Classifying genotype F of hepatitis B virus into F1 and F2 subtypes

AIM: To explore the propriety of providing hepatitis B virus(HBV) genotypes F and H with two distinct genotypes.METHODS: Eleven HBV isolates of genotype F (HBV/F)were recovered from patients living in San Francisco,Japan, Panama, and Venezuela, and their full-length sequences were determined. Phylogenetic analysis was carried out among them along with HBV isolates previously reported.RESULTS: Seven of them clustered with reported HBV/F isolates in the phylogenetic tree constructed on the entire genomic sequence. The remaining four flocked on another branch along with three HBV isolates formerly reported as genotype H. These seven HBV isolates, including the four in this study and the three reported, had a sequence divergence of 7.3-9.5% from the other HBV/F isolates,and differed by ＞ 13.7% from HBV isolates of the other six genotypes (A-E and G). Based on a marked genomic divergence, falling just short of ＞8% separating the seven genotypes, these seven HBV/F isolates were classified into F2 subtype and the former seven into F1 subtype provisionally. In a pairwise comparison of the S-gene sequences among the 7 HBV/F2 isolates and against 47HBV/F1 isolates as well as 136 representing the other six genotypes (A-E and G), two clusters separated by distinct genetic distances emerged.CONCLUSION: Based on these analyses, classifying HBV/F isolates into two subtypes (F1 and F2) would be more appropriate than providing them with two distinct genotypes (F and H).

Genotype and phylogenetic characterization of hepatitis B virus among multi-ethnic cohort in Hawaii

AIM: Hepatitis B virus (HBV) genomes in carriers from Hawaii have not been evaluated previously. The aim of thepresent study was to evaluate the distribution of HBV genotypes and their clinical relevance in Hawaii.METHODS: Genotyping of HBV among 61 multi-ethnicc arriers in Hawaii was performed by genetic methods.Three complete genomes and 61 core promoter/precore regions of HBV were sequenced directly.RESULTS: HBV genotype distribution among the 61 carderswas 23.0% for genotype A, 14.7% for genotype B and 62.3% for genotype C. Genotypes A, B and C were obtained from the carriers whose ethnicities were Filipino and Caucasian,Southeast Asian, and various Asian and Micronesian,respectively. All cases of genotype B were composed of recombinant strains with genotype C in the precore plus core region named genotype Ba. HBeAg was detected more frequently in genotype C than in genotype B (68.4% vs 33.3%, P<0.05) and basal core promoter (BCP) mutation (T1762/A1764) was more frequently found in genotype C than in genotype B. Twelve of the 38 genotype C strains possessed C at nucleotide (nt) position 1858 (C-1858).However there was no significant difference in clinical characteristics between C-1858 and T-1858 variants. Based on complete genome sequences, phylogenetic analysis revealed one patient of Micronesian ethnicity as having C1858 clustered with two isolates from Polynesia with T-1858.In addition, two strains from Asian ethnidties were clustered with known isolates in carriers from Southeast Asia.CONCLUSION: Genotypes A, B and C are predominant types among multi-ethnic HBV carriers in Hawaii, and distribution of HBV genotypes is dependent on the ethnic background of the carriers in Hawaii.