Prior Toxoplasma Gondii Infection Ameliorates Liver Fibrosis Induced by Schistosoma Japonicum through Inhibiting Th2 Response and Improving Balance of Intestinal Flora in Mice

Schistosomiasis is an immunopathogenic disease in which a T helper (Th) cell type 2-like response plays vital roles. Hepatic fibrosis is its main pathologic manifestations, which is the leading cause of hepatic cirrhosis. Co-infections of Schistosoma japonicum (Sj) with other pathogens are frequently encountered but are easily ignored in clinical studies, and effective therapeutic interventions are lacking. In this study, we explored the effect of Toxoplasma gondii (Tg) prior infection on Th1/Th2 response, community shifts in gut microbiome (GM), and the pathogenesis of schistosomiasis in murine hosts. Mice were prior infected with Tg before Sj infection. The effects of co-infection on Th1/Th2 response and hepatic fibrosis were analyzed. Furthermore, we investigated this issue by sequencing 16S rRNA from fecal specimens to define the GM profiles during co-infection. Tg prior infection markedly reduced the granuloma size and collagen deposit in livers against Sj infection. Prior infection promoted a shift toward Th1 immune response instead of Th2. Furthermore, Tg infection promoted the expansion of preponderant flora and Clostridiaceae was identified as a feature marker in the GM of the co-infection group. Redundancy analysis (RDA)/canonical correspondence analysis (CCA) results showed that liver fibrosis, Th1/Th2 cytokines were significantly correlated (P < 0.05) with the GM compositions. Tg infection inhibits hepatic fibrosis by downregulating Th2 immune response against Sj infection, and further promotes the GM shifts through “gut–liver axis” in the murine hosts. Our study may provide insights into potential anti-fibrosis strategies in co-infection individuals.