The T1858 variant predisposing to the precore stop mutation correlates with one of two major genotype F hepatitis B virus clades

The precore mutation G(1896) --> A occurs frequently in anti-HBe-positive carriers of HBsAg with T-1858 in the stem of the encapsidation signal. Hepatitis B virus (HBV) genotype F, considered an Amerindian genotype, subdivides into two clades and the precore mutation occurs in Central American F strains. To investigate the relationship between substitutions at position 1858 and these clades, the precore and small S genes of 48 strains of HBV genotype F were subjected to phylogenetic analyses. Isolates of one clade, formed mainly of Central American strains, all had T-1858 and Thr(45) in the S gene, whereas in the other clade, formed mainly of South American strains and one strain from Polynesia, all had C-1858 and Leu(45). The latter strain was related to strains from Venezuela and Colombia, supporting an Amerindian contribution to the Polynesian population. The position of the Polynesian strain in the phylogenetic tree indicates that the two clades have resulted from an early split, showing a high degree of genetic stability of the stem of the HBsAg encapsidation signal.