Immunologic responses of the bovine fetus to parvovirus infection

Effects of bovine parvovirus (PBV) infection on the bovine fetal immune system were studied. Five fetuses obtained by cesarean section at 5, 10, 20, 40, and 60 days after they were inoculated and 2 control fetuses at 130 and 153 days of gestation were studied. Virus was recovered from the BPV-inoculated fetuses. between 5 and 10 days postinoculation (PI) fetal blood lymphocyte counts tripled, due primarily to an increase in E-rosetting lymphocytes. There were transient increases in fetal serum immunoglobulin (Ig) M (peaking at PI day 20), marked and gradual increase in IgG1, and minimal increase of IgG2. Serum-neutralizing antibodies were detected at PI day 10 and increased to a titer of 1:2056 by day 60. Peripheral blood lymphocytes of all fetuses responded well to the nonspecific mitogens phytohemagglutinin, concanavalin A, and pokeweed mitogen. Histopathologically, there was lymphoid hyperplasia, most evident in lymph nodes draining the site of PBV inoculation. There was no indication of lymphoid depletion or necrosis in lymph nodes, spleen, or thymus of PBV-inoculated fetuses. These data indicate that under the conditions of this study, inoculation of the isolate of PBV may stimulate an immune response in the fetus.