Patterns in Sexual Behavior and STI Risk among MSM using ART to Treat or Prevent HIV

Abstract

Background: Men who have sex with men (MSM) face a disproportionately high burden of HIV. Recent advances in biomedical prevention of HIV such as treatment as prevention (TasP) and pre-exposure prophylaxis (PrEP) promise to improve the reach of HIV prevention efforts in MSM communities, but questions remain regarding the impact of these prevention methods on sexual behavior and STI risk. This dissertation investigated the impact of antiretroviral therapy (ART) on sexual behavior and STI risk among newly HIV-infected MSM and transgender women (TW) in Lima, Peru and among PrEP-using MSM in Seattle, WA. Methods: This dissertation used data from MSM and TW participating in an expanded TasP study in Lima, Peru, to answer the question of whether ART use is associated with differences in sexual behavior and STI risk. In Aim 1, sexual behavior and STI incidence were compared between participants who had been randomized to receive ART either immediately or 24 weeks after diagnosis of early HIV infection. Two analyses were completed to answer the question of whether PrEP use is associated with changes in sexual behavior or increased risk of STIs. In Aim 2, data from the Public Health, Seattle & King County (PHSKC) STD Clinic was used to measure changes in sexual behavior after PrEP initiation. In Aim 3, data from the same clinic was used to compare STI incidence and time to first symptomatic STI among PrEP users to a propensity score-matched comparison group of non-users. Results: In Aim 1, we found that while sexual risk behavior decreased in both study arms following HIV diagnosis, there was no difference in sexual behavior between the study groups. Incidence of bacterial STIs was high in both study arms, and participants randomized to receive ART after 24 weeks had higher incidence of chlamydia, but no difference in gonorrhea or syphilis incidence. In Aim 2, we found that 12 months after initiation of PrEP, MSM were more likely to report never using condoms and less likely to report unknown HIV-status partners compared to the PrEP initiation visit. There was no change in the number of sexual partners or reporting HIV-positive or HIV-negative partners. In Aim 3, we found that MSM using PrEP had higher incidence of chlamydia, gonorrhea, and early syphilis and faster time to first symptomatic STI compared to propensity score-matched PrEP non-users. Conclusions: We observed decreased condom use and increased risk of bacterial STIs among HIV-negative PrEP users, no differences in sexual behavior associated with ART use among HIV-positive individuals, and overall high STI rates in both study populations. This work highlights the need for continued monitoring of sexual behavior in the changing context of biomedical HIV prevention and emphasizes the continued need for STI prevention, screening, and clinical care among high-risk MSM populations.