title: Virological characteristics of hepatitis B genotype G/A2 recombination virus in Japan.
abstract: OBJECTIVE
  We identified four cases of infection with hepatitis B virus genotype G and A2 recombinant (HBV/G/A2) strains, which were initially overlooked by enzyme immunoassay-based genotyping. The patients were all men who have sex with men (MSM) and inhabited several metropolitan areas of Japan, suggesting that the recombinant strains may be circulating among high-risk groups such as MSM. Here, we investigated the genomic structure and virological properties of the HBV/G/A2 strains.
  
  
  METHODS
  Complete genome sequences of the isolates were determined and phylogenetically analyzed. Replication efficiency of HBV/G/A2 was investigated by transfecting plasmids containing 1.24-fold viral genome. The in vivo viral kinetics of HBV/G/A2 were investigated using chimeric mice with humanized livers.
  
  
  RESULTS
  Phylogenetic analysis revealed that the four strains were almost identical (>99.7% homologous). The preS2/S region of these strains was highly homologous to that of genotype A2 and the remaining region was almost identical to that of genotype G, reflecting inter-genotypic recombination. Interestingly, in all four cases, genotype A was co-infected as a minor population. In vitro analysis revealed that HBV/G/A2 had a low replication rate. Although detectable viremia was not measurable following the inoculation of HBV/G/A2 into chimeric mice, subsequent superinfection of HBV genotype A greatly enhanced HBV/G/A2 replication and viral spread.
  
  
  CONCLUSIONS
  We found that four cases of HBV/G/A2 recombinant among MSM patients in the metropolitan areas of Japan, and HBV/A co-infections are required for its efficient replication. High-risk groups such as MSM should be carefully tested for infection of genotype G-derived variants.
authors.affiliation: Department of Virology and Liver Unit, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan.|Department of Clinical Laboratory, Nagoya City University Hospital, Nagoya, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Tsuzuki
authors.affiliation: Department of Virology and Liver Unit, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan.|Division of Gastroenterology and Hepatology, St Marianna University School of Medicine, Kawasaki, Japan.
authors.forename: Tsunamasa
authors.initials: T
authors.lastname: Watanabe
authors.affiliation: Gastroenterology and Metabolism, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan.
authors.forename: Etsuko
authors.initials: E
authors.lastname: Iio
authors.affiliation: Department of Infectious Diseases and Immunology Clinical Research Center, National Hospital Organization Nagoya Medical Center, Nagoya, Japan.
authors.forename: Seiichiro
authors.initials: S
authors.lastname: Fujisaki
authors.affiliation: Department of Infectious Diseases and Immunology Clinical Research Center, National Hospital Organization Nagoya Medical Center, Nagoya, Japan.
authors.forename: Shiro
authors.initials: S
authors.lastname: Ibe
authors.affiliation: Department of Virology and Liver Unit, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan.|Department of Clinical Laboratory, Nagoya City University Hospital, Nagoya, Japan.
authors.forename: Satomi
authors.initials: S
authors.lastname: Kani
authors.affiliation: Department of Virology and Liver Unit, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan.
authors.forename: Susumu
authors.initials: S
authors.lastname: Hamada-Tsutsumi
authors.affiliation: Department of Infectious Diseases and Immunology Clinical Research Center, National Hospital Organization Nagoya Medical Center, Nagoya, Japan.
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Yokomaku
authors.affiliation: Department of Infectious Diseases and Immunology Clinical Research Center, National Hospital Organization Nagoya Medical Center, Nagoya, Japan.
authors.forename: Yasumasa
authors.initials: Y
authors.lastname: Iwatani
authors.affiliation: Department of Infectious Diseases and Immunology Clinical Research Center, National Hospital Organization Nagoya Medical Center, Nagoya, Japan.
authors.forename: Wataru
authors.initials: W
authors.lastname: Sugiura
authors.affiliation: Division of Gastroenterology and Hepatology, St Marianna University School of Medicine, Kawasaki, Japan.
authors.forename: Chiaki
authors.initials: C
authors.lastname: Okuse
authors.affiliation: Division of Gastroenterology, Aichi Medical University, Nagakute, Japan.|Department of Gastroenterology, Kainan Hospital, Yatomi, Japan.
authors.forename: Akihiko
authors.initials: A
authors.lastname: Okumura
authors.affiliation: Department of Internal Medicine, Kyorin University School of Medicine, Mitaka, Japan.
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Sato
authors.affiliation: Department of Virology and Liver Unit, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan.|Department of Clinical Laboratory, Nagoya City University Hospital, Nagoya, Japan.
authors.forename: Yasuhito
authors.initials: Y
authors.lastname: Tanaka
keywords: chimeric mice; co-infection; genotype A; genotype G/A recombination; hepatitis B virus; men who have sex with men