Rare pre-core stop-codon mutant nt. 1897 predominates over wide-spread mutant nt. 1896 in an unusual course of chronic hepatitis B

We present a patient with an unusual course of hepatitis B e antigen (HBeAg)-negative chronic hepatitis B who had repeated reactivations of his disease progressing to cirrhosis with terminal liver failure. Each flare up presented like an acute hepatitis with very high titres of hepatitis B virus (HBV) and high inflammatory activity followed by rapid clearance of viraemia. The pre-core genome of HBV isolated from sera during 5 years of follow up was analysed. Direct sequencing of polymerase chain reaction (PCR) products derived from consecutive sera showed a rare pre-core stop-codon mutation at nucleotide (nt.) 1897 G→A with an accompanying mutation nt. 1857 C→T as well as a stop-codon mutation nt. 1896 G→A. By cloning and sequencing of PCR products the mutant strain with mutation nt. 1897 was shown to predominate over viral strains with a mutation nt. 1896 during the course of disease, although the stop-codon mutation nt. 1896 in general is observed more frequently. Both mutations allow viral replication by stabilizing the encapsidation signal 'ε'. This allowed HBV replication at a very high level as observed during flare ups. The absence of HBeAg may be responsible for the massive cytotoxic T-cell response towards hepatocytes which might explain the rapid progression to liver cirrhosis although no, or very little, HBV replication was observed for long periods. However, there is no clear explanation as to why the nt. 1897 mutant strain overwhelmed the other virus strains.