Comparison of envelope and precore/core variants of hepatitis B virus (HBV) during chronic HBV infection.

We analyzed entire pre-C/C and pre-S/S coding genes of hepatitis B virus (HBV) in serial serum samples from four chronic HBV carriers with 4-5 years of follow-up. Two patients with chronic active hepatitis became seronegative for HB e antigen (HBeAg), but the hepatitis did not subside, while the other two were persistent asymptomatic carriers with normal aminotransferase values. DNAs amplified by PCR were cloned and sequenced (subtype adr). After HBeAg became negative, one patient had 96-183 bp deletions in 4/6 clones for C gene. In addition, both patients had 129-183 bp deletions in 3/6 and 2/5 clones for pre-S1 gene, respectively. Divergence rate of deduced amino acid for both pre-C/C and pre-S/S regions from the adr subtype was significantly higher in patients with chronic hepatitis than in asymptomatic carriers. Furthermore, the divergence rate for pre-S/S region was usually greater in asymptomatic carriers as well as chronic hepatitis patients compared with that for pre-C/C region. However, no significant difference was found in the rate of amino acid divergence for the entire HBV genes between the serial samples in all patients studied here. These results suggest that active hepatitis induces variation of HBV gene and defective virus is often selected along with the disappearance of HBeAg. In addition, the fact that patients with active liver disease possess greater numbers of mutant clones than asymptomatic carriers suggests that viral mutants are being immune-selected.