The role of interleukin-22 in hepatitis C virus infection.
In this study, we analyzed if IL-22 displays, similar to other IL-10 like cytokines such as IL-28A, antiviral properties in hepatic cells. Using RT-PCR and immunoblotting, we demonstrated that hepatic cell lines and primary hepatocytes express the functional IL-22 receptor complex consisting of IL-22R1 and IL-10R2. Hepatic IL-22 mRNA expression as measured by quantitative PCR was up-regulated in autoimmune and viral hepatitis compared to cholestatic liver diseases, while IL-22 serum levels did not differ significantly between patients with viral hepatitis and normal controls. IL-22 did not significantly change the expression levels of IFN-alpha/-beta and of the antiviral proteins MxA and 2',5'-OAS. Consequently, it had in comparison to IFN-alpha no relevant antiviral activity in in vitro models of HCV replication and infection. Taken together, hepatic IL-22 expression is up-regulated in viral hepatitis but IL-22 does not directly regulate antiviral proteins and has, in contrast to IFN-alpha, no effect on HCV replication.