Browsing by Author "Shey, Muki"

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    Open Access
    Activation of MAIT cells by antigen presenting cells: a comprehensive analysis and assessment of HIV and TB disease on these interactions
    (2019) Balfour, Avuyonke; Shey, Muki; Meintjies, Graeme
    MAIT cells are non-classical, innate-like T lymphocyte subsets, which recognize microbial vitamin B metabolites and rapidly respond by producing pro-inflammatory cytokines such as IFN-γ, TNF-α and cytotoxic molecules, which may result in the killing of bacteria-infected cells. Unlike conventional T cells, MAIT cells can be activated by either antigen presentation on MR1 or directly by cytokines. MAIT cells play a protective role against bacterial infections in mice but so far, no human studies have confirmed a direct role of MAIT cells in the control of bacterial infections or prevention of disease progression. Circulating MAIT cell numbers decrease in patients with active TB, but findings regarding functional changes have been conflicting. The aims of this study were to assess the cellular interactions between antigen presenting cells and MAIT cells, and determine the effect of TB, HIV and HIV-associated TB on MAIT cell numbers, activation, inhibitory and functional profile. We recruited 26 healthy controls (HC) without HIV or TB disease, 30 people with HIV only, 30 with active TB only, and 26 with HIV-associated TB. All TB patient samples were obtained before treatment. Blood was collected from all participants and peripheral blood mononuclear cells (PBMC) isolated from the blood and cryopreserved. Later, PBMC were thawed, rested and stimulated with BCG expressing GFP (BCG-GFP) and heat-killed (HK) M.tb. Media only, LPS and PHA were used as stimulation controls. The numbers, functional profile, inhibitory and activation status of MAIT cells were determined by flow cytometry. Soluble cytokines were measured by ELISA and multiplex Luminex assays. For HIV-infected participants with no TB and patients with HIV-associated TB, the median CD4 counts were 501 cells/µL and 228 cells/µL, and HIV viral loads were 1673 copies/mL and 66509 copies/mL, respectively. 63% and 69% of HIV infected patients were on ART in the HIV alone and HIV/TB groups, respectively. We observed lower frequencies of circulating MAIT cells in individuals with active TB only or HIV only compared to HC. HIV/TB resulted in lower but nonsignificant MAIT cell frequencies and numbers compared to HC. In response to stimulation with whole mycobacteria, MAIT cells were more highly activated (expressing high HLA-DR) in people with TB and HIV-associated TB compared to HC. Furthermore, MAIT cells from people with active TB only had significantly upregulated PD-1 expression compared to HC. MAIT cells from individuals with active TB and HIV-associated TB had a lower capacity to degranulate (express CD107a) and produce IFN-γ compared to HC. HIV-infection alone did not affect these functions. The levels of soluble IFN-α2 were reduced in the groups with HIV only and active TB only while IFN-γ was reduced in all patient groups. Blocking experiments revealed that MAIT cell activation in response to BCG was primarily through MR1 antigen presentation pathway. The level of monocyte and dendritic cell infection (expression of GFP) was similar in all groups. We observed a positive correlation between monocyte infection and the frequencies of MAIT cells producing IFN-γ in people with active TB only. We also observed a positive correlation between the amount of soluble IL-12 and the proportion of MAIT cells producing IFN-γ and CD107a in HC and in people with HIV infection, respectively. Our data show that HIV, TB and or HIV/TB result in a decrease in circulating MAIT cells, impaired functional profile, and a significant alteration in activation status and inhibitory potential. The MR1 antigen presentation was the predominant pathway for MAIT cell activation. There was also a relationship observed between MAIT cell activation and magnitude of innate response to mycobacterial antigens. These results provide further evidence of the potential role of MAIT cells in infectious disease pathogenesis and demonstrate how HIV and TB alter their function.
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    Advances in childhood immunisation in South Africa: where to now? Programme managers' views and evidence from systematic reviews
    (BioMed Central Ltd, 2012) Wiysonge, Charles; Ngcobo, Nthombenhle; Jeena, Prakash; Madhi, Shabir; Schoub, Barry; Hawkridge, Anthony; Shey, Muki; Hussey, Gregory
    BACKGROUND: The Expanded Programme on Immunisation (EPI) is one of the most powerful and cost-effective public health programmes to improve child survival. We assessed challenges and enablers for the programme in South Africa, as we approach the 2015 deadline for the Millennium Development Goals. METHODS: Between September 2009 and September 2010 we requested national and provincial EPI managers in South Africa to identify key challenges facing EPI, and to propose appropriate solutions. We collated their responses and searched for systematic reviews on the effectiveness of the proposed solutions; in the Health Systems Evidence, Cochrane Library, and PubMed electronic databases. We screened the search outputs, selected systematic reviews, extracted data, and assessed the quality of included reviews (using AMSTAR) and the quality of the evidence (using GRADE) in duplicate; resolving disagreements by discussion and consensus. RESULTS: Challenges identified by EPI managers were linked to healthcare workers (insufficient knowledge of vaccines and immunisation), the public (anti-immunisation rumours and reluctance from parents), and health system (insufficient financial and human resources). Strategies proposed by managers to overcome the challenges include training, supervision, and audit and feedback; strengthening advocacy and social mobilisation; and sustainable EPI funding schemes, respectively. The findings from reliable systematic reviews indicate that interactive educational meetings, audit and feedback, and supportive supervision improve healthcare worker performance. Structured and interactive communication tools probably increase parents' understanding of immunisation; and reminders and recall, use of community health workers, conditional cash transfers, and mass media interventions probably increase immunisation coverage. Finally, a national social health insurance scheme is a potential EPI financing mechanism; however, given the absence of high-quality evidence of effects, its implementation should be pilot-tested and the impacts and costs rigorously monitored. CONCLUSION: In line with the Millennium Development Goals, we have to ensure that our children's right to health, development and survival is respected, protected and promoted. EPI is central to this vision. We found numerous promising strategies for improving EPI performance in South Africa. However, their implementation would need to be tailored to local circumstances and accompanied by high-quality monitoring and evaluation. The strength of our approach comes from having a strong framework for interventions before looking for systematic reviews. Without a framework, we would have been driven by what reviews have been done and what is easily researchable; rather than the values and preferences of key immunisation stakeholders.
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    Diagnosis, treatment and determinants of mortality in patients hospitalized with HIV-associated tuberculosis
    (2021) Schutz,Charlotte; Meintjes, Graeme; Wilkinson, Robert J; Shey, Muki
    Background: HIV-associated tuberculosis (HIV-TB) comprises 9% of global tuberculosis cases but contributes a disproportionate 17% of tuberculosis deaths. Tuberculosis is the leading cause of death, hospitalization and in-hospital death in HIV-positive patients world-wide with case fatality rates in hospitalized patients ranging between 13% and 32%. Underlying causes of mortality remain poorly characterized and better characterization of causes could inform development of novel management strategies to improve survival. This study aimed to assess determinants of mortality in hospitalized HIV-TB patients. I assessed the association of clinical, microbiologic and treatment factors, host soluble inflammatory mediators, markers of tuberculosis dissemination, antituberculosis drug concentrations and markers of microbial translocation with 12-week mortality in hospitalized HIV-TB patients. Methods: We conducted a prospective observational cohort study and enrolled adult HIV-positive patients hospitalized with a new diagnosis of HIV-TB in Khayelitsha Hospital in Cape Town between 2014-2016. Detailed tuberculosis diagnostic testing was performed (including urine Xpert testing) and we collected clinical samples for analysis at baseline. We performed intensive pharmacokinetic studies in a subset of patients on the third day of antituberculosis therapy. Patients were followed up for 12 weeks to ascertain vital status. Results: We enrolled 682 participants and included 576 patients with tuberculosis in the cohort analyses. Twelve-week mortality was 124/576 (21.5%) with 46/124 (37.1%) deaths occurring within 7 days of enrolment. Determinants of mortality included tuberculosis dissemination, rifampicin resistance and having features of sepsis syndrome. Using principal components analysis, we characterised an innate immune profile which was associated with mortality and with biomarkers of disseminated tuberculosis. A large proportion of patients had sub-optimal concentrations of rifampicin and isoniazid. Patients who presented with elevated lactate concentrations had higher rifampicin concentration and exposure. Opportunistic infections other than tuberculosis and microbial translocation did not have a significant association with mortality. Conclusions: There was high early mortality in hospitalized HIV-TB patients. An innate immune profile was associated with tuberculosis dissemination and mortality. Rifampicin and isoniazid concentrations and exposure were sub-optimal. These findings provide novel pathophysiologic insight and provide rationale to test high dose rifampicin and immune modulatory therapy for safety and efficacy to improve survival in this patient population.
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    Genetic variation in TLR genes in Ugandan and South African populations and comparison with HapMap data
    (Public Library of Science, 2012) Baker, Allison R; Qiu, Feiyou; Randhawa, April Kaur; Horne, David J; Adams, Mark D; Shey, Muki; Barnholtz-Sloan, Jill; Mayanja-Kizza, Harriet; Kaplan, Gilla; Hanekom, Willem A; Boom, W Henry; Hawn, Thomas R; Stein, Catherine M
    Genetic epidemiological studies of complex diseases often rely on data from the International HapMap Consortium for identification of single nucleotide polymorphisms (SNPs), particularly those that tag haplotypes. However, little is known about the relevance of the African populations used to collect HapMap data for study populations conducted elsewhere in Africa. Toll-like receptor (TLR) genes play a key role in susceptibility to various infectious diseases, including tuberculosis. We conducted full-exon sequencing in samples obtained from Uganda (n = 48) and South Africa (n = 48), in four genes in the TLR pathway: TLR2, TLR4, TLR6, and TIRAP. We identified one novel TIRAP SNP (with minor allele frequency [MAF] 3.2%) and a novel TLR6 SNP (MAF 8%) in the Ugandan population, and a TLR6 SNP that is unique to the South African population (MAF 14%). These SNPs were also not present in the 1000 Genomes data. Genotype and haplotype frequencies and linkage disequilibrium patterns in Uganda and South Africa were similar to African populations in the HapMap datasets. Multidimensional scaling analysis of polymorphisms in all four genes suggested broad overlap of all of the examined African populations. Based on these data, we propose that there is enough similarity among African populations represented in the HapMap database to justify initial SNP selection for genetic epidemiological studies in Uganda and South Africa. We also discovered three novel polymorphisms that appear to be population-specific and would only be detected by sequencing efforts.