The predominant genotypes of hepatitis B virus in Thailand

In Thailand, chronic liver disease (CLD) as a consequence of infection with hepatitis B virus (HBV) constitutes a public-health burden. Control and tr eatment are complicated by the virus exhibiting an unusually high mutation rate, with some genotypes apparently causing more severe disease than other s. Restriction-fragment-length-polymorphism (RFLP) analysis of the pre-S re gion of the viral genome, amplified by PCR, was used to determine which gen otypes were most prevalent among Thai patients chronically infected with th e virus. The patients were chronic HBV carriers (40) or cases of chronic he patitis (34), cirrhosis (14) or hepatocellular carcinoma (30). As indicated by the results of earlier studies on CLD patients in South-east Asia, geno type C (68.6%) was clearly predominant. RFLP patterns permitted the C1 (12. 7%), C7 (45.7%), C8 (10.2%) and BI (29.7%) subtypes to be identified. Two s amples that could not be typed by RFLP were analysed by direct sequencing, categorized as type C, and tentatively designated as subtype C9. As compari son of the present data with those previously obtained by direct sequencing of PCR products indicates that RFLP analysis is as specific and reliable a s sequencing and less expensive and time-consuming, RFLP analysis may be pa rticularly useful for epidemiological studies.