Prevalence of core promotor and precore mutants of hepatitis B virus in thailand by RFLP and sequencing.

ABSTRACT

Hepatitis B virus has been known to frequently undergo mutations of its genome at various sites, mostly due to it employing a reverse transcriptase devoid of proofreading capacity in the course of its replication. The purpose of the present study has been to screen 257 HBsAg-positive chronic liver disease patients, more specifically 78 cases chosen at random out of those negative for HBeAg and 33 of the HBeAg-positive cases serving as controls for three discreet point mutations in the precore/core region of hepatitis B virus. To that end, HBV DNA extracted from sera was amplified by polymerase chain reaction (PCR) using semi-nested primers and subsequently subjected to restriction fragment length polymorphism (RFLP) analysis, 36 HBeAg-negative versus 30 HBeAg-positive sera, respectively, as well as to direct sequencing in some samples randomly selected to corroborate the RFLP results. Our results showed double mutations at positions 1762 and 1764 of the core promoter in between 25/36 (69.4%) and 19/25 (76%) of the sera tested, a missense mutation of the start codon in between 8/36 (22.2%), and 5/25 (20%) and a mutation turning codon 1896 into a stop codon in between 9/36 (25%) and 6/25 (24%) determined by RFLP and sequencing, respectively. These data indicate the double mutation at positions 1762 and 1764 to be the most prevalent among HBeAg-negative chronic hepatitis patients in Thailand whereas, in contrast to reports from other Asian countries, the mutation at nucleotide 1896 occurred in a mere 25%, while on the other hand the mutation abolishing the start of protein synthesis was observed to occur at a higher frequency than determined in several other geographical areas.