title: Genetic characterization of an H5N1 avian influenza virus from a vaccinated duck flock in Vietnam.
abstract: This study reports the genetic characterization of a highly pathogenic avian influenza virus subtype H5N1 isolated from a moribund domestic duck in central Vietnam during 2012. In the moribund duck's flock, within 6 days after vaccination with a commercial H5N1 vaccine (Re-5) to 59-day-old birds, 120 out of 2,000 ducks died. Genetic analysis revealed a substantial number of mutations in the HA gene of the isolate in comparison with the vaccine strains, Re-1 and Re-5. Similar mutations were also found in selected Vietnamese H5N1 strains isolated since 2009. Mutations in the HA gene involved positions at antigenic sites associated with antibody binding and also neutralizing epitopes, with some of the mutations resulting in the modification of N-linked glycosylation of the HA. Those mutations may be related to the escape of virus from antibody binding and the infection of poultry, interpretations which may be confirmed through a reverse genetics approach. The virus also carried an amino acid substitution in the M2, which conferred a reduced susceptibility to amantadine, but no neuraminidase inhibitor resistance markers were found in the viral NA gene. Additional information including vaccination history in the farm and the surrounding area is needed to fully understand the background of this outbreak. Such understanding and expanded monitoring of the H5N1 influenza viruses circulating in Vietnam is an urgent need to provide updated information to improve effective vaccine strain selection and vaccination protocols, aiding disease control, and biosecurity to prevent H5N1 infection in both poultry and humans.
authors.affiliation: Research Center for Animal Hygiene and Food Safety, Obihiro University of Agriculture and Veterinary Medicine, 2-11 Inada, Hokkaido, Obihiro, 080-8555, Japan.
authors.forename: Vuong Nghia
authors.initials: VN
authors.lastname: Bui
authors.forename: Haruko
authors.initials: H
authors.lastname: Ogawa
authors.forename: Dai Quang
authors.initials: DQ
authors.lastname: Trinh
authors.forename: Tham Hong Thi
authors.initials: TH
authors.lastname: Nguyen
authors.forename: Nga Thi
authors.initials: NT
authors.lastname: Pham
authors.forename: Duc Anh
authors.initials: DA
authors.lastname: Truong
authors.forename: Anh Ngoc
authors.initials: AN
authors.lastname: Bui
authors.forename: Jonathan
authors.initials: J
authors.lastname: Runstadler
authors.forename: Kunitoshi
authors.initials: K
authors.lastname: Imai
authors.forename: Khong Viet
authors.initials: KV
authors.lastname: Nguyen
mesh_terms: D000818:Animals; D004372:Ducks / Q000821:virology*; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000235:genetics*; D057131:Immune Evasion; D053124:Influenza A Virus, H5N1 Subtype / Q000145:classification / Q000235:genetics* / Q000276:immunology / Q000302:isolation & purification*; D007252:Influenza Vaccines / Q000008:administration & dosage* / Q000276:immunology; D005585:Influenza in Birds / Q000276:immunology / Q000821:virology*; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D012367:RNA, Viral / Q000235:genetics; D017422:Sequence Analysis, DNA; D014744:Vietnam
chemical_list: D019267:Hemagglutinin Glycoproteins, Influenza Virus; D007252:Influenza Vaccines; D012367:RNA, Viral; C109963:hemagglutinin, avian influenza A virus