Immunosuppression in goats inoculated with parainfluenza type 3 virus

The humoral and cellular immune responses of goats experimentally infected with an ovine isolate of parainfluenza type 3 virus (PI-3) were examined. Virus neutralization and enzyme-linked immunosorbent assays were used to determine antibody in the serum and CSF. Lymphocyte stimulation, measured by [3H]thymidine incorporation into peripheral blood leukocytes, was used to determine cellular responses to phytomitogens and virus. There were significant suppression of peripheral blood leukocyte responses to T-cell mitogens early in the course of infection and delayed onset of virus-specific cell-mediated immunity. Delay in antibody formation did not occur. The suppression of mitogen response has been reported with other paramyxovirus infections. The importance of the suppressed cellular immune response for potentiating other infective agents is discussed.