ERVW-1 and primary biliary cholangitis: Previous in situ hybridization studies with betaretrovirus gag-pol-env probes showed that 75% of biliary epithelial cells isolated from patients with PBC exhibited HBRV RNA signal, which was substantiated by the identification of proviral integrations by LM-PCR, and HBRV RNA using the Quantigene hybridization assay [19].