“…Mother-to-child transmission is clearly an important mode of spread for HIV-1 [1], Although this may occur by several routes, including intrapartum transmission [2] and breast feeding [3], it is currently believed that intrauterine transplacental infection of the fetus in utero is the most important mechanism of vertical transmission [4], Evidence of intrauterjne transmission of HIV-1 includes idenlification of HIV-i DNA sequences in the cord blood or the peripherai blood of babies shortly after birth |5,6] and in fetal lissues [7], The placentai syncytiotrophobiast (ST) forms a continuous, muliinucleated epithelium in direct contact with maternal blood in the intervillous space [8], Thus, a key event in the infection of the placenia and transmission of HIV lo the fetus may be the interaction of blood-borne virus particles with ST. Despite the fact that HIV can enter ST cells [9], the trophoblast is assumed to restrict the rate of virus transmission, because irophoblasl cells exhibit restricted permissiveness for HIV [9.10] and the limited virus shedding is followed by continuous decline in HIV gene activities resulting in sequestration of provirus [II], These fmdings suggest thai multiple cofaclors are likely to be involved in ihc iransplaccntal transmission of the virus.…”