Alteration in immune response of mice with dual infection of Toxocara canis and Japanese encephalitis virus.

Concurrent dual infections of mice with Toxocara canis and Japanese encephalitis virus (JEV) showed a distinct synergistic effect of the parasite on sublethal JEV infection. Dose-dependent effects were evident in the mice infected dually and with T. canis alone; leucocytosis with suppression of eosinophilia in the peripheral blood and reduction in migration inhibition factor produced by spleen cells in response to T. canis and JEV antigens were recorded, particularly in the former group. These changes were accompanied by reductions in both antibody response to sheep erythrocytes and T cell numbers in the spleen. No appreciable changes were recorded in the mice infected with JEV alone. Thus, the T cell immuno-suppression induced by T. canis might have triggered the viral encephalitis caused by JEV in the dual infections.