Breaking self-tolerance toward cytochrome P4502E1 (CYP2E1) in chronic hepatitis C: Possible role for molecular mimicry

Background & aims: Circulating auto-antibodies targeting conformational antigens on cytochrome P4502E1 (CYP2E1) are detectable in patients with chronic hepatitis C (CHC) and are associated with more severe necro-inflammation. This study investigated the antigen specificity and the possible origin of these auto-antibodies. Methods: CYP2E1 site-directed mutagenesis and molecular simulation were used to characterize the epitope specificity of CHC-associated anti-CYP2E1 auto-antibodies. Results: Immunoprecipitation experiments using differently mutated human CYP2E1s revealed that conformational anti-CYP2E1 antibodies targeted two epitopes located on the molecule surface in an area between Lys³²⁴-Glu³⁴⁶ at J-K'' helices overlapping. Such epitopes were not recognized by the sera targeting linear CYP2E1 antigens. The CYP2E1^324-346 peptide showed good homology with two sequences (NS5b^438-449 and NS5b^456-465) within the NS5b protein of hepatitis C virus (HCV). Consistently, conformational anti-CYP2E1 IgG bind to GST-conjugated NS5b^438-449 and NS5b^456-465 more efficiently than those recognizing CYP2E1 linear antigens. Competition experiments confirmed the cross-reactivity of conformational anti-CYP2E1 IgG with both NS5b^438-449 and NS5b^456-465. Moreover, mice immunized with GST-conjugated NS5b^438-449 or NS5b^456-465 peptides developed antibodies recognizing human CYP2E1. Conclusions: In CHC patients cross-reactivity between CYP2E1 and specific sequences in HCV-NS5b protein can promote the development of auto-antibodies targeting conformational epitopes on the CYP2E1 surface that might contribute to hepatic injury.