Background: The viral factors of hepatitis B virus (HBV), such as genotypes and mutations, were reported to affect the development of fulminant hepatitis B (FHB), but the mechanism is still unclear. Objectives: To investigate HBV mutations associated with FHB, especially in the subgenotype B1/Bj HBV (HBV/B1), which are known to cause FHB frequently in Japan. Study design: A total of 96 serum samples from acute self-limited hepatitis B (AHB) patients and 13 samples from FHB patients were used for full-genome/partial sequencing. A total of 107 chronic infection patients with HBV were also examined for the distribution of mutants. Results: In the analysis of full-genome sequences of HBV/B1 (FHB, n= 11; non-FHB, n= 35) including those from the databases, mutations at nt 1961 [T1961V (not T)] and nt 1962 [C1962D (not C)], which change S21 in the core protein, were found more frequently in FHB than in non-FHB (100% vs. 20%, 55% vs. 3%, respectively). When our FHB and AHB samples were compared, T1961V and C1962D were significantly more frequent in FHB than in AHB, both in the overall analysis (46% vs. 6%, 39% vs. 3%, respectively) and in HBV/B1 (100% vs. 29%, 100% vs. 14%, respectively). A newly developed PCR system detecting T1961V showed that HBV/B1 and low viral load were independent factors for the mutation among chronic infection patients. Conclusions: T1961V/C1962D mutations were found frequently in FHB, especially in HBV/B1. The resulting S21 substitution in the core protein may play important roles in the development of FHB.
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