Innate molecular and anatomic mucosal barriers against HIV infection in the genital tract of HIV‐exposed seronegative individuals.

Sexual transmission is the single most common mechanism for acquiring infection with human immunodeficiency virus (HIV), and the efficiency of transmission reflects the biology of the mucosal site. The localization and phenotypic characterization of HIV target cells and receptors and the presence of immune molecules are therefore important to define at sites of HIV exposure. To complicate the picture, HIV‐binding receptors and antiviral immune molecules can be protective under certain circumstances but can exert an opposite effect at other mucosal sites, concentrations, and time points. Considering the additional physiological changes induced by inflammation, hormones, and semen deposition, it is an enormous challenge to design relevant experimental models for evaluating prophylactic compounds or biological events. Studies in mucosal samples of HIV‐exposed seronegative individuals are among the many opportunities to explore the biological events of HIV transmission under physiological circumstances.