Pathogenesis of Avian Influenza H7N1 and H7N7 Viruses in Poultry: Virulence Determinants, Adaptation and Within-Host Infection Dynamics of Low and High Pathogenicity Viruses

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Avian influenza viruses (AIV) belong to the genus Influenza A Virus in the family Orthomyxoviridae. They contain a single-stranded ribonucleic acid (RNA) genome composed of eight gene segments encoding at least 11 viral proteins. According to the antigenic variation of the surface glycoproteins the hemagglutinin (HA) and neuraminidase (NA), 16 HA (H1 - H16) and 9 NA (N1 – N9) subtypes have been identified. While AIV of all subtypes induce mild illness, if any, in poultry, virulence of H5 and H7 subtypes varies widely ranging from asymptomatic to highly lethal infections. Major outbreaks were caused by highly pathogenic (HP) subtypes which evolved from low pathogenic (LP) ancestors after circulation in domesticated birds. Virulence markers of AIV is multigenic exist which extend beyond the HA proteolytic cleavage site. During the last two decades, devastating outbreaks caused by AIV H7 subtypes have been reported in Europe. In this project, virulence determinates and pathogenesis of some H7N1 and H7N7 will be determined in different poultry species.