Prenatal immunization by the oral route: stimulation of Brucella antibody in fetal lambs.

No simple means exists for immunizing infants and large animals in utero. The feasibility of stimulating immune response by the oral route was investigated by using the fetal lamb as experimental model and Brucella as prototype antigen. Antigenic stimulation was assessed by serum agglutinin levels. Primary and secondary responses were elicited in fetal lambs by Brucella antigen introduced into the amniotic fluid 10 to 50 days prenatally. One lamb born 75 days after primary exposure in utero mounted a secondary response to antigen at 2 days of age. The evidence of immunization by the oral route suggests that local intestinal immunity also might be acquired in fetal life by this route.