BACKGROUND: The pathogenesis of severe hepatitis B remains unknown. Reports have indicated that hepatitis B virus（HBV）mutations are important factors in the pathogenesis of this disease. This study was to investigate the genetic heterogeneity of HBV strains from serum samples of patients with fulminant hepatitis B.
METHODS: Full-length HBV genomes from 4 patients with severe hepatitis B were cloned and sequenced to observe mutations in every open reading-frame (ORF). Se-rum samples of another 25 patients with severe hepatitis B, 30 patients with chronic hepatitis B, and 25 HBV carriers were collected for sequencing and comparison of mutations in preS2, preC and core promoter regions.
RESULTS: Of 4 HBV full-length genome sequences, 3 had a G to A mutation at nucleotide A1896 in the preC region and 1 had double mutations of T1762-A1764 in the core promoter region. The 4 sequences showed mutations in the known B or T cell epitopes of the preS2 and C regions. For the other 3 groups, more mutations were seen in the preS2 region in the HBV isolates from the patients with severe hepatitis B than those from the patients with chronic hepatitis B and HBV carriers (P<0.01). There was a significant difference of mutations in the T cell epitope region of preS2 between the patients with severe hepatitis B and those with chronic hepatitis B or HBV carriers (P<0.01). In the preC and core promoter regions, the mutation frequencies of T1653 and C1753 were 48.0% and 24.0% respectively in the patients with severe hepatitis B, but none of these mutations were observed in the patients with chronic hepatitis B group or HBV carriers (P<0.01). The mutation frequency of T1762-A1764 was 76.0% in the patients with severe hepatitis B, 40.0% in the patients with chronic hepatitis B (P<0.01), and 16.0% in the HBV carriers (P<0.01). There was a significant difference in A1896 mutation between the patients with severe hepatitis B and the patients with chronic hepatitis B (P<0.05) or the HBV carriers (P<0.05).
CONCLUSION: Our observations suggest that the accumulation and persistence of high frequency mutations or complex mutations may be associated with the development and deterioration of HBV infection.