PROJECT SUMMARY Human immunodeficiency virus-1 (HIV-1) can be managed with anti-retroviral therapies (ART), but a cure remains elusive. This is due to a reservoir of latently infected cells, which are established early in infection. Elimination of these reservoirs is crucial for curing HIV. Several strategies to deplete the viral reservoirs are under investigation, such as the shock and kill strategy, which stimulates latently infected cells into active viral production using a latency reversal agent (LRA). This strategy allows cytotoxic lymphocytes, such as such as CD8T cells and natural killer (NK) cells, to kill HIV infected cells, to kill HIV-infected cells. Unfortunately, these cytotoxic cells are insufficient to clear the infection due to immune exhaustion as a result of chronic inflammation. As a result, current research is focusing on determining molecules and signaling pathways that can boost the cytotoxicity of effector lymphocytes. NK cells have been shown to be important in the control of SIV and HIV infection. However, chronic HIV- 1 infection leads to pathologic changes in NK cells, including defective functionality, and control of viremia with antiretrovirals has been reported to restore some but not all NK cells activity. Interleukin-15 (IL15) is a critical cytokine that trigger the Janus Kinase (JAK)/ signal transducer and activator of transcription (STAT) pathway signaling cascade, which plays a vital role in NK cell function. IL15 is particularly important for NK cell development, differentiation, maturation, cytotoxicity, cytokine production, proliferation, and survival. Nonreceptor tyrosine phosphatases (NTPs) protein tyrosine phosphatase nonreceptor type 1 (PTPN1) and type 2 (PTPN2) can downregulate STAT signaling pathway by dephosphorylating JAKs, STATs, and other proteins through their catalytic domain. Previous studies in the lab have shown that targeting PTPN1 and PTPN2 with the small molecule 3-Hydroxy-1,2,3-benzotriazin-4(3H)-one (HODHBt), enhances the effector function of CD8+ T and NK cells. In Aim 1, I will assess the role of both phosphatases controlling the activation and expression of cytotoxic proteins in NK cells by using a newly identified double inhibitor ABBV-CLS-484 (Osunprotafib or AC- 484) and by generating CRISPR-knockouts of PTPN1 and/or PTPN2. Using a primary HIV-infected CD4 T cell model, I will test the cytolytic activity of autologous NK cells either treated with AC-484 or CRISPR-knockouts against a viral HIV-1 panel including subtype A, B, C, and D. In Aim 2, I will use NSG-Tg (IL15) mice to evaluate HIV control in vivo. By understanding the critical importance of PTPN1 and PTPN2 phosphatases in NK cell cytolytic function, we can better develop more effective cure strategies against HIV. Completion of the proposed project will also help me to develop the necessary research and professional skills that are essential for my career as an HIV investigator.