Adenovirus-induced immune response in ovine fetuses

Ovine fetuses were examined for immune responsiveness to ovine adenovirus (strain ORT/111) at 70-80 days of gestation. Nineteen days after experimental infection, all infected fetuses, along with their eventual non-infected twins, had neutralizing serum antibodies to the virus in the titre range of 1 : 32-1 : 128. The antibodies were identified electrophoretically as subclass IgG1 and IgG2. No other Ig-class was involved in the immune response. Infection of the fetuses accounted for antibody production in the maternal organism, too. Immunofluorescence tests detected a periarteriolar, diffuse or focal occurrence of IgG-positive cells in the fetal spleen, and in pulmonary, renal and cotyledon tissue samples. IgM-positive cells were found exclusively in the spleen, always in a low number and in diffuse distribution. No Ig-carrier cells were detected in the liver, thymus and lymph nodes. The blood contained both IgG and IgM-positive cells at a proportion of 6-7 and 1-2%, respectively. Spleen cell cultures stimulated in vitro with ovine adenovirus antigen showed an average 3HTdR incorporation rate of 22%.