Prostate is a reservoir for HIV even in men with controlled viral load, finds study

Stimulation of the prostate can provoke the release of HIV into semen, even in men who are taking HAART and have undetectable viral load in their blood, according to a small study reported in the July 23^rd edition of AIDS. The study investigators believe that their findings could have important implications for HIV prevention and speculate that prostate stimulation (and subsequent HIV shedding) during sex may contribute to the high HIV infection rates seen in gay men.

A separate study, also reported on aidsmap.com recently found that older HIV-positive men have a significantly increased risk of prostate cancer.

Most studies investigating HIV in semen have treated seminal fluid as arising from a single source. In fact, four separate organs and glands are involved in the production of semen, all of which may be compartments for the local replication of HIV.

One of the organs involved in semen production is the prostate. It is known that the prostate can harbour bacterial and fungal infections, and that antibiotics have poor penetration into the prostate.

Investigators from San Diego speculated that antiretrovirals may also have poor penetration into the prostate, and wished to see if the prostate could be a reservoir for HIV.

Nine men with chronic HIV infection were enrolled to a study to address this issue. Mean CD4 cell count at baseline was 483 cells/mm³, and mean viral load 20,800 copies/ml. Seven of the men had been taking a stable HAART regimen for at least three months and three of the men had a viral load in their blood below 50 copies/ml. None of the men had a sexually transmitted infection.

Every week for eleven weeks the men provided a semen sample. This was obtained by masturbation in the morning. The men were instructed not to have sex in the 48 hours before they produced their semen samples. Samples from weeks five to ten were provided after individuals had performed a massage of their prostate.

HIV was detected in semen (above 25 copies/ml) with greater frequency in the samples provided after prostate massage. Only eleven of the 44 semen samples provided without prostate massage had detectable HIV compared to 24 of the 53 samples obtained after individuals had performed a prostate massage (p = 0.035).

The three individuals who had both an undetectable HIV viral load in their blood and, without prostate massage, their semen, provided at least one semen sample each with detectable HIV after prostate massage.

Baseline blood viral loads did not change significantly during the study, the exception being one individual whose viral load fell from over 40,000 copies/ml to undetectable. Investigators speculate that improved adherence was the reason.

“These data are further evidence of the significant compartmentalization between the blood and the genital tract,” write the investigators.

They conclude that the prostate is a sanctuary site for HIV, even in individuals who are taking HAART and have an undetectable viral load in their blood.

“There are significant transmission implications related to the prostate as a reservoir for HIV,” comment the investigators. They explain, “if prostate massage simulates receptive anal intercourse in [gay] men, then anal intercourse may increase the amount of HIV RNA in the receptive partner’s semen, which he could then transmit in his next sexual encounter. This mechanism could contribute to the high HIV infection rates historically seen among men who have sex with men.”

The investigators call for further studies to evaluate the anatomical source of infecting HIV and the HIV transmission risk attributable to prostate stimulation.