title: Classifying genotype F of hepatitis B virus into F1 and F2 subtypes.
abstract: OBJECTIVE
  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 47 HBV/F1 isolates as well as 136 representing the other six genotypes (A-E and G), two clusters separated by distinct genetic distances emerged.
  
  
  CONCLUSIONS
  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).
authors.affiliation: Department of Internal Medicine and Molecular Science, Nagoya City University Graduate School of Medical Sciences, Nagoya 467-8601, Japan.
authors.forename: Hideaki
authors.initials: H
authors.lastname: Kato
authors.forename: Kei
authors.initials: K
authors.lastname: Fujiwara
authors.forename: Robert G
authors.initials: RG
authors.lastname: Gish
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Sakugawa
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Yoshizawa
authors.forename: Fuminaka
authors.initials: F
authors.lastname: Sugauchi
authors.forename: Etsuro
authors.initials: E
authors.lastname: Orito
authors.forename: Ryuzo
authors.initials: R
authors.lastname: Ueda
authors.forename: Yasuhito
authors.initials: Y
authors.lastname: Tanaka
authors.forename: Takanobu
authors.initials: T
authors.lastname: Kato
authors.forename: Yuzo
authors.initials: Y
authors.lastname: Miyakawa
authors.forename: Masashi
authors.initials: M
authors.lastname: Mizokami
mesh_terms: D000595:Amino Acid Sequence; D019143:Evolution, Molecular; D016679:Genome, Viral; D005838:Genotype; D006509:Hepatitis B / Q000821:virology*; D006515:Hepatitis B virus / Q000145:classification* / Q000235:genetics*; D006801:Humans; D017720:Molecular Epidemiology; D008969:Molecular Sequence Data; D010802:Phylogeny; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA