current and future prospects of the aforementioned approaches for antibody-mediated therapy of CDI.
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Clostridioides difficile infection occurs when the bacterium produces toxin that causes diarrhea and inflammation of the colon. These guidelines indicate the preferred approach to the management of adults with C. difficile infection and represent the official practice recommendations of the American College of Gastroenterology. The scientific evidence for these guidelines was evaluated using the Grading of Recommendations Assessment, Development, and Evaluation process. In instances where the evidence was not appropriate for Grading of Recommendations Assessment, Development, and Evaluation but there was consensus of significant clinical merit, key concept statements were developed using expert consensus. These guidelines are meant to be broadly applicable and should be viewed as the preferred, but not the only, approach to clinical scenarios.
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Use of the subcutaneous (SC) route for administering monoclonal antibodies (mAbs) to treat chronic conditions has been hindered because of an incomplete understanding of fundamental mechanisms controlling mAb absorption from the SC site, and due to the limited translatability of preclinical studies. In this paper, we report on the development and evaluation of a whole-body physiologically-based model to predict mAb pharmacokinetics following SC administration. The circulatory model is based on the physiological processes governing mAb transport and includes two mAb-specific parameters representing differences in pinocytosis rate and the diffusive/convective transport rates among mAbs. At the SC administration site, two additional parameters are used to represent mAb differences in lymphatic capillary uptake and in pre-systemic clearance. Model development employed clinical intravenous (IV) plasma PK data from 20 mAbs and SC plasma PK data from 12 of these mAbs, as obtained from the literature. The resulting model reliably described both the IV and SC measured plasma concentration data. In addition, a metric based on the positive charge across the mAb’s complementarity determining region vicinity was found to positively correlate with the model-based estimates of the mAb-specific parameter governing organ/tissue pinocytosis transport and with estimates of the mAb’s SC lymphatic capillary clearance. These two relationships were incorporated into the model and accurately predicted the SC PK profiles of three out of four separate mAbs not included in model development. The whole-body physiologically-based model reported herein, provides a platform to characterize and predict the plasma disposition of monoclonal antibodies following SC administration in humans.
Article
Introduction: Clostridium difficile infection (CDI) is the most common healthcare-associated infection worldwide. As standard CDI antibiotic therapies can result in unacceptably high recurrence rates, novel therapeutic strategies for CDI are necessary. A recently emerged immunological therapy is a monoclonal antibody against C. difficile toxin B. Areas covered: In this review, the authors summarize the available pharmacological, preclinical, and clinical data for the CDI treatment based on anti-toxin A (actoxumab) and anti-toxin B (bezlotoxumab) human monoclonal antibodies (HuMabs), and discuss about the potentiality of a therapy that includes HuMab combined administration for CDI. Expert opinion: Although only bezlotoxumab is indicated to reduce recurrence of CDI, experimental studies using a combination of HuMabs actoxumab and bezlotoxumab have shown that bolstering the host immune response against both the C. difficile toxins may be effective in primary and secondary CDI prevention. Besides neutralizing both the key virulence factors, combination of two HuMabs could potentially offer an advantage for a yet to emerge C. difficile strain, which is a steady threat for patients at high risk of CDI. However, as actoxumab development was halted, passive immunotherapy with actoxumab/bezlotoxumab is actually impracticable. Future research will be needed to assess HuMab combination as a therapeutic strategy in clinical and microbiological cure of CDI.
Article
Introduction: Clostridium difficile infection is a major economic and clinical burden, due to its high frequency of recurrence. Currently recommended treatments are not efficient for prevention and may contribute to the risk of recurrent infection. In recent years, research has focused on strategies to lessen this risk. Bezlotoxumab is a monoclonal antibody that prevents recurrences of C. difficile infection through the antagonism of toxin B. Areas covered: In this review, the authors discuss the burden of C. difficile infection and its recurrences, the mechanisms underlying the recurrences, and current C. difficile treatments. They subsequently analyze the strategic therapeutic rationale for bezlotoxumab use, as well as the supporting clinical evidence. Expert opinion: Bezlotoxumab is an attractive solution for reducing the unacceptable level of recurrence that occurs with the currently recommended C. difficile treatments and other alternative therapies under consideration. Even though bezlotoxumab has not been tested in large-scale trials exclusively in cases of already established recurrent C.difficile infection (rCDI), it has an advantage over current treatments in that it does not interfere with the patient’s gut flora while directly neutralizing the key virulence factor. Although cost remains an important factor against its widespread use, simpler administration, fewer side-effects, and better social acceptability justify its consideration for treating rCDI.
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Two structurally defined, functionalized glycans of lipoteichoic acid (LTA, also known as PS-III) from C. difficile, which have one or two repeating units of LTA linked to the core trisaccharide, were efficiently synthesized via a convergent [2 + 3] or [2 + 2 + 3] strategy. The α-linkage of both N-acetylglucosamine residues in the repeating unit were constructed with glycosyl imidates of azidosugars as donors, while the phosphodiester bridges between the oligosaccharides were fashioned using H-phosphonate chemistry. Both synthetic targets contained a 3-aminopropyl group at the core trisaccharide reducing end, facilitating their conjugation to other biomolecules to afford conjugates useful for various biological studies and applications.
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A systematic review was performed to evaluate how the maximum recommended starting dose (MRSD) was determined in first-in-human (FIH) studies with monoclonal antibodies (mAbs). Factors associated with the choice of each MRSD determination method were also identified. PubMed was searched for FIH studies with mAbs published in English between January 1, 1990 and December 31, 2013, and the following information was extracted: MRSD determination method, publication year, therapeutic area, antibody type, safety factor, safety assessment results after the first dose, and number of dose escalation steps. Seventy-nine FIH studies with mAbs were identified, 49 of which clearly reported the MRSD determination method. The no observed adverse effects level (NOAEL)-based approach was the most frequently used method, whereas the model-based approach was the least commonly used method (34.7% vs 16.3%). The minimal anticipated biological effect level (MABEL)- or minimum effective dose (MED)-based approach was used more frequently in 2011–2013 than in 1990–2007 (31.6% vs 6.3%, P=0.036), reflecting a slow, but steady acceptance of the European Medicines Agency’s guidance on mitigating risks for FIH clinical trials (2007). The median safety factor was much lower for the MABEL- or MED-based approach than for the other MRSD determination methods (10 vs 32.2–53). The number of dose escalation steps was not significantly different among the different MRSD determination methods. The MABEL-based approach appears to be safer and as efficient as the other MRSD determination methods for achieving the objectives of FIH studies with mAbs faster.
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Clostridium difficile infection (CDI), a leading cause of nosocomial infection, is a serious disease in North America, Europe and Asia. CDI varies greatly from asymptomatic carriage to life threatening diarrhea, toxic megacolon and toxemia. The incidence of community acquired infection has increased due to the emergence of hypervirulent antibiotic-resistant strains. These new strains contribute to the frequent occurrence of disease relapse; complicating treatment, increasing hospital stays, and increasing morbidity and mortality among patients. It is critical therefore to develop new therapeutic approaches that bypass the development of antimicrobial resistance and avoid disruption of gut microflora. Here we describe the construction of a single heteromultimeric V H H-based neutralizing agent (VNA) targeting the two primary virulence factors of Clostridium difficile , toxin A (TcdA) and B (TcdB). Designated VNA2-Tcd, this agent has sub-nanomolar toxin neutralization potencies for both C. difficile toxins in cell assays. When given systemically by parenteral administration, VNA2-Tcd protected against CDI in gnotobiotic piglets and mice, and to a lesser extent in hamsters. Protection from CDI was also observed in gnotobiotic piglets treated by gene therapy with an adenovirus promoting expression of VNA2-Tcd.
