[Show abstract][Hide abstract] ABSTRACT: Two potassium (K(+))-uptake systems, Trk and Kdp, are operative in Mycobacterium tuberculosis (Mtb), but the environmental factors triggering their expression have not been determined. The current study has evaluated the expression of these genes in the Mtb wild-type and a trk-gene knockout strain at various stages of logarithmic growth in relation to extracellular K(+) concentrations and pH. In both strains, mRNA levels of the K(+)-uptake encoding genes were relatively low compared to those of the housekeeping gene, sigA, at the early- and mid-log phases, increasing during late-log. Increased gene expression coincided with decreased K(+) uptake in the context of a drop in extracellular pH and sustained high extracellular K(+) concentrations. In an additional series of experiments, the pH of the growth medium was manipulated by the addition of 1N HCl/NaOH. Decreasing the pH resulted in reductions in both membrane potential and K(+) uptake in the setting of significant induction of genes encoding both K(+) transporters. These observations are consistent with induction of the genes encoding the active K(+) transporters of Mtb as a strategy to compensate for loss of membrane potential-driven uptake of K(+) at low extracellular pH. Induction of these genes may promote survival in the acidic environments of the intracellular vacuole and granuloma.
[Show abstract][Hide abstract] ABSTRACT: To measure circulating anti-citrullinated peptide antibodies (ACPA) and cytokines pre- and 6 months post-therapy as a strategy to predict and optimize responses to traditional disease-modifying antirheumatic drugs (DMARDs) in early RA, which is an unmet need in developing countries.
A cohort of 140 predominantly (88.5 %) black female South African patients with early RA was treated with synthetic DMARDs, mostly methotrexate (MTX) alone, or in combination with low-dose oral corticosteroids (CS). Circulating ACPA and a panel of circulating cytokines/chemokines/growth factors were measured at baseline and after 6 months of therapy in relation to disease activity and Shared Epitope (SE).
Following 6 months of therapy, the median simplified disease activity index (SDAI) declined from a baseline of 41.4 to 16.0 (p = 0.0001) for the entire cohort, which was paralleled by significant falls in median serum ACPA levels (516.6 vs. 255.7 units/ml, p = <0.0001) and several of the circulating cytokines (IL-4, IL-7, IL-8, G-CSF, VEGF; p < 0.0010 - p < 0.0001) which were most evident in the subgroup of patients treated with a combination of MTX and CS. Although biomarker concentrations decreased most notably in the low-disease activity group post-therapy, no significant correlations between these biomarkers and disease activity were observed, Baseline ACPA levels, but not SDAI or cytokines, were significantly higher in the subgroup of risk allele-positive patients (561.1 vs. 331.9 units/ml, p < 0.05), while no associations with ACPA and a smoking history were evident.
The use of DMARDs in RA is associated with significant decreases in ACPA and cytokines which did not correlate with changes in SDAI, precluding the utility of serial measurement of these biomarkers to monitor early responses to therapy, but may have prognostic value.
[Show abstract][Hide abstract] ABSTRACT: Despite advances in antimicrobial chemotherapy and access to sophisticated intensive care facilities, bacterial community-acquired pneumonia (CAP) continues to carry an unacceptably high mortality rate of 10-15% in hospitalized cases. CAP, considered by many to be the most under-estimated disease worldwide, poses a particular threat to the elderly whose numbers are steadily increasing in developed countries. Indeed elderly patients with severe CAP, as well as those with other risk factors, are at significant risk for development of inflammation-mediated acute cardiac events which may undermine the success of antimicrobial therapy. Adjunctive anti-inflammatory strategies are therefore of considerable potential benefit in this setting. Currently, the most promising of these are the macrolides, corticosteroids, and, more recently, statins, all of which target immune/inflammatory cells. In addition, recent insights into the immunopathogenesis of acute coronary events in patients with CAP have revealed a probable pivotal role of platelet activation, potentially modifiable by agents which possess anti-inflammatory and/or platelet-targeted activities. Statins, which not only possess anti-inflammatory activity, but which also appear to target several pathways involved in platelet activation, seem particularly well-suited as adjuncts to antibiotic therapy in bacterial CAP. Following a brief consideration of the immunopathogenesis of bacterial CAP, this review is focused on mechanisms of platelet activation by CAP pathogens, as well as the pharmacological control thereof, with emphasis on statins.
