title: Characterization of a large cluster of influenza A(H1N1)pdm09 viruses cross-resistant to oseltamivir and peramivir during the 2013-2014 influenza season in Japan.
abstract: Between September 2013 and July 2014, 2,482 influenza 2009 pandemic A(H1N1) [A(H1N1)pdm09] viruses were screened in Japan for the H275Y substitution in their neuraminidase (NA) protein, which confers cross-resistance to oseltamivir and peramivir. We found that a large cluster of the H275Y mutant virus was present prior to the main influenza season in Sapporo /: Hokkaido, with the detection rate for this mutant virus reaching 29% in this area. Phylogenetic analysis suggested the clonal expansion of a single mutant virus in Sapporo /: Hokkaido. To understand the reason for this large cluster, we examined the in vitro and in vivo properties of the mutant virus. We found that it grew well in cell culture, with growth comparable to that of the wild-type virus. The cluster virus also replicated well in the upper respiratory tract of ferrets and was transmitted efficiently between ferrets by way of respiratory droplets. Almost all recently circulating A(H1N1)pdm09 viruses, including the cluster virus, possessed two substitutions in NA, V241I and N369K, which are known to increase replication and transmission fitness. A structural analysis of NA predicted that a third substitution (N386K) in the NA of the cluster virus destabilized the mutant NA structure in the presence of the V241I and N369K substitutions. Our results suggest that the cluster virus retained viral fitness to spread among humans and, accordingly, caused the large cluster in Sapporo/Hokkaido. However, the mutant NA structure was less stable than that of the wild-type virus. Therefore, once the wild-type virus began to circulate in the community, the mutant virus could not compete and faded out.
authors.affiliation: Influenza Virus Research Center, National Institute of Infectious Diseases, Tokyo, Japan.
authors.forename: Emi
authors.initials: E
authors.lastname: Takashita
authors.affiliation: Division of Virology, Department of Microbiology and Immunology, Institute of Medical Science, University of Tokyo, Tokyo, Japan.
authors.forename: Maki
authors.initials: M
authors.lastname: Kiso
authors.affiliation: Influenza Virus Research Center, National Institute of Infectious Diseases, Tokyo, Japan.
authors.forename: Seiichiro
authors.initials: S
authors.lastname: Fujisaki
authors.affiliation: Pathogen Genomics Center, National Institute of Infectious Diseases, Tokyo, Japan.
authors.forename: Masaru
authors.initials: M
authors.lastname: Yokoyama
authors.affiliation: Influenza Virus Research Center, National Institute of Infectious Diseases, Tokyo, Japan.
authors.forename: Kazuya
authors.initials: K
authors.lastname: Nakamura
authors.affiliation: Influenza Virus Research Center, National Institute of Infectious Diseases, Tokyo, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Shirakura
authors.affiliation: Pathogen Genomics Center, National Institute of Infectious Diseases, Tokyo, Japan.
authors.forename: Hironori
authors.initials: H
authors.lastname: Sato
authors.affiliation: Influenza Virus Research Center, National Institute of Infectious Diseases, Tokyo, Japan.
authors.forename: Takato
authors.initials: T
authors.lastname: Odagiri
authors.affiliation: Division of Virology, Department of Microbiology and Immunology, Institute of Medical Science, University of Tokyo, Tokyo, Japan ERATO Infection-Induced Host Responses Project, Japan Science and Technology Agency, Saitama, Japan Department of Special Pathogens, International Research Center for Infectious Diseases, Institute of Medical Science, University of Tokyo, Tokyo, Japan Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, Wisconsin, USA.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Kawaoka
authors.affiliation: Influenza Virus Research Center, National Institute of Infectious Diseases, Tokyo, Japan mtashiro2@gmail.com.
authors.forename: Masato
authors.initials: M
authors.lastname: Tashiro
mesh_terms: D000146:Acids, Carbocyclic; D000998:Antiviral Agents / Q000494:pharmacology*; D003517:Cyclopentanes / Q000494:pharmacology*; D024882:Drug Resistance, Viral / Q000235:genetics; D006146:Guanidines / Q000494:pharmacology*; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000187:drug effects* / Q000235:genetics; D007564:Japan; D053139:Oseltamivir / Q000494:pharmacology*; D014764:Viral Proteins / Q000235:genetics
chemical_list: D000146:Acids, Carbocyclic; D000998:Antiviral Agents; D003517:Cyclopentanes; D006146:Guanidines; D014764:Viral Proteins; D053139:Oseltamivir; C414210:peramivir