Detection of hepatitis B antigen in circulating immune complexes in acute and chronic hepatitis

By using polyethylene glycol precipitation at low concentration (PEG test) and the radiolabeled C1q binding test, immune complexes were detected sera from acute (23/28) and chronic (28/32) hepatitis patients, hemodialyzed patients with chronic hepatitis B surface (HBs) antigenemia (7/19), and asymptomatic HBs antigen carriers (2/11). After treatment of PEG precipitates with acidic pH, heating, or proteolytic enzyme (protease), electroimmunodiffusion or radioimmunoassay revealed the presence of HBs antigen or antibody in dissociated immune complexes in sera from several acute and chronic hepatitis patients. Electron microscopy showed immune complexes of HB virus in 9 of 12 PEG precipitates obtained from PEG-test-positive sera; these 9 precipitates were from patients with acute or chronic hepatitis and the other three from chronic HBs Ag carriers. Free HB virus particles were observed after protease digestion of PEG precipitates. Neither immune complexes nor virus particles were seen in precipitates from PEG-test-negative but HBs-Ag-positive sera from chronic carriers.