Control of HIV infection in individuals treated with highly active antiretroviral therapy (HAART) is the most effective means for reducing mortality and morbidity of chronically infected individuals. We are now challenged with the goal of functionally curing individuals that have HAART suppressed HIV. The HIV reservoir in HAART treated individuals'remains elusive to our current therapeutic strategies so new strategies are now focused on exploiting the inherent potential of HIV-specific CD8 T cells to target and kill infected cells in order to fully resolve the infection or at least maintain control without the useof HAART. In order to utilize the host repertoire of HIV-specific CD8 T cells to achieve the goal of curing HIV infected individuals, we have to develop strategies that can stably rejuvenate nonfunctional HIV-specific CD8 T cells so that they re-acquire and retain antiviral functions after expansion. To achieve this goal, we have developed a research program that focuses on understanding the mechanism for acquisition and maintenance of acquired gene expression programs in exhausted HIV-specific CD8 T cells. The following aims are designed to identify genes that are targeted for stable epigenetic programming, develop methods for modifying these programs to erase the transcriptional memory of the HIV-specific CD8 T cell, and reactivate the cells in way that facilitates an effective antiviral response during encounter with n HIV-antigen presenting cell.
The specific aims of this proposal are:
Aim 1. To determine if gene expression program preservation in exhausted HIV-specific CD8 T cells is coupled to maintenance of DNA methylation at transcriptional regulatory regions. a) To identify T-cell exhaustion gene expression programs that are epigenetically preserved following HAART mediated viral control. b) To identify epigenetically poised transcriptional programs in HIV-specific CD8 T cells from HAART treated donors.
Aim 2. To determine if HIV-specific CD8 T cells generated from acute antigen exposure retain a de novo DNA methylation capacity. a) To determine when HIV-specific CD8 T cells lose the ability to perform DNMT3a mediated de novo methylation. b) To determine if HIV-specific CD8 T cells from elite controllers acquire an epigenetic fingerprint similar to HIV-specific CD8 T cells generated from vaccination.
Aim 3. To determine if modulation of DNA methylation reprogramming of HIV-specific CD8 T cells by Il- 15 and other strategies rescues HIV specific CD8 function and killing. a) To determine if IL-15 mediated differentiation of exhausted CD8 T cells results in short and long term heritable changes in gene regulations. b) To determine if inhibition of PD-1 engagement enhances DNA methylation re-programming of HIV-specific CD8 T cells. c) To determine if overexpression of the de novo DNA methyltransferase 3a facilitates DNA methylation reprogramming of exhausted HIV-specific CD8 T cells.
Immune dysfunction is a major barrier to eradicating HIV and curing infected individuals. Since the generation of an effective antiviral immune response against HIV is the goal of current vaccine and therapeutic strategies, it is critical to understand the mechanism(s) that mediate the progressive decline in virus-specific T cell responses during chronic HIV infection.