Detection of hepatitis B virus core gene products in sera and liver of HBV-infected individuals.

The C gene of hepatitis B virus (HBV) codes for at least two different proteins (p 21c and p 17e). To investigate the expression of C-gene-encoded proteins in vivo, serum and liver samples from HBsAg-positive patients as well as serial serum samples from an HBV-transfected chimpanzee were studied. Antibodies directed against bacterially synthesized C-fusion proteins were used in Western blots to test for the presence of p 21c and p 17e. In serial serum samples from the chimpanzee, p 21c and p 17e were detected concomitantly during the acute phase of the infection. When sera of patients with chronic HBV infection were studied, all sera containing p 17e were found to be positive also for p 21c. Sera positive for HBV DNA but negative for HBeAg were only positive for p 21c, indicating that HBeAg/p 17e is not an absolutely reliable marker for infectivity. In liver tissue specimens from 20 patients with HBV-related liver diseases, p 21c was detected in five cases, indicating viral replication. The p 17e antigen, however, was present only in low amounts in three of these five, suggesting that synthesis of p 21c and p 17e is not strictly coupled. C/Pol-gene-encoded fusion proteins were found in the liver tissue of only one patient with cirrhosis, supporting our previous finding that detectable levels of these proteins are expressed rarely.