Abstract
Tibet is a highly hepatitis B virus (HBV) endemic area. Two types of C/D recombinant HBV are commonly isolated in Tibet and have been previously described. In an effort to better understand the molecular characteristic of these C/D recombinant strains from Tibet, we undertook a multistage random sampling project to collect HBsAg positive samples. Molecular epidemiological and bio-informational technologies were used to analyze the characteristics of the sequences found in this study. There were 60 samples enrolled in the survey, and we obtained 19 whole-genome sequences. 19 samples were all C/D recombinant, and could be divided into two sub-types named C/D1 and C/D2 according to the differences in the location of the recombinant breakpoint. The recombination breakpoint of the 10 strains belonging to the C/D1 sub-type was located at nt750, while the 9 stains belonging to C/D2 had their recombination break point at nt1530. According to whole-genome sequence analysis, the 19 identified strains belong to genotype C, but the nucleotide distance was more than 5% between the 19 strains and sub-genotypes C1 to C15. The distance between C/D1with C2 was 5.8±2.1%, while the distance between C/D2 with C2 was 6.4±2.1%. The parental strain was most likely sub-genotype C2. C/D1 strains were all collected in the middle and northern areas of Tibet including Lhasa, Linzhi and Ali, while C/D2 was predominant in Shannan in southern Tibet. This indicates that the two recombinant genotypes are regionally distributed in Tibet. These results provide important information for the study of special HBV recombination events, gene features, virus evolution, and the control and prevention policy of HBV in Tibet.
Highlights
Hepatitis B virus (HBV) infection is a serious health problem and represents a substantial disease burden in China
Carriers of HBV are at increased risk for developing cirrhosis and hepatocellular carcinoma (HCC) [2]
HBV genotypes/sub-genotypes may play an important role in causing different disease progression profiles during chronic hepatitis B infection
Summary
Hepatitis B virus (HBV) infection is a serious health problem and represents a substantial disease burden in China. During 2006, a nationwide hepatitis B investigation was carried out in China. Carriers of HBV are at increased risk for developing cirrhosis and hepatocellular carcinoma (HCC) [2]. HBV genotypes/sub-genotypes may play an important role in causing different disease progression profiles during chronic hepatitis B infection. Eight confirmed genotypes (A to H), two tentative genotypes (I and J) and more than forty sub-genotypes of HBV have been reported around the world [6]. HBV genotypes and sub-genotypes vary in geographical distribution. It has been reported that genotype A and D are found worldwide; while genotypes B and C are found most commonly in East and Southeast Asia; genotype E prevails in Africa; genotype F in native Americans; genotype G is found mainly in Europe and the USA, and genotype H is predominantly isolated in Mexico [7]
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