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The discovery of antibiotics and other antimicrobials, and their widespread application in human medicine since the middle of the twentieth century has saved millions of human lives. Additionally, their application in veterinary medicine and especially in food science has constituted an important way of controlling the dispersion of microbial pathogens. This has played a major role not only in the dramatic increase in average life expectancy in humans, but also in extending the “shelf life” of foods; however, antibiotic overuse and misuse, together with the microbial ability to share DNA by horizontal gene transfer, have resulted in the generation of antibiotic-resistant bacterial strains that quickly spread throughout the world. As a result, the antibiotic of choice can be rendered totally ineffective both in human therapy and as a food additive. The focus of this chapter is a handful of gram-negative and gram-positive bacteria that are developing antibiotic resistance and represent a major hazard in food preservation.
Article
The increasing incidence and severity of Clostridium difficile infection (CDI) is becoming a major issue in public health. The identification of new therapeutic options able to control severe cases and reduce the risk of recurrence is a research priority. Toxins A (TcdA) and B (TcdB) and host immune response are the major determinants of CDI pathogenesis and may be a possible target for new therapies. The aim of this review was to critically describe the evidence available on the effect of monoclonal antibodies (MAbs) on CDI, putting them into clinical context and highlighting possible advantages and barriers to their use. Experimental animal studies revealed the potential of MAbs to protect against CDI progression and recurrence, especially when a combination of anti-TcdA and anti-TcdB is used. Only one clinical trial confirmed that this combined approach is well tolerated and effective in controlling CDI recurrences in at-risk subjects with refractory CDI. Other clinical trials are currently ongoing and explore alternative molecules. Toxin-targeted MAbs are one of the most promising approaches and at-risk subjects and those experiencing recurrence are the ideal targets for this second-line treatment. However, CDI epidemiology is rapidly changing and MAbs may also represent a powerful option for other patients.
Clostridium difficile is a spore-forming gram-positive bacterium that causes sometimes severe infections of the gut of affected individuals. The high prevalence of C. difficile infections has caused the Center for Disease Control to characterize this disease as “an immediate health threat that requires urgent and aggressive action.” A major issue with existing treatments for C. difficile is their reliance on antibiotics to kill the bacterium. These antibacterial agents cause disruptions in the gut flora that normally compete with C. difficile, rendering the gut lumen susceptible to a new round of infection or to germination of persistent C. difficile spores. This cycle of infection and recurrence underscores the need for novel approaches to the treatment and prevention of C. difficile infections. This review summarizes previous and ongoing efforts to develop active and passive immunization strategies for the prevention of primary and recurrent C. difficile infections.
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Clostridium difficile is a spore-forming anaerobic gram-positive organism that is the leading cause of antibiotic-associated nosocomial infectious diarrhea in the Western world. This article describes the evolving epidemiology of C difficile infection (CDI) in the twenty-first century, evaluates the importance of vaccines against the disease, and defines the roles of both innate and adaptive host immune responses in CDI. The effects of passive immunotherapy and active vaccination against CDI in both humans and animals are also discussed. Copyright © 2015 Elsevier Inc. All rights reserved.
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Most hospital-acquired infections arise from colonising bacteria. Intensive care patients and immunocompromised individuals are at highest risk for microbial invasion and subsequent infection due to multiple invasive procedures in addition to frequent application of chemotherapeutics and presence of poor microperfusion leading to mucosal disruption. In this narrative review, we summarise the literature on bacterial colonisation in intensive care patients, in particular the epidemiology, the clinical impact and respective infection control strategies of three pathogens, i.e., Enterococcus spp., extended-spectrum ß-lactamase producing gram-negative bacteria and Clostridium difficile, which have evolved from commensals to a public health concern today.
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Antibodies for the treatment of Clostridium difficile infection (CDI) have been demonstrated to be effective in the research and clinical environments. Early uncertainties about molecular and treatment modalities now appear to have converged upon the systemic dosing of mixtures of human IgG1. Although multiple examples of high-potency monoclonal antibodies (MAbs) exist, significant difficulties were initially encountered in their discovery. This minireview describes historical and contemporary MAbs and highlights differences between the most potent MAbs, which may offer insight into the pathogenesis and treatment of CDI.
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We recently published our findings indicating that anti-TcdB antibodies were effective as treatment for C. difficile infection, but that anti-TcdA actually worsened prognosis in the gnotobiotic piglet model. To further investigate the roles of the two toxins, we administered purified toxins separately or together, systemically, to piglets and found that both toxins, either alone or together, are able to elicit severe lesions systemically, and are also able to cross into the gut lumen and cause large intestinal lesions typical of infection. We also found that anti-TcdA administered before systemic challenge with TcdA again did not protect from development of disease, but, in this case, did not appear to worsen prognosis. Further work is still needed, but these findings add to the growing knowledge regarding the roles of the C. difficile toxins.
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AIMS: Many monoclonal antibodies (MAbs) have been studied in healthy volunteers in phase 1, but few data have been published on the safety of that practice. We aimed to review the available data, and thereby to estimate the risks of participation in phase 1 trials of MAbs. METHODS: We searched PubMed, the ClinicalTrials.gov database, and Google, using the search terms 'monoclonal antibody', 'phase 1' and 'healthy volunteers'. RESULTS: We identified 70 completed trials of MAbs in healthy volunteers, but the published data were too sparse to allow confident assessment of the risks of MAbs in healthy volunteers. Our best estimate of risk of a life-threatening adverse event was between 1:425 and 1:1700 volunteer-trials, but all such events occurred in a single trial (of TGN1412). CONCLUSIONS: In a phase 1 trial of a small-molecule, the risk of death or a life-threatening adverse event appears to be 1:100,000-1,000,000 volunteer-trials, which is similar to the risk of many ordinary daily activities. Most people would consider that level of risk to be 'minimal' or 'negligible', and, therefore, acceptable. On that basis, the safety record of MAbs in healthy volunteers has been ruined by the TGN1412 disaster. However, that experience is unlikely to be repeated, because of improvements in governance and practice of phase 1 trials. If the experience of TGN1412 is disregarded, it seems reasonable to continue using healthy volunteers in phase 1 trials of MAbs, provided that there are scientific and medical reasons to conclude that the risk is truly minimal.
