The H9N2 low pathogenic avian influenza virus (LPAIV) is considered a prime candidate for evolving into a highly pathogenic AIV (HPAIV) following circulation in domestic poultry, due to its widespread endemism in Eurasia and the donation of internal genes to H5 and H7 HPAIV. In this study, we investigated if a LP H9N2 virus could acquire increased pathogenicity following nineteen serial passages in week-old chickens. We show that the H9N2 virus remained low pathogenic in chickens after nineteen serial passages, evidenced by a lack of mortality in chickens despite efficient viral replication in chicken organs. An overregulation of cytokine response to infection, typical of highly pathogenic viruses, was not observed in tissue organs analyzed by quantitative PCR. The serial passaging of the H9N2 virus led to reduced virulence in chicken embryos and reduction in Hemagglutinin heat stability after passaging. The positive selection of Leucine at amino acid position 226 (L226) after 19 passages suggests the H9N2 can gain mammalian adaptation markers following circulation in domestic poultry. In addition, we carried out four experiments to determine the effectiveness of aerosol exposure of H6N1, H10N7, H10N8 and H13N6 LPAIV’s in causing infection, immune dysregulation and mortality in chickens compared to intranasal and oral inoculation routes. From our study, we observed mortality of chickens exposed to H6N1 and H10N8 viruses via aerosols. Aerosol exposure also resulted in more efficient replication in the respiratory tracts of chickens than intranasal or oral inoculated chickens. In addition, overexpression of pro-inflammatory (IL-6, IL-1ß) and antiviral (INF- γ) cytokines was observed in chickens exposed to aerosols compared to intranasal and oral inoculation. Our results show that the aerosol route of exposure is efficient at causing infection in chickens and should be factored into control and prevention strategies against AIV.
| Identifer | oai:union.ndltd.org:uottawa.ca/oai:ruor.uottawa.ca:10393/36501 |
| Date | January 2017 |
| Creators | Akinlolu, Jegede |
| Contributors | Lin, Min, Kumar, Ashok |
| Publisher | Université d'Ottawa / University of Ottawa |
| Source Sets | Université d’Ottawa |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
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