Induction of adaptive immune responses against respiratory viruses using in ovo delivered toll-like receptor (TLR) ligands

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Respiratory viral infections caused by infectious bronchitis virus (IBV) and infectious laryngotracheitis virus (ILTV) in chickens are prevalent in Canada and globally leading to losses that amount to billions of dollars to the poultry industry. Laboratory weakened viruses are used as vaccines for the control of these viral infections. For two major reasons, outbreaks of these respiratory viral infections occur in vaccinated chickens. Firstly, the virus such as IBV and ILTV used in vaccines can regain the ability to cause diseases by spreading through the flock. Secondly, the field strains of IBV can mutate against the pressure imposed by vaccination. Therefore it is critical to develop novel and more sustainable control measures against these viral infections. One of the potential ways is the use of immune stimulants to induce natural resistance leading to long-term immunity against encountered pathogens. In order to establish this means of control, we will study: (1) the ability of immune stimulants that are known to stimulate natural immunity to induce long-term immunity against IBV and ILTV infections, (2) the mechanisms by which these immune stimulants establish long-term resistance against these viral infections and (3) whether the induced long-term resistance is effective when seeder infection models of IBV and ILTV viruses are used mimicking the field conditions. The proposed studies will lead to the formulation of novel control strategies against respiratory viral infections in chickens benefiting the Canadian Poultry Research Council thus the Canadian poultry producers.