Schistosoma mansoni Infection but Not Egg Antigen Promotes Recovery from Colitis in Outbred NMRI Mice

Background The ability of intestinal helminths to manipulate the immune system of their host towards a Th2 response has been proposed to modulate auto-immune and allergic diseases. Aims This initial study investigated the anti-inflammatory potential of S. mansoni and soluble egg antigen (SEA) in a murine model of colitis. Methods Colitis was induced in female NMRI mice by 5% dextran sulfate sodium (DSS) for 7 days, either 9 weeks post-infection with S. mansoni or during treatment with SEA. In addition to clinical signs of colitis, colon histology, immunohistochemistry, and flow cytometry of leukocytes were performed. Colon cytokines were measured using a quantitative real-time technique. Results Infection with cercariae of S. mansoni attenuated DSS-induced colitis. Clinical symptoms such as weight loss and shortening of colon length were significantly prevented. Histological scores and cell infiltration were affected and expression of pro-inflammatory cytokines in the colons of infected DSS colitis mice was reduced. In contrast, application of SEA failed to improve colitis, even though some findings like earlier manifestation of inflammation and local induction of Th2 cytokines were similar to the effects of cercarial infection. Conclusions The results presented here suggest that SEA treatment could not protect mice from acute colitis. However, both infection with S. mansoni and injection of SEA affect mucosal immune responses.