Detection of antibodies to proteins encoded by the X-region of hepatitis B virus (HBV) in sera of patients with chronic HBV infection: correlation with other HBV markers.

The genome of hepatitis B virus (HBV) contains a fourth open reading frame (ORF), designated X-region. It was the aim of our study to test sera of patients with chronic HBV infection for the presence of antibodies reactive with a 17 kd gene product of the X-ORF. For this purpose, a 35S-X-ORF-encoded protein, synthesized in vitro, was applied as antigen for the detection of antibodies to HBx proteins in sera of 86 individuals. Antibodies reacting with a gene product of the X-ORF were present in 10 out of 24 HBsAg-positive patients with hepatocellular carcinoma (PLC) or liver cirrhosis and in one out of 8 HBsAg-carriers. In addition, the antibodies could also be detected in 6 out of 35 sera from patients with PLC or cirrhosis negative for HBsAg but positive for anti-HBc and anti-HBs. Antibodies to a gene product of the X-ORF can be detected in sera of patients with chronic HBV-related liver disease, independently of HBsAg and the HBeAg/anti-HBe system.