Th2-Associated Cytokines Display an Inverse Relationship with Hepatic Egg Load in Hamsters Infected with Schistosoma mansoni

Background Schistosomiasis is a parasitic infection caused by Schistosoma species that afflicts over 250 million people worldwide. The Schistosoma mansoni species specifically targets the gastrointestinal system and triggers a Th2-type immune response through its eggs, resulting in granuloma formation. This study sought to examine whether the quantity of S. mansoni eggs influences the immune response in infected hamsters.

Methods Eight-week-old hamsters were infected with S. mansoni cercariae using the paddling technique. Bisex and monosex worm populations were generated through poly-miracidial and mono-miracidial intermediate-host infections, respectively. The hepatic and intestinal egg burdens were quantified, cytokine and mRNA expression of key egg-derived proteins were analyzed in infected animals via qRT-PCR.

Results Notably, the Th1 cytokine response to S. mansoni infection was independent of hepatic egg burden, while Th2 cytokines IL-4, IL-5, and IL-13 showed an inverse correlation in the liver. Bisex-infected animals had increased expression levels of up to 4.6-fold (IL-4), 10-fold (IL-5), and 30-fold (IL-13). Hepatic IL-4 and IL-13 levels inversely correlated with egg-derived factors like IPSE/alpha-1, kappa-5, and omega-1. In contrast, IL-4, IL-5, and IL-13 expression in the colon was unaffected by intestinal egg burden.

Conclusion Our findings indicate an inverse correlation between hepatic egg burden, soluble egg factors, and the Th2 immune response in the liver, but not in the colon. This suggests a protective mechanism in the liver to limit the Th2 response under high egg burden, likely due to prolonged embryogenesis. The absence of correlation in the colon supports this hypothesis, where eggs transit more quickly.

Publication History

Article published online:
20 January 2025