Mucosal infection of neonatal rhesus monkeys with cell-free SIV.

Although the mechanisms for maternal transmission are unknown, approximately half of the infants congenitally infected with the human immunodeficiency virus type 1 (HIV-1) seem to become infected late in gestation or during delivery. Previously, we have developed a rhesus monkey model for congenital infection by injecting cell-free simian immunodeficiency virus (SIV) directly into amniotic fluid. Our results suggested that fetal infection may have occurred via skin or mucous membrane exposure. Mucosal surfaces have also been implicated as a portal of virus entry by a study in which the presence of serosanguinous fluid in neonatal gastric aspirates correlated with an increased rate of HIV-1 transmission. To test whether cell-free virus could transverse intact neonatal mucosal surfaces, we administered SIVmac251 orally to four rhesus monkey neonates within 1 hr following cesarean section delivery. All four neonates developed viremia and were positive by cocultivation and PCR. Seroconversion occurred in three of the four neonates. The SIV dose given was within physiological range as shown by end-point dilution of virus stock and viremic plasma samples of juvenile rhesus monkeys. This primate model for mucosal transmission of cell-free virus features a high infection rate, thus making studies of mucosal immunity and the development of strategies to prevent intrapartum virus transmission possible.