Complete genome sequence and phylogenetic analysis of hepatitis B virus isolated from turkish patients with chronic HBV infection

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Hepatitis viruses are the leading causes of chronic liver disease resulting in chronic hepatitis, cirrhosis, and hepatocellular carcinoma in the world and also in Turkey. Although Turkey has an intermediate rate of hepatitis B virus (HBV) infection with a prevalence reported as 5%, a complete HBV genome sequence has not been published. In this study, the molecular characterization and phylogenetic analysis are described of 11 complete HBV genomes isolated from 11 naïve patients (5 male, 6 female; ages: 18--54 years old, median 35 years old) with chronic HBV infection. Of 11 patients, 7 and 4 were HBeAg positive/anti-HBe negative and HBeAg negative/anti-HBe positive, respectively. All patients had no co-infection with HCV, HDV, or HIV. HBV DNA was extracted from the sera of the patients. The complete genome was amplified by PCR and cloned into a TA vector. The PCR products were sequenced directly and the complete HBV genome sequences were determined. Ten HBV genomes were 3182 base pairs in length. There was a 183 bp deletion (between nucleotides 2987--3169) in pre-S region in one HBeAg positive patient. There were two pre-core stop codons (G1896A) in two HBeAg negative and three core promoter dual mutations (T1762/A1764) in one HBeAg positive and two HBeAg negative patients' HBV genomes. Phylogenetic analysis of all complete genomes yielded that all Turkish sequences were clustered in genotype D branch (ten in subgenotype D1 and one in subgenotype D2). The analysis of S gene amino acid sequences revealed that surface gene subtypes of one and ten HBV strains were subtype ayw3 and ayw2, respectively. This study indicates that Turkish patients with chronic hepatitis B infection show very little genotypic heterogeneity. Genotype D of HBV DNA and subtype ayw2 of surface gene represent almost the whole Turkish patient population infected with HBV.