HBV genotype distribution in Japan and it's clinical significance

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The geographic distribution of HBV genotypes in Japan and its clinical relevance are poorly understood. 720 Japanese patients with chronic HBV infection was determined HBV genotype by PCR-RFLP. 1.7 %, 12.2 %, 84.7 %, 0.4 %, 1.0 % were classified into HBV genotype A, B, C, D and mixed. 94.2 % of patients in the Japan mainland had genotype C, while 60.0 % of the patients in Okinawa and 22.9 % in the Tohoku, the northern part of mainland, harbored genotype b. Compared with genotype C patients, genotype B patients showed elder age, lower rate of positive HBeAg, lower level of serum HBV DNA. These results indicate tat genotypes C and B are predominant in Japan, and there are significant differences in geographic distribution and clinical characteristics among the patients with the different genotypes. The clinical and virological differences of HBV genotypes B and C are unclear. To evaluate the differences of HBV genotype B and C, we carried out a case-control study in 50 each of Japanese patients chronically infected with HBV genotype B and C, who were matched for age and sex. HBeAg was more frequently detected, while anti-HBe was less common in genotype B than C patients. The occurrence of A-to-G mutation at nt 1896 in the precore region was comparable between genotype B and C patients, and it correlated with anti-HBe. The double mutation in core promoter was more frequent in genotype C than B patients, and did not correlate with HBeAg. By multiple logistic regression analysis, double mutations in core promoter was associated significantly with genotype C, age 35 years and more advanced liver disease, but it was not associated with sex, HBeAg, HBV DNA or the precore mutation. These results highlights differences in clinical and virological characteristics between patients infected with HBV of genotypes B and C.