Heterosexual transmission of HIV-1 is associated with high plasma viral load levels and a positive viral isolation in the infected partner

Risk factors for heterosexual HIV transmission are not fully understood. In fact, a proportion of people with sexual exposure to HIV remain uninfected despite multiple and continuous intercourse with HIV-infected partners. In this work, we have analyzed those virologic parameters potentially involve d in the transmission of HIV through heterosexual contact. Thirty-eight cou ples with continuous unprotected sexual intercourse were included. HIV tran smission occurred in 10 of 38 coup;les. No differences in clinical characte ristics, exposure time, sexual practices, CD4 counts, or polymorphism in CC R5 were found between transmitter and nontransmitter groups. In contrast, v irologic data were different between both groups; median values of viral lo ad were 21.139 and 5.484 RNA copies/ml of plasma in the transmitter and non transmitter groups, respectively, and a significant difference was found in mean viral load values (p = .03, Mann-Whitney test). Viral isolation was o btained in 90% of transmitters, but in only 44% of nontransmitter subjects (p = .02, Fisher's exact test). These data show that viral load levels and a positive viral isolation in culture must be considered as risk factors fo r heterosexual transmission of HIV-I.