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Determinants of Per-Coital-Act HIV-1 Infectivity Among African HIV-1–Serodiscordant Couples

2012; Oxford University Press; Volume: 205; Issue: 3 Linguagem: Inglês

10.1093/infdis/jir747

1537-6613

James P. Hughes, Jared M. Baeten, Jairam R. Lingappa, Amalia Magaret, Anna Wald, Guy de Bruyn, James Kiarie, Mubiana Inambao, William Kilembe, Carey Farquhar, Connie Celum,

HIV Research and Treatment

(See the editorial commentary by Gray and Wawer on pages 351–2.) Background. Knowledge of factors that affect per-act infectivity of human immunodeficiency virus type 1 (HIV-1) is important for designing HIV-1 prevention interventions and for the mathematical modeling of the spread of HIV-1. Methods. We analyzed data from a prospective study of African HIV-1–serodiscordant couples. We assessed transmissions for linkage within the study partnership, based on HIV-1 sequencing. The primary exposure measure was the HIV-1–seropositive partners’ reports of number of sex acts and condom use with their study partner. Results. Of 3297 couples experiencing 86 linked HIV-1 transmissions, the unadjusted per-act risks of unprotected male-to-female (MTF) and female-to-male (FTM) transmission were 0.0019 (95% confidence interval [CI], .0010–.0037) and 0.0010 (95% CI, .00060–.0017), respectively. After adjusting for plasma HIV-1 RNA of the HIV-1–infected partner and herpes simplex virus type 2 serostatus and age of the HIV-1–uninfected partner, we calculated the relative risk (RR) for MTF versus FTM transmission to be 1.03 (P = .93). Each log10 increase in plasma HIV-1 RNA increased the per-act risk of transmission by 2.9-fold (95% CI, 2.2–3.8). Self-reported condom use reduced the per-act risk by 78% (RR = 0.22 [95% CI, .11–.42]). Conclusions. Modifiable risk factors for HIV-1 transmission were plasma HIV-1 RNA level and condom use, and, in HIV-1–uninfected partners, herpes simplex virus 2 infection, genital ulcers, Trichomonas vaginalis, vaginitis or cervicitis, and male circumcision.