Repeated suppression of lymphocyte blastogenesis following vaccinations of CPV-immune dogs with modified-live CPV vaccines.

A commercially available modified-live canine parvovirus (CPV) vaccine was evaluated for its immunosuppressive properties in eight random-bred dogs, all with circulatory antibody to CPV. Three of the eight dogs exhibited a significant decrease in lymphocyte blastogenesis after vaccine administration. In these dogs, this decrease in blastogenesis was of short duration and was consistently observed after repeated administrations of the vaccine. Neither gastroenteritis, fever nor leukopenia, signs indicative of virulent canine parvovirus infection, were detected in these animals. In addition, lymphocytes from these dogs lacked Ia antigen expression. This study demonstrated that the immunomodulating effects of ML-CPV is not observed in all animals yet is consistent in affected individuals.