[Show abstract][Hide abstract] ABSTRACT: Background. The 4 serotypes of dengue virus, DENV-1-4, are the leading cause of arboviral disease globally. The ideal dengue vaccine would provide protection against all serotypes after a single dose. Methods. Two randomized, placebo-controlled trials were performed with 168 flavivirus-naive adults to demonstrate the safety and immunogenicity of a live attenuated tetravalent dengue vaccine (TV003), compared with those of a second tetravalent vaccine with an enhanced DENV-2 component (TV005), and to evaluate the benefit of a booster dose at 6 months. Safety data, viremia, and neutralizing antibody titers were evaluated. Results. A single dose of TV005 elicited a tetravalent response in 90% of vaccinees by 3 months after vaccination and a trivalent response in 98%. Compared with TV003, the higher-dose DENV-2 component increased the observed frequency of immunogenicity to DENV-2 in the TV005 trial. Both the first and second doses were well tolerated. Neither vaccine viremia, rash, nor a significant antibody boost were observed following a second dose. Conclusions. A single subcutaneous dose of TV005 dengue vaccine is safe and induces a tetravalent antibody response at an unprecedented frequency among vaccinees. A second dose has limited benefit and appears to be unnecessary. Studies to confirm these findings and assess vaccine efficacy will now move to populations in regions where DENV transmission is endemic. Clinical Trials Registration. NCT01072786 and NCT01436422.
Full-text · Article · Mar 2015 · The Journal of Infectious Diseases
[Show abstract][Hide abstract] ABSTRACT: Background. Campylobacter jejuni is a common cause of diarrhea and is associated with serious postinfectious sequelae. Although symptomatic and asymptomatic
infections are recognized, protective immunity is not well understood. Previous data suggests that interferon γ (IFN-γ) may
be associated with protection. To better define the clinical and immunologic development of protective immunity to C. jejuni, we assessed the ability of an initial infection to prevent clinical illness after a second experimental infection.
Methods. Subjects with no clinical or immunologic evidence of prior infection with C. jejuni received an initial challenge with C. jejuni CG8421 with rechallenge 3 months later. The primary endpoint was campylobacteriosis, as defined by diarrhea and/or systemic
signs. Close inpatient monitoring was performed. Serum immunoglobulin A (IgA) and immunoglobulin G (IgG), fecal IgA, IgA antibody-secreting
cells (ASCs), and IFN-γ production were evaluated. All subjects were treated with antibiotics and were clinically well at
Results. Fifteen subjects underwent a primary infection with C. jejuni CG8421; 14 (93.3%) experienced campylobacteriosis. Eight subjects received the second challenge, and all experienced campylobacteriosis
with similar severity. Immune responses after primary infection included serum IgA, IgG, ASC, and IFN-γ production. Responses
were less robust after secondary infection.
Conclusions. In naive healthy adults, a single infection with CG8421 did not protect against campylobacteriosis. Although protection has
been demonstrated with other strains and after continuous environmental exposure, our work highlights the importance of prior
immunity, repeated exposures, and strain differences in protective immunity to C. jejuni.
Clinical Trials Registration. NCT01048112
[Show abstract][Hide abstract] ABSTRACT: Background:
Dengue virus (DENV) causes hundreds of millions of infections annually. Four dengue serotypes exist, and previous infection with one serotype increases the likelihood of severe disease with a second, heterotypic DENV infection.
In a randomized, placebo-controlled study, the safety and immunogenicity of 4 different admixtures of a live attenuated tetravalent (LATV) dengue vaccine were evaluated in 113 flavivirus-naive adults. Serum neutralizing antibody levels to all 4 dengue viruses were measured on days 0, 28, 42, and 180.
A single dose of each LATV admixture induced a trivalent or better neutralizing antibody response in 75%-90% of vaccinees. There was no significant difference in the incidence of adverse events between vaccinees and placebo-recipients other than rash. A trivalent or better response correlated with rash and with non-black race (P < .0001). Black race was significantly associated with a reduced incidence of vaccine viremia.
TV003 induced a trivalent or greater antibody response in 90% of flavivirus-naive vaccinees and is a promising candidate for the prevention of dengue. Race was identified as a factor influencing the infectivity of the LATV viruses, reflecting observations of the effect of race on disease severity in natural dengue infection.
