Influence of sexual risk behaviour and STI co-infection dynamics on the evolution of HIV set point viral load in MSM

Abstract

HIV set-point viral load (SPVL) is an important predictor of HIV progression and transmission. Although it has been reported that anti-retroviral therapy (ART) reduces viral load (VL), increased SPVL levels have been observed in MSM in the decade following the introduction of ART in the Netherlands. Several studies have been devoted to explain these counter-intuitive trends in SPVL. However, to our knowledge, none of these studies has investigated an explanation in which it arises as the result of a sexually transmitted infection (STI) co-factor in detail. In this study, we adapted an event-based, individual-based model to investigate how STI co-infection and sexual risk behaviour affect the evolution of HIV SPVL in MSM before and after the introduction of ART. The results suggest that both STI co-factors and sexual risk behaviour have an effect on SPVL. However, the observed trends in SPVL cannot be explained by sexual risk behaviour and STI co-factors only. We recommend to develop mathematical models including also factors related to viral evolution as reported earlier in the literature. However, this requires more complex models, and the collection of more data for parameter estimation than what is currently available.