Background: Retroviruses have been implicated in the aetiology of various autoimmune diseases. We used immunoblots as a surrogate test to find out whether retroviruses play a part in the development of primary biliary cirrhosis. Methods: We did western blot tests for HIV-1 and the human intracisternal A-type particle (HIAP), on serum samples from 77 patients with primary biliary cirrhosis, 126 patients with chronic liver disease, 48 patients with systemic lupus erythematosus, and 25 healthy volunteers. Findings: HIV-1 p24 gag seroreactivity was found in 27 (35%) of 77 patients with primary biliary cirrhosis, 14 (29%) of 48 patients with systemic lupus erythematosus, 14 (50%) of 28 patients with chronic viral hepatitis, and nine (39%) of 23 patients with either primary sclerosing cholangitis or biliary atresia, compared with only one (4%) of 24 patients with alcohol-related liver disease or α1-antitrypsin-deficiency liver disease, and only one (4%) of 25 healthy volunteers (p = 0.003). Western blot reactivity to more than two HIAP proteins was found in 37 (51%) of patients with primary biliary cirrhosis, in 28 (58%) of patients with systemic lupus erythematosus, in 15 (20%) of patients with chronic viral hepatitis, and in four (17%) of those with other biliary diseases. None of the 23 patients with either alcohol-related liver disease or α1-antitrypsin deficiency, and only one of the healthy controls showed the same reactivity to HIAP proteins (p < 0.0001). Our results showed a strong association between HIAP seroreactivity and the detection of autoantibodies to double-stranded DNA. HIAP seroreactivity was also strongly associated with the detection of mitochondrial, nuclear, and extractable nuclear antigens. Interpretation: The HIV-1 and HIAP antibody reactivity found in patients with primary biliary cirrhosis and other biliary disorders may be attributable either to an autoimmune response to antigenically related cellular proteins or to an immune response to uncharacterised viral proteins that share antigenic determinants with these retroviruses.
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