HIV Detectable in Semen of MSM Despite Suppression in Blood: First Longitudinal Study, Mark Mascolini, 7th IAS Conference on HIV Pathogenesis, Treatment and Prevention (2013)

This report summarizes the first longitudinal study regarding the amount of HIV detectable in semen samples of men who have sex with men (MSM) who have undetectable viral loads in blood samples due to antiretroviral therapy (ART). Previous studies have shown that undetectable viral load in blood samples does not necessarily correlate with undetectable viral load in semen, but most data derives from studies of heterosexual men involved in medically assisted reproductive programs. This study found that "HIV detection in semen was not associated with STIs, CDC stage, nadir or current CD4 count, duration of undetectable HIV in plasma, adherence to antiretroviral therapy, or number of sex partners."

The study used a sample of 153 MSM with undetectable blood viral loads. The researchers tested the men's semen for STI infections and HIV viral loads at the beginning of the study and again after four weeks. They found that 3.2% of the subjects' semen had detectable viral loads at the initial visit but not at four weeks; 1.3% had detectable viral loads at both visits; and 9.1% had detectable viral loads at four weeks but not at the initial visit. The seeming lack of correlation between undetectable viral loads in blood and semen has implications for prevention efforts. The study found significantly higher seminal HIV prevalence in the MSM subjects compared to previous studies involving heterosexual men. Whether these levels of HIV in semen are infectious warrants further investigation.