Understand the role of CARD8 inflammasome in HIV-1 infection

Abstract Despite antiretroviral therapy (ART), HIV-1 infection is not curable due to the presence of viral latent reservoirs primarily in long-lived resting memory CD4+ T cells. The viral latent reservoirs are the major barrier to HIV-1 eradication. The “shock and kill” strategy for HIV-1 eradication involves the use of latency-reversing agents (LRAs) to induce viral gene expression, which renders the infected cells susceptible to viral cytopathic effects or immune clearance. However, in ART-treated patients, the latent HIV-1 resides in cells is resistant to viral- or immune-mediated apoptotic cell death and often carries mutations to escape recognition by T cells or antibodies. Therefore, novel approaches to target immutable components of the virus such as essential viral protein functions are needed. Inflammasome is a critical molecular complex that mediates inflammation and pyroptotic cell death in response to microbial or danger signals. In humans, the physiologic ligand(s) for the CARD8 inflammasome remains unknown. Our studies demonstrate that HIV-1 protease degrades the CARD8 N-terminal domain and releases the C-terminus for inflammasome activation. In HIV-1-infected cells, the viral protease remains inactive as a subunit of viral Gag-Pol polyprotein. After virus budding, it is activated through Gag-Pol dimerization. We show that premature activation of intracellular HIV-1 protease by non-nucleoside reverse transcriptase inhibitors (NNRTI) triggers CARD8 sensing and killing of HIV-infected macrophages and CD4+ T cells. All subtypes of HIV-1 can be sensed by CARD8 despite substantial viral diversity. Our finding suggests that targeted activation of CARD8 inflammasome is a promising strategy to eliminate latent HIV-1 reservoirs. In this proposed study, we will: 1) perform ex vivo assessment and optimization of the CARD8-based “shock and kill strategy” for clearing latent HIV-1 in patient CD4+ T cells; 2) understand the molecular mechanisms of HIV-1 protease- mediated CARD8 inflammasome activation; 3) test CARD8-based “shock and kill” strategy in humanized mouse model of HIV-1 latency. Our proposed study will advance the understanding of the physiological mechanisms of CARD8 inflammasome activation and its role in HIV-1 infection, which will provide critical implications to HIV cure research.