Article
Enterocolitis caused by Clostridium difficile (C. difficile) is a serious, sometimes fatal, disease of neonatal foals and older horses. Toxins A and B (TcdA and B) produced by C. difficile are important virulence factors. Immunisation of mares with receptor binding domains of toxins may prevent or reduce the severity of C. difficile colitis in foals. To determine whether antibodies generated in the pregnant mare to the binding regions of TcdA and B will neutralise TcdA and B toxicity. Sequences encoding the binding domains of each toxin were isolated by PCR amplification from C. difficile JF09, a foal isolate, and cloned and expressed into pET15b. Thirteen mares were immunised twice 2 weeks apart with 200 μg of each recombinant protein with Quil A 2 months prior to foaling. Antibodies were assayed in the sera and colostrum by ELISA and for ability to block the cytopathic activity of each of toxin for equine endothelial cells. All mares produced strong serum antibody responses to the binding domain of each toxin. A high level of toxin-specific antibodies was also detected in colostrum and in most foal sera 2 days after suckling. Diluted sera and colostrum premixed with either TcdA or B had no effect on the morphology of equine endothelial cells. Application of the same concentration of toxins alone or premixed with nonimmune mare/foal serum or colostrum led to an unambiguous cytopathic effect that ranged from complete degradation to varying degrees of cell rounding. Immunisation of pregnant mares with recombinant binding domains of TcdA and B of C. difficile resulted in the production of specific antibodies in serum and colostrum that blocked the cytopathic activity of toxins. Results of studies support the feasibility of a prepartum vaccine against C. difficile enterocolitis in foals.
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EpidemiologyTreatment for the initial episodeTreatment for recurrent CDADPreventionSummaryAcknowledgementReferences
Article
Clostridium difficile is the most important definable cause of healthcare acquired diarrhea. The increasing incidence and mortality associated with this enteric pathogen and the significant rate of treatment failures and recurrences with current antibiotics emphasize the need for the discovery of new and improved therapeutic and preventative agents. We review upcoming novel therapeutic agents and the clinical evidence to support their efficacy in treating C. difficile infection. We also provide an extensive comparison of antimicrobial susceptibilities of C. difficile based on in vitro susceptibilities published in the literature. This review was conducted by a thorough examination of the public sources, including journals and scientific meeting abstracts, up to February 2009. A number of new therapeutic agents are in development and being tested in clinical trials. However, high costs and concerns for resistance may limit the use of these antimicrobials for the treatment of C. difficile infection. Passive and active immunotherapy may have important future roles as therapeutic and preventative strategies for C. difficile infection.
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New therapies are needed to manage the increasing incidence, severity, and high rate of recurrence of Clostridium difficile infection. We performed a randomized, double-blind, placebo-controlled study of two neutralizing, fully human monoclonal antibodies against C. difficile toxins A (CDA1) and B (CDB1). The antibodies were administered together as a single infusion, each at a dose of 10 mg per kilogram of body weight, in patients with symptomatic C. difficile infection who were receiving either metronidazole or vancomycin. The primary outcome was laboratory-documented recurrence of infection during the 84 days after the administration of monoclonal antibodies or placebo. Among the 200 patients who were enrolled (101 in the antibody group and 99 in the placebo group), the rate of recurrence of C. difficile infection was lower among patients treated with monoclonal antibodies (7% vs. 25%; 95% confidence interval, 7 to 29; P<0.001). The recurrence rates among patients with the epidemic BI/NAP1/027 strain were 8% for the antibody group and 32% for the placebo group (P=0.06); among patients with more than one previous episode of C. difficile infection, recurrence rates were 7% and 38%, respectively (P=0.006). The mean duration of the initial hospitalization for inpatients did not differ significantly between the antibody and placebo groups (9.5 and 9.4 days, respectively). At least one serious adverse event was reported by 18 patients in the antibody group and by 28 patients in the placebo group (P=0.09). The addition of monoclonal antibodies against C. difficile toxins to antibiotic agents significantly reduced the recurrence of C. difficile infection. (ClinicalTrials.gov number, NCT00350298.)
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Renewed interest in Clostridium difficile infections (CDI) is stimulating research into the pathogenesis and virulence factors for this pathogen. This review summarizes recent progress in the field, particularly in relation to the changing epidemiologic trends and new investigational treatments. Elucidation of the role of different toxins of C. difficile (tcdA, tcdB and binary toxin) is deepening our understanding of CDI. Stain typing of C. difficile isolates is documenting the spread of an emergent strain (BI/NAP1/027) associated with large outbreaks of severe disease. Typing of isolates around the world shows global spread of this strain. Reliance upon metronidazole is questioned due to a lower response rate and newer investigational therapies are reported. After being considered a manageable pathogen for decades, C. difficile recently caused large outbreaks of severe disease. Refocused research is determining patients who are at risk for CDI, what methods are more effective in diagnosing CDI and what new treatments may be effective. This article reviews the recent findings in the literature regarding this difficult and challenging pathogen.
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Toxin B, a potent cytotoxin produced by Clostridium difficile, was purified to homogeneity from 6-day broth cultures of a toxigenic isolate. Cytotoxin was purified approximately 4000-fold by sequential ammonium sulfate precipitation, DEAE-Sepharose chromatography, and high performance liquid chromatography on a Mono Q anion-exchange column. The molecular weight of reduced purified toxin was 50,000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, compared to 150,000 for unreduced toxin. Dose-response studies indicated that subpicogram concentrations of purified toxin caused rounding of approximately 20,000 IMR-90 fibroblasts. The phenomenon of cell rounding caused by toxin B was correlated with the ratio of globular to filamentous actin in fibroblasts as measured by two techniques. The toxin caused a significant increase in the ratio of globular to filamentous actin which was nearly completed prior to the onset of rounding. We conclude that cell rounding of fibroblasts exposed to toxin B is related to an increase in the ratio of globular to filamentous actin which is produced by small numbers of toxin molecules/cell.
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The effect of purified toxin A and partially purified toxin B on rabbit ileum and colon was investigated. Toxin A caused tissue damage which was followed by permeability changes and fluid accumulation in both tissues. Toxin A did not increase the permeability of the colon to the extent observed for ileum; secreted fluid contained less protein of plasma origin. Toxin B had no effect on either tissue. Secretory and tissue damaging properties of crude C difficile toxins were found to be due to toxin A.
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Examination of the biological activities of the two known toxins of Clostridium difficile revealed that one of the toxins (toxin A) elicited a hemorrhagic fluid response in rabbit intestinal loops and a positive fluid response in infant mice. The other toxin (toxin B) did not produce a significant fluid response in either model, although the toxin was more lethal in infant mice. Both toxins elicited erythematous and hemorrhagic skin reactions and increased vascular permeability in rabbit skin.
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Toxin A but not toxin B, appears to mediate intestinal damage in animal models of Clostridium difficile enteritis. The purpose of this study was to investigate the electrophysiologic and morphologic effects of purified C. difficile toxins A and B on human colonic mucosa in Ussing chambers. Luminal exposure of tissues to 16-65 nM of toxin A and 0.2-29 nM of toxin B for 5 h caused dose-dependent epithelial damage. Potential difference, short-circuit current and resistance decreased by 76, 58, and 46%, respectively, with 32 nM of toxin A and by 76, 55, and 47%, respectively, with 3 nM of toxin B, when compared with baseline (P < 0.05). 3 nM of toxin A did not cause electrophysiologic changes. Permeability to [3H]mannitol increased 16-fold after exposure to 32 nM of toxin A and to 3 nM of toxin B when compared with controls (P < 0.05). Light and scanning electron microscopy after exposure to either toxin revealed patchy damage and exfoliation of superficial epithelial cells, while crypt epithelium remained intact. Fluorescent microscopy of phalloidin-stained sections showed that both toxins caused disruption and condensation of cellular F-actin. Our results demonstrate that the human colon is approximately 10 times more sensitive to the damaging effects of toxin B than toxin A, suggesting that toxin B may be more important than toxin A in the pathogenesis of C. difficile colitis in man.
