Effect of feline panleukopenia virus infection on development of humoral and cellular immunity.

Cats were infected with feline panleukopenia virus (FPLV) at various ages pre- and post-parturition. All fetuses infected at 35 days of gestation from one queen and a single fetus infected at 45 days of gestation from a second queen had a significant delay in time of skin allograft rejection. Older fetuses and newborn kittens infected with FPLV did not show this delay in rejection time. Adult cats infected with FPLV demonstrated a significant decrease in lymphocyte responsiveness to two T cell mitogens, phytohemagglutinin and Concanavalin A, however there was no significant decrease in lymphocyte response to pokeweed mitogen, a T cell and B cell mitogen. Primary and secondary antibody responses to rabbit red blood cells (RRBC) were not affected by FPLV infection. The results suggest that FPLV has its primary immunosuppressive effect on T cell activity. This effect does not appear to be as severe as that observed for feline leukemia virus of kittens nor as for canine distemper virus in dogs.