Radioimmunoassay for DetectingHepatitisB Core Antigenin Serum from Patientswith ChronicHepatitisB Infection

The core antigen component of hepatitis B virus (HBV), HBcAg, may be used as a marker of viral replication.We describe a radioimmunoassay for HBcA9 in serum, and compare results with those by other similar methods. Samples are centrifuged over a sucrose gradient containing2mercaptoethanol,and the resultingpellets are resuspended In a nonionic detergent solution. After a bead coated with anti-HBcAg is incubated with this suspension, ‘al-labeled anti-HBcAg is added, and is also bound by the antigen. The specificity of the methodwas verifiedby blocking with purified lgG antibodiesto HBcAg. When wetested by this methodfor HBcAg in sera from 60 patients with chronic HBV Infection, all those with circulatingHBV-DNA polymerase tested p081tive for HBcAg. All sera from HBV-negative controlsshowed no detectable HBcAg. The correlationbetween the presence of HBcAg and HBV-DNA polymerase was significant (r = 0.715, p <0.001). Samples can be tested more quicklyand easily with this method, and itssensitivitycompareswell with that of other similar methods.