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Neutrophil infiltration is a prominent feature of Clostridium difficile-associated enteritis and colitis. The aim of this study was to examine the importance of neutrophil recruitment and neutrophil-mediated tissue damage in C. difficile toxin A-induced enteritis. Competitive binding experiments using purified 3H-toxin A demonstrated the presence of a single class of medium affinity receptors on rabbit neutrophils (Kd 7 x 10(-8) M). Pertussis toxin and the nonhydrolyzable GTP analog GTPgamma S both inhibited 3H-toxin A binding (by 56 and 65%, respectively), indicating that the rabbit neutrophil toxin A receptor is G protein linked. Toxin A elicited a dose-dependent (25-200 micrograms/ml) stimulation of neutrophil migration in vitro, and this functional effect was also pertussis toxin sensitive (69% inhibition). Treatment of neutrophils with R15.7, a blocking monoclonal antibody to the leuocyte adhesion molecule CD18, inhibited toxin A-stimulated neutrophil migration by 85% in vitro. Pretreatment of rabbits with R15.7 also prevented neutrophil infiltration of toxin A-exposed ileal loops in vivo as determined by histologic examination and by ileal tissue myeloperoxidase levels. Furthermore, R15.7 effected a substantial inhibition of fluid secretion (by 65%), mannitol permeability (by 66%), and histologic damage in toxin A-exposed ileal loops. Anti-CD18 (R15.7) had no inhibitory effect on cholera toxin enterotoxicity. These data demonstrate that C. difficile toxin A is a proinflammatory toxin whose enterotoxic effects are substantially dependent upon neutrophil recruitment.
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This study investigated whether differences in fecal and serum antitoxin A antibody levels may account for the duration of Clostridium difficile-associated diarrhea (CDAD) and the occurrence of relapses. By an enzyme linked-immunosorbent assay, we tested 40 patients with CDAD including 25 patients without immunodeficiency and 15 patients receiving antineoplastic drugs. Two hundred eighty serum samples and 80 normal stool samples were investigated as controls. In nonimmunocompromised patients, serum immunoglobulin (IgG) and fecal IgA antitoxin A antibody titers were significantly higher in patients who suffered a single episode (n = 21) than in those with relapsing CDAD (n = 4) whose titers were at control levels. Of these 25 patients, eight suffered from diarrhea which lasted for more than 2 weeks. These patients had significantly lower serum- and feces-specific antibody levels than the others who presented symptoms of shorter duration. In cytostatic-treated patients, antitoxin A antibody levels were similar to controls, but relapses occurred in a single case. These data suggest an association between a defective humoral response to toxin A and a more severe form of C. difficile infection. They also indicate that other host-related factors control the severity of CDAD and remain to be elucidated.
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Many individuals have serum antibodies against Clostridium difficile toxins. Those with an impaired antitoxin response may be susceptible to recurrent, prolonged, or severe C difficile diarrhoea and colitis. To examine whether treatment with intravenous immunoglobulin might be effective in patients with severe pseudomembranous colitis unresponsive to standard antimicrobial therapy. Two patients with pseudomembranous colitis not responding to metronidazole and vancomycin were given normal pooled human immunoglobulin intravenously (200-300 mg/kg). Antibodies against C difficile toxins were measured in nine immunoglobulin preparations by ELISA and by cytotoxin neutralisation assay. Both patients responded quickly as shown by resolution of diarrhoea, abdominal tenderness, and distension. All immunoglobulin preparations tested contained IgG against C difficile toxins A and B by ELISA and neutralised the cytotoxic activity of C difficile toxins in vitro at IgG concentrations of 0.4-1.6 mg/ml. Passive immunotherapy with intravenous immunoglobulin may be a useful addition to antibiotic therapy for severe, refractory C difficile colitis. IgG antitoxin is present in standard immunoglobulin preparations and C difficile toxin neutralising activity is evident at IgG concentrations which are readily achieved in the serum by intravenous immunoglobulin administration.
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Clostridium difficile-associated diarrhea (CAD) is a very common nosocomial infection that contributes significantly to patient morbidity and mortality as well as to the cost of hospitalization. Previously, strains of toxin A-negative, toxin B-positive C. difficile were not thought to be associated with clinically significant disease. This study reports the characterization of a toxin A-negative, toxin B-positive strain of C. difficile that was responsible for a recently described nosocomial outbreak of CAD. Analysis of the seven patient isolates from the outbreak by pulsed-field gel electrophoresis indicated that this outbreak was due to transmission of a single strain of C. difficile. Our characterization of this strain (HSC98) has demonstrated that the toxin A gene lacks 1.8 kb from the carboxy repetitive oligopeptide (CROP) region but apparently has no other major deletions from other regions of the toxin A or toxin B gene. The remaining 1.3-kb fragment of the toxin A CROP region from strain HSC98 showed 98% sequence homology with strain 1470, previously reported by M. Weidmann in 1997 (GenBank accession number Y12616), suggesting that HSC98 is toxinotype VIII. The HSC98 strain infecting patients involved in this outbreak produced the full spectrum of clinical illness usually associated with C. difficile-associated disease. This pathogenic spectrum was manifest despite the inability of this strain to alter tight junctions as determined by using in vitro tissue culture testing, which suggested that no functional toxin A was produced by this strain.
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Many clinical laboratories use toxin A immunoassays to test for Clostridium difficile. To describe the clinical course of a patient infected with a toxin variant strain of C. difficile that was not detected by toxin A immunoassay; to genetically characterize this strain; and to estimate the number of laboratories that use only toxin A immunoassays. Case report, molecular investigation, and laboratory survey. Tertiary care hospital in Chicago, Illinois. An 86-year-old man. Restriction endonuclease analysis, polymerase chain reaction, and survey of regional clinical laboratories. An elderly hospitalized man died of advanced pseudomembranous colitis. Four stool specimens submitted over a 2-month period had tested negative on toxin A immunoassay, but a strain of C. difficile with a 1.8-kb deletion of the toxin A gene was recovered from each specimen. This strain, identified as restriction endonuclease analysis type CF4, is closely related to a widely disseminated variant, toxinotype VIII. Toxin A immunoassay was the only test being performed for detection of C. difficile at 31 of 67 (46%) regional clinical laboratories. Toxin A variant strains of C. difficile cause serious disease and are undetectable in clinical laboratories that use only toxin A immunoassays for C. difficile testing.
