Introduction: Extensive observational data suggest that HSV-2 infection may facilitate HIV acquisition, increase HIV viral load, and accelerate HIV progression and onward transmission. To explore these relationships, we examined the impact of pre-existing HSV-2 infection in an international HIV vaccine trial.
Methods: We analyzed the associations between prevalent HSV-2 infection and HIV-1 acquisition and progression among 1836 men who have sex with men (MSM). We used Cox proportional hazards regression models to estimate the association between HSV-2 infection and both HIV acquisition and ART initiation, and linear regression to explore the effect of HSV-2 on pre-ART viral load.
Results: HSV-2 infection increased risk of HIV-1 acquisition among all volunteers (adjusted hazard ratio 2.2; 95% CI, 1.4 to 3.5). Adjusting for demographic variables, circumcision, Ad5 titer and significant risk behaviors, the risk of HIV acquisition among HSV-2 infected placebo recipients was three fold higher than HSV-2 seronegatives (hazard ratio 3.3; 95% CI, 1.6 to 6.9). Past HSV-2 infection was associated with a 0.2 log10 copies/ml higher adjusted mean set point viral load (95% CI, 0.3 lower to 0.6 higher). HSV-2 infection was not associated with time to ART initiation.
Conclusions: Among MSM in an HIV-1 vaccine trial, pre-existing HSV-2 infection was a major risk factor for HIV acquisition. Past HSV-2 did not significantly increase HIV viral load or early disease progression. HSV-2 seropositive persons will likely prove more difficult than HSV-2 seronegative persons to protect against HIV infection using vaccines or other prevention strategies.
(C) 2014 by Lippincott Williams & Wilkins