In Thailand, hepatitis B virus infection along with its fatal sequelae liver cirrhosis and hepatocellular carcinoma constitutes a public health burden of endemic proportions. The second phase of the infection is usually characterized by cessation of HBV DNA replication and seroconversion to anti-HBe. However, persistent viremia with active liver disease has been encountered in some anti-HBe positive patients, a discrepancy explained by mutations in the precore/core region of the viral genome. The resulting failure to synthesize HBeAg may help the virus evade immune clearance, while HBV replication and expression of HBcAg proceed unchecked. Discreet types of mutation in the precore/core region have been found at varying prevalence depending on the predominant HBV genotype in the respective geographical areas. The purpose of the present study has been to elucidate both prevalence and type along with the nucleotide positions of the mutations prevailing among Thai chronic hepatitis patients. We subjected 68 patients to serological tests for HBeAg, as well as semi-nested PCR with subsequent DNA sequencing. HBV DNA was detected in 87.5% of HBeAg positive and 40.9 % of HBeAg negative patients, respectively. Mutations in the core promoter amounted to 28.6 % in HBeAg positive and 75% in HBeAg negative patients, in the start codon of the precore gene to 37.5% and in codon 28 to 18.8% in HBeAg negative patients. Our results have shown mutations affecting the core promoter of HBeAg to be by far the most prevalent in Thai patients, followed by mutations of the start codon whereas those changing codon 28 into a stop codon are less frequently encountered than has been reported from other areas indicating a distinct HBV genotype prevailing in Thailand.
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