The NS segment of H5N1 avian influenza viruses (AIV) enhances the virulence of an H7N1 AIV in chickens.
Some outbreaks involving highly pathogenic avian influenza viruses (HPAIV) of subtypes H5 and H7 were caused by avian-to-human transmissions. In nature, different influenza A viruses can reassort leading to new viruses with new characteristics. We decided to investigate the impact that the NS-segment of H5 HPAIV would have on viral pathogenicity of a classical avian H7 HPAIV in poultry, a natural host. We focussed this study based on our previous work that demonstrated that single reassortment of the NS-segment from an H5 HPAIV into an H7 HPAIV changes the ability of the virus to replicate in mammalian hosts. Our present data show that two different H7-viruses containing an NS-segment from H5-types (FPV NS GD or FPV NS VN) show an overall highly pathogenic phenotype compared with the wild type H7-virus (FPV), as characterized by higher viral shedding and earlier manifestation of clinical signs. Correlating with the latter, higher amounts of IFN-β mRNA were detected in the blood of NS-reassortant infected birds, 48 h post-infection (pi). Although lymphopenia was detected in chickens from all AIV-infected groups, also 48 h pi those animals challenged with NS-reassortant viruses showed an increase of peripheral monocyte/macrophage-like cells expressing high levels of IL-1β, as determined by flow cytometry. Taken together, these findings highlight the importance of the NS-segment in viral pathogenicity which is directly involved in triggering antiviral and pro-inflammatory cytokines found during HPAIV pathogenesis in chickens.
Centre de Recerca en Sanitat Animal (CReSA), UAB-IRTA, Campus de la Universitat Autònoma de Barcelona, Bellaterra, Cerdanyola del Vallès 08193, Spain. vergaraa@staff.uni-marburg.de.
Júlia
J
Vergara-Alert
Núria
N
Busquets
Maria
M
Ballester
Aida J
AJ
Chaves
Raquel
R
Rivas
Roser
R
Dolz
Zhongfang
Z
Wang
Stephan
S
Pleschka
Natàlia
N
Majó
Fernando
F
Rodríguez
Ayub
A
Darji
D000818:Animals; D002645:Chickens; D054884:Host-Pathogen Interactions; D053124:Influenza A Virus, H5N1 Subtype / Q000235:genetics / Q000276:immunology / Q000472:pathogenicity* / Q000502:physiology; D057916:Influenza A Virus, H7N1 Subtype / Q000235:genetics / Q000276:immunology / Q000472:pathogenicity* / Q000502:physiology; D005585:Influenza in Birds / Q000276:immunology* / Q000821:virology; D011201:Poultry Diseases / Q000276:immunology* / Q000821:virology; D016865:Reassortant Viruses / Q000235:genetics / Q000276:immunology / Q000472:pathogenicity* / Q000502:physiology; D017361:Viral Nonstructural Proteins / Q000235:genetics*; D014774:Virulence; D014779:Virus Replication
C108309:NS protein, influenza virus; D017361:Viral Nonstructural Proteins