Introduction: HIV in the genital tract is often genetically distinct from that in the bloodstream.  This variation results from differing host cell selection, local immune responses, and varying penetration of drugs into the genital tract.  Male genital secretions are a complex mixture of cells and secretions from the testes, epidydimis, vas deferens, seminal vesicles, prostate, urethral and paraurethral glands.  Since the prostate can harbor bacterial and fungal infections, it was investigated as a reservoir for HIV.

Methods: Seven male participants submitted genital secretion samples weekly for 11 weeks in this self-controlled trial.  Samples from weeks 1-4 and 11 were collected without prior prostate massage (PM), and samples from weeks 5-10 were submitted after PM.  4/7 subjects were on stable antiretroviral regimens (>3months) before starting the trial; 3/7 were on no antiretrovirals.  There were no medication changes during the trial.  HIV RNA was extracted from 1 ml of seminal plasma (SP) from each sample via the Boom method (Nuclisens, Biomerieux) and then quantitated (Amplicor, Roche).  At study enrollment subjects tested negative for active sexually transmitted infections, and they remained asymptomatic throughout.

Results: 4/7 participants had undetectable SP HIV RNA in all samples without prior PM but then became detectable in 1-3 samples collected after prior PM (mean 473 cop/ml, range 4-3488).  No correlation was discerned between PM and the amount of SP collected.  The remaining 3/7 participants had SP samples with detectable HIV RNA at all collections, which showed no correlation with PM.  Blood plasma HIV RNA levels measured at the start and the end of the study were unchanged in all subjects except one who showed a steep decrease in blood plasma HIV RNA levels from 42,102 cop/ml to <50 cop/ml.  The SP HIV RNA levels from this subject varied greatly (3,041 to 285,732 cop/ml) but did not correlate to prior PM.

Conclusion: These data suggest that the prostate is a reservoir for HIV.  This has significant transmission consequences, as PM resembles receptive anal intercourse in men who have sex with men.  Prostate stimulation via anal intercourse could therefore increase the amount of HIV RNA in the receptive partner’s genital secretions, which could then be transmitted when he became the insertive partner.  These data could, in part, explain the high HIV infection rates historically seen in men who have sex with men.