Biology subjects

Meintjes, G.

Publications and source records attributed to Meintjes, G..

6 recordsLinked to original sources

bioRxiv2026

Contribution of cytotoxic CD8 T cells, neutrophils and type 1 interferon signaling to hyperinflammatory pathology in HIV associated TB meningitis

Immune dysregulation contributes to death and disability in tuberculous meningitis. People living with HIV have the least evidence that anti-inflammatory therapy improves the poor outcome. Improving therapy relies on a more refined understanding of the host immune response. Single-cell RNA sequencing of 188,983 CSF cells from 25 adults with HIV-associated TBM revealed a predominance of cytotoxic CD8 T cells with low cytokine expression. In microbiologically-confirmed TBM, there was greater cytotoxicity in T, NK and {gamma}{delta} cells, and higher type 1 interferon stimulation in T and B lymphocytes. Neutrophils expressed markers suggesting heightened cytokine stimulation, enhanced effector function, and IL-8-mediated neutrophil recruitment. In a longitudinal cohort, type 1 interferon signaling increased in blood and CSF following treatment initiation. Overall, findings indicate a hyper-inflammatory immune response in the CSF of HIV-associated TBM patients characterised by an accumulation of granzyme-rich cytotoxic CD8 T cells, highly activated neutrophils and host-detrimental type 1 interferon signaling.

immunology↗

bioRxiv2025

Two distinct cytokine response clusters identified in healthcare workers with apparent resistance to infection with Mycobacterium tuberculosis despite sustained occupational exposure

IntroductionEvidence exists that some individuals resist ("Resisters") Mycobacterium tuberculosis (Mtb) infection despite sustained exposure, but the protective mechanisms involved are not fully understood. We investigated immune responses induced by ex vivo stimulation of peripheral blood mononuclear cells (PBMC) with live Mtb in Resisters compared to those with latent TB infection (LTBI). MethodsHIV-uninfected healthcare workers working in high TB exposure healthcare facilities for over 5 years were screened for Mtb sensitization using the interferon-gamma release assay (IGRA) and the tuberculin skin test (TST). We identified Resisters (TST<10mm and IGRA<0.35 IU/mL, n=129) and those with LTBI (TST[≥]10mm and IGRA[≥]0.35 IU/mL n=145). We selected a subset of extreme resisters (TST=0mm and IGRA<0.2 IU/mL; n=26) and extreme LTBI (TST[≥]15mm and IGRA[≥]1 IU/mL; n=24) for these analyses. Blood was collected and PBMC isolated and cultured with live H37Rv Mtb for 18 hours. Supernatants were collected and used for measuring 65 secreted analytes by Luminex. We also evaluated cell-associated cytokine expression by CD4 T cells and monocytes in these participants using flow cytometry. ResultsUsing the feature selection in R, we identified a set of 4 cytokines: IL-17A, MCP-1, IL-8, and MDC, which collectively classified extreme Resisters from extreme LTBI with an area-under-the-curve (AUC) of 0.67 (0.54-0.85). Focusing only on the extreme Resisters, and using hierarchical clustering, participants in this group segregated into two main clusters (Resister_c1 and Resister_c2). Further analyses identified 37 cytokines that were significantly higher and 15 cytokines that were lower in Resister_c2 compared with Resister_c1. A set of 5 cytokines (TRAIL, MIP-1{beta}, Fractalkine, GRO- and IL-1) collectively classified these two clusters with an AUC of 1 (1-1). CD4 T cell and monocyte responses to Mtb did not significantly differ between the two clusters. ConclusionsMtb-specific immune responses segregate extreme Resisters into two distinct clusters in individuals with apparent resistance to Mtb infection and may allow discrimination of individuals with true resistance from those with infection but have alternative immune responses not detected by IGRA and TST.

immunology↗

bioRxiv2024

In vitro host transcriptomics during Cryptococcus neoformans, Cryptococcus gattii, and Candida albicans infection of South African volunteers

Cryptococcus neoformans, Cryptococcus gattii and Candida albicans are opportunistic fungal pathogens associated with infections in immunocompromised hosts. Cryptococcal meningitis (CM) is the leading fungal cause of HIV-related deaths globally, with the majority occurring in Africa. The human immune response to C. albicans infection has been studied extensively in large genomics studies whereas cryptococcal infections, despite their severity, are comparatively understudied. Here we investigated the transcriptional response of immune cells after in vitro stimulation with in vitro C. neoformans, C. gattii and C. albicans infection of peripheral blood mononuclear cells (PBMCs) collected from healthy South African volunteers. We found a lower transcriptional response to cryptococcal stimuli compared to C. albicans and unique expression signatures from all three fungal stimuli. This work provides a starting point for further studies comparing the transcriptional signature of CM in immunocompromised patients, with the goal of identifying biomarkers of disease severity and possible novel treatment targets.

