Determining the Role of TGF-β Signaling in Maintaining HIV Latency in the Gut
Gastrointestinal (GI) tract tissues harbor a large pool of cells latently infected with HIV. However, their exact identity and the mechanisms of latency are unknown. Transforming growth factor (TGF)-β has several functions in gut homeostasis, including the formation and maintenance of tissue-resident memory (TRM) CD8 T cells. Signaling by TGF-β induces expression of CD103, an αE integrin that binds to epithelial E-cadherin. CD4 TRMs also exist, but only a small proportion express CD103, and the role of TGF-β in their formation, function, and maintenance is unknown. We will test the hypothesis that a majority of latently infected cells in the gut are CD103+ CD4 TRMs and that continuous TGF-β signaling in these cells promotes the establishment and long-term maintenance of latency. In preliminary studies, we optimized immunohistochemical assays and flow-cytometry panels to detect and quantitate CD4 TRM populations from human rectal and ileal biopsies. We propose to purify these cell populations from HIV-positive participants in the UCSF SCOPE cohort and compare HIV DNA/RNA levels in TRMs that do or do not express CD103. We will also analyze archived rectal biopsies to assess the effects of antiretroviral drugs on the size of these populations. In addition, we will explore potential mechanisms by which TGF-β-mediated signaling helps maintain latency in the primary sorted populations. Finally, we will study the latency-promoting potential of TGF-β in the J-Lat model of latency. Gut tissues will be analyzed during the first 5–7 months of the study, and the in vitro studies will be done within the following 2–3 months. These studies will help to reveal the identity of latently infected cells in the gut and shed light on the mechanism by which latency is maintained in this critical sanctuary.