Cocaine use has significant adverse effects on HIV progression, including increased HIV-1 viral load and decreased CD4+ count independent of antiretroviral treatment. However, the biological mechanisms by which cocaine use accelerates HIV progression remain unknown. We hypothesize that differential methylation and methylation associated genetic variants (methylation quantitative trait loci, mQTL) associated with cocaine use contribute to worsen HIV progression. This hypothesis is built upon preclinical and clinical evidence demonstrating that cocaine alters epigenetic programming and that epigenetic regulation is critical for HIV-1 integration and replication. Specifically, cocaine enhances HIV-1 replication and compromises immune function in part by dysregulating gene expression on HIV-1 entry co-receptors, enhancing HIV-1 cellular toxicity, and dysregulating interleukins in the host. Thus, cocaine associated epigenetic changes seem likely be involved in HIV-1 pathogenesis and host immune defense. To test our hypotheses, we will first conduct a large methylome-wide association study (MWAS) for cocaine use related HIV progression in African Americans (AAs) using a well-established longitudinal HIV cohort, the Veterans Aging Study Cohort (VACS). Next, we will identify mQTL variants for cocaine use-associated HIV progression in this same sample. Finally, we will conduct an association analysis of mQTL in AAs from the independent Urban Health Study Genetics Cohort (UHSGC) and extended association testing to European Americans in the two cohorts. As preliminary data, we completed a MWAS of 240 samples and found that 174 CpG sites were associated with baseline HIV viral load. Methylation of CpGs on tumor necrosis factor-? (TNF- ?) was negatively correlated with CD4+ count and positively correlated with viral load. TNF-? is known to be involved in cocaine?s enhancement on HIV-1 replication. The study will be led by a new investigator and conducted by a research team from Yale and RTI International with the diverse expertise. Our long-term goal is to understand the mechanisms underlying the adverse effects of cocaine use on HIV progression. This project addresses a high priority OAR AIDS research topic and is response to PAS-16-018. The proposed study leverages existing genetic/clinical datasets from two HIV cohorts, high density of CpG site coverage, and other funding resources to identify cocaine related epigenetic changes and genetic variants that predict longitudinal HIV outcomes. The findings will help prioritize genes for future research on their functions and roles in HIV progression under the influence of cocaine use. Given the relatively stable but reversible features of DNA methylation, the identified CpGs could represent new biomarkers for monitoring treatment response and yield novel molecular targets for developing new medications.