The immunological mechanisms of in ovo vaccination

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In ovo vaccination is an alternative approach to post-hatch vaccination of chickens. It is a safe, animal and user-friendly method that enables vaccination ~60,000 eggs per hour. The technology has been well developed for vaccination against viral diseases using viral vectors and efforts to extend the technology for bacterial and parasitic vaccines are in progress. Although in ovo vaccination can be successful, the immature immune system of a neonate shows functional deficiencies that limit the success rate of this technology. The in ovo vaccines currently used in the poultry industry are live replicating viruses. To extend and improve this technology for application of inactivated vaccines or adjuvanted subunit vaccines, it is of utmost importance that we understand early life immune ontology and the cellular and molecular mechanisms that affect antigen uptake at mucosal surfaces and induction of immune responses. We will investigate if the avian neonatal immunological milieu is polarised towards Th2-type immunity with dampening of Th1-type responses as previously shown in mammals. Innate immunity also shows functional deficiency in antigen-presenting cells; expression and signalling of Toll-like receptors undergo maturational changes associated with distinct functional responses. Therefore, this project will test the hypothesis that the inherent regulatory constraints of the neonate innate and adaptive immune system can be surmounted by appropriate stimulation. A variety of approaches have been proposed including improved trained innate immunity, altered innate receptor agonists and novel age-specific adjuvantation systems. Gaining a thorough understanding of the immune ontology and cellular and molecular factors that can influence the induction of immune responses in neonates will part of this project.