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To review the epidemiology and characteristics of patients who died or underwent colectomy secondary to fulminant Clostridium difficile colitis. In patients with C. difficile colitis, a progressive, systemic inflammatory state may develop that is unresponsive to medical therapy; it may progress to colectomy or death. The authors reviewed 2,334 hospitalized patients with C. difficile colitis from January 1989 to December 2000. Sixty-four patients died or underwent colectomy for pathologically proven C. difficile colitis. In 2000, the incidence of C. difficile colitis in hospitalized patients increased from a baseline of 0.68% to 1.2%, and the incidence of patients with C. difficile colitis in whom life-threatening symptoms developed increased from 1.6% to 3.2%. Forty-four patients required a colectomy and 20 others died directly from C. difficile colitis. Twenty-two percent had a prior history of C. difficile colitis. A recent surgical procedure and immunosuppression were common predisposing conditions. Lung transplant patients were 46 times more likely to have C. difficile colitis and eight times more likely to have severe disease. Abdominal computed tomography scan correctly diagnosed all patients, whereas 12.5% of toxin assays and 10% of endoscopies were falsely negative. Patients undergoing colectomy for C. difficile colitis had an overall death rate of 57%. Significant predictors of death after colectomy were preoperative vasopressor requirements and age. C. difficile colitis is a significant and increasing cause of death. Surgical treatment of C. difficile colitis has a high death rate once the fulminant expression of the disease is present.
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Recent reports suggest that Clostridium difficile colitis may be evolving into a more severe disease. During the second half of 2002 we noted an increase in the number of patients with severe C. difficile-associated diarrhea (CDAD) in our institution. We describe cases of CDAD at our institution over a 13-year period and investigate changes in illness severity. We undertook a retrospective chart review of all cases of CDAD diagnosed at the Centre hospitalier universitaire de Sherbrooke from Jan. 1, 1991, to Dec. 31, 2003. Because the hospital serves a well-defined population of Quebec, we were also able to calculate population-based incidence during this period. We abstracted data on individual patients from patient charts and from hospital and pharmacy computer databases. We defined cases of CDAD as having a positive C. difficile cytotoxicity assay result, or endoscopic or histopathological evidence of pseudomembranous colitis. A case was considered complicated if one or more of the following was observed: megacolon, perforation, colectomy, shock requiring vasopressor therapy, or death within 30 days after diagnosis. A total of 1721 cases of CDAD were diagnosed during the study period. The incidence increased from 35.6 per 100,000 population in 1991 to 156.3 per 100,000 in 2003; among patients aged 65 years or more, it increased from 102.0 to 866.5 per 100,000. The proportion of cases that were complicated increased from 7.1% (12/169) in 1991-1992 to 18.2% (71/390) in 2003 (p < 0.001), and the proportion of patients who died within 30 days after diagnosis increased from 4.7% (8/169) in 1991-1992 to 13.8% (54/390) in 2003 (p < 0.001). A high leukocyte count (20.0 small ha, Cyrillic 10(9)/L or greater) and an elevated creatinine level (200 micromol/L or greater) were strongly associated with adverse outcomes: in 2003, 45 (40.9%) of 110 patients with a high leukocyte count or creatinine level, or both, had complicated CDAD and 28 (25.5%) died within 30 days after diagnosis. After adjustment for age and other confounding factors, patients initially given oral vancomycin therapy had a risk of progression to complicated CDAD that was 79% lower than the risk among patients initially treated with metronidazole (adjusted odds ratio 0.2, 95% confidence interval 0.06-0.8, p = 0.02). An epidemic of CDAD with an increased case-fatality rate has had important consequences on the elderly population of our region. Our observational data suggest that the equivalence of vancomycin and metronidazole in the treatment of CDAD needs to be questioned.
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Antibody-based therapies are currently undergoing a renaissance. After being developed and then largely abandoned in the twentieth century, many antibody preparations are now in clinical use. However, most of the reagents that are available target non-infectious diseases. Interest in using antibodies to treat infectious diseases is now being fuelled by the wide dissemination of drug-resistant microorganisms, the emergence of new microorganisms, the relative inefficacy of antimicrobial drugs in immunocompromised hosts and the fact that antibody-based therapies are the only means to provide immediate immunity against biological weapons. Given the need for new antimicrobial therapies and many recent technological advances in the field of immunoglobulin research, there is considerable optimism regarding renewed applications of antibody-based therapy for the prevention and treatment of infectious diseases.
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Tefibazumab (Aurexis) is a humanized monoclonal antibody being evaluated as adjunctive therapy for the treatment of Staphylococcus aureus infections. This open-label, dose escalation study evaluated the safety and pharmacokinetics of tefibazumab in 19 healthy volunteers aged 18 to 69 years. Each subject received a single administration of tefibazumab at a dose of 2, 5, 10, or 20 mg/kg of body weight infused over 15 min. Plasma samples for pharmacokinetic assessments were obtained before infusion as well as 1, 6, 12, and 24 h and 3, 4, 7, 21, 28, 42, and 56 days after dosing. Plasma concentrations of tefibazumab were detected 1 h after the end of the infusion, with a mean maximum concentration of drug in serum (Cmax) of 59, 127, 252, and 492 μg/ml following doses of 2, 5, 10, and 20 mg/kg, respectively. The median time to maximum concentration of drug in serum (Tmax) was 1.0 h for each dose. The mean elimination half-life (t1/2) was approximately 22 days. The volume of distribution (V) was 4.7, 6.7, 7.2, and 7.2 liters after doses of 2, 5, 10, and 20 mg/kg, respectively. Clearance (CL) was 6.0, 9.2, 10.2, and 9.9 ml/hr, respectively. At the highest dose, plasma levels of tefibazumab were >100 μg/ml for 21 days. On day 56, the mean plasma concentrations were 6.3, 10.0, 16.4, and 30.5 μg/ml for the 2, 5, 10, and 20 mg/kg doses, respectively. Tefibazumab exhibited linear kinetics across doses of 5, 10, and 20 mg/kg. No anti-tefibazumab antibodies were detected after dosing in any subject. There were no serious adverse events, and tefibazumab was well tolerated over the entire dose range.
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In March 2003, several hospitals in Quebec, Canada, noted a marked increase in the incidence of Clostridium difficile-associated diarrhea. In 2004 we conducted a prospective study at 12 Quebec hospitals to determine the incidence of nosocomial C. difficile-associated diarrhea and its complications and a case-control study to identify risk factors for the disease. Isolates of C. difficile were typed by pulsed-field gel electrophoresis and analyzed for binary toxin genes and partial deletions in the toxin A and B repressor gene tcdC. Antimicrobial susceptibility was evaluated in a subgroup of isolates. A total of 1703 patients with 1719 episodes of nosocomial C. difficile-associated diarrhea were identified. The incidence was 22.5 per 1000 admissions. The 30-day attributable mortality rate was 6.9 percent. Case patients were more likely than matched controls to have received fluoroquinolones (odds ratio, 3.9; 95 percent confidence interval, 2.3 to 6.6) or cephalosporins (odds ratio, 3.8; 95 percent confidence interval, 2.2 to 6.6). A predominant strain, resistant to fluoroquinolones, was found in 129 of 157 isolates (82.2 percent), and the binary toxin genes and partial deletions in the tcdC gene were present in 132 isolates (84.1 percent). A strain of C. difficile that was resistant to fluoroquinolones and had binary toxin and a partial deletion of the tcdC gene was responsible for this outbreak of C. difficile-associated diarrhea. Exposure to fluoroquinolones or cephalosporins was a risk factor.
