Oral transmission of human immunodeficiency virus by infected seminal fluid and milk: A novel mechanism

Salivary transmission by the 30 million human immunodeficiency virus (HIV) carriers is rare, despite kissing, aerosolization, and dental treatment. Th e main protective mechanism of saliva is reported to be inactivation of HIV -transmitting leukocytes by its unique hypotonicity; however, the successfu l oral transmission of HIV by seminal fluid and milk is unexplained. Whethe r seminal fluid and milk successfully transmit HIV orally by overcoming the recipient's salivary hypotonic inactivation of HIV-transmitting leukocytes was tested. Isotonic salt solution and normal donor samples of milk, colos trum, seminal fluid, and blood were studied for their ability to overcome t he salivary hypotonic inactivation. All samples, in physiologic volumes, pr evented the hypotonic saliva from inactivating HIV-transmitting leukocytes by providing solutes and retarding diffusion. This indicates that successfu l oral transmission of HIV by seminal fluid, milk, and colostrum may be due to their isotonicity, which overcomes hypotonic salivary inactivation of H IV-transmitting leukocytes.