Impact of herpes simplex virus type 2 on HIV-1 acquisition and progression in an HIV vaccine trial (the Step study)

J Acquir Immune Defic Syndr. 2011 Jul 1;57(3):238-44. doi: 10.1097/QAI.0b013e31821acb5.


Introduction: Extensive observational data suggest that herpes simplex virus type 2 (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 preexisting 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. We used Cox proportional hazards regression models to estimate the association between HSV-2 infection and both HIV acquisition and antiretroviral therapy (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% confidence interval (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 3-fold higher than HSV-2 seronegatives (adjusted hazard ratio 3.3; 95% CI: 1.6 to 6.9). Past HSV-2 infection was associated with a 0.2 log10 copies per milliliter 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 men who have sex with men in an HIV-1 vaccine trial, preexisting 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.

Trial registration: NCT00095576.

Publication types

  • Multicenter Study
  • Randomized Controlled Trial
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • AIDS Vaccines / immunology*
  • Adolescent
  • Adult
  • Anti-HIV Agents / therapeutic use
  • HIV Infections / drug therapy
  • HIV Infections / pathology
  • HIV Infections / prevention & control*
  • HIV Infections / transmission*
  • HIV-1 / immunology*
  • Herpes Simplex / complications*
  • Herpes Simplex / immunology
  • Herpesvirus 2, Human / immunology*
  • Homosexuality, Male
  • Humans
  • Male
  • Middle Aged
  • Risk Factors
  • Viral Load
  • Young Adult


  • AIDS Vaccines
  • Anti-HIV Agents

Associated data


Grant support