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The pathogenesis of Clostridium difficile enterocolitis appears to involve colonization of the bowel followed by release of toxin A, an enterotoxin, and toxin B, a cytotoxin. The purpose of this study was to determine the effect of purified toxins A and B on intestinal secretion, epithelial permeability, and morphology in perfused rabbit ileal loops. Intestinal permeability after toxin exposure was assessed by blood-to-lumen clearance of [3H]mannitol. Toxin A at doses of 5–100 μg/10 cm ileal loop caused a threefold to fivefold increase in [3H]mannitol permeability (p < 0.001) vs. equal concentrations of toxin B or buffer control. In addition, perfusate from toxin A-exposed loops contained significantly more neutrophils (p < 0.001) than toxin B or control loops. Toxin A caused severe epithelial cell necrosis with destruction of villi and polymorphonuclear infiltration. Electron microscopy of mucosa subjected to a low dose of toxin revealed widespread nonspecific dilatation of endoplasmic reticulum and mitochondrial swelling. In contrast to these effects of toxin A in ileal loops, in vitro experiments with ileal explants in short-term organ culture revealed that toxin A had no effect on epithelial cell permeability, protein synthesis, release of alkaline phosphatase, or morphology. Our results show that purified toxin A but not toxin B causes severe inflammatory enteritis in rabbit ileal loops, but has no discernable effect on rabbit ileum in vitro. We speculate that toxin A may contribute significantly to intestinal damage in C. difficile-associated colitis and diarrhea.
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Objective: To determine the safety and efficacy of prophylaxis with palivizumab in reducing the incidence of hospitalization because of respiratory syncytial virus (RSV) infection in high-risk infants. Methods: A randomized, double-blind, placebo-controlled trial was conducted at 139 centers in the United States, the United Kingdom, and Canada. During the 1996-1997 RSV season, 1,502 children with prematurity (35 weeks) or bronchopulmonary dysplasia (BPD) were randomly assigned to receive five injections of either palivizumab ( 15 ing/kg) or an equivalent volume of placebo by intramuscular injection every 30 days. The primary endpoint was hospitalization with confirmed RSV infection. Children were observed for 150 days (30 days from the last injection). Those with hospitalization as a result of RSV infection were evaluated for total number of days in the hospital, total days with increased supplemental oxygen, total days with moderate or severe lower respiratory tract illness, and incidence and total days of intensive care and mechanical ventilation. The incidence of hospitalization for respiratory illness not caused by RSV and the incidence of otitis media were also evaluated. The placebo and palivizumab groups were balanced at entry for demographics and RSV risk factors. Ninety-nine percent of children in both groups completed the protocol and about 93% received all five scheduled injections. Results: Palivizumab prophylaxis resulted in a 55% reduction in hospitalization as a result of RSV (10.6% placebo vs 4.8% palivizumab). Children with prematurity but without BPD had a 78% reduction in RSV hospitalization (8.1% vs 1.8%); children with BPD had a 39% reduction (12.8% vs 7.9%). When gender, entry age, entry weight, BPD, and gestational age were included in a logistic regression model, the effect of prophylaxis with palivizumab remained statistically significant. The palivizumab group had proportionally fewer total RSV hospital days, fewer RSV hospital days with increased oxygen, fewer RSV hospital days with a moderate to severe lower respiratory tract illness, and a lower incidence of intensive care unit admission. Palivizumab was safe and well tolerated. No significant differences were observed in reported adverse events between the two groups. Few children (0.3%) discontinued injections for related adverse events. Reactions at the site of injection were uncommon (1.8% placebo vs 2.7% palivizumab); the most frequent reaction was mild and transient erythema. Mild or moderate elevations of aspartatc aminotransferase occurred in 1.6% of placebo recipients and 3.6% of palivizumab recipients; for alanine aminotransferase, these percentages were 2.0% and 2.3%), respectively. Hepatic and renal adverse events related to the study drug were similar in the two groups. Conclusions: Monthly intramus-cular administration of palivizumab is safe and effective for prevention of serious RSV illness in premature children and those with BPD.
Article
Objective To determine the safety and efficacy of prophylaxis with palivizumab in reducing the incidence of hospitalization because of respiratory syncytial virus (RSV) infection in high-risk infants. Methods A randomized, double-blind, placebo-controlled trial was conducted at 139 centers in the United States, the United Kingdom, and Canada. During the 1996 to 1997 RSV season, 1502 children with prematurity (≤35 weeks) or bronchopulmonary dysplasia (BPD) were randomized to receive 5 injections of either palivizumab (15 mg/kg) or an equivalent volume of placebo by intramuscular injection every 30 days. The primary endpoint was hospitalization with confirmed RSV infection. Children were followed for 150 days (30 days from the last injection). Those with hospitalization as a result of RSV infection were evaluated for total number of days in the hospital, total days with increased supplemental oxygen, total days with moderate or severe lower respiratory tract illness, and incidence and total days of intensive care and mechanical ventilation. The incidence of hospitalization for respiratory illness not caused by RSV and the incidence of otitis media were also evaluated. The placebo and palivizumab groups were balanced at entry for demographics and RSV risk factors. Ninety-nine percent of children in both groups completed the protocol and ∼93% received all five scheduled injections. Results Palivizumab prophylaxis resulted in a 55% reduction in hospitalization as a result of RSV (10.6% placebo vs 4.8% palivizumab). Children with prematurity but without BPD had a 78% reduction in RSV hospitalization (8.1% vs 1.8%); children with BPD had a 39% reduction (12.8% vs 7.9%). When gender, entry age, entry weight, BPD, and gestational age were included in a logistic regression model, the effect of prophylaxis with palivizumab remained statistically significant. The palivizumab group had proportionally fewer total RSV hospital days, fewer RSV hospital days with increased oxygen, fewer RSV hospital days with a moderate/severe lower respiratory tract illness, and a lower incidence of intensive care unit admission. Palivizumab was safe and well tolerated. No significant differences were observed in reported adverse events between the two groups. Few children discontinued injections for related adverse events (0.3%). Reactions at the site of injection were uncommon (1.8% placebo vs 2.7% palivizumab); the most frequent reaction was mild and transient erythema. Mild or moderate elevations of aspartate aminotransferase occurred in 1.6% of placebo recipients and 3.6% of palivizumab recipients; for alanine aminotransferase these percentages were 2.0% and 2.3%, respectively. Hepatic and renal adverse events related to the study drug were similar in the two groups. Conclusions Monthly intramuscular administration of palivizumab is safe and effective for prevention of serious RSV illness in premature children and those with BPD.
Article
The mechanism by which Clostridium difficile toxin B causes cells in culture to round was investigated. Cultured human lung fibroblasts and rabbit aortic smooth muscle cells were treated with partially purified or purified toxin B and monitored by light and transmission electron microscopy (TEM). Both preparations caused progressive cell rounding which correlated with disorganization of actin-containing myofilament bundles. Thin myofilaments became fragmented and finally disappeared (after 24 h) and dense bodies became more prominent, while all other organelles appeared unaffected.
