Role of interleukin-33 during <i>Schistosoma mansoni </i>infection (MPF7P.713)

The host immune response to Schistosoma infection is characterized by two main phases, Th1 and Th2 consecutively, the later one being related to the excretion of mature eggs by the adult female worm. Interleukin-33 (IL-33), a Th2 inducing cytokine, has been reported to be associated with schistosomiasis. Here we assessed the role of this epithelial related cytokine on the time course of the experimental S. mansoni infection in mouse. IL-33 knockout (KO) and wild type (WT) 6-week-old BALB/c female mice were infected with 50 cercariae and sacrificed at 0, 6, 8 and 10 weeks post infection. We monitored symptoms of mice, the worms and eggs burden, kinetics of immune cells in the liver and spleen, and cytokine levels. The size of granuloma induced in the liver and intestine were also measured. There was no significant difference between KO and WT mice in the survival rate, worms and eggs burden; nevertheless some sparse differences related to the increase of eosinophils were detected at 8 weeks post-infection. A very few number of KO mice displayed a severe anemia and colonic bleeding at the end of the experiment, suggesting some intestinal effects of IL-33 as epithelial alarmin. Our results suggest that although IL-33, the Th2 inducing cytokine, was reported to be crucial in other helminthic diseases, it may have little impact on the course of S. mansoni infection.