Inactivation of the ISR/ATF4 signaling pathway stabilizes HIV reservoirs

About This Grant

PROJECT SUMMARY Stable HIV reservoirs remain a significant challenge for the eradication of HIV-1 (HIV). While several anti- HIV latency strategies have been proposed to control HIV reservoirs, few have proven effective in reducing the size of the HIV reservoir in clinical settings. This suggests that our current understanding of how HIV achieves its persistent infection is limited and underscores the need for the development of alternative innovative tools for HIV cure. Recently, we and others characterized a unique integrated stress response (ISR)/ATF4 signaling pathway that is essential for HIV transcription and early seeding of HIV. Conversely, when ATF4 is knocked down, HIV transcription is inhibited. We further defined ATF4 as a new transcription factor of HIV, exploited by HIV for its own transcription after the recruitment of ATF4 to the ATF/CREB consensus site at the 5’ HIV long-terminal repeat. ATF4 induction leads to HIV activation from latency, indicating that ISR/ATF4 signaling activation promotes HIV transcription while the suppression of ISR signaling is associated with the establishment of HIV latency. Of note, prolonged activation of ISR/ATF4 signaling also induces cell death, mediated by ATF4 binding to the promoter of the CHOP gene, an essential protein driving apoptosis during persistent ISR/ATF4 activation. In a primary CD4+ T cell model of latency, prolonged ISR/ATF4 signaling activation disrupts latent HIV and selectively induces apoptosis in HIV+ CD4+ T cells, without affecting bystander HIV-negative CD4+ T cells. Notably, using viral outgrowth assays, we discovered that prolonged ISR/ATF4 signaling activation reduces replication-competent HIV by up to 2,300-fold in resting CD4+ T cells isolated from people with HIV receiving suppressive antiretroviral therapy (ART). Therefore, we hypothesize that the suppression of ISR/ATF4 signaling is essential for HIV persistence. This will be tested through three specific aims: Aim 1: Investigate how activation of the ISR/ATF4 signaling pathway eliminates HIV-latently infected T cells and brain microglia. Aim 2: Elucidate the unique mechanisms by which ISR/ATF4 signaling controls the stable HIV reservoir for the establishment of HIV latency. Aim 3: Determine the effectiveness of activating ISR/ATF4 signaling in eliminating HIV reservoirs in the hu-BLT mouse model of HIV latency in vivo.