Biology subjects

Ndhlovu, Z. M.

Publications and source records attributed to Ndhlovu, Z. M..

4 recordsLinked to original sources

bioRxiv2025

CD68+ Follicular Macrophages Harbor HIV Reservoirs in Human Lymph Node Tissues During Suppressive ART

Uncertainty persists regarding the contribution of tissue macrophages to HIV reservoirs, largely due to insufficient characterization of these reservoirs within their native tissue microenvironments. This study aimed to characterize and quantify macrophage reservoirs in human lymph node (LN) tissues in terms of their phenotype, location, and their potential for sustained productive infection during suppressive antiretroviral therapy. We examined the topology, nature, and size of macrophage reservoirs in lymph nodes (LNs) from 45 PLWH subtype C on suppressive ART and 14 matched controls using in situ imaging and multiplexed immunofluorescence microscopy. Germinal center CD68+ macrophages harbored HIV gag-pol DNA, HIV gag-pol RNA and Gagp24 protein. Digital droplet PCR confirmed the presence of proviral reservoirs in myeloid cells within LNs. High-resolution imaging techniques revealed that infected macrophages within GCs displayed distinct morphological characteristics, featuring larger and irregular shapes. In contrast, phagocytic macrophages exhibited intracellular staining for CD4+ T cells, had regular shapes, and were predominantly found outside the GCs. Our findings provide detailed quantitative, spatial, and phenotypic characterization of macrophage reservoirs in LNs, offering a clear estimation of the extent to which macrophages contribute to persistent HIV reservoirs in these tissues. These findings establish a basis for developing targeted strategies aimed at the elimination of these reservoirs in LN tissues. Author summaryHIV hides in reservoirs within immune cells across the body in the blood and various tissues, making it a complex challenge to cure. Therefore, it is essential to identify and understand all sources of HIV reservoirs aid the development of an HIV cure. Macrophages are increasingly recognized as key contributors of viral reservoir persistence. However, the role of macrophages as latent HIV reservoirs remains unclear due to limited studies in human tissues. In this study we investigated macrophage reservoirs in human lymph nodes to answer key questions: where do they hide, how can we identify them, what is their contribution to the lymph node reservoir burden, and are they truly able to support productive viral replication? We found that macrophages residing within lymph node germinal centers, identified by CD68 expression, contained HIV DNA, RNA, and Gagp24 protein. Moreover, using high resolution microscopy, we were able to distinguish between productively infected macrophages from those that engulfed T cells. By unveiling these unique features of macrophage reservoirs, our research paves the way for the design of targeted therapy aimed at eliminating these reservoirs, towards an HIV cure.

immunology↗

bioRxiv2020

CXCR5 gene expression in human lymph node CD8+ T cells is regulated by DNA methylation and nucleosomal occupancy

CD8+ T cells play an important role in viral and tumour control. However, in human lymph nodes (LNs), only a small subset of CD8+ T cells called follicular CD8+ T cells (fCD8s) expresses CXCR5, the chemokine receptor required for cell migration into B cell follicles, thought to promote immune evasion. Here we obtained LNs from HIV infected persons to investigate regulation of CXCR5 expression in lymphoid CD8+ T cells, and compared this to the more abundant CXCR5 expressing T follicular CD4+ helper cells (GCTfh). Our results show that DNA hypermethylation and closed chromatin at the transcriptional start site (TSS) prevent CXCR5 expression in non-fCD8s. We also found that greater nucleosomal density at the CXCR5 TSS could be responsible for reduced CXCR5 expression in fCD8s relative to GCTfh. Together, these data provide critical insights into both the underlying molecular mechanisms that repress CXCR5 expression in non-fCD8s and the plausible mechanism responsible for the low CXCR5 expression in fCD8s, with implications for HIV cure strategies. Author SummaryA paucity of CD8+ T cells that express CXCR5, the chemokine receptor critical for entering the B cell follicles of secondary lymphoid tissues have recently been described. Animal studies have revealed transcriptional networks that govern the expression of CXCR5 in CD8+ T cells. However, it is not known if similar or additional networks regulate the expression of CXCR5 in human CD8+ T cells. In this study, we demonstrated that DNA methylation coupled with chromatin compaction at the transcriptional start site (TSS) of CXCR5 gene prevent the expression CXCR5 in human CD8+ T cells. In addition, we observed greater nucleosomal occupancy at the TSS of CXCR5 gene which could impact expression levels of CXCR5 in human CXCR5+CD8+ T cells. This study revealed multitiered epigenetic mechanisms that repress CXCR5 expression in human CD8+ T cells, with implications for HIV cure strategy or eradication of B cell-derived tumours.