[Show abstract][Hide abstract] ABSTRACT: Mycobacteria form lipid-rich biofilms that restrict the efficacy of antimicrobial chemotherapy, possibly necessitating the use of lipophilic antibiotics. In the current study, the activity of one such agent, clofazimine, against Mycobacterium tuberculosis and Mycobacterium smegmatis planktonic cells and biofilms was investigated. Minimum inhibitory concentrations (MICs) of clofazimine were determined for planktonic cultures, whilst minimum bactericidal concentrations (MBCs) were determined for planktonic, biofilm-producing and biofilm-encased organisms using standard bacteriological procedures. The effects of clofazimine on biofilm formation and the stability of pre-formed biofilm were measured using a crystal violet-based spectrophotometric procedure. In the case of M. smegmatis, clofazimine was found to be active against planktonic phase (MICs and MBCs of 2.5 mg/L and >20 mg/L, respectively) and biofilm-producing organisms (MBC of 2.5 mg/L); clofazimine demonstrated greater activity against M. tuberculosis, corresponding values of 0.06, 5 and 0.3 mg/L. Although clofazimine inhibited biofilm production both by M. tuberculosis and M. smegmatis (P < 0.05 at ≥0.07 mg/L and ≥0.3 mg/L, respectively) and appeared to reduce the pre-formed M. tuberculosis biofilm, addition of antimicrobial agent to pre-existing biofilm matrices failed to kill biofilm-encased organisms. In conclusion, clofazimine is more effective against M. tuberculosis than against M. smegmatis, exhibiting bactericidal activity both for actively growing and slowly replicating bacilli but not for non-replicating organisms of both species.
Journal of Global Antimicrobial Resistance 12/2014; 3(1). DOI:10.1016/j.jgar.2014.12.001 · 1.09 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Pneumococcal polysaccharide vaccines (PPVs) and conjugate vaccines (PCVs), of which PPV23 and PCV13 are the current front runners, have had a significant, beneficial impact on public health. With regard to PPV23, there has been some debate, however, about its protective efficacy against all-cause pneumonia, as opposed to invasive pneumococcal disease, in high-risk cases. PCVs, on the other hand, have been included in many national immunisation programmes for prevention of severe pneumococcal disease in infants and young children, as well as for adults in various high-risk categories. Although innovative and effective, the protective efficacy of PCVs, the composition of which is based on the geographic prevalence and virulence of pneumococcal serotypes, is limited due to colonisation of the nasopharynx with non-vaccine serotypes. This phenomenon of serotype replacement has provided the impetus for development of new generation recombinant protein and whole cell pneumococcal vaccines with the potential to provide serotype-independent protection. In addition to an overview of the successes and limitations of PPVs and PCVs, this review is focused on emerging and pipeline protein-based and whole cell vaccines, preceded by a consideration of conserved pneumococcal virulence factors which are potential vaccine candidates.
Journal of Infection 10/2014; 69(4). DOI:10.1016/j.jinf.2014.06.006 · 4.44 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A number of significant challenges remain with regard to the diagnosis, treatment, and prevention of infections with Streptococcus pneumoniae (pneumococcus), which remains the most common bacterial cause of community-acquired pneumonia. Although this infection is documented to be extremely common in younger children and in older adults, the burden of pneumonia it causes is considerably underestimated, since the incidence statistics are derived largely from bacteremic infections, because they are easy to document, and yet the greater burden of pneumococcal pneumonias is non-invasive. It has been estimated that for every bacteremic pneumonia that is documented, three non-bacteremic infections occur. Management of these infections is potentially complicated by the increasing resistance of the isolates to the commonly used antibiotics. Furthermore, it is well recognized that despite advances in medical care, the mortality of bacteremic pneumococcal pneumonia has remained largely unchanged over the past 50 years and averages approximately 12%. Much recent research interest in the field of pneumococcal infections has focused on important virulence factors of the organism, on improved diagnostic and prognostication tools, on defining risk factors for death, on optimal treatment strategies involving both antibiotics and adjunctive therapies, and on disease prevention. It is hoped that through these endeavors the outlook of pneumococcal infections will be improved.
