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Models of H9N2 avian influenza virus infection and vaccination in chickens

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dc.contributor.advisor Greer, Amy
dc.contributor.author Xie, Xiao Ting
dc.date.accessioned 2021-12-23T20:39:09Z
dc.date.available 2021-12-23T20:39:09Z
dc.date.copyright 2021-12
dc.date.created 2021-12-06
dc.identifier.uri https://hdl.handle.net/10214/26614
dc.description.abstract This thesis presents within-host compartment models to describe the chicken immune responses to H9N2 avian influenza virus (AIV) vaccination and infection and examined the effects of vaccination on outbreak dynamics in a flock-level compartment model. Within-host models of the gastrointestinal and respiratory systems were used to identify type-I interferon (IFN) pathways and an eclipse phase which contribute to localized virus shedding patterns based on virus shedding data from chickens experimentally infected with H9N2 AIV. The hemagglutinin inhibition (HI) antibody response to vaccination was assessed at the host level to determine the duration at which seroprotective HI antibody titres are maintained post-vaccination. The contributions of both the HI antibody response and the cytotoxic T lymphocyte (CTL) response on virus clearance were assessed in a model of a vaccinated host. The effect of vaccination using four candidate vaccines at the flock-level was compared to outbreak dynamics in an unvaccinated flock. The studies demonstrated in several key findings. First, the inclusion of an eclipse phase and the type-I IFN pathways involved in gastrointestinal and respiratory H9N2 AIV infection in chickens differ in the model, which may in part explain the differences in virus shedding patterns. Second, prime-and-boost vaccination strategies provide seroprotective HI antibody titres for the duration of a broiler chicken lifespan, but a third vaccination should be considered for layers considering antibody clearance over time. Third, a delayed CTL response to virus infection allows for virus clearance within the expected timeframe in vaccination chickens, resulting in reduced shedding overall. Finally, vaccination of chicken flocks dramatically reduces outbreak size compared to unvaccinated flocks, however further research is required to examine the transmission rate of H9N2 AIV between vaccinated birds, which would ultimately serve to obtain more accurate simulations of disease spread within flocks. This research represents an important first step in developing compartment models as a tool to examine the host response to H9N2 AIV vaccination and infection, and in identifying key gaps in empirical data which would serve to improve our understanding of the impact of vaccination at both the host and flock levels. en_US
dc.description.sponsorship University of Guelph’s Food from Thought initiative (Canada First Research Excellence Fund), Ontario Veterinary College en_US
dc.language.iso en en_US
dc.publisher University of Guelph en
dc.rights Attribution-NonCommercial-NoDerivatives 4.0 International *
dc.rights.uri http://creativecommons.org/licenses/by-nc-nd/4.0/ *
dc.subject avian influenza en_US
dc.subject math modelling en_US
dc.subject vaccination en_US
dc.title Models of H9N2 avian influenza virus infection and vaccination in chickens en_US
dc.type Thesis en_US
dc.degree.programme Population Medicine en_US
dc.degree.name Doctor of Philosophy en_US
dc.degree.department Department of Population Medicine en_US
dcterms.relation Xie, X. T., Yitbarek, A., Uddin Khan, S., Sharif, S., Poljak, Z., & Greer, A. L. (2020). A within-host mathematical model of H9N2 avian influenza infection and type-I interferon response pathways in chickens. Journal of theoretical biology, 499, 110320. https://doi.org/10.1016/j.jtbi.2020.110320 en_US
dcterms.relation Xie, X. T., Yitbarek, A., Astill, J., Singh, S., Khan, S. U., Sharif, S., Poljak, Z., & Greer, A. L. (2021). Within-host model of respiratory virus shedding and antibody response to H9N2 avian influenza virus vaccination and infection in chickens. Infectious Disease Modelling, 6, 490–502. https://doi.org/10.1016/j.idm.2021.02.005 en_US
dc.degree.grantor University of Guelph en


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