title: Exposure to a low pathogenic A/H7N2 virus in chickens protects against highly pathogenic A/H7N1 virus but not against subsequent infection with A/H5N1.
abstract: Recent evidences have demonstrated that the presence of low pathogenic avian influenza viruses (LPAIV) may play an important role in host ecology and transmission of avian influenza viruses (AIV). While some authors have clearly demonstrated that LPAIV can mutate to render highly pathogenic avian influenza viruses (HPAIV), others have shown that their presence could provide the host with enough immunological memory to resist re-infections with HPAIV. In order to experimentally study the role of pre-existing host immunity, chickens previously infected with H7N2 LPAIV were subsequently challenged with H7N1 HPAIV. Pre-infection of chickens with H7N2 LAPIV conferred protection against the lethal challenge with H7N1 HPAIV, dramatically reducing the viral shedding, the clinical signs and the pathological outcome. Correlating with the protection afforded, sera from chickens primed with H7N2 LPAIV reacted with the H7-AIV subtype in hemagglutination inhibition assay and specifically with the N2-neuraminidase antigen. Conversely, subsequent exposure to H5N1 HPAIV resulted in a two days-delay on the onset of disease but all chickens died by 7 days post-challenge. Lack of protection correlated with the absence of H5-hemagglutining inhibitory antibodies prior to H5N1 HPAIV challenge. Our data suggest that in naturally occurring outbreaks of HPAIV, birds with pre-existing immunity to LPAIV could survive lethal infections with HA-homologous HPAIV but not subsequent re-infections with HA-heterologous HPAIV. These results could be useful to better understand the dynamics of AIV in chickens and might help in future vaccine formulations.
authors.affiliation: Centre de Recerca en Sanitat Animal, Universitat Autònoma de Barcelona- Institut de Recerca i Tecnologia Agroalimentàries, Campus de la Universitat Autònoma de Barcelona, Bellaterra, Cerdanyola del Vallès, Spain.
authors.forename: Júlia
authors.initials: J
authors.lastname: Vergara-Alert
authors.forename: Ana
authors.initials: A
authors.lastname: Moreno
authors.forename: Juliana G
authors.initials: JG
authors.lastname: Zabala
authors.forename: Kateri
authors.initials: K
authors.lastname: Bertran
authors.forename: Taiana P
authors.initials: TP
authors.lastname: Costa
authors.forename: Iván
authors.initials: I
authors.lastname: Cordón
authors.forename: Raquel
authors.initials: R
authors.lastname: Rivas
authors.forename: Natàlia
authors.initials: N
authors.lastname: Majó
authors.forename: Núria
authors.initials: N
authors.lastname: Busquets
authors.forename: Paolo
authors.initials: P
authors.lastname: Cordioli
authors.forename: Fernando
authors.initials: F
authors.lastname: Rodriguez
authors.forename: Ayub
authors.initials: A
authors.lastname: Darji
mesh_terms: D000818:Animals; D000914:Antibodies, Viral / Q000097:blood / Q000276:immunology; D000956:Antigens, Viral / Q000097:blood / Q000276:immunology*; D002645:Chickens; D056738:Cross Protection; D006385:Hemagglutination Inhibition Tests; D053124:Influenza A Virus, H5N1 Subtype / Q000276:immunology / Q000472:pathogenicity*; D057916:Influenza A Virus, H7N1 Subtype / Q000276:immunology*; D057917:Influenza A Virus, H7N2 Subtype / Q000276:immunology / Q000472:pathogenicity*; D005585:Influenza in Birds / Q000276:immunology* / Q000401:mortality / Q000821:virology; D009439:Neuraminidase / Q000037:antagonists & inhibitors / Q000097:blood / Q000276:immunology*; D013045:Species Specificity; D015996:Survival Rate; D014774:Virulence; D017201:Virus Shedding
chemical_list: D000914:Antibodies, Viral; D000956:Antigens, Viral; D009439:Neuraminidase