genomics↗

bioRxiv2022

Phenotypic profile of Mycobacterium tuberculosis-specific CD4 T cell responses in HIV-positive patients who develop Tuberculosis-associated Immune Reconstitution Inflammatory Syndrome

BackgroundTuberculosis-associated immune reconstitution inflammatory syndrome (TB-IRIS) is a frequent complication of co-treatment for TB and HIV-1. We characterized Mtb-specific CD4 T cell phenotype and transcription factor profile associated with the development of TB-IRIS. MethodsWe examined the role of CD4 T-cell transcription factors in a murine model of mycobacterial IRIS. In humans, we compared longitudinally on antiretroviral therapy (ART) the magnitude, activation, transcription factor profile and cytotoxic potential of Mtb-specific CD4 T cells between TB-IRIS (n=25) and appropriate non-IRIS control patients (n=18) using flow cytometry. ResultsIn the murine model, CD4 T cell expression of Eomes, but not Tbet, was associated with experimentally induced IRIS. In patients, TB-IRIS onset was associated with the expansion of Mtb-specific IFN{gamma}+CD4 T cells (p=0.039). TB-IRIS patients had higher HLA-DR expression (p=0.016), but no differences in the expression of T-bet or Eomes were observed. At TB-IRIS onset, Eomes+Tbet+Mtb-specific IFN{gamma}+CD4+ T cells showed higher expression of Granzyme B in TB-IRIS patients (p=0.026). ConclusionWhile the murine model of MAC-IRIS suggests that Eomes+CD4 T cells underly IRIS, TB-IRIS was not associated with Eomes expression in patients. Mtb-specific IFN{gamma}+CD4 T cell responses in TB-IRIS patients are differentiated, highly activated and potentially cytotoxic.

immunology↗

bioRxiv2021

Flow cytometry method for absolute counting and single-cell phenotyping of mycobacteria

Detection and accurate quantitation of viable Mycobacterium tuberculosis is fundamental to understanding mycobacterial pathogenicity, tuberculosis (TB) disease progression and outcomes; TB transmission; drug action, efficacy and drug resistance. Despite this importance, methods for determining numbers of viable bacilli are limited in accuracy and precision owing to inherent characteristics of mycobacterial cell biology - including the tendency to clump, and "differential" culturability - and technical challenges consequent on handling an infectious pathogen under biosafe conditions. We developed an absolute counting method for mycobacteria in liquid cultures using a bench-top flow cytometer, and the low-cost fluorescent dyes Calcein-AM (CA) and SYBR-gold (SG). During exponential growth CA+ cell counts are highly correlated with CFU counts and can be used as a real-time alternative to simplify the accurate standardisation of inocula for experiments. In contrast to CFU counting, this method can detect and enumerate cell aggregates in samples, which we show are a potential source of variance and bias when using established methods. We show that CFUs comprise a sub-population of intact, metabolically active mycobacterial cells in liquid cultures, with CFU-proportion varying by growth conditions. A pharmacodynamic application of the flow cytometry method, exploring kinetics of fluorescent probe defined subpopulations compared to CFU is demonstrated. Flow cytometry derived Mycobacterium bovis BCG time-kill curves differ for rifampicin and kanamycin versus isoniazid and ethambutol, as do the relative dynamics of discrete morphologically-distinct subpopulations of bacilli revealed by this high-throughput single-cell technique.

microbiology↗

bioRxiv2016

A population genomics approach to assessing the genetic basis of within-host microevolution underlying recurrent cryptococcal meningitis infection

Recurrence of meningitis due to Cryptococcus neoformans after treatment causes substantial mortality in HIV/AIDS patients across sub-Saharan Africa. In order to determine whether recurrence occurred due to relapse of the original infecting isolate or reinfection with a different isolate weeks or months after initial treatment, we used whole-genome sequencing to assess the genetic basis of infection in 17 HIV-infected individuals with recurrent cryptococcal meningitis. Comparisons revealed a clonal relationship for 15 pairs of isolates recovered before and after recurrence showing relapse of the original infection. The two remaining pairs showed high levels of genetic heterogeneity; in one pair we found this to be a result of infection by mixed genotypes, whilst the second was a result of nonsense mutations in the gene encoding the DNA mismatch repair proteins MSH2, MSH5 and RAD5. These nonsense mutations led to a hypermutator state, leading to dramatically elevated rates of synonymous and non-synonymous substitutions. Hypermutator phenotypes owing to nonsense mutations in these genes have not previously been reported in Cryptococcus neoformans and represent a novel pathway for rapid within-host adaptation and evolution of resistance to firstline antifungal drugs.

genomics↗