Carotid intima-media thickness (cIMT), a subclinical marker of atherosclerosis, is consistently higher among HIV-infected patients than in the HIV non-infected general population, even after adjusting for traditional risk factors. We hypothesize that HIV-related factors exacerbate the effects of genetic variations of genes encoding calcium (Ca2+) homeostasis directly or indirectly, which can accelerate and accentuate cIMT. However, to date this pathway has not been fully elucidated. Leading to this application, we have (a) identified SNPs in Ca2+ channels ryanodine receptors 2 and 3 (RYR2 and RYR3) that are significantly associated with increased common carotid artery (CCA) cIMT in the Fat Redistribution and Metabolic Change in HIV infection (FRAM) study, (b) replicated the association of the RYR3 variant in the Multicenter AIDS Cohort Study (MACS), (c) identified other variants in RYR3 associated with CCA cIMT in Women's Interagency HIV Study (WIHS), and d) identified variants in RYR3 that increased risk of atherosclerotic cardiovascular outcomes, specifically heart failure, among hypertensive patients on Ca2+ channel blockers compared to other antihypertensive drugs in the Genetics of Hypertension Associated Treatment (GenHAT) study. In this application we will test the innovative hypothesis related to the association of genes involved in regulation of Ca2+ homeostasis with pre-clinical atherosclerosis and systematically conduct a multi-stage study in three well-characterized HIV cohorts. In Aim 1- stage I, we will sequence 9 genes encoding Ca2+ channels and related proteins in subjects from the upper tail (1/3rd of each cohort) ranked CCA cIMT distribution (466 from WIHS and 312 from MACS) and the 778 individuals age and race frequency matched in the lower tail (1/3rd), to discover genetic variants and their association with cIMT. In Aim 1- stage II, we will genotype all significant variants from stage I (p<0.05 in all cohorts individuall or in meta-analysis) in the remaining 780 individuals in MACS and WIHS and confirm the association with quantitative cIMT in all 2,336 HIV-infected subjects and estimate effect size. In Aim 2, we will replicate these findings in 537 participants in an independent cohort, FRAM, which measured cIMT with a different method than in WIHS and MACS. In Aim 3, we will assess whether these replicated associations can also be validated for coronary artery calcium (CAC), an alternate measure for subclinical atherosclerosis in 938 participants in MACS and in Aim 4, we will examine if these variants influence cIMT in 1,014 HIV non-infected controls (309 in MACS, 477 in WIHS and 228 in FRAM). Our proposed genetic study will help elucidate Ca2+- dependent mechanisms of atherosclerosis in the context of HIV, which potentially could be used to develop novel genetic markers for screening and new drugs for atherosclerosis prevention in HIV patients. (End of Abstract)