COMPLEMENT-MEDIATED CYTOTOXICITY AND INHIBITION OF LIGAND-BINDING TO HEPATOCYTES BY WOODCHUCK HEPATITIS VIRUS-INDUCED AUTOANTIBODIES TO ASIALOGLYCOPROTEIN RECEPTOR

Hepadnavirus invasion in woodchucks has been identified as a potent in ducer of autoantibodies against asialoglycoprotein receptor (anti-ASGP R), a molecule essentially unique to hepatocytes that mediate clearanc e of desialylated serum proteins. We evaluated the possible pathogenet ic importance of anti-ASGPR triggered by woodchuck hepatitis virus (WH V), using anti-ASGPR-reactive serum immunoglobulins (Igs) from five an imals with different stages of WHV hepatitis or self-limited WHV infec tion and isolated woodchuck hepatocytes or HepGZ cells as targets. The results revealed that WHV-induced anti-ASGPR can specifically inhibit asialoglycoprotein recognition by both homologous and heterologous li ver cells, as tested in an asialofetuin (ASFN)-binding radioassay. How ever, the extent of the interference significantly varied (from 85% in hibition to none) for anti-ASGPR with similar titer from different ani mals, indicating a high degree of heterogeneity in the ASGPR epitope s pecificity and in the potential biological effects of these autoantibo dies. The WHV triggered anti-ASGPR also induced complement-mediated he patocytolysis in a microculture tetrazolium (MTT) assay, which ranged from 8.9% +/- 0.3% to 33.6% +/- 3.6% (mean +/- SD) for different anima ls and target cell numbers. This cytopathic effect was strictly ASGPR- specific, complement-dependent, and was not related to the anti-ASGPR ability to inhibit ligand-hepatocyte binding. Our findings indicate th at among pathways by which anti-ASGPR autoimmunity could cause liver d amage, hepadnavirus-induced anti-ASGPR might impair hepatocytes by bot h disrupting clearance of desialylated proteins and activation of the complement-mediated cytolysis. These cytopathic effects might contribu te to the pathogenesis, aggravate severity, and prolong recovery from liver injury in viral hepatitis.