title: Antigenic and genetic evolution of low-pathogenicity avian influenza viruses of subtype H7N3 following heterologous vaccination.
abstract: Outbreaks of low-pathogenicity avian influenza (LPAI) viruses of the H7N3 subtype were first detected in Italy in October 2002, and the virus continued to circulate between 2002 and 2004 in a densely populated poultry area in the northeast portion of that country. This virus circulated in unvaccinated and vaccinated poultry farms, and the infection was controlled in August 2003 by culling, control of movements, improved biosecurity, and heterologous vaccination. In 2004, H7N3 reoccurred in vaccinated poultry farms in which infection had been successfully controlled by the vaccination program. To shed light on this occurrence and the temporal pattern and genetic basis of antigenic drift for avian influenza viruses (AIVs) in the absence and presence of heterologous vaccination, a collection of H7N3 viruses isolated in 2002 and 2004 were characterized genetically and antigenically. Molecular analysis showed that viruses isolated in the 2004 outbreaks after the implementation of vaccination had acquired specific amino acid signatures, most of which were located at reported antibody binding sites of the hemagglutinin (HA) protein. Antigenic characterization of these 2004 isolates showed that they were antigenically different from those isolated prior to the implementation of vaccination. This is the first report on antigenic and genetic evolution of H7 LPAI viruses following the application of heterologous vaccination in poultry. These findings may have an impact on control strategies to combat AI infections in poultry based on vaccination.
authors.affiliation: OIE/FAO and National Reference Laboratory for Avian Influenza and Newcastle Disease, OIE Collaborating Centre for Infectious Diseases at the Human-Animal Interface, IZSVe, Legnaro, Italy.
authors.forename: Maria Serena
authors.initials: MS
authors.lastname: Beato
authors.forename: Yifei
authors.initials: Y
authors.lastname: Xu
authors.forename: Li-Ping
authors.initials: LP
authors.lastname: Long
authors.forename: Ilaria
authors.initials: I
authors.lastname: Capua
authors.forename: Xiu-Feng
authors.initials: XF
authors.lastname: Wan
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D004196:Disease Outbreaks; D019143:Evolution, Molecular; D040961:Genetic Drift; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000235:genetics / Q000276:immunology; D057920:Influenza A Virus, H7N3 Subtype / Q000145:classification* / Q000235:genetics / Q000276:immunology* / Q000302:isolation & purification; D007252:Influenza Vaccines / Q000008:administration & dosage*; D005585:Influenza in Birds / Q000453:epidemiology / Q000517:prevention & control* / Q000821:virology*; D007558:Italy / Q000453:epidemiology; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000235:genetics / Q000276:immunology; D011200:Poultry; D012367:RNA, Viral / Q000235:genetics; D012641:Selection, Genetic; D017422:Sequence Analysis, DNA
chemical_list: D019267:Hemagglutinin Glycoproteins, Influenza Virus; D007252:Influenza Vaccines; D050505:Mutant Proteins; D012367:RNA, Viral