Investigating the sexual partnerships of transgender women in Lima, Peru to improve targeted HIV interventions

Background: Transgender women (TW) have a high burden of HIV but remain understudied in HIV research. One poorly understood aspect of HIV risk among TW is the source of HIV infection in epidemics driven by sexual transmission. TW primarily report sexual partnerships with hetero- or bisexual cisgender men, populations that generally have a low HIV prevalence and therefore limited potential to transmit. This dissertation investigated the characteristics and behavior of partners of TW (PTW), as well as the sexual and HIV transmission networks of TW, to determine if sexual networks of TW overlap with those of men who have sex with men (MSM) and if HIV is transmitted between the populations. Methods: Three distinct methods were used to answer these questions. Previously collected data from a study conducted among MSM and TW in Lima were used to compare partnership behavior among TW, PTW, and MSM, focusing specifically on sexual concurrency (Aim 1). A modified respondent-driven sampling study was conducted in Lima to collect data from a large sample of TW and their sexual partners (Aim 2). Finally, HIV sequences were used to complete a molecular epidemiology study examining overlap in HIV transmission clusters of TW and MSM (Aim 3). Results: In Aim 1, we found that PTW engage in risky partnership behavior, and have higher rates of concurrent partnerships than either MSM or TW. In Aim 2, we found that partners differed in identity and behavior from MSM, that only 7% of PTW reported male partners, and that those with male partners were more likely to identify as homosexual, sell sex, and engage in receptive condomless anal intercourse (CAI). These results suggested little overlap in TW and MSM sexual networks. In Aim 3, we found that HIV transmission networks of MSM and TW do overlap, with over 50% of TW who were found in molecular transmission clusters also clustering with MSM. Conclusions: PTW are a unique population, separate in sexual identity and sex-seeking behavior from MSM, and may engage in behavior that puts their partners at risk for HIV. A majority of PTW do not report male sexual partners, however, overlap in TW and MSM HIV transmission networks indicates that HIV is transmitted between the two sexual networks. This work highlights the need for further research to understand who is driving HIV transmission between TW and MSM, and if those with both male and TW partners are a distinct group that could be targeted by HIV prevention and treatment interventions.