Article
Clostridium difficile toxin A, a 308-kilodalton protein exotoxin, is the principal causative agent of antibiotic-associated, C. difficile-induced colitis. In the current study, the prevalence of specific human serum and secretory antibody to toxin A and the possible protective effect of secretory, intestinal anti-toxin A antibody are examined. Serum (n = 35), colonic aspirates (n = 35), and duodenal aspirates (n = 20) were collected from adults at diagnostic endoscopy. Patients with evidence of colitis or a history of recent antibiotic use were excluded from the study. Specific serum immunoglobulin (Ig) A and IgG antitoxin A antibodies were detected in 60% and 57% of subjects, respectively, by enzyme-linked immunosorbent assay. Fifty-seven percent of colonic aspirates contained IgA antitoxin, whereas only 10% of duodenal aspirates were positive (P = 0.002). Binding of toxin A to its intestinal receptor was studied using [3H]toxin A and purified rabbit ileal brush border membranes. Toxin A binding was significantly inhibited by colonic aspirates with high IgA anti-toxin A antibody levels (0.503 +/- 0.055 pmol toxin A bound per milligram of brush border membrane protein, mean +/- SE) in comparison with antitoxin A-negative aspirates (0.778 +/- 0.089 pmol; P = 0.02) and control (0.766 +/- 0.004 pmol; P = 0.03). In the current study, a specific intestinal secretory IgA antibody response to C. difficile toxin A in humans is reported. This antibody response is more evident in the colon, the site of C. difficile infection, than in the upper intestinal tract. Our data suggest that human colonic IgA antitoxin may protect against C. difficile colitis by inhibiting the binding of toxin A to its intestinal epithelial cell receptor.
Article
This study was undertaken to examine toxin production by Clostridium difficile 8864, a naturally occurring isolate that has been reported to produce toxin B in the absence of toxin A. To date, this is the only strain of C. difficile reported to produce only one of the toxins. The results of our initial studies with antibodies against toxins A and B confirmed these observations. Toxin B from strain 8864 and from VPI strain 10463, a strain that produces high levels of both toxin A and toxin B, was purified to homogeneity by sequential anion-exchange chromatography on DEAE-Sepharose CL-6B, gel filtration on Ultrogel AcA22, and immunoadsorption chromatography, and their toxic activities were compared. Our results showed that toxin B from strain 8864 and toxin B from C. difficile VPI strain 10463 were comparable in their cytotoxic activities and that the 8864 toxin B was more lethal. In addition, we observed that toxin B from strain 8864 was weakly enterotoxic, which may explain the ability of this strain to cause intestinal disease in hamsters treated with antibiotics. Analysis with specific antibodies showed that the toxin B molecules from these strains were highly related but contained distinct epitopes. The results of hybridization studies with probes specific for the toxin B gene of VPI strain 10463 demonstrated differences between the toxin B genes of the two strains. In addition, probes specific for the toxin A gene of VPI strain 10463 showed that strain 8864 contains a region which shows identity with the 5' end of the toxin A gene but not the region of the gene which encodes a hydrophobic region and the repeating units.
Article
A cytotoxigenic Clostridium difficile strain that fails to produce toxin A but causes hemorrhage and bloody fluid accumulation in ligated ileal loops of rabbits and hemorrhage and diarrhea in hamsters is described. The lack of reaction of DNA from this strain in hybridization studies with a toxin A gene-specific 4.5-kb probe and polymerase chain reaction studies with six toxin A-specific primers indicate the absence of the toxin A gene. The cytotoxin produced by this strain was not responsible for the enterotoxic or hemorrhagic activity and shared characteristics with toxin B, i.e., its cytotoxicity was neutralized by antibodies to toxigenic strains of C. difficile and Clostridium sordellii. Polymerase chain reaction studies with toxin B-specific primers showed that the DNA from this strain produced a 690-bp product in addition to the expected 591-bp product.
Article
The contribution of toxin B to Clostridium difficile-associated infection is undefined. Toxin B induces dramatic phenotypic alterations (cytotoxic effects) in cultured mesenchymal and nonintestinal epithelial cells, yet its effects on intestinal epithelial cells are not clearly understood. The alterations induced by toxin B in nonintestinal cells appear to be secondary to toxin-induced redistribution of filamentous actin. It has not been determined whether toxin B exerts similar effects on cultured intestinal epithelial cells or whether such phenotypic alterations are of any physiological consequence. To address these questions, we examined the effect of C. difficile toxin B on the phenotype and barrier function of T84 cell monolayers. Our studies show that the cytotoxic effects of toxin B, i.e., cell rounding, do extend to cultured intestinal epithelial cells (T84). In addition, toxin B dramatically reduces the barrier function of T84 monolayers grown on collagen-coated filters. Toxin B-induced redistribution of filamentous actin appears to be responsible for the alterations in both intestinal epithelial cell phenotype and barrier function. Specifically, filamentous actin comprising the perijunctional actomyosin ring, known to be important in regulating tight junction permeability, is condensed into discrete plaques. Flux studies confirm that the permeability defect is at the level of the tight junction. We conclude that toxin-induced changes in actin distribution perturb intercellular junctional contacts and thereby ablate epithelial barrier function. There was no evidence of cell death as determined by lactate dehydrogenase release assays.
Article
The pathogenicity of Clostridium difficile is due to the production of two toxins (toxins A and B). We prepared monoclonal antibodies against toxin A and determined whether axenic mice passively immunized with the monoclonal antibodies were protected against C. difficile disease. The mice were kept in an isolator and were given ascites fluid intravenously prior to challenge with a toxinogenic strain of C. difficile. Control mice and mice receiving ascites fluid devoid of toxin antibody died within 2 days and had high levels of toxins A and B in their feces. Mice that received ascites fluid containing high amounts of toxin A monoclonal antibodies directed against the repeating units of the toxin survived. In protected mice, toxin B levels were similar to those in dying mice, but toxin A levels were greatly reduced. These data show that passive immunity induced by monoclonal antibodies against toxin A was effective against pseudomembranous cecitis.
Article
We tested the hypothesis that children with chronic relapsing colitis induced by Clostridium difficile toxin have defective antibody responses to C. difficile toxins as a cause of their underlying illness. Six such children were tested for serum IgG and IgA antibody to C. difficile toxin A. These six children had lower IgG anti-toxin A levels than 24 healthy children (p = 0.026) and 18 healthy adults (p = 0.0008). Five patients treated with 400 mg intravenously administered gamma-globulin per kilogram every 3 weeks had significant increases in IgG (p = 0.01) but not IgA anti-toxin A (p = 0.406) levels, and all five had clinical resolution of their gastrointestinal symptoms as well as clearing of C. difficile cytotoxin B from their stools. These observations suggest that a deficiency of IgG anti-toxin A may predispose children to the development of chronic relapsing C. difficile-induced colitis. In such cases, intravenous gamma-globulin therapy may be effective in producing clinical remission.
Article
The pathogenesis of Clostridium difficile enterocolitis appears to involve colonization of the bowel followed by release of toxin A, an enterotoxin, and toxin B, a cytotoxin. The purpose of this study was to determine the effect of purified toxins A and B on intestinal secretion, epithelial permeability, and morphology in perfused rabbit ileal loops. Intestinal permeability after toxin exposure was assessed by blood-to-lumen clearance of [3H]mannitol. Toxin A at doses of 5-100 micrograms/10 cm ileal loop caused a threefold to fivefold increase in [3H]mannitol permeability (p less than 0.001) vs. equal concentrations of toxin B or buffer control. In addition, perfusate from toxin A-exposed loops contained significantly more neutrophils (p less than 0.001) than toxin B or control loops. Toxin A caused severe epithelial cell necrosis with destruction of villi and polymorphonuclear infiltration. Electron microscopy of mucosa subjected to a low dose of toxin revealed widespread nonspecific dilatation of endoplasmic reticulum and mitochondrial swelling. In contrast to these effects of toxin A in ileal loops, in vitro experiments with ileal explants in short-term organ culture revealed that toxin A had no effect on epithelial cell permeability, protein synthesis, release of alkaline phosphatase, or morphology. Our results show that purified toxin A but not toxin B causes severe inflammatory enteritis in rabbit ileal loops, but has no discernable effect on rabbit ileum in vitro. We speculate that toxin A may contribute significantly to intestinal damage in C. difficile-associated colitis and diarrhea.
