[Characterization of basal core promoter/precore gene mutations in chronically infected patients with hepatitis B virus genotype D in Mersin Province, Turkey]. / Mersin ilinde hepatit B virus genotip D ile kronik enfekte hastalarda bazal kor promotor/prekor gen bölgesi mutasyonlarinin karakterizasyonu.

ABSTRACT

The basal core promoter (BCP) and precore (PC) gene regions of hepatitis B virus (HBV) genome are important for the viral replication and synthesis of "e" antigen. Genetic variability has been described in PCP and PC gene regions, commonly in HBeAg negative patients. The aim of this study was to determine the frequency of the predominant mutation patterns of BCP/PC gene regions and their correlations with HBeAg status, HBV-DNA levels, and liver biochemical profiles in chronic hepatitis B (CHB) patients infected with genotype D, in Mersin province which is located at Mediteranean part of Turkey. A total of 54 CHB patients (33 male, 21 female; mean age 40.05±12.91 years) infected with HBV genotype D were enrolled in the study. Serum HBV-DNA levels, serological markers (HBsAg, anti-HBs, HBeAg, anti-HBe, anti-HBc) and biochemical profiles (ALT and AST) were analyzed in all patients. BCP and PC gene regions were determined by polymerase chain reaction (PCR) and mutations of these regions were determined by direct sequencing of PCR products then aligned with known wild-type HBV sequences. BCP [nucleotide (nt.) 1753-1762/1764] and/or PC (nt. 1896) mutations were detected in 87.75% (43/49) of the patients. Mutation rates were detected as 97.1% (33/34) and 66.7% (10/15) in the HBeAg negative and in HBeAg positive patient groups, respectively (p=0.008). PC nt. G1896A mutation was more common in HBeAg negative samples than in HBeAg positive samples (73.5% vs. 20%, p=0.001), however there was no significant differences in the occurrence of BCP mutations between the two groups (p=0.331). No correlation was found between the presence of BCP and/or PC mutations and serum HBV-DNA or ALT-AST levels. Our study reveals that significant number of chronically infected patients with genotype D HBV have BCP and PC variants. G1896A stop codon mutation in precore region seems to have a significant role in the loss of HBeAg in our patients. The results of our study provided important data about the frequency and the genetic heterogeneity of different kinds of mutations occurring at BCP and PC gene regions.