Bacterial vaginosis associated with increased risk of female-to-male HIV-1 transmission: A prospective cohort analysis among african couples

Background: bacterial vaginosis (bv),a disruption of the normal vaginal flora,has been associated with a 60% increased risk of hiv-1 acquisition in women and higher concentration of hiv-1 rna in the genital tract of hiv-1-infected women. however,whether bv,which is present in up to half of african hiv-1-infected women,is associated with an increase in hiv-1 transmission to male partners has not been assessed in previous studies. methods and findings: we assessed the association between bv on female-to-male hiv-1 transmission risk in a prospective study of 2,236 hiv-1-seropositive women and their hiv-1 uninfected male partners from seven african countries from a randomized placebo-controlled trial that enrolled heterosexual african adults who were seropositive for both hiv-1 and herpes simplex virus (hsv)-2,and their hiv-1-seronegative partners. participants were followed for up to 24 months; every three months,vaginal swabs were obtained from female partners for gram stain and male partners were tested for hiv-1. bv and normal vaginal flora were defined as a nugent score of 7-10 and 0-3,respectively. to reduce misclassification,hiv-1 sequence analysis of viruses from seroconverters and their partners was performed to determine linkage of hiv-1 transmissions. overall,50 incident hiv-1 infections occurred in men in which the hiv-1-infected female partner had an evaluable vaginal gram stain. hiv-1 incidence in men whose hiv-1-infected female partners had bv was 2.91 versus 0.76 per 100 person-years in men whose female partners had normal vaginal flora (hazard ratio 3.62,95% ci 1.74-7.52). after controlling for sociodemographic factors,sexual behavior,male circumcision,sexually transmitted infections,pregnancy,and plasma hiv-1 rna levels in female partners,bv was associated with a greater than 3-fold increased risk of female-to-male hiv-1 transmission (adjusted hazard ratio 3.17,95% ci 1.37-7.33). conclusions: this study identified an association between bv and increased risk of hiv-1 transmission to male partners. several limitations may affect the generalizability of our results including: all participants underwent couples hiv counseling and testing and enrolled in an hiv-1 prevention trial,and index participants had a baseline cd4 count ≥250 cells/mm 3 and were hsv-2 seropositive. given the high prevalence of bv and the association of bv with increased risk of both female hiv-1 acquisition and transmission found in our study,if this association proves to be causal,bv could be responsible for a substantial proportion of new hiv-1 infections in africa. normalization of vaginal flora in hiv-1-infected women could mitigate female-to-male hiv-1 transmission. trial registration: clinicaltrials.com nct00194519. © 2012 cohen et al.