Restoring HLA-I Expression to Enhance CD8 T Cell-Mediated Clearance of HIV-Infected Cells

About This Grant

PROJECT ABSTRACT Human immunodeficiency virus-1 (HIV-1) can be controlled with antiretroviral therapy (ART), but a cure remains elusive due to the persistence of latently infected reservoirs. These reservoirs remain transcriptionally silent, allowing the virus to evade immune clearance and rebound when therapy is interrupted. One proposed strategy to eliminate the latent reservoir is the shock and kill approach, which utilizes latency-reversing agents (LRAs) to reactivate viral gene expression, thereby enabling clearance by cytotoxic CD8 T cells. However, HIV accessory proteins such as Nef and Vpu downregulate HLA-I on infected cells, preventing recognition by CD8 T cells even after reactivation. IL-15 is a particular LRA of interest, along with its superagonist N-803, that can expand effector lymphocytes and enhance their cytolytic activity; however, its ability to rescue HLA-I expression on HIV-infected cells remains uninvestigated. IL-15 signals through the JAK/STAT pathway, which is negatively regulated by the non-receptor tyrosine phosphatases PTPN1 and PTPN2. Small-molecule inhibitors of these phosphatases, including 3-Hydroxy-1,2,3- benzotriazin-4(3H)-one (HODHBt) and ABBV-CLS-484 (AC-484), enhance STAT signaling, promote viral reactivation, and increase HLA-I expression on infected CD4 T cells. Preliminary data demonstrate that IL-15 can restore HLA-I expression on HIV-infected cells, and this effect is enhanced with PTPN1/2 inhibition. However, viral strains belonging to subtypes AD and D exert resistance to IL-15-mediated HLA-I rescue on HIV-infected CD4 T cells, suggesting subtype-specific mechanisms. In Aim 1, I will test whether IL-15-mediated HLA-A, -B, and -C rescue is possible when CD4 T cells are infected with viral strains isolated from the latent reservoir of people with HIV across a variety of subtypes and then assess if rescue is associated with increased recognition and killing of infected cells by HIV-specific CD8 T cells. In Aim 2, I will dissect the mechanism by which viral strains belonging to subtypes AD and D promote resistance to IL-15 signaling and whether this is associated with the viral protein Nef, the protein responsible for HLA-I downregulation. By uncovering how the IL- 15/STAT/PTPN1/2 axis regulates HLA-I expression and CD8 T cell recognition of HIV-infected CD4 T cells, this project will inform the design of cure strategies that enhance immune clearance of latent reservoirs. Completion of these studies will also provide rigorous training in immunology, virology, and translational therapeutics to prepare me for a career as an independent HIV investigator.