Immune Microenvironments That Impact HIV Persistence and Expression During ART

ABSTRACT A formidable barrier to a cure for HIV-1 infection is the existence of latently infected cells that sporadically activate HIV transcription during antiretroviral therapy (ART) and reignite widespread virus replication upon cessation of ART. Viral RNA expressing (vRNA+) cells are detected at low frequencies in secondary lymphoid

tissues (SLT) of people with HIV (PWH) on ART, constitute the major HIV RNA reservoir in the human body, and are likely the principal source of rebound viremia when ART is stopped. Little is known about the microenvironment of vRNA+ cells in SLT of PWH during ART. In lymph nodes and spleen from PWH on

prolonged ART the majority of vRNA+ cells reside outside of B cell follicles and only a minority are TFH. We observed that vRNA+ cells are preferentially located adjacent to B cells not only in follicular, but also in extrafollicular regions (EF) of SLT in PWH and SIV-infected rhesus macaques on ART; frequencies of B cells in

EF of SLT correlate with frequencies of vRNA+ cells. In an ex vivo tonsil model of HIV infection, germinal center B cells (GCB) upregulate HIV expression in TFH. Gene expression analysis revealed GCB induce expression of multiple cytokines including IL-10, pro-survival molecules, and markers of immune activation.

Further studies revealed that upregulation of HIV expression is not confined to GCB, but that multiple subsets of tonsil B cells upregulate HIV replication in both TFH and non-TFH CD4+ T cells. IL-10 was shown to augment survival of HIV-expressing cells in the tonsil model, and we observed that the majority of vRNA+ cells

in spleen from two PWH expressed IL-10. We hypothesize that B cells are major drivers of vRNA expression in CD4+ T cells in secondary lymphoid tissues of PWH on ART through induction of pro- survival factors, including IL-10, as well as immune activation. In Aim 1, we will determine the location, phenotype, and microenvironment of vRNA+ cells in spleen, lymph nodes, and ileum of PWH on prolonged

ART using state-of-the-art immunostaining techniques to assess the hypothesis that vRNA+ cells preferentially exist adjacent to B cells and express pro-survival and activation markers. In Aim 2, we will evaluate the impact of SLT B cells on HIV expression in non-TFH CD4+ T cells, and evaluate the role of IL-10 and immune

activation using HIV GFP reporter viruses in SLT from people without HIV infection, as well as spleen and lymph node tissues from people with HIV infection on prolonged ART. In Aim 3 we will determine whether depletion of B cells leads to reductions in numbers of vRNA+ cells in SLT during ART using SIV-infected

rhesus macaques. Collectively, these studies will provide a wealth of new information on the cells that express HIV in SLT and factors within their microenvironment that promote or impair HIV expression during ART. This knowledge could be used to develop strategies to reverse or alternatively enhance viral latency in vivo to

achieve a functional remission of HIV.