Generally speaking, DNA viruses have fewer genetic mutations than RNA viruses; yet HBV, a DNA virus, is characterized by a viral proliferation mechanism including reverse transcription, and high rates of mutation.[56] HBV genotypes are

classifications selleckchem used to denote differences in the nucleic acid sequence associated with these genetic mutations. At present, nine genotypes have been identified, from A through J (with genotype I being a subtype of C). Types A, B, C and D account for nearly all genotypes extant in Japan. HBV genotype detection techniques include RFLP (restriction fragment length polymorphism), EIA (enzyme immunoassay), and nucleic acid sequence phylogenetic analysis. Of these only EIA, the technique developed by Usuda et al., is approved by Japanese national

medical insurance. EIA uses a combination of monoclonal antibodies capable of recognizing genotype-specific amino acids in the PreS2 domain.[57] Many differences have been reported in the clinical picture of HBV genotypes, which are useful for predicting outcomes and therapeutic effects, as shown in Table 9.[58] Western strains (HBV/A2/Ae) Asian/African strains (HBV/A1/Aa) Often becomes chronic (5%–10%) Increasing prevalence, particularly in younger age groups Asian strains (HBV/Ba) Japanese strains (HBV/B1/Bj) Often becomes fulminant 10%–20% of total Southeast Asia (HBV/Cs) East Asia (HBV/Ce) High rate HCC Around 85% of total HBV genotype A MLN8237 mouse has been linked to horizontal infection among young people in Japan, with a steady increase seen in the relative incidence of HBV genotype A, most notably in urban areas.[59] Recent studies have demonstrated a marked increase in infection rates for HBV genotype Ae, a genotype traditionally more prevalent in Western countries. This trend medchemexpress is particularly noticeable among young people in Japan, and has been attributed to sexual transmission and illicit drug usage. The normal pattern for a person who becomes infected with HBV during adulthood is a period of acute hepatitis after which the virus is eliminated, leading

to quiescence of hepatitis. But with HBV genotype A, the virus tends to remain in the body after the acute phase, making the patient more likely to become a HBV carrier.[5] Nevertheless, outcomes are generally favorable for infections with HBV genotype A. HBV genotype B is divided into two subtypes: HBV genotype Bj, found in Japan, and HBV genotype Ba, found in the rest of Asia. The Japanese strain (HBV genotype Bj) is distributed widely throughout Japan, from the Tohoku region and parts of Hokkaido in the north to Okinawa in the south. It generally causes very mild disease; most cases remain indefinitely as asymptomatic carriers with a negligible incidence of HCC. However, the Bj subtype has a mutation that can enter site 1896 in the pre-core region.