Harnessing Stem-Like CD8 T Cells for Immunotherapies to Eradicate HIV Reservoirs

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Project Abstract Although combination antiretroviral therapy (cART) effectively suppresses human immunodeficiency virus (HIV) replication, it does not cure HIV infection and requires costly lifelong treatment. A major challenge for curing HIV infection is the long-lived latent HIV reservoir, which evades immune recognition and is responsible for viral rebound shortly after interruption of cART. Substantial research efforts have focused on eliminating latently infected cells through so-called “shock and kill” strategy, which reactivates latent HIV using latency- reversing agents (LRAs) to allow for the “kill” by cytolysis or immune-mediated clearance. Particularly, eradication of theHIV reservoir by anti-HIV T cells, which maintain antiviral immunity in patients as a “living” drug, presents a promising strategy to either fully resolve the infection or maintain long-term control without cART treatment. However, clearance of the HIV reservoir by T-cell based immunotherapy remains challenging because of 1) T- cell exhaustion, 2) the need of lifelong anti-HIV immunity to replace cART, 3) sanctuary sites like B cell follicles that exclude most HIV-specific CD8 T cells, and 4) unclear impact of LRAs, most of which target epigenetic pathways, on the function and differentiation of antiviral CD8 T cells in vivo. We and others have recently characterized a stem-like CD8 T cell subset in chronic lymphocytic choriomeningitis virus (LCMV), simian immunodeficiency virus (SIV), and HIV infections, as well as in mouse and human tumors. Compared to terminally exhausted CD8 T cells, stem-like CD8 T cells are less exhausted, mediate long-term immunity, and respond more potently after treatment of immunotherapies in animals and human. In chronic LCMV, SIV, and HIV infections, these cells express CXCR5, migrate to B cell follicles and kill infected T follicular helper cells, a major latent reservoir of HIV and SIV. In addition, frequency of these cells inversely correlates with viremia of SIV or HIV. Most recently, we showed that the single-cell transcriptomic and epigenetic profiles of stem-like CD8 T cells are distinct from other CD8 subsets generated after acute or chronic LCMV infection. In addition, we identified a transcriptional program involving transcription factor TOX that is essential for stem-like CD8 T cell differentiation and the long-term persistence of antiviral CD8 T cells during chronic viral infection. Here, I will determine the transcriptional and epigenetic programs of stem-like CD8 T cells required for optimal T-cell based immunotherapy against HIV. I will use animal models of chronic LCMV and SIV infections as well as samples from HIV patients, and employ cutting-edge technologies, including single-cell profiling of T-cell transcriptomes and epigenomes, CRISPR/Cas9 screening, and chimeric antigen receptor (CAR) T-cell therapy, to determine how “shock” by epigenetic modifying LRAs affects the program and antiviral immunity of stem-like CD8 T cells and whether transcriptional and epigenetic programs of stem-like CD8 T cells can be adopted to enhance the “kill” of the HIV reservoir by T-cell based immunotherapies. The results from this study will build the foundation for novel immunotherapies that achieve long-term remission from HIV infection without a need for cART.