[Current status in hepatitis virus research]

Seroconversion from eAg to anti-e is frequently seen in the course of chronic hepatitis B infection. This phenomenon is closely related to mutation of the precore region; a G-to-A substitution of nucleotide position 1986 replaces tryptophan to translational stop codon. This mutant is responsible for the fulminant hepatitis or acute exacerbation of chronic hepatitis B. The hepatitis C virus shows a high rate of genome variations, especially at the envelope (E and NS1) region, where a neutralizing epitope is believed to exist. According to the sequence identity, the hepatitis C virus is divided into four subtypes. The virus appears to evolve separately in geographically different areas and the subtyping may have some clinical implications, such as in interferon treatment. Hepatitis E virus has three open reading frames and share the high nucleotide identity among strains isolated from Myanmar and China. Hepatitis E is endemic in the developing world and is not present in industrialized countries.