MECHANISM OF MONOCYTE-MACROPHAGE-MEDIATED TRANSMISSION OF HIV

Observations from our laboratory support the theory that HIV-infected monocyte-macrophages present in genital tract secretions have an impor tant role in sexual transmission of HIV, Light and electron microscopy were used to study the behavior of HIV-infected, primary human monocy tes, These cells progress on surfaces, putting forward a leading pseud opod from which they secrete HIV. When added to cultures of CD4(-), ce rvix-derived epithelial cells, monocytes advanced between epithelial c ells while secreting virus anteriorly. Epithelial cells subsequently b ecome productively infected. Infection of epithelia could be blocked b y sera from HIV-seropositive individuals. These findings support the s upposition that transmission of HIV may occur via cell-mediated infect ion of intact epithelia, The observations also hint at the possibility that HIV-infected monocyte-macrophages in semen or cervical-vaginal s ecretions could cross intact epithelia by passing between epithelial c ells. To test this hypothesis supravital-stained mouse macrophages mer e inoculated into the vaginas of mice. Four hours later numerous stain ed cells were observed in the connective tissue beneath the vaginal ep ithelium and in the iliac lymph nodes. We speculate that direct infect ion of epithelial cells and/or cell trafficking across epithelia may b e involved in sexual transmission of HIV.