Abstract The overall goal of our research is to reduce HIV-related health inequities among Latinx immigrant populations. We propose to determine the effectiveness of Hermanos de Luna y Sol (HLS), a community-based, group intervention delivered in Spanish, designed to reduce HIV sexual risk among Latinx immigrants who identify as gay/bisexual men or men who have sex with men (GBMSM). The study is designed as a quasi-experimental, community control, with Oakland, CA as the intervention group and Chicago, IL as the control. Assessments will be conducted at -3 and 0 mos., and follow-ups at 3, 6, and 12 mos. Participants (N=360; n=180 per city) will be recruited using Time-location sampling (a venue-based sampling designed to reduce sample bias). HLS, the intervention at the heart of this study, offers several novel features: it focuses on immigrant, Spanish- speaking populations; it addresses racism and homophobia as factors shaping HIV risk; and uses a community-based approach centered on community involvement (e.g., civic participation, volunteering) as a means to foster sexual health and community building. The study will help identify effective interventions to prevent HIV among Latinx immigrant GBMSM, a marginalized population for which HIV preventive interventions are severely lacking. This study capitalizes on an existing intervention designed for Spanish speaking populations; is the first of its kind to rigorously test the intervention’s effectiveness among Latinx immigrant GBMSM using a community control design. The study applies the best possible scientific approach to obtain estimates of intervention effectiveness. If successful, the intervention would be relatively easy to disseminate via community organizations and the Centers for Disease Control and Prevention. Ultimately, the study will help move forward efforts to reduce racial/ethnic health inequities, one of the nation’s major public health priorities. This proposal is directly relevant to the RFA on Transformative Research to Address Health Disparities and Advance Health Equity at Minority serving Institutions. The project is led by SFSU – a Hispanic Serving Institution-- in collaboration with two Latinx community-based organizations: La Familia and Chicago Queer Latinx Collaborative. We are a multidisciplinary research team with the depth and breadth of experience on HIV prevention with Latinx and GBMSM communities to successfully conduct the study. All senior personnel are of Latin American descent, fully bilingual (Spanish and English), and three of them are women. The proposed study is strongly aligned with NIH UNITED Initiative of fostering racial equity and inclusion in biomedical research and is responsive to priority areas of multiple NIH institutes and centers, such NIMHD, NIMH, and the Office of AIDS Research.

Public Health Relevance Statement Latinx gay/bisexual men and men who have sex with men experience disproportionately high HIV prevalence, a burden intensified among immigrant Latinx populations. Yet, scientifically tested HIV prevention interventions for those populations remain scarce. This proposal strongly aligns with the goals of the RFA on Transformative Research to Address Health Disparities and Advance Health Equity at Minority serving Institutions; and it directly addresses NIH’s UNITED Initiative of fostering racial equity and inclusion in biomedical research. We propose to determine the effectiveness of a community-based HIV prevention intervention (Hermanos de Luna y Sol) to reduce HIV sexual risk behavior among Latinx immigrant men who identify as gay/bisexual or men who have sex with men. The intervention was developed in Spanish with input from community members. If effective, it could be relatively easy to disseminate and, hence, improve the efforts to reduce HIV incidence and related inequities across racial/ethnic and sexual minority groups.