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Enhancing Host Immunity to Avian Influenza Virus using Toll-like Receptor Agonists in Chickens

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Title: Enhancing Host Immunity to Avian Influenza Virus using Toll-like Receptor Agonists in Chickens
Author: St. Paul, Michael
Department: Department of Pathobiology
Program: Pathobiology
Advisor: Sharif, Shayan
Abstract: Toll-like receptors (TLRs) are evolutionarily conserved pattern recognition receptors that mediate host-responses to pathogens. In mammals, TLR ligands promote cellular activation and the production of cytokines. Several TLR ligands have been employed prophylactically for the control of bacterial or viral diseases in the mouse model. However, the TLR-mediated responses in chickens have not been well described. Importantly, the utility of TLR agonists for the control of viral pathogens, such as avian influenza virus (AIV), has not been fully explored in chickens. To this end, the studies described in this thesis characterized the kinetics of in vivo responses in chickens to the TLR4 ligand lipopolysaccharide (LPS) and the TLR21 ligand CpG ODN. It was demonstrated that both of these ligands induced the up-regulation of several immune system genes in the spleen, including those associated with pro-inflammatory and antiviral responses, as well antigen presentation. By harnessing the immunostