Nelita du Plessis

The Contraceptive Depot Medroxyprogesterone Acetate Impairs Mycobacterial Control and Inhibits Cytokine Secretion in Mice Infected with Mycobacterium tuberculosis

ABSTRACT The contraceptive depot medroxyprogesterone acetate (DMPA), with progestin as the single active compound, possesses selective glucocorticoid activity and can alter the expression of glucocorticoid receptor-regulated genes. We therefore propose that pharmacological doses of DMPA used for endocrine therapy could have significant immune modulatory effects and impact on susceptibility to, as well as clinical manifestation and outcome of, infectious diseases. We investigated the effect of contraceptive doses of DMPA in two different murine Mycobacterium tuberculosis models. Multiplex bead array analysis revealed that DMPA altered serum cytokine levels of tumor necrosis factor alpha (TNF-α), granulocyte colony-stimulating factor (G-CSF), and interleukin 10 (IL-10) in C57BL/6 mice and gamma interferon (IFN-γ) in BALB/c mice. DMPA also suppressed antigen-specific production of TNF-α, G-CSF, IL-10, and IL-6 and induced the production of IP-10 in C57BL/6 mice. In BALB/c mice, DMPA altered the antigen-specific secretion of IFN-γ, IL-17, granulocyte-macrophage colony-stimulating factor (GM-CSF), IL-6, and monocyte chemotactic protein 1 (MCP-1). Furthermore, we show that C57BL/6 mice treated with doses of DMPA, which result in serum concentrations similar to those observed in contraceptive users, have a significantly higher bacterial load in their lungs. Our data show for the first time that DMPA impacts tuberculosis (TB) disease severity in a mouse model and that the effects of this contraceptive are not confined to infections of the genital tract. This could have major implications for the contraceptive policies not only in developing countries like South Africa but also worldwide.

Medroxyprogesterone Acetate Alters Mycobacterium Bovis BCG-Induced Cytokine Production in Peripheral Blood Mononuclear Cells of Contraceptive Users

Most individuals latently infected with Mycobacterium tuberculosis (M.tb) contain the infection by a balance of effector and regulatory immune responses. This balance can be influenced by steroid hormones such as glucocorticoids. The widely used contraceptive medroxyprogesterone acetate (MPA) possesses glucocorticoid activity. We investigated the effect of this hormone on immune responses to BCG in household contacts of active TB patients. Multiplex bead array analysis revealed that MPA demonstrated both glucocorticoid and progestogenic properties at saturating and pharmacological concentrations in peripheral blood mononuclear cells (PBMCs) and suppressed antigen specific cytokine production. Furthermore we showed that PBMCs from women using MPA produced significantly lower levels of IL-1α, IL-12p40, IL-10, IL-13 and G-CSF in response to BCG which corresponded with lower numbers of circulating monocytes observed in these women. Our research study is the first to show that MPA impacts on infections outside the genital tract due to a systemic effect on immune function. Therefore MPA use could alter susceptibility to TB, TB disease severity as well as change the efficacy of new BCG-based vaccines, especially prime-boost vaccine strategies which may be administered to adult or adolescent women in the future.

Host blood RNA signatures predict the outcome of tuberculosis treatment

Biomarkers for tuberculosis treatment outcome will assist in guiding individualized treatment and evaluation of new therapies. To identify candidate biomarkers, RNA sequencing of whole blood from a well-characterized TB treatment cohort was performed. Application of a validated transcriptional correlate of risk for TB revealed symmetry in host gene expression during progression from latent TB infection to active TB disease and resolution of disease during treatment, including return to control levels after drug therapy. The symmetry was also seen in a TB disease signature, constructed from the TB treatment cohort, that also functioned as a strong correlate of risk. Both signatures identified patients at risk of treatment failure 1–4 weeks after start of therapy. Further mining of the transcriptomes revealed an association between treatment failure and suppressed expression of mitochondrial genes before treatment initiation, leading to development of a novel baseline (pre-treatment) signature of treatment failure. These novel host responses to TB treatment were integrated into a five-gene real-time PCR-based signature that captures the clinically relevant responses to TB treatment and provides a convenient platform for stratifying patients according to their risk of treatment failure. Furthermore, this 5-gene signature is shown to correlate with the pulmonary inflammatory state (as measured by PET-CT) and can complement sputum-based Gene Xpert for patient stratification, providing a rapid and accurate alternative to current methods.

Mycobacterium bovis BCG infection severely delays Trichuris muris expulsion and co-infection suppresses immune responsiveness to both pathogens

BackgroundThe global epidemiology of parasitic helminths and mycobacterial infections display extensive geographical overlap, especially in the rural and urban communities of developing countries. We investigated whether co-infection with the gastrointestinal tract-restricted helminth, Trichuris muris, and the intracellular bacterium, Mycobacterium bovis (M. bovis) BCG, would alter host immune responses to, or the pathological effect of, either infection.ResultsWe demonstrate that both pathogens are capable of negatively affecting local and systemic immune responses towards each other by modifying cytokine phenotypes and by inducing general immune suppression. T. muris infection influenced non-specific and pathogen-specific immunity to M. bovis BCG by down-regulating pulmonary TH1 and Treg responses and inducing systemic TH2 responses. However, co-infection did not alter mycobacterial multiplication or dissemination and host pulmonary histopathology remained unaffected compared to BCG-only infected mice. Interestingly, prior M. bovis BCG infection significantly delayed helminth clearance and increased intestinal crypt cell proliferation in BALB/c mice. This was accompanied by a significant reduction in systemic helminth-specific TH1 and TH2 cytokine responses and significantly reduced local TH1 and TH2 responses in comparison to T. muris-only infected mice.ConclusionOur data demonstrate that co-infection with pathogens inducing opposing immune phenotypes, can have differential effects on compartmentalized host immune protection to either pathogen. In spite of local and systemic decreases in TH1 and increases in TH2 responses co-infected mice clear M. bovis BCG at the same rate as BCG only infected animals, whereas prior mycobacterial infection initiates prolonged worm infestation in parallel to decreased pathogen-specific TH2 cytokine production.

Monocytic Myeloid-Derived Suppressor Cells in Chronic Infections

Heterogeneous populations of myeloid regulatory cells (MRC), including monocytes, macrophages, dendritic cells, and neutrophils, are found in cancer and infectious diseases. The inflammatory environment in solid tumors as well as infectious foci with persistent pathogens promotes the development and recruitment of MRC. These cells help to resolve inflammation and establish host immune homeostasis by restricting T lymphocyte function, inducing regulatory T cells and releasing immune suppressive cytokines and enzyme products. Monocytic MRC, also termed monocytic myeloid-derived suppressor cells (M-MDSC), are bona fide phagocytes, capable of pathogen internalization and persistence, while exerting localized suppressive activity. Here, we summarize molecular pathways controlling M-MDSC genesis and functions in microbial-induced non-resolved inflammation and immunopathology. We focus on the roles of M-MDSC in infections, including opportunistic extracellular bacteria and fungi as well as persistent intracellular pathogens, such as mycobacteria and certain viruses. Better understanding of M-MDSC biology in chronic infections and their role in antimicrobial immunity, will advance development of novel, more effective and broad-range anti-infective therapies.

Tuberculosis: progress and advances in development of new drugs, treatment regimens, and host-directed therapies

Tuberculosis remains the worlds leading cause of death from an infectious disease, responsible for an estimated 1 674 000 deaths annually. WHO estimated 600 000 cases of rifampicin-resistant tuberculosis in 2016-of which 490 000 were multidrug resistant (MDR), with less than 50% survival after receiving recommended treatment regimens. Concerted efforts of stakeholders, advocates, and researchers are advancing further development of shorter course, more effective, safer, and better tolerated treatment regimens. We review the developmental pipeline and landscape of new and repurposed tuberculosis drugs, treatment regimens, and host-directed therapies (HDTs) for drug-sensitive and drug-resistant tuberculosis. 14 candidate drugs for drug-susceptible, drug-resistant, and latent tuberculosis are in clinical stages of drug development; nine are novel in phase 1 and 2 trials, and three new drugs are in advanced stages of development for MDR tuberculosis. Specific updates are provided on clinical trials of bedaquiline, delamanid, pretomanid, and other licensed or repurposed drugs that are undergoing investigation, including trials aimed at shortening duration of tuberculosis treatment, improving treatment outcomes and patient adherence, and reducing toxic effects. Ongoing clinical trials for shortening tuberculosis treatment duration, improving treatment outcomes in MDR tuberculosis, and preventing disease in people with latent tuberculosis infection are reviewed. A range of HDTs and immune-based treatments are under investigation as adjunctive therapy for shortening duration of therapy, preventing permanent lung injury, and improving treatment outcomes of MDR tuberculosis. We discuss the HDT development pipeline, ongoing clinical trials, and translational research efforts for adjunct tuberculosis treatment.

The Functional Response of B Cells to Antigenic Stimulation: A Preliminary Report of Latent Tuberculosis.

Mycobacterium tuberculosis (M.tb) remains a successful pathogen, causing tuberculosis disease numbers to constantly increase. Although great progress has been made in delineating the disease, the host-pathogen interaction is incompletely described. B cells have shown to function as both effectors and regulators of immunity via non-humoral methods in both innate and adaptive immune settings. Here we assessed specific B cell functional interaction following stimulation with a broad range of antigens within the LTBI milieu. Our results indicate that B cells readily produce pro- and anti-inflammatory cytokines (including IL-1β, IL-10, IL-17, IL-21 and TNF-α) in response to stimulation. TLR4 and TLR9 based stimulations achieved the greatest secreted cytokine-production response and BCG stimulation displayed a clear preference for inducing IL-1β production. We also show that the cytokines produced by B cells are implicated strongly in cell-mediated communication and that plasma (memory) B cells (CD19+CD27+CD138+) is the subset with the greatest contribution to cytokine production. Collectively our data provides insight into B cell responses, where they are implicated in and quantifies responses from specific B cell phenotypes. These findings warrant further functional B cell research with a focus on specific B cell phenotypes under conditions of active TB disease to further our knowledge about the contribution of various cell subsets which could have implications for future vaccine development or refined B cell orientated treatment in the health setting.

Helminth-M. Tb Co-Infection

Tuberculosis (TB) and helminthiasis are each responsible for a high public health burden in the developing world, especially in sub-Saharan Africa, where approximately one third of the population is infected with Mycobacterium tuberculosis and the greatest number of helminth infections occur. M. tb infection is classically described as a TH1 pathology and there is much interest in exploring how concurrent worm infections might alter immune responses to mycobacterial infections. In the mammalian host, polarised mycobacterium-specific TH1 immune responses correlate with protection, whereas helminth infection induces TH2 immunity. Theoretically, immunomodulation elicited by helminths could attenuate host immune responses against a concomitant mycobacterial infection. Our current understanding of the immunology of helminth infections suggests that interaction with anti-TB immune responses could exacerbate the effects of M. tb infection. Although preliminary results suggest that helminth infections might alter immune responses against bacilli, necessitating altered therapeutic approaches, the full impact of helminth-induced immune responses on the development of protective immunity to mycobacteria remains ambiguous and the implication of helminth co-infection on the natural and vaccine-induced protection against major infectious diseases remains complex and requires further investigation.

Phenotypically resembling myeloid derived suppressor cells are increased in children with HIV and exposed/infected with Mycobacterium tuberculosis.

Increased disease susceptibility during early life has been linked to immune immaturity, regulatory T‐cell/TH2 immune biasing and hyporesponsiveness. The contribution of myeloid derived suppressor cells (MDSCs) remains uninvestigated. Here, we assessed peripheral MDSC in HIV‐infected and ‐uninfected children with tuberculosis (TB) disease before, during and after TB treatment, along with matched household contacts (HHCs), HIV‐exposed, ‐infected and ‐uninfected children without recent TB exposure. Serum analytes and enzymes associated with MDSC accumulation/activation/function were measured by colorimetric‐ and fluorescence arrays. Peripheral frequencies of cells phenotypically resembling MDSCs were significantly increased in HIV‐exposed uninfected (HEU) and M.tb‐infected children, but peaked in children with TB disease and remained high following treatment. MDSC in HIV‐infected (HI) children were similar to unexposed uninfected controls; however, HAART‐mediated MDSC restoration to control levels could not be disregarded. Increased MDSC frequencies in HHC coincided with enhanced indoleamine‐pyrrole‐2,3‐dioxygenase (IDO), whereas increased MDSC in TB cases were linked to heightened IDO and arginase‐1. Increased MDSC were paralleled by reduced plasma IP‐10 and thrombospondin‐2 levels in HEU and significantly increased plasma IL‐6 in HI HHC. Current investigations into MDSC‐targeted treatment strategies, together with functional analyses of MDSCs, could endorse these cells as novel innate immune regulatory mechanism of infant HIV/TB susceptibility.

Tuberculosis: advances and challenges in development of new diagnostics and biomarkers

Tuberculosis remains the leading cause of death from an infectious disease worldwide. Early and accurate diagnosis and detection of drug-sensitive and drug-resistant tuberculosis is essential for achieving global tuberculosis control. Despite the introduction of the Xpert MTB/RIF assay as the first-line rapid tuberculosis diagnostic test, the gap between global estimates of incidence and new case notifications is 4·1 million people. More accurate, rapid, and cost-effective screening tests are needed to improve case detection. Diagnosis of extrapulmonary tuberculosis and tuberculosis in children, people living with HIV, and pregnant women remains particularly problematic. The diagnostic molecular technology landscape has continued to expand, including the development of tests for resistance to several antituberculosis drugs. Biomarkers are urgently needed to indicate progression from latent infection to clinical disease, to predict risk of reactivation after cure, and to provide accurate endpoints for drug and vaccine trials. Sophisticated bioinformatic computational tools and systems biology approaches are being applied to the discovery and validation of biomarkers, with substantial progress taking place. New data have been generated from the study of T-cell responses and T-cell function, serological studies, flow cytometric-based assays, and protein and gene expression studies. Alternative diagnostic strategies under investigation as potential screening and triaging tools include non-sputum-based detection with breath-based tests and automated digital radiography. We review developments and key achievements in the search for new tuberculosis diagnostics and biomarkers. We highlight gaps and challenges in evaluation and rollout of new diagnostics and biomarkers, and prioritise areas needing further investment, including impact assessment and cost-benefit studies.