A MONOCLONAL-ANTIBODY AGAINST THE X-PROTEIN OF HEPATITIS-B VIRUS - FINE MAPPING OF ITS EPITOPE AND APPLICATION IN A QUANTITATIVE ELISA OF THE X-PROTEIN IN SERA OF HEPATITIS-B PATIENTS

A HBx-specific mouse monoclonal antibody was developed and its epitope mapped to a hydrophilic segment (94)HKRTLGL(100) using the multipin p eptide synthesis technique. A sensitive ELISA with a threshold of 5 to 10 ng was developed to identify the HBx-positive hepatitis B cases an d measure the levels of HBx in sera. The same patient sera were also a nalyzed for the presence of anti-HBx using the purified recombinant an tigen. HBx was present in 23% of the cases (15/65) whereas only 14% of the cases (9/65) were positive for anti-HBx. The mean value of HBx in acute hepatitis sera was higher (522 ng/ml) than in cirrhosis cases ( 48 ng/ml). PCR amplification of the S gene showed that all 15 HBx-posi tive cases were also positive for the viral DNA.