Card, C. | bioRxiv Science

bioRxiv2025

Antigen stimulation drives clonal expansion of latent CD4+ T cells using a full-length HIV latency reporter

HIV persistence despite years of ART suppression poses a major barrier to cure. Using a full-length latency reporter to generate HIV-infected, transcriptionally silent CD4+ T cells in vitro, we show that cognate DC:T cell interactions drive clonal expansion of latent T cells in an antigen dependent manner and that a pro-survival state within proliferating cells is reinforced through IL-7 signaling. Interestingly, we describe a dominant role for CD28 co-stimulation in regulating robust latent T cell proliferation which was partially reversed by PD-1 blockade. Our studies show that a gradual reduction in antigenic stimulation was sufficient to induce proliferative responses without measurable proviral reactivation. Thus, the magnitude of TCR/co-stimulatory signals during cognate APC:T cell interactions are key regulators of the underlying proliferative and survival programs maintaining the latent reservoir under ART suppression. Significance StatementViral replication can be effectively suppressed by antiretroviral therapy (ART) but is not curative due to persistence of latent virus in a stable reservoir in resting CD4+ T cells. We show that antigen recognition through cell-cell interactions is an important driver of latent T cell proliferation, and that modulating TCR stimulatory signaling independently regulates proliferative, survival and proviral reactivation potential in infected T cells. Our observations show that latent T cells retain their ability to engage other immune cells to support their long-term survival under ART suppression, similar to uninfected T cells. These characteristics of latent T cell pools represent an additional hurdle to eradicating the reservoir.

immunology↗

bioRxiv2020

Endothelial cells promote productive HIV infection of resting CD4+ T cells by an integrin-mediated cell adhesion-dependent mechanism

Resting CD4+ T cells do not support HIV replication in vitro, yet are primary targets of early HIV infection events in vivo. There is an established role for factors in the tissue microenvironment, including endothelial cells, in enhancing the susceptibility of resting CD4+ T cells to productive infection, yet the mechanisms behind this are not well understood. Endothelial cells facilitate immune cell trafficking throughout the body. Cell adhesion molecules expressed by endothelial cells engage integrins on activated and memory T cells and mediate transmigration into inflamed tissues. These cell trafficking pathways have overlapping roles in facilitating HIV replication but their relevance to endothelial cell-mediated enhancement of HIV susceptibility in resting CD4+ T cells has not previously been examined. We used flow cytometry to characterize the phenotype resting CD4+ T cells that became productively infected when exposed to HIV in the presence of endothelial cells. Infected CD4+ T cells were primarily central memory cells enriched for high expression of the integrins LFA-1 and VLA-4 and had variable expression of α4β7, CCR6 and CD69. Blocking LFA-1 and VLA-4 on resting CD4+ T cells abrogated infection in the co-culture model, indicating that engagement of these integrins is essential for enhancement of resting CD4+ T cell HIV susceptibility by endothelial cells. Cellular activation of CD4+ T cells did not appear to be the primary mechanism enabling HIV replication since only a small proportion of resting CD4+ T cells became activated over the course of the co-culture and fewer than half of infected cells had an activated phenotype. The demonstration that endothelial cells enhance the cellular HIV susceptibility of resting memory CD4+ T cells through cell trafficking pathways engaged during the transmigration of memory T cells into inflamed tissues highlights the physiological relevance of these findings for HIV acquisition and opportunities for intervention.Author Summary HIV acquisition risk per coital act is relatively low, but this risk is amplified by various behavioural and biological variables. Genital inflammation is a key biological variable associated with increased risk of HIV acquisition, but the mechanisms driving this are incompletely understood. Inflammation is a complex process, with direct effects on HIV target cells as well as the tissue in which those cells reside and encounter virus. The first HIV target cells in vivo are resting memory CD4+ T cells, yet these cells are do not support viral replication when purified and exposed to HIV in vitro. Rather, signals from tissue microenvironment are required to support viral replication within resting memory CD4+ T cells. Endothelial cells line tissue vasculature and guide immune cell trafficking to inflamed tissues through engagement of integrins by endothelial-expressed cell adhesion molecules. We show here that these same cell-trafficking pathways enable endothelial cells to promote HIV replication within resting memory CD4+ T cells in vitro. Blockade of integrins on resting memory CD4+ T cells prevented endothelial enhancement of HIV infection. These findings further our understanding of the determinants of cellular susceptibility to HIV infection and offer a potential mechanism by which inflammation promotes HIV acquisition.View Full Text

immunology↗