Preview · Article · Jan 2013 · The Journal of Infectious Diseases
[Show abstract][Hide abstract] ABSTRACT: M01ZH09, S. Typhi (Ty2 Delta aroC Delta ssaV) ZH9, is a single oral dose typhoid vaccine with independently attenuating deletions. A phase II randomized, double-blind, placebo-controlled, dose-escalating trial evaluated the safety and immunogenicity of M01ZH09 to 1.7 x 10(10) colony-forming units (CFU). 187 Healthy adults received vaccine or placebo in four cohorts. Serologic responses and IgA ELISPOT were measured. At all doses, the vaccine was well tolerated and without bacteremias. One subject had a transient low-grade fever. 62.2-86.1% of subjects seroconverted S. Typhi-specific LPS IgG and 83.3-97.4% IgA; 92.1% had a positive S. Typhi LPS ELISPOT. M01ZH09 is safe and immunogenic up to 1.7 x 10(10)CFU. Efficacy testing of this single-dose oral typhoid vaccine is needed.
[Show abstract][Hide abstract] ABSTRACT: A robust human challenge model for Campylobacter jejuni is an important tool for the evaluation of candidate vaccines. The previously established model conveys a potential risk of Guillain-Barré syndrome attributable to lipooligosaccharide ganglioside mimicry. This work establishes a new C. jejuni human challenge model that uses a strain (CG8421) without ganglioside mimicry and that applies Campylobacter-specific cellular immunity screening to achieve high attack rates at lower inoculum doses.
Healthy Campylobacter-naive adults participated in an open-label challenge trial. Participants were dosed with C. jejuni CG8421 and followed as inpatients. Pattern of illness, bacterial shedding, and immunologic responses were determined.
Following screening, 23 subjects received 1 X 10(6) or 1 X 10(5) colony-forming units of C. jejuni, with attack rates (percentage of patients who became ill) of 100% (1 X 10(6) colony-forming units) or 93% (1 X 10(5) colony-forming units). Every subject shed CG8421; the median time to diarrhea onset was 72.3 h (interquartile range, 53.9-99.9 h). Symptoms included abdominal cramps (74%), nausea (65%), and fever (39%). No major safety concerns occurred, including bacteremia, hypotension, or postinfectious sequelae. Unexpectedly, recrudescent infection occurred in 2 subjects (1 subject without Campylobacter-specific adaptive immune responses and 1 with azithromycin resistance acquired in vivo); both infections cleared after receipt of additional antibiotics. Cumulative Campylobacter-specific immune responses were as follows: serologic response occurred in 87% (immunoglobulin [Ig] A) and 48% (IgG) of subjects, in vitro interferon-gamma production occurred in 91% of subjects, and 96% of subjects had IgA antibody-secreting cells and fecal IgA detected.
The C. jejuni CG8421 challenge model provides a safe and effective tool, without the risk of Guillain-Barré syndrome. The model demonstrates high attack rates after lower doses of challenge inoculum, provides further understanding of immunologic responses, and permits future investigation of candidate Campylobacter vaccines.
Preview · Article · Nov 2009 · Clinical Infectious Diseases
[Show abstract][Hide abstract] ABSTRACT: Mannose-binding lectin (MBL) is an evolutionarily conserved protein that functions in human innate immunity by binding to
microbial surfaces and promoting opsonophagocytosis. MBL has been shown to bind to Cryptosporidium sporozoites, and earlier work has suggested that the protective role of MBL may be most important in childhood. We evaluated
the association between polymorphisms in the MBL gene (MBL2), serum MBL deficiency, and infection with Cryptosporidium, Entamoeba histolytica, and Giardia intestinalis in children. A large, prospective cohort of Bangladeshi preschool children was followed up for >3 years. Clinical outcomes,
serum MBL levels, and MBL2 polymorphisms and haplotypes were determined. Statistically significant associations with E. histolytica and G. intestinalis were not found. Serum MBL deficiency, polymorphisms in the −221 promoter region, and the YO/XA MBL2 haplotype were strongly associated with Cryptosporidium infections, particularly recurrent infection. Children with multiple infections with Cryptosporidium were more likely to be MBL deficient (odds ratio [OR], 10.45), carry the −221 promoter variant (OR, 4.02), and have the YO/XA
haplotype (OR, 4.91). We have identified a potentially important component of the human innate immune response to Cryptosporidum infection. Further work is needed to evaluate the mechanism of protection of MBL in Cryptosporidium infection
Full-text · Article · Nov 2009 · The Journal of Infectious Diseases
[Show abstract][Hide abstract] ABSTRACT: The recrudescence of infection with Campylobacter jejuni after appropriate antibiotic treatment has not been previously reported in an immunocompetent adult. We present the complete
clinical, microbiologic, and immunologic evaluation of a closely monitored healthy male with recrudescent C. jejuni infection occurring in the absence of immunodeficiency following experimental infection with a well-characterized strain.
