α-Enolase Autoantibodies Cross-Reactive to Viral Proteins in a Mouse Model of Biliary Atresia

Background & Aims

Biliary atresia (BA) is a neonatal cholangiopathy of unknown etiology. The bile duct injury that occurs in patients with BA might result from a hepatobiliary viral infection followed by an autoimmune response against the bile duct epithelia. We aimed to identify autoantigens recognized by serum antibodies in the Rhesus rotavirus (RRV)-induced mouse model of BA; findings were correlated with BA in humans.

Methods

Bile duct epithelial proteins were screened for their reactivity with serum antibodies from the mouse model of BA using immunoblot assays. Unique proteins that reacted with sera antibodies were identified by mass spectrometry and verified using enzyme-linked immunosorbent assay (ELISA) and immunoblot analyses. Candidate autoantibodies in BA patient sera were analyzed by ELISA.

Results

A bile duct epithelial antigen that reacted strongly with serum immunoglobulin (Ig) G from the mouse model of BA was identified as α-enolase. α-Enolase autoantibody specificity was confirmed by ELISA and immunoblot analyses. Anti-RRV and anti-enolase antibodies cross-reacted with enolase and RRV proteins; we identified regions of sequence homology between RRV and enolase. Serum samples from patients with BA had increased levels of anti-enolase IgM and IgG.

Conclusions

We have identified autoantibodies against α-enolase in a mouse model of BA (infected with RRV) and in serum samples from patients, indicating a role of humoral autoimmunity in disease pathogenesis. The cross-reactivity between an anti-enolase antibody and RRV proteins indicates that molecular mimicry might activate humoral autoimmunity in BA patients; further studies are required.

Keywords: Neonatal Immunity, Neonatal Cholestasis, Biliary Obstruction

Abbreviations used in this paper: ALT, alanine aminotransferase, BA, biliary atresia, BLASTp, basic local alignment search tool for proteins, BSS, Hank's balanced salt solution, ELISA, enzyme-linked immunosorbent assay, FITC, fluorescein isothiocyanate, HRP, horseradish peroxidase, Ig, immunoglobulin, MOWSE, molecular weight search, NMC, normal mouse cholangiocyte, RRV, Rhesus rotavirus, VP, viral protein