HIV Load in Plasma and Semen – do They Match Each Other?

Earlier this year, the Swiss Federal Commission for HIV/AIDS sparked controversy when they suggested that HIV-infected individuals on antiretroviral therapy who are fully adherent and maintaining undetectable plasma viremia (< 50 HIV RNA copies/ml) for at least six months and having no concurrent sexually transmitted infections, essentially cannot transmit HIV through heterosexual vaginal intercourse. A recent French study (Marcelin, et al. AIDS. 2008;22:1677-9), however, found that 5% of men in serodiscordant couples had intermittently detectable HIV in their semen, despite meeting the criteria specified in the Swiss statement. One possible reason for detectable semen viral load despite undetectable HIV in the blood is that antiretroviral drugs may fail to reach the genital compartment. Like the brain, the testes are isolated by a physical barrier that prevents certain substances, including many drugs, from passing through.