INCIDENCE AND CLINICAL-SIGNIFICANCE OF HEPATITIS-B VIRUS PRECORE GENETRANSLATION INITIATION MUTATIONS IN E-ANTIGEN-NEGATIVE PATIENTS

Hepatitis Be antigen (HBeAg)-negative chronic hepatitis B (CHB) is ass ociated with hepatitis B virus (HBV) variants harbouring changes in th e precore region. Most commonly, a G to A point mutation at nucleotide 1896 (m1896) creates a novel translation stop codon that prevents HBe Ag production. In the Mediterranean region the m1896 mutation prevails in greater than 98% of HBeAg-negative CHB patients. In this study the prevalence of additional mutations in the precore region was investig ated among patients with chronic HBV infection. Precore sequences were determined by sequencing serum HBV DNA amplified by polymerase chain reaction (PCR) with primers flanking the precore/core region. Thirty-o ne HBeAg-negative and five HBeAg-positive individuals were studied. Al l HBeAg-negative patients (100%) harboured the m1896 mutation and 20 ( 64.5%) also had a G to A mutation at nucleotide 1899 (m1899), Addition al mutations affecting the translation initiation of the precore gene were found in seven (22.5%) patients, all with active liver disease, f ive of whom had episodes of HBV reactivation. HBeAg-positive patients had no mutations in these positions and neither did any of the five HB eAg-negative patients with normal levels of liver enzymes, representin g the healthy carrier state of HBV infection. Serial sample analysis f rom one patient revealed that the initiation codon mutation developed following HBeAg seroconversion and the appearance of m1896. During per iods of high HBV replication, the ratio of mutant to wild-type ATG was found to increase in parallel with HBV DNA levels. These data show th at a significant proportion of HBeAg-negative patients who already har bour the 1896 stop codon mutation may subsequently develop precore tra nslation initiation mutations, which appear to be associated with enha nced HBV replication and severe liver disease.