Oral HIV-exposure elicits mucosal HIV-neutralizing antibodies in uninfected men who have sex with men.

Objective: To determine whether oral sexual exposure to HIV-1 (HIV) results in HIV-neutralizing activity in saliva of uninfected men who have sex with infected men?

Design: Saliva samples were collected from HIV IgG seronegative men (n = 25) whose male partners were HIV infected and from low-risk healthy controls (n = 22) and analyzed for HIV-neutralizing capacity.

Methods: The presence of neutralizing activity in saliva was tested in a peripheral blood mononuclear cell-based assay using primary HIV isolates. Self-reporting questionnaires described the individuals' sexual behaviors and routes of possible HIV exposure.

Results: Of 25 exposed, uninfected individuals (EUI), 21 reported receptive unprotected oral intercourse, whereas three of the 25 reported unprotected anal receptive intercourse. Whole saliva from both EUI and low-risk healthy controls contained HIV-neutralizing activity. However, a significant difference was seen when analyzing the salivary IgA1 fraction: 13 of 25 EUI neutralized HIV, whereas none of the 22 controls had this capacity. The neutralizing capacity of the EUI males persisted during 2 years of follow-up.

Conclusion: Unprotected oral sex evokes a salivary IgA1-mediated HIV-neutralizing response that persists over time during continuous exposure in uninfected male partners of infected men.