genetics↗

bioRxiv2019

Integrated Single-Cell Analysis of Multicellular Immune Dynamics during Hyper-Acute HIV-1 Infection

Cellular immunity is critical for controlling intracellular pathogens, but the dynamics and cooperativity of the evolving host response to infection are not well defined. Here, we apply single-cell RNA-sequencing to longitudinally profile pre- and immediately post-HIV infection peripheral immune responses of multiple cell types in four untreated individuals. Onset of viremia induces a strong transcriptional interferon response integrated across most cell types, with subsequent pro-inflammatory T cell differentiation, monocyte MHC-II upregulation, and cytolytic killing. With longitudinal sampling, we nominate key intra- and extracellular drivers that induce these programs, and assign their multi-cellular targets, temporal ordering, and duration in acute infection. Two individuals studied developed spontaneous viral control, associated with initial elevated frequencies of proliferating cytotoxic cells, inclusive of a previously unappreciated proliferating natural killer (NK) cell subset. Our study presents a unified framework for characterizing immune evolution during a persistent human viral infection at single-cell resolution, and highlights programs that may drive response coordination and influence clinical trajectory.

immunology↗

bioRxiv2018

Frequencies of circulating Th1-biased T follicular helper cells in acute HIV-1 infection correlate with the development of HIV-specific antibody responses and lower set point viral load

Despite decades of focused research, the field has yet to develop a prophylactic vaccine. In the RV144 vaccine trial, non-neutralizing antibody responses were identified as a correlate for prevention of HIV acquisition. However, factors that predict the development of such antibodies are not fully elucidated. We sought to define the contribution of circulating T follicular helper (cTfh) cell subsets to the development of non-neutralizing antibodies in HIV-1 clade C infection. Study participants were recruited from an acute HIV-1 clade C infection cohort. Plasma anti-gp41, -gp120, -p24 and -p17 antibodies were screened using a customized multivariate Luminex assay. Phenotypic and functional characterization of cTfh were performed using HLA class II tetramers and intracellular cytokine staining. In this study, we found that acute HIV-1 clade C infection skewed differentiation of functional cTfh subsets towards increased Tfh1 (p=0.02) and Tfh2 (p<0.0001) subsets, with a concomitant decrease in overall Tfh1-17 (that shares both Tfh1 and Tfh17 properties) (p=0.01) and Tfh17 subsets (p<0.0001) compared to HIV negative subjects. Interestingly, the frequencies of Tfh1 during acute infection (5.0-8.0 weeks post-infection) correlated negatively with set point viral load (p=0.03, r=-60) and were predictive of p24-specific plasma IgG titers at one year of infection (p=0.003, r=0.85). Taken together, our results suggest that circulating the Tfh1 subset plays an important role in the development of anti-HIV antibody responses and contributes to HIV suppression during acute HIV-1 infection. These results have implications for vaccine studies aimed at inducing long lasting anti-HIV antibody responses.\n\nImportanceThe HIV epidemic in southern Africa accounts for almost half of the global HIV burden with HIV-1 clade C being the predominant strain. It is therefore important to define immune correlates of clade C HIV control that might have implications for vaccine design in this region. T follicular helper (Tfh) cells are critical for the development of HIV-specific antibody responses and could play a role in viral control. Here we showed that the early induction of circulating Tfh1 cells during acute infection correlated positively with the magnitude of p24-specific IgG and was associated with lower set point viral load. This study highlights a key Tfh cell subset that could limit HIV replication by enhancing antibody generation. This study underscores the importance of circulating Tfh cells in promoting non-neutralizing antibodies during HIV-1 infection.

immunology↗