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 Lys(324)-Glu(346) 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. (C) 2010 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.