Article
In this investigation, the role of antibodies against Clostridium difficile toxins A and B in protecting hamsters against C. difficile-associated ileocecitis was examined. We also studied the transfer of protection against C. difficile-associated intestinal disease from immunized female hamsters to their infants. Adult female hamsters immunized parenterally with toxoid A or a mixture containing both toxoids A and B were protected against clindamycin-induced C. difficile-associated fatal ileocecitis. On the other hand, hamsters immunized with toxoid B or a broth filtrate from a nontoxigenic strain of C. difficile were not protected against C. difficile-induced ileocecitis. Antibody against the immunizing toxoid could be demonstrated in both the serum and the cecal contents of hamsters. Some infant hamsters from mothers immunized with toxoid A or AB were protected against C. difficile-associated ileocecitis, while infant hamsters from mothers immunized with toxoid B or a nontoxigenic broth filtrate were not protected against disease. Neutralizing antibodies to toxins A and B could be demonstrated in both maternal milk and serum, as well as in infant serum and intestinal contents. Foster-mothering experiments demonstrated that maternal protection of infants against C. difficile-associated ileocecitis was transferred to infant hamsters through breast milk. These results suggest that toxin A may play a more important role in the pathogenesis of C. difficile-associated ileocecitis in hamsters than toxin B. Furthermore, variations in the severity of C. difficile-associated illness in infants and adults may reflect the lack or presence of passively or actively acquired immunity against C. difficile toxins.
Article
101 patients with Clostridium-difficile-associated diarrhoea or colitis were prospectively randomised to 10-day oral courses of metronidazole, 250 mg four times a day, or vancomycin, 500 mg four times a day. 7 did not complete the protocol and were dropped from analysis. Pseudomembranous colitis (PMC) was diagnosed after endoscopy in 33 patients. Of the remaining patients without PMC, 38 had both C difficile culture and cytotoxin and 23 had only culture evidence of C difficile. 52 evaluable patients received vancomycin and 42 received metronidazole. There were two treatment failures with metronidazole and none with vancomycin (p = 0.20); and two relapses with metronidazole versus six with vancomycin (p = 0.17). Treatment in 1 patient in each group was discontinued because of drug intolerance. Response and relapse rates of the 33 patients with PMC were no different from those of the remaining patients. Pharmacy cost for the dosage used was $387.48 to $520.00 for vancomycin and $11.84 for metronidazole. Metronidazole and vancomycin have equivalent efficacy and relapse rates and are tolerated to a similar extent by patients with C-difficile-related diarrhoea and colitis, but metronidazole is considerably more economical.
Article
Clostridium difficile, the agent that causes pseudomembranous colitis associated with antibiotic therapy, has been identified in recent years as a common nosocomial pathogen. First described in 1935 by Hall and O'Toole, this gram-positive anaerobic bacillus was named “the difficult clostridium” because it resisted early attempts at isolation and grew very slowly in culture1. Although the organism released potent toxins in broth culture, the fact that it was found in stool specimens from healthy neonates led to its classification as a commensal. C. difficile subsequently passed into obscurity. In the 1960s and 1970s antibiotic-associated pseudomembranous colitis became a major clinical . . .
Article
Clostridium difficile is now regarded as the most prevalent nosocomial pathogen, infecting as many as a quarter of hospitalized patients. The pathophysiology of infection with this unusual enteric pathogen involves alteration of the normal enteric flora by antibiotics, ingestion of spores, and colonization by C. difficile. The organism then releases potent exotoxins that produce an inflammatory colitis and diarrhea. A spectrum of host responses occurs, ranging from the asymptomatic carrier state to life-threatening pseudomembranous colitis. Effective therapy with vancomycin or metronidazole is available, but relapses occur in 15% to 20% of patients and may necessitate multiple courses of therapy.
Article
We conducted a prospective, randomized study to compare the efficacy of oral fusidic acid, oral metronidazole, oral vancomycin, and oral teicoplanin for the treatment of Clostridium difficile—associated diarrhea. Treatment resulted in clinical cure for 94% of the patients who were treated with vancomycin, 96% of those treated with teicoplanin, 93% of those treated with fusidic acid, and 94% of those treated with metronidazole. Clinical symptoms recurred in 16% of patients treated with vancomycin, 7% of those treated with teicoplanin, 28% of those treated with fusidic acid, and 16% of those treated with metronidazole. There was asymptomatic carriage of C. difficile toxin in 13% of patients treated with vancomycin,4% of those treated with teicoplanin, 24% of those treated with fusidicacid, and 16% of those treated with metronidazole. No adverse effectsrelated to therapy with vancomycin or teicoplanin were observed. Considering the costs of treatment, our findings suggest that metronidazole is the drug of choice for C. difficile—associated diarrhea and that glycopeptides should be reserved for patients who cannot tolerate metronidazole or who do not respond to treatment with this drug.
Article
Clostridium difficile produces two toxins (A and B) which cause antibiotic-associated diarrhoea and pseudomembranous colitis. One of the most puzzling aspects of C. difficile infection is the wide spectrum of clinical presentation which ranges from asymptomatic carriage to fulminant, life-threatening colitis. This review examines the hypothesis that immune responses to C. difficile underlie these dramatic variations in disease presentation and course. Animals can be protected from C. difficile colitis by passive or active immunization against toxins A and B. Human antibody responses to these toxins are evident in approximately 60% of the general population. A number of clinical studies indicate that antitoxin responses in both serum and intestinal secretions may be protective whereas an inadequate immune response predisposes to severe or recurrent C. difficile diarrhoea. Thus there is now considerable interest in developing methods for passive and active immunization to combat this prevalent nosocomial intestinal pathogen.
Article
Guidelines for clinical practice are intended to suggest preferable approaches to particular medical problems as established by interpretation and collation of scientifically valid research, derived from extensive review of published literature. When data are not available that will withstand objective scrutiny, a recommendation may be made based on a consensus of experts. Guidelines are intended to apply to the clinical situation for all physicians without regard to specialty. Guidelines are intended to be flexible, not necessarily indicating the only acceptable approach, and should be distinguished from standards of care that are inflexible and rarely violated. Given the wide range of choices in any health care problem, the physician should select the course best suited to the individual patient and the clinical situation presented. These guidelines are developed under the auspices of the American College of Gastroenterology and its Practice Parameters Committee. These guidelines are also approved by the governing boards of American College of Gastroenterology and Practice Parameters Committee. Expert opinion is solicited from the outset for the document. Guidelines are reviewed in depth by the committee, with participation from experienced clinicians and others in related fields. The final recommendations are based on the data available at the time of the production of the document and may be updated with pertinent scientific developments at a later time. The following guidelines are intended for adults and not for pediatric patients.