RESUMO
Mutations that prevent the expression of the hepatitis B e antigen frequently emerge in the immunoreactive phase of infection. The predominant mutation, the precore G-->A-1896 mutation, is restricted by the variability at position 1858 and is rare in strains with cytosine at nucleotide 1858. The C-1858 variant is characteristic of genotype A. It also occurs in genotypes C and F, but not in B, D, or E, explaining the geographical variation in the prevalence of precore mutants. C-1858 strains have been frequently observed in southeast Asia, but have not been phylogenetically characterized. By sequencing eight complete hepatitis B virus genomes, C-1858 variants of east Asian origin were found to constitute a phylogenetic entity within genotype C that probably diverged several hundred years ago. Further study of the distribution of this variant is warranted.
Assuntos
Variação Genética , Antígenos E da Hepatite B/genética , Vírus da Hepatite B/classificação , Filogenia , Precursores de Proteínas/genética , Genótipo , Hepatite B/virologia , Antígenos E da Hepatite B/sangue , Vírus da Hepatite B/genética , Humanos , Dados de Sequência Molecular , Mutação , Análise de Sequência de DNARESUMO
Hepatitis B virus (HBV) is spread worldwide. Seven genotypes, A-G, have been described, differing by more than 8% of the genome. In eastern Asia and Oceania genotypes B and C are predominant. However, little is known about genotypes in Mongolia and Australian aborigines. We analysed the preS and S regions of HBV from 9 Mongols and 5 Australian Aborigines. All Mongolian strains were of genotype D and were most similar to Central Asian sequences. All the Australian strains were genetically of serotype ayw3, and could not be reliably classified by the S region analysis, but placed on a separate branch. By preS analysis, they were however clearly of genotype C. The 6-7% nucleotide difference from published Asian genotype C sequences suggests that they diverged from Asian genotype C branch more than 1000 years ago.
