PROJECT SUMMARY/ABSTRACT Hispanic/Latino sexual minority men (HLSMM) account for 24% of new HIV diagnoses in the U.S. and are understudied in HIV prevention research. Although methamphetamine use is one of the most significant drivers of HIV infections among sexual minority men and is highly stigmatized, little is known about how intersecting drug use stigma and sexual minority stigma impact methamphetamine use and HIV vulnerability among HLSMM. As a result, HIV prevention interventions may not be equipped to address the converging impact of intersecting stigma on social, psychological, and biological processes that contribute to HIV risk in this critical population. This Mentored Research Scientist Development Award (K01) will support the exceptional candidate during his upcoming years of research and training and support his transition toward research independence. The candidate’s proposed research aims to test a social-ecological model of structural- and network-level manifestations of intersecting drug use stigma and sexual minority stigma. This innovative research incorporates social, psychological, and biological processes influencing drug use and HIV vulnerability among HLSMM. To accomplish these goals, the candidate requires training and expert mentorship in three critical areas: 1) network science and network determinants of health, 2) inflammatory biomarkers of HIV vulnerability, and 3) designing and testing multilevel intersectional stigma interventions. In addition to mentorship from leading experts in HIV prevention research, training will be accomplished through coursework, training institutes, working groups, scientific productivity, and career development activities. Training in these areas will be applied through several mentored research projects. The specific aims of the proposed research are to 1) Determine the independent and intersecting impact of structural drug use stigma and structural sexual minority stigma on methamphetamine use and HIV behavioral vulnerability among HIV-negative HLSMM in the U.S., 2) Assess the network-level effects of independent and intersecting drug use stigma and sexual minority stigma on methamphetamine use severity and HIV behavioral vulnerability via emotion dysregulation and social support in HIV-negative HLSMM who use methamphetamine; and 3) Examine the network-level effects of independent and intersecting drug use stigma and sexual minority stigma on rectal inflammatory biomarkers (rectal cytokines) that may be linked to enhanced HIV biological vulnerability. Aim 1 will be accomplished by analyzing data from five waves (2017-2022) of a cohort study of HLSMM. Aims 2 and 3 will be achieved by conducting a longitudinal pilot study of 200 HLSMM who use methamphetamine. This high-impact research will fill a critical gap in HIV prevention among HLSMM and inform the development of a multilevel intervention for HLSMM who use methamphetamine, accelerating the progress toward ending the HIV epidemic am...