Polyinosinic–polycytidylic acid attenuates hepatic fibrosis in C57BL/6 mice with Schistosoma japonicum infection

The development of hepatic fibrosis is the principal cause of morbidity and mortality in human beings infected with schistosoma. In this study, we investigated the effect of polyinosinic–polycytidylic acid (poly I:C) on Schistosoma japonicum (S. japonicum) egg-induced liver fibrosis. S. japonicum cercariae infected mice were injected with poly I:C at the onset of egg granuloma formation (early phase poly I:C treatment) or after the formation of liver fibrosis (late phase poly I:C treatment). Our results showed that both early and late phase poly I:C treatment significantly reduced collagen deposition and hepatic stellate cell activation in the liver. Poly I:C is one of the most effective adjuvants for Th1 type responses, and its protective effect on liver fibrosis was accompanied by increased IFN-α, IFN-β, IFN-γ, IL-12, TNF-α, and IL-10 mRNA expression, and decreased IL-4 and IL-5 mRNA expression. Moreover, poly I:C injection also enhanced the mRNA expression of natural killer group 2 member D (NKG2D) and tumor necrosis factor related apoptosis-inducing ligand (TRAIL). Therefore, it is indicated that poly I:C can significantly attenuate S. japonicum egg-induced hepatic fibrosis, which may be partly dependent on the increased Th1 response and decreased Th2 response.