A model system of oral HIV exposure, using human palatine tonsil, reveals extensive binding of HIV infectivity, with limited progression to primary infection.

Oral exposure to human immunodeficiency virus (HIV) type 1 results in systemic infection, but many details surrounding virus transmission remain unresolved. We developed a mucosal model, using human palatine tonsil with intact external epithelium, to study events after oral exposure to HIV. When applied to the external epithelium, semen from an HIV-seropositive patient and cell-free virus both established HIV infection in individual tonsillar cells. However, clusters of infected tonsillar cells were detected where the epithelial surface was damaged. Investigation of the initial events in HIV transmission revealed extensive and stable binding of HIV virions and seminal cells to tonsil epithelium. In experiments modeling physiologically relevant events, the addition of seminal plasma resulted in enhanced virion binding to epithelial cells. These results indicate that, although extensive binding of HIV virions and seminal cells can be demonstrated at an exposed mucosal surface, there is only limited progression from binding to primary infection.