After antibiotic treatment, the initial infection was clinically cleared and microbiologically undetectable. Subsequently,
two episodes of recrudescence occurred, with no change in in vitro antibiotic sensitivity being detected. The immune responses of the individual were compared to those of other participants
in the experimental infection study: innate immune responses, including fecal cytokines and C-reactive protein, were intact;
however, measures of Campylobacter-specific adaptive immune responses were absent, including serum antibodies, antibody-secreting cells, and in vitro gamma interferon responses. No primary or secondary immunodeficiency was identified. Recrudescent Campylobacter infections after treatment may be more common than has previously been appreciated. This work adds to our understanding of
the human immune response to natural Campylobacter infection and reiterates the importance of pathogen-specific adaptive immune responses to this globally important pathogen.
Full-text · Article · Nov 2009 · Clinical and vaccine Immunology: CVI
[Show abstract][Hide abstract] ABSTRACT: Cryptosporidiosis in young children prompts local inflammation in the intestinal tract. We studied a cohort of young children
with cryptosporidiosis to determine whether systemic inflammatory responses occur and, if so, to evaluate whether inflammation
persists after infection. Cryptosporidiosis was associated with increased levels of interleukin-8 and tumor necrosis factor-α
systemically, which persisted at 6 months after enrollment. The level of intestinal tumor necrosis factor-α was elevated at
enrollment, but elevated levels did not persist. Worsening of malnutrition, particularly stunting, was observed after infection.
The association of cryptosporidiosis, inflammation, and stunting in children with cryptosporidiosis warrants further evaluation.
Preview · Article · Oct 2006 · Clinical Infectious Diseases
[Show abstract][Hide abstract] ABSTRACT: Mannose-binding lectin (MBL) is a component of the innate immune response and binds microbial surfaces through carbohydrate recognition domains. MBL deficiency may contribute to susceptibility to a variety of infectious diseases, particularly in young children. MBL binds to the Cryptosporidium sporozoite and may be important in resistance to cryptosporidiosis.
We studied the association of serum MBL levels and cryptosporidiosis in a case-control study of young Haitian children with cryptosporidiosis versus children who were control subjects.
Ninety-nine children were enrolled, as follows: 49 children with cryptosporidiosis, 41 healthy controls, and 9 children with diarrhea from other causes. Case children were more malnourished than controls, and 49% had persistent or chronic diarrhea. At enrollment, mean serum MBL levels were markedly lower in children with cryptosporidiosis (P = .002), as was the number of children with an MBL deficiency of < or = 70 ng/mL (P = .005). In multivariate analysis, the association of cryptosporidiosis and MBL deficiency persisted (P = .002; adjusted odds ratio, 22.4), as did the association of cryptosporidiosis with general malnutrition. The subset of children with cryptosporidiosis and MBL deficiency were more likely to be male (P = .025).
MBL may be an important component of innate immune protection against Cryptosporidium infection in young children. Additional studies are necessary to determine whether MBL intestinal losses, deficient epithelial expression, and/or genetic polymorphisms in the MBL gene contribute to MBL deficiency in cryptosporidiosis and other enteric infections in young children.
[Show abstract][Hide abstract] ABSTRACT: Salmonella enterica serovar Typhi strains with mutations in the Salmonella pathogenicity island-2 (SPI-2) may represent an effective strategy for human vaccine development, and a vectoring system for heterologous antigens. S. Typhi (Ty2 aroC-ssaV-) M01ZH09 is an attenuated, live, oral typhoid vaccine harboring defined deletion mutations in ssaV, which encodes an integral component in the SPI-2 type III secretion system (TTSS), as well as a mutation in an aromatic biosynthetic pathway needed for bacterial growth in vivo (aroC). SPI-2 mutant vaccines have yet to be evaluated in a large, randomized human trial. A simplified or single-oral dose oral typhoid vaccine using the SPI-2 strategy would offer significant advantages over the currently licensed typhoid vaccines. We performed a double-blinded, placebo-controlled, dose-escalating clinical trial in 60 healthy adult volunteers to determine the tolerability and immunogenicity of a single dose of M01ZH09. Three groups of 20 healthy adult volunteers were enrolled; 16 in each group received a single oral dose of the freeze-dried vaccine at 5 x 10(7), 5 x 10(8) or 5 x 10(9)CFU in a bicarbonate buffer. Four volunteers in each cohort received placebo in the same buffer. Adverse events were infrequent and not statistically different between vaccine and placebo recipients, although two subjects in the mid-range dose and three subjects in the highest dose had temperature measurements >37.5 degrees C. No blood or urine cultures were positive for M01ZH09, and fecal shedding was brief. The immune response was dose-related; the highest vaccine dose (5 x 10(9)CFU) was the most immunogenic. All tested subjects receiving the highest dose had a significant ASC response (mean 118 spots/10(6) cells). A >or=4-fold increase in antibody titer for S. Typhi LPS or flagellin was detected in 75% of volunteers in the highest-dose cohort by day 28. The SPI-2 mutant vaccine, M01ZH09, is a promising typhoid vaccine candidate and deserves further study as a vectoring system for heterologous vaccine antigens.
