PROJECT SUMMARY Although antiretroviral therapy (ART) is successful to block active replication of HIV, it does not completely eradicate the infection. HIV remains persistently infected and viral load can rebound after ART withdrawal, presenting a major obstacle for cure of HIV/AIDS. Investigation of host machineries that regulate HIV replication will help to improve the understanding of the mechanisms supporting HIV persistent infection. It will also provide new strategies to perturb host regulatory factors for eliminating residual HIV. This topic is especially relevant for the HIV-infected drug users, since drug abuse creates a profound impact on HIV infection, increasing the difficulty to manage HIV viral reservoirs. Our earlier effort includes the identification of novel host restriction factors specifically associated with a rare subset of HIV-infected individuals (<1%), termed elite controllers (ECs), who can maintain long-term control over HIV replication in the absence of ART. In a preliminary study, we performed RNA sequencing analysis and identified alternative splicing variants in cells from ECs, HIV-infected individuals undergoing suppressive ART, ART-naive HIV-infected individuals, and healthy controls. Differential gene expression patterns that are specific to ECs and may influence HIV resistance were identified, including alternative RNA splicing and exon usage variants of the CREM/ICER gene (cAMP-responsive element modulator/inducible cAMP early repressors). The knockout and knockdown of specific ICER exons resulted in significantly increased HIV infection. Overexpression of ICER isoforms decreased HIV infection. We also preliminarily showed that ICER isoforms are dysregulated in cocaine users. Together, these earlier studies confirm that CREM/ICER is a unique and novel host restriction factor suppressing HIV replication. We propose to comprehensively investigate their roles in regulating HIV infection, particularly for cocaine users. Furthermore, we also propose to identify other host gene isoforms that are dysregulated by cocaine use, which overall promote HIV persistent infection. Our central hypothesis is that certain host genes, including CREM/ICER, undergo profound RNA splicing to generate distinct isoforms in HIV-infected cocaine users and thus support HIV persistent infection in this population, which can be targeted to benefit HIV functional cure and mitigate HIV- induced inflammation. These studies include three related but independent aims. In Aim 1, we will determine correlations of CREM/ICER, HIV infection, inflammation, and cocaine use parameters. In Aim 2, we will investigate roles of CREM/ICER in mediating cocaine’s effect on HIV infection and inflammation. In Aim 3, we will identify novel gene isoforms in CD4+ T cells and monocytes dysregulated by cocaine use.