NUCLEOTIDE-SEQUENCE OF PRECORE REGION OF HEPATITIS-B VIRUS-DNA IN HBSAG-POSITIVE CARRIERS IN MALAYSIA

As most published studies on precore mutants have been carried out on isolates from patients with liver diseases, and it is unclear whether HBsAg carriers with viraemia in the absence of HBeAg are also generall y infected by such mutants, it was decided to sequence the precore reg ion in same HBV-DNA isolated from HBsAg-positive carriers. Precore seq uences of HBV-DNA from 43 HBsAg carriers in Malaysia were studied. Thr ee HBV subtypes were identified according to the nucleotide sequence o f the precore region. Most of the carriers were found to be infected b y the subtype adr. Mutations were detected in the precore regions. The most common conserved mutation was a silent mutation involving conver sion from T to C (CCT to CCC) at position 1858 at codon 15 (proline). It was found that 4/43 (9.3%) had a mutation at the penultimate codon where TGG was changed to TAG. All 4 isolates with the TAG mutation had nt T at position 1858. Of the 4 carriers who were infected by these m utant viruses, 2 were coinfected with the wild type, 1 was infected on ly by a variant with the mutation at position 1896, while another was infected by a variant with mutations at positions 1896 and 1899. Three of the 4 were anti-HBe positive while 1 was HBeAg positive. Alanine a minotransaminase activities in all 4 carriers were normal This study t herefore demonstrated that variants with stop codons at the penultimat e codon could be found in asymptomatic carriers in Malaysia.