HIV dynamics in seminal plasma during primary HIV infection

Abstract

HIV dynamics in seminal plasma during primary HIV infection was evaluated through an observational study of individuals with primary HIV infection at the University of Washington Primary Infection Clinic. Seminal plasma HIV RNA was quantified using a real-time reverse transcription PCR assay. Blood plasma RNA was quantified by bDNA or PCR-based assays. Longitudinal analyses of HIV RNA levels over time used random effects regression analysis. From 1993 to 2005, 110 men collected 327 semen specimens. Initial blood and seminal plasma RNA levels in untreated men were only moderately correlated (Spearman r = 0.38, p = 0.0002). Estimated peak and set point levels were lower in semen than blood by 0.8 (p = 0.001) and 0.7 (p < 0.001) log(10) copies/ml, respectively. RNA decay rates were similar in the two compartments (p = 0.4). For 2 months after infection, mean HIV RNA levels in seminal plasma remained above a threshold level (3.8 log(10) copies/ml) that has been associated with recovery of infectious virus in vitro. HIV-positive men are likely to be most infectious in the first months following HIV acquisition. However, the modest relationship between HIV RNA levels in blood and seminal plasma suggests that the relative risk of HIV transmission during primary infection may vary from current estimates that are solely based on blood levels. Incorporating seminal plasma HIV levels into future mathematical models may increase the accuracy of these models.

FIG. 1.

Circles (•) represent the initial HIV RNA level in seminal plasma among 89 subjects who were untreated at the time of the collection of their first semen specimens. Plus signs (+) represent median HIV RNA level by month since the estimated date of HIV infection. The dashed line represents the threshold at 3.8 log₁₀ copies/ml associated with the ability to culture infectious virus. The proportions of subjects whose initial specimens had seminal plasma HIV RNA levels above this threshold were for specimens collected within 1 month of HIV infection, 67%, 1–2 months after infection, 47%, 2–3 months after infection, 29%, 3–4 months after infection, 20%, 4–5 months after infection, 44%, 5–6 months after infection, 75%, and greater than 6 months after infection, 25%.

FIG. 2.

HIV RNA levels in blood and seminal plasma in untreated subjects over time. Circles represent HIV RNA levels in blood plasma from subjects who were not receiving antiretroviral therapy at the time of the specimen collection. Triangles represent HIV RNA levels in seminal plasma from untreated subjects. The solid line is the initial slope of viral decay in blood and the viral set point in blood after 100 days following HIV infection; the dashed line indicates the same in seminal plasma.