(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
