Sperm Itself Transmits HIV

(Ivanhoe Newswire) -- Sperm itself -- not just the fluid that carries it -- may play a leading role the spread of HIV by infecting dendritic cells (DCs), which then carry the virus and pass it to T cells.

During sexual intercourse, HIV-infected men transmit HIV through their semen, which carries free-floating virus as well as HIV-infected leukocytes. Traces of HIV have been detected on sperm as well, but the role sperm play in viral transmission has been a matter of debate. After all, men with vasectomies can transmit HIV. Now, a team led by Ana Ceballos at the University of Buenos Aires in Argentina has shown that HIV attaches to the surface of sperm, which then become HIV carriers and pass the virus on to DCs and other HIV targets.

Sperm express molecules known to interact with HIV's envelope, among them heparan sulfate. According to the authors, HIV relies on heparan sulfate to attach to sperm. Once attached, the virus is transmitted from sperm to DCs in culture. DCs matured after interacting with the sperm and produced tolerance-promoting cytokines. The authors speculate that this immune-suppressing profile might also help the virus spread.

Sperm may reach DCs by passing through microabrasions in the vaginal or anal lining that occur during intercourse, the authors are quoted as saying. Or they might contact the finger-like projections of DCs that extend to the surface of mucosal linings. The team found that a slightly acidic pH, similar to the pH in the vagina after sex, promoted HIV-sperm binding and subsequent sperm-related DC infection.

SOURCE: Journal of Experimental Medicine, October 26, 2009

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