Breaking self-tolerance toward cytochrome P4502E1 (CYP2E1) in chronic hepatitis C: possible role for molecular mimicry.
OBJECTIVE
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.
Sutti
Salvatore
S
Department of Medical Sciences and Interdisciplinary Research Centre for Autoimmune Diseases, University Amedeo Avogadro of East Piedmont Novara, Italy.
Vidali
Matteo
M
Mombello
Cristina
C
Sartori
Massimo
M
Ingelman-Sundberg
Magnus
M
Albano
Emanuele
E
D000595:Amino Acid Sequence; D000818:Animals; D000918:Antibody Specificity; D001323:Autoantibodies / Q000097:blood; D001483:Base Sequence; D003429:Cross Reactions; D019392:Cytochrome P-450 CYP2E1 / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D017931:DNA Primers / Q000235:genetics; D000939:Epitopes / Q000235:genetics; D016174:Hepacivirus / Q000235:genetics / Q000276:immunology; D019698:Hepatitis C, Chronic / Q000201:enzymology* / Q000276:immunology* / Q000821:virology; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D051379:Mice; D008958:Models, Molecular; D018716:Molecular Mimicry; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000235:genetics / Q000276:immunology; D017634:Self Tolerance; D017386:Sequence Homology, Amino Acid; D040681:Structural Homology, Protein; D017361:Viral Nonstructural Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D012324:RNA-Dependent RNA Polymerase
D001323:Autoantibodies; D019392:Cytochrome P-450 CYP2E1; D017931:DNA Primers; D000939:Epitopes; D011994:Recombinant Proteins; D017361:Viral Nonstructural Proteins; C087036:NS-5 protein, hepatitis C virus; D012324:RNA-Dependent RNA Polymerase