Determining and Overcoming barriers in translating HIV-1 protease mediated activation of the CARD8 inflammasome to HIV cure research

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Project Summary/Abstract Human immunodeficiency virus (HIV) has maintained its status as a global epidemic since the 1980’s and 38 million people are living with HIV globally. While new HIV infections have been decreasing and antiretroviral therapies (ART) can maintain viral suppression in PLWH, there is no effective cure for elimination of the virus from the body. HIV is adept in escaping the normal immune response through the seeding of viral latent reservoirs primarily in quiescent CD4+ T cells. Upon halting ART these latent reservoirs are capable of spreading infection. In addition to this hurdle, HIV is able to escape the adaptive immune response due to the reliance upon recognition of the highly mutable HIV envelope. Therefore, it is critical to develop a cure strategy that can sense a highly immutable aspect of HIV such as those with essential enzymatic activity. Our previous work has shown that HIV-1 protease is one such protein that can be a target for a cure strategy. The pattern recognition receptor caspase recruitment domain-contain protein 8 (CARD8) is able to sense HIV-1 protease and activate pyroptosis, an inflammatory version of programmed cell death. This strategy requires the premature intracellular activation of the protease which can be achieved through the use of non-nucleoside reverse transcriptase inhibitors (NNRTIs) Efavirenz or Rilpivirine. Upon addition of NNRTIs to HIV infected cells, CARD8 activates the inflammasome and induces pyroptosis. Additionally, my previous work showed that inhibition of the negative regulator of dipeptidyl peptidase 9 (DPP9) is able to enhance NNRTI-mediated pyroptosis. However, during the discovery of this method for viral reservoir clearance, we found significant variation in the activation of the CARD8 inflammasome that could be ascribed to both the virus and the host. In fact, pyroptosis efficiency varied across viral strains, CARD8 isoforms, cell types, CD4+ T cell activation state, and CD4+ T cell donors. Therefore, the central hypothesis of this study is that there are genetic variants in both the virus and the host that can confer resistance to NNRTI induced HIV-1 protease activation of the CARD8 inflammasome and which may be overcome by CARD8 inflammasome sensitization through DPP9 inhibition. I will first test clinical and in vivo applications of CARD8 enhancement through DPP9 inhibition in Aim 1 by testing clinical isolates and enhancement in a humanized mouse model. Experiments in Aim 2 will identify the critical viral components needed for CARD8 sensing of HIV-1 protease activity to inform a genome wide association study of HIV-1 to identify variants responsible for pyroptosis variation. Aim 3 will elucidate host factors that may cause variation in protease sensing or inflammasome activation. This will be ascertained through the study of isoform expression in the key cellular targets for HIV-1 infection, through the identification of donors with varying killing efficiency, and through potentially identifying novel negative regulators of CARD8. Collectively, these studies will describe the potential efficacy of NNRTI induced CARD8 inflammasome activation as a viral reservoir reduction strategy and is the first step in translating this work to the clinic.