Analysis of the entire nucleotide sequence of hepatitis B virus genotype B in the Philippines reveals a new subgenotype of genotype B.

The entire nucleotide sequences were determined for hepatitis B virus (HBV) genotype B (HBV/B) genomes extracted from five patients in the Philippines and designated GenBank AB219426, AB219427, AB219428, AB219429 and AB219430. The serotype of the first four isolates was ayw and that of GenBank AB219430 was adw. Divergences of entire sequences were 1.0-2.0 % between the first four isolates and 3.8-4.2 % between these four and GenBank AB219430. Phylogenetic-tree analysis revealed that, worldwide, HBV/B comprises five subgenotypes: B1, B2, B3, B4 and the new Philippines group, designated B5. Divergences of the entire genome sequences between four isolates in subgenotype B5 and isolates from other countries (subgenotypes) were 4.4-4.8 % with Vietnam (B4), 2.9-3.5 % with Indonesia (B3), 4.7-5.1 % with China (B2) and 5.4-6.0 % with Japan (B1). Similarly, GenBank AB219430 showed the lowest divergences: 3.4 % with the isolate from Indonesia (B3), 5.0 % with Vietnam (B4), 5.4 % with China (B2) and 6.1 % with Japan (B1). This is the first report of entire nucleotide sequences of HBV/B from the Philippines and the results show that these sequences belong to a new subgenotype, B5. The present study identified that HBV/B isolates throughout the world are divided genetically into five subgenotypes, the relationships between geographical distances and the genetic distances of HBV/B being well-correlated.