THE ROLE OF IL-4 IN ADULT ACQUIRED AND CONGENITAL TOXOPLASMOSIS

The course of Toxoplasma gondii infection was studied in IL-4-deficien t mice from three genetic backgrounds and their wild-type counterparts following peroral inoculation of tissue cysts. Survival rates were si gnificantly reduced in disease-susceptible C57 BL/6 mice and Fl (C57BL /6 x 129Sv) mice deficient in IL-4 compared with wild-type controls. I n contrast, this difference was not observed in T. gondii-resistant BA LB/c mice. However, brain tissue cyst burdens in IL-4-deficient mice w ere either equivalent to (C57BL/6 and BALB/c mice) or significantly le ss (B6/129 mice) than similarly infected wild-type mice. Thus strain-s pecific differences in the course of T. gondii were demonstrated in th e absence of IL-4. The course of T. gondii infection was also compared between B6/129 IL-4-deficient mice and their wildtype counterparts fo llowing peroral challenge with 20 tissue cysts on day 12 of pregnancy. Age-matched non-pregnant IL-4-/- and IL-4+/+ mice were also infected to assess the role of IL-4 on T. gondii infection during pregnancy. Di sease phenotypes, as measured by mortality, were reversed if infection s were initiated during pregnancy compared with non-pregnant infection . Thus significant mortality occurred immediately post partum in IL-4/+ mothers, while all IL-4-/- mothers survived. Cyst burdens 28 days p .i. were significantly lower in IL-4-/- mothers than IL-4+/+ mothers a nd both IL-4-/- and IL-4+/+ non-pregnant mice. Congenital disease tran smission as measured by foetal death or vertical disease transmission was independent of the presence or absence of IL-4. These studies demo nstrate a role for IL-4 in pregnancy-induced immunosuppression and the associated increased susceptibility to T. gondii infection. (C) 1998 Australian Society for Parasitology. Published by Elsevier Science Ltd .