[Show abstract][Hide abstract] ABSTRACT: Antibody-secreting cell (ASC) and antibodies in lymphocyte supernatant (ALS) assays are used to assess intestinal mucosal responses to enteric infections and vaccines. The ALS assay, performed on cell supernatants, may represent a convenient alternative to the more established ASC assay. The two methods, measuring immunoglobulin A to Salmonella enterica serovar Typhi lipopolysaccharide, were compared in volunteers vaccinated with a live-attenuated typhoid vaccine M01ZH09. The specificity of the ALS assay compared to the ASC assay was excellent (100%), as was sensitivity (82%). The ALS assay was less sensitive than the ASC assay at <or=42 spots/10(6) peripheral blood lymphocytes.
Preview · Article · Oct 2005 · Clinical and Diagnostic Laboratory Immunology
[Show abstract][Hide abstract] ABSTRACT: M01ZH09 (Salmonella enterica serovar Typhi [Ty2 aroC(-) ssaV(-)] ZH9) is a live oral-dose typhoid vaccine candidate. M01ZH09 was rationally modified with 2 independently attenuating mutations, including a novel mutation in Salmonella pathogenicity island (SPI)-2. We demonstrate that M01ZH09, in a single oral dose, is well tolerated and prompts broad immune responses, regardless of whether prevaccination with a bicarbonate buffer is given.
Thirty-two healthy adult subjects were randomized and given 5x109 cfu of M01ZH09, with (presentation 1) or without (presentation 2) prevaccination with a bicarbonate buffer. Immunogenicity data included Salmonella Typhi lipopolysaccharide (LPS)-specific immunoglobulin (Ig) A antibody-secreting cells (enzyme-linked immunospot [ELISPOT] assay), IgG serologic responses to Salmonella Typhi LPS, lymphocyte proliferation, and interferon (IFN)- gamma production.
The vaccine was well tolerated; adverse events after vaccination were mild. No fever or prolonged vaccine shedding occurred. Immunogenicity data demonstrated that 88% and 93% of subjects who received presentation 1 and presentation 2, respectively, had a positive response by ELISPOT assay; 81% of subjects in both groups underwent IgG seroconversion on day 14. Both groups had similar cellular immune responses to presentation 1 and presentation 2; lymphocyte proliferation to Salmonella Typhi flagellin occurred in 63% and 67% of subjects, respectively, and 69% and 73% of subjects, respectively, had an increase in IFN- gamma production.
The oral typhoid vaccine M01ZH09 is well tolerated and highly immunogenic in a single oral dose, with and without prevaccination with a bicarbonate buffer. Field studies to demonstrate protective efficacy are planned.
Preview · Article · Sep 2005 · The Journal of Infectious Diseases
[Show abstract][Hide abstract] ABSTRACT: Typhoid fever remains an important global health problem and causes significant morbidity and mortality in less developed countries. A safe, single dose oral vaccine against Typhoid fever would offer a simplified vaccination strategy against this disease. A live attenuated Salmonella strain may also be useful in delivering recombinant antigens to the gut-associated lymphoid tissue. The MICRO-TY vaccine (Ty2,aroC-ssaV- ZH9) is a novel genetically attenuated S. typhi vaccine designed with mutations to limit both growth (aroC-) and systemic spread (ssaV-). We performed a placebo controlled, double blinded, dose-escalating randomized trial of 60 subjects to access the safety and immunogenicity of this single oral dose vaccine. This was the first extensive human testing of a strain carrying the ssaV- mutation. Three groups of 20 healthy adult volunteers were enrolled; 16 in each group received a single oral dose of the freeze-dried vaccine at 5 x 10 7, 5 x 10,8 or 5 x 109 CFU in a bicarbonate buffer, the remainder received placebo in a bicarbonate buffer. Clinical evaluation continued for 6 months. Adverse events (AEs) were infrequent and were not statistically different between vaccine and placebo recipients or between dosage groups. AE's included abdominal discomfort, myalgias and headache. No blood or urine cultures were positive for S. typhi and fecal shedding of the vaccine was extremely brief (range of 1-6 days). The highest vaccine dose (5 x109) was the most immunogenic. All subjects receiving this dose had an increase in S. typhi lipopolysaccharide (LPS) IgA antibody secreting cells (ASC) detected by ELISPOT assay (range 8->400). In the lower doses (5 x 107 and 5 x 108), 50% of volunteers had ASC increases. Seroconversions (≥4 fold dilution increase in end-point titer) by ELISA for IgG to S.typhi LPS were also most common in the highest-dose group. The single-dose, oral MICRO-TY vaccine is well-tolerated and highly immunogenic. It warrants further evaluation as a candidate typhoid vaccine and as a potential carrier for other recombinant vaccine antigens.