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).

Distribution of HBV genotypes among HBV carriers in Benin:phylogenetic analysis and virological characteristics of HBV genotype E

AIM: To determine the distribution of Hepatitis B virus (HBV) genotypes in Benin, and to clarify the virological characteristics of the dominant genotype.METHODS: Among 500 blood donors in Benin, 21 HBsAg-positive donors were enrolled in the study. HBV genotypes were determined by enzyme immunoassay and restriction fragment length polymorphism. Complete genome sequences were determined by PCR and direct sequencing.RESULTS: HBV genotype E (HBV/E) was detected in 20/21 (95.2%), and HBV/A in 1/21 (4.8%). From the age-specific prevalence of HBeAg to anti-HBe seroconversion (SC) in 19 HBV/E subjects, SC was estimated to occur frequently in late teens in HBV/E.The comparison of four complete HBV/E genomes from HBeAg-positive subjects in this study and five HBV/E sequences recruited from the database revealed that HBV/E was distributed throughout West Africa with very low genetic divers ity (nucleotide homology 96.7-99.2%).Based on the sequences in the basic core promoter (BCP)to precore region of the nine HBV/E isolates compared to those of the other genotypes, a nucleotide substitution in the BCP, G1757A, was observed in HBV/E.CONCLUSION: HBV/E is predominant in the Republic of Benin, and SC is estimated to occur in late teens in HBV/E. The specific nucleotide substitution G1757A in BCP, which might influence the virological characteristics,is observed in HBV/E.

Acute hepatitis B of genotype H resulting in persistent infection

A 47-year-old man presented with general fatigue and dark urine.The laboratory data showed increased levels of hepatic transaminases.The patient was positive for hepatitis B virus(HBV)markers and negative for antihuman immunodeficiency virus.The HBV-DNA titer was set to 7.7 log copies/mL.The patient was diagnosed with acute hepatitis B.The HBV infection route was obscure.The serum levels of hepatic transaminases decreased to normal ranges without any treatment,but the HBVDNA status was maintained for at least 26 mo,indicating the presence of persistent infection.We isolated HBV from the acute-phase serum and determined the genome sequence.A phylogenetic analysis revealed that the isolated HBV was genotype H.In this patient,the elevated peak level of HBV-DNA and the risk alleles at human genome single nucleotide polymorphisms s3077and rs9277535 in the human leukocyte antigen-DP locus were considered to be risk factors for chronic infection.This case suggests that there is a risk of persistent infection by HBV genotype H following acute hepatitis;further cases of HBV genotype H infection must be identified and characterized.Thus,the complete determination of the HBV genotype may be essential during routine clinical care of acute hepatitis B outpatients.