F1000 Prime Reports 09/2014; 6:82. DOI:10.12703/P6-82
[Show abstract][Hide abstract] ABSTRACT: Alterations in whole genome expression profiles following exposure of the pneumococcus (strain 172, serotype 23F) to cigarette smoke condensate (160 μ g/mL) for 15 and 60 min have been determined using the TIGR4 DNA microarray chip. Exposure to CSC resulted in the significant (P < 0.014-0.0006) upregulation of the genes encoding the two-component regulatory system 11 (TCS11), consisting of the sensor kinase, hk11, and its cognate response regulator, rr11, in the setting of increased biofilm formation. These effects of cigarette smoke on the pneumococcus may contribute to colonization of the airways by this microbial pathogen.
BioMed Research International 06/2014; 2014:976347. DOI:10.1155/2014/976347 · 2.71 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Abstract Manganese (as Mn(2+)), a superoxide dismutase mimetic, catalyzes the formation of the relatively stable membrane-permeable reactive oxygen species (ROS) hydrogen peroxide (H2O2), a mediator of intracellular redox signaling in immune and inflammatory cells. The goal of this study was to investigate the potential for Mn(2+), via its pro-oxidative properties, to activate production of pro-inflammatory cytokines/chemokines IL-1β, IL-6, IL-8, IFNγ, TNFα, and G-CSF by human monocyte-derived macrophages in vitro. For these studies, the cells were isolated from peripheral blood mononuclear leukocytes and matured to generate a population of large CD14/CD16 co-expressing cells. The monocyte-derived macrophages were then exposed to bacterial lipopolysaccharide (LPS, 1 μg/ml) or MnCl2 (25-100 μM)-alone or in combination-for 24 h at 37 °C, after which cell-free supernatants were analyzed using a multiplex cytokine assay procedure. Exposure of the cells to LPS caused modest statistically insignificant increases in cytokine production; MnCl2 caused dose-related increases in production of all six cytokines (achieving statistical significance of p < 0.0171- < 0.0005 for IL-1β, IL-6, IL-8, IFNγ, and TNFα). In the case of LPS and MnCl2 combinations, the observed increases in production of IL-1β, IL-6, IL-8, IFNγ, and G-CSF were greater than those seen with cells exposed to the individual agents. The Mn(2+)-mediated induction of cytokine production was associated with increased production of H2O2 and completely attenuated by inclusion of the H2O2-scavenger dithiothreitol, and partially by inhibitors of NF-κB and p38MAP kinase. The findings from the studies here help to further characterize the pro-inflammatory mechanisms that may underpin clinical disorders associated with excess exposure to Mn(2+), particularly those disorders seen in the central nervous and respiratory systems.
Journal of Immunotoxicology 05/2014; 12(1). DOI:10.3109/1547691X.2014.902877 · 2.05 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Few studies have examined immune activation profiles in patients with advanced HIV-1 subtype C infection or assessed their potential to predict responsiveness to HAART. BioPlex, ELISA, and nephelometric procedures were used to measure plasma levels of inflammatory biomarkers in HIV-1 subtype C-infected patients sampled before and after 6 months of successful HAART (n = 20); in patients failing HAART (n = 30); and in uninfected controls (n = 8). Prior to HAART, CXCL9, CXCL10, β 2M, sTNF-R1, TGF- β 1, IFN- γ , IL-6, TNF, and sCD14 were significantly elevated in HIV-1-infected patients compared to controls (P < 0.01). All of these markers, with the exception of sTNF-R1, were also elevated in patients failing HAART (P < 0.05). The persistently elevated levels of CXCL9, CXCL10, and β 2M in patients failing therapy in the setting of a marked reduction in these markers in patients on successful HAART suggest that they may be useful not only to monitor immune activation during HAART, but also to distinguish between good and poor responders. In the case of sCD14 and TGF- β 1, the levels of these biomarkers remained persistently elevated despite HAART-induced virological suppression, a finding that is consistent with ongoing monocyte-macrophage activation, underscoring a potential role for adjuvant anti-inflammatory therapy.
Mediators of Inflammation 04/2014; 2014:198413. DOI:10.1155/2014/198413 · 3.24 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The clinical relevance of the anti-inflammatory properties of beta-2 agonists remains contentious possibly due to differences in their molecular structures and agonist activities. The current study has compared the effects of 3 different categories of β 2-agonists, namely, salbutamol (short-acting), formoterol (long-acting) and indacaterol (ultra-long-acting), at concentrations of 1-1000 nM, with human blood neutrophils in vitro. Neutrophils were activated with either N-formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLP, 1 µM) or platelet-activating factor (PAF, 200 nM) in the absence and presence of the β 2-agonists followed by measurement of the generation of reactive oxygen species and leukotriene B4, release of elastase, and expression of the β 2-integrin, CR3, using a combination of chemiluminescence, ELISA, colorimetric, and flow cytometric procedures respectively. These were correlated with alterations in the concentrations of intracellular cyclic-AMP and cytosolic Ca(2+). At the concentrations tested, formoterol and indacaterol caused equivalent, significant (P < 0.05 at 1-10 nM) dose-related inhibition of all of the pro-inflammatory activities tested, while salbutamol was much less effective (P < 0.05 at 100 nM and higher). Suppression of neutrophil reactivity was accompanied by elevations in intracellular cAMP and accelerated clearance of Ca(2+) from the cytosol of activated neutrophils. These findings demonstrate that β 2-agonists vary with respect to their suppressive effects on activated neutrophils.
Mediators of Inflammation 03/2014; 2014:105420. DOI:10.1155/2014/105420 · 3.24 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Chronic inflammation of both infective and non-infective origin has been implicated in the aetiology of approximately 30% of all human epithelial malignancies. The primary carcinogens are reactive oxygen species (ROS) derived from activated, infiltrating cells of the innate immune system, especially neutrophils, which inflict oxidative damage on the DNA of bystander epithelial cells. The consequence is gene modifications which initiate cellular transformation. The process of tumourigenesis is exacerbated by the sustained generation of pro-proliferative ROS, as well as by the release of neutrophil-derived cytokines and proteases, all of which contribute to tumour promotion and progression. It is now well recognised that, in addition to inflammation causing cancer, many cancers per se induce an inflammatory response, with a high magnitude of neutrophil influx being indicative of a poor prognosis. In this setting, CXC chemokines produced by tumours not only promote neutrophil influx and hyperreactivity, but also cause autocrine activation of the proliferation of the chemokine-producing tumour cells. These various mechanisms of inflammation-mediated tumourigenesis are the primary focus of this review, together with a consideration of neutrophil-targeted anti-inflammatory strategies with potential as adjunctive cancer therapy.
South African Journal of Science 01/2014; 110(1/2):1-6. DOI:10.1590/sajs.2014/20130207 · 0.96 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Community-acquired pneumonia (CAP) remains a leading cause of morbidity and mortality among the infectious diseases. Despite the implementation of national pneumococcal polyvalent vaccine-based immunisation strategies targeted at high-risk groups, Streptococcus pneumoniae (the pneumococcus) remains the most common cause of CAP. Notwithstanding the HIV pandemic, major challenges confronting the control of CAP include the range of bacterial and viral pathogens causing this condition, the ever-increasing problem of antibiotic resistance worldwide, and increased vulnerability associated with steadily aging populations in developed countries. These and other risk factors, as well as diagnostic strategies, are covered in the first section of this review. Thereafter, the review is focused on the pneumococcus, specifically the major virulence factors of this microbial pathogen and their role in triggering overexuberant inflammatory responses which contribute to the immunopathogenesis of invasive disease. The final section of the review is devoted to a consideration of pharmacological, anti-inflammatory strategies with adjunctive potential in the antimicrobial chemotherapy of CAP. This is focused on macrolides, corticosteroids, and statins with respect to their modes of anti-inflammatory action, current status, and limitations.
Mediators of Inflammation 12/2013; 2013(12):490346. DOI:10.1155/2013/490346 · 3.24 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Beta2-adrenoreceptor agonists (β2-agonists) are primarily bronchodilators, targeting airway smooth muscle and providing critical symptomatic relief in conditions such as bronchial asthma and chronic obstructive pulmonary disease. These agents also possess broad-spectrum, secondary, anti-inflammatory properties. These are mediated largely, though not exclusively, via interactions with adenylyl cyclase-coupled β2-adrenoreceptors on a range of immune and inflammatory cells involved in the immunopathogenesis of acute and chronic inflammatory disorders of the airways. The clinical relevance of the anti-inflammatory actions of β2-agonists, although often effective in the experimental setting, remains contentious. The primary objectives of the current review are: firstly, to assess the mechanisms, both molecular and cell-associated, that may limit the anti-inflammatory efficacy of β2-agonists; secondly, to evaluate pharmacological strategies, several of which are recent and innovative, that may overcome these limitations. These are preceded by a consideration of the various types of β2-agonists, their clinical applications, and spectrum of anti-inflammatory activities, particularly those involving adenosine 3',5'-cyclic adenosine monophosphate-activated protein kinase-mediated clearance of cytosolic calcium, and altered gene expression in immune and inflammatory cells.
Drug Design, Development and Therapy 11/2013; 7:1387-1398. DOI:10.2147/DDDT.S50995 · 3.03 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Background. While the detrimental effects of smoking among HIV-positive patients have been well documented, there is a paucity of data regarding cigarette smoking prevalence among these patients in South Africa (SA).Objectives. To establish the frequency, demographics, knowledge of harmful effects, and knowledge of smoking cessation strategies among HIV-positive patients in Johannesburg, SA.Methods. We conducted a prospective cross-sectional survey using a structured questionnaire to interview HIV-positive patients attending the HIV Clinic at the Charlotte Maxeke Johannesburg Academic Hospital between 1 July and 31 October 2011.Results. Of 207 HIV-positive patients attending an antiretroviral therapy (ART) roll-out clinic, 31 (15%) were current smokers (23.2% of males and 7.4% of females) and a further 45 (21.7%) were ex-smokers. Most of the current smokers (30/31 patients) indicated their wish to quit smoking, and among the group as a whole, most patients were aware of the general (82.1%) and HIV-related (77.8%) risks of smoking and of methods for quitting smoking. Despite this, however, most (62.3%) were not aware of who they could approach for assistance and advice.Conclusions. Given the relatively high prevalence of current and ex-smokers among HIV-positive patients, there is a need for the introduction of smoking-cessation strategies and assistance at ART roll-out clinics in SA.
South African medical journal = Suid-Afrikaanse tydskrif vir geneeskunde 11/2013; 103(11):858-60. DOI:10.7196/samj.7388 · 1.63 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Community-acquired bacterial pneumonia (CAP) remains one of the most common opportunistic infections in patients who are infected with the human immunodeficiency virus (HIV). The risk of CAP increases as the CD4 cell count decreases. The common bacterial pathogens that cause CAP in HIV-infected persons are similar to those in HIV-uninfected individuals, with the pneumococcus being the most common pathogen. Prevention of CAP remains critical and necessitates a comprehensive approach addressing, among many other factors, cigarette smoking cessation strategies, antiretroviral therapy adherence, and immunization against those infections for which effective vaccinations are available.
Clinics in chest medicine 06/2013; 34(2):205-216. DOI:10.1016/j.ccm.2013.01.006 · 2.07 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The predisposition of cigarette smokers for development of oral and respiratory infections caused by both microbial and viral pathogens is well recognised, with those infected with the human immunodeficiency virus (HIV) at particularly high risk. The current review consists of three major sections. The first of these is focused on the suppressive effects of smoking on the protective functions of airway epithelium, alveolar macrophages, dendritic cells, natural killer (NK) cells and adaptive immune mechanisms, as well as chronic systemic activation of neutrophils. This is followed by a consideration of the effects of cigarette smoke on microbial pathogens, specifically promotion of microbial virulence and antibiotic resistance. In addition to interactions between smoking and HIV infection, the final section covers specific infections/clinical syndromes associated with cigarette smoking, including those of the upper and lower respiratory tract, gastrointestinal tract, central nervous and other organ systems, as well as the benefits of smoking cessation.
The Journal of infection 05/2013; 67(3). DOI:10.1016/j.jinf.2013.05.004 · 4.44 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Matrix metalloproteinase-3 (MMP-3) is involved in the immunopathogenesis of rheumatoid arthritis (RA), but little is known about its relationship to genetic susceptibility and biomarkers of disease activity, especially acute phase reactants in early RA. MMP-3 was measured by ELISA in serum samples of 128 disease-modifying, drug-naïve patients and analysed in relation to shared epitope genotype, a range of circulating chemokines/cytokines, acute phase reactants, autoantibodies, cartilage oligomeric protein (COMP), and the simplified disease activity index (SDAI). MMP-3 was elevated >1.86 ng/ml in 56.25% of patients (P < 0.0001), correlated with several biomarkers, notably IL-8, IL-6, IFN γ, VEGF and COMP (r values = 0.22–0.33, P < 0.014–0.0001) and with CRP and SAA levels (r = 0.40 and 0.41, resp., P < 0.0000) and SDAI (r = 0.29, P < 0.0001), but not with erosions or nodulosis. However, the correlations of CRP and SAA with SDAI were stronger (respective values of 0.63 and 0.54, P < 0.001 for both). COMP correlated with smoking, RF, and MMP-3.
MMP-3 is significantly associated with disease activity, inflammatory mediators and cartilage breakdown, making it a potential biomarker of disease severity, but seemingly less useful than CRP and SAA as a biomarker of disease activity in early RA.
Mediators of Inflammation 04/2013; 2013(4):183653. DOI:10.1155/2013/183653 · 3.24 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Inhalable clofazimine-containing dry powder microparticles (CFM-DPI) and native clofazimine (CFM) were evaluated for activity against Mycobacterium tuberculosis in human monocyte-derived macrophage cell cultures and in low-dose aerosol infected mice. Both formulations resulted in 99% killing at 2.5 μg/ml in vitro. In mice, 480 μg and 720 μg CFM-DPI inhaled twice per week over four weeks reduced colony-forming units in the lung by as much as log(10) 2.6; 500 μg oral CFM achieved log(10) 0.7 reduction.
[Show abstract][Hide abstract] ABSTRACT: Although the well-recognised predisposition of cigarette smokers for development of severe pneumococcal disease may be attributable to impairment of local host defences, less is known about the direct effects of smoke exposure on airway pathogens, or their virulence factors. In the current study, we have investigated the effects of cigarette smoke condensate (CSC) on biofilm formation by Streptococcus pneumoniae, as well as on the pore-forming activity of its major toxin, pneumolysin.Biofilm formation following exposure of the pneumococcus to CSC (20-160 μg·mL(-1)) was measured using a crystal violet-based spectrophotometric procedure, while the pore-forming activity of recombinant pneumolysin was determined by a fura-2/AM-based spectrofluorimetric procedure to monitor the uptake of extracellular Ca(2+) by isolated human neutrophils.Exposure of the pneumococcus or pneumolysin to CSC resulted in significant dose-related augmentation of biofilm formation (P≤0.05 at 80 and 160 μg·mL(-1)) and substantial attenuation of the pore-forming interactions of pneumolysin, respectively.Augmentation of biofilm formation and inactivation of pneumolysin as a consequence of smoking, are likely to favour microbial colonization and persistence, both being essential precursors of pneumococcal disease.
European Respiratory Journal 06/2012; 41(2). DOI:10.1183/09031936.00213211 · 7.64 Impact Factor