Transplacental transmission of HIV: a potential role for HIV binding lectins

Although the majority of vertical transmission of HIV occurs around the time of birth, 1.5-2% of pregnancies in HIV-positive women appear to result in the vertical transmission of HIV across the placenta. HIV infection of a number of placental cell types has been demonstrated, but the exact mechanisms of intrauterine vertical transmission remain obscure. The recent discovery of the HIV binding lectins dendritic cell-specific ICAM-grabbing non-integrin (DC-SIGN) and DC-SIGN-related molecule (DC-SIGNR) provides one possible explanation. Cells expressing these lectins are able to adsorb the virus and mediate high efficiency HIV infection of other cell types. Both lectins are expressed by the placenta, with DC-SIGN expression also being present on maternal cells intimately associated with the placenta. This review focuses on possible mechanisms by which these lectins may potentiate the intrauterine vertical transmission of HIV.