title: Effect of age on the pathogenesis and innate immune responses in Pekin ducks infected with different H5N1 highly pathogenic avian influenza viruses.
abstract: The pathogenicity of H5N1 highly pathogenic avian influenza (HPAI) viruses in domestic ducks varies between different viruses and is affected by the age of the ducks, with younger ducks presenting a more severe disease. In order to better understand the pathobiology of H5N1 HPAI in ducks including the role of host responses, 2 and 5-week-old Pekin ducks were infected with three different H5N1 HPAI viruses. Virus-induced pathology ranged from no clinical signs to severe disease and mortality, with the 2-week-old ducks being more severely affected by the more virulent viruses. However, these more virulent viruses induced higher body temperatures in the 5-week-old ducks than in the 2-week-old ducks indicating possible differences in innate immune responses. To analyze the ducks host responses to H5N1 HPAI virus infection, expression of innate immune-related genes was measured in the spleens and lungs of infected ducks at the peak of virus infection. IFN-α, RIG-I, and IL-6 RNA levels were increased in spleens regardless of the virus given and the age of the ducks, however differences were observed in the levels of up-regulation of IFN-α and RIG-I between the 2 and the 5-week-old ducks with the more virulent virus. Differences in IL-2 gene expression were also observed. In the lungs, the levels of expression of innate immune-related genes were lower than in the spleen, with mostly up-regulation of RIG-I and IL-6 and down-regulation of IFN-α and IL-2; no significant difference in expression was found between the 2 and the 5-week-old ducks. The differences observed in the innate immune responses to infection with H5N1 HPAI viruses could explain in part the differences in pathogenicity found between the 2 and 5-week-old ducks, however earlier time points after infection and additional innate immune-related genes should be examined.
authors.affiliation: Exotic and Emerging Avian Viral Diseases Research Unit, Southeast Poultry Research Laboratory, Agricultural Research Service, US Department of Agriculture, 934 College Station Road, Athens, GA 30605, USA. mary.pantin-jackwood@ars.usda.gov
authors.forename: Mary J
authors.initials: MJ
authors.lastname: Pantin-Jackwood
authors.forename: Diane M
authors.initials: DM
authors.lastname: Smith
authors.forename: Jamie L
authors.initials: JL
authors.lastname: Wasilenko
authors.forename: Caran
authors.initials: C
authors.lastname: Cagle
authors.forename: Eric
authors.initials: E
authors.lastname: Shepherd
authors.forename: Luciana
authors.initials: L
authors.lastname: Sarmento
authors.forename: Darrell R
authors.initials: DR
authors.lastname: Kapczynski
authors.forename: Claudio L
authors.initials: CL
authors.lastname: Afonso
mesh_terms: D000367:Age Factors; D000818:Animals; D016207:Cytokines / Q000096:biosynthesis; D004372:Ducks / Q000276:immunology* / Q000821:virology*; D020869:Gene Expression Profiling; D007113:Immunity, Innate; D053124:Influenza A Virus, H5N1 Subtype / Q000276:immunology* / Q000472:pathogenicity*; D005585:Influenza in Birds / Q000276:immunology* / Q000473:pathology / Q000821:virology*; D008168:Lung / Q000276:immunology / Q000473:pathology; D011971:Receptors, Immunologic / Q000096:biosynthesis; D013154:Spleen / Q000276:immunology / Q000473:pathology; D016019:Survival Analysis
chemical_list: D016207:Cytokines; D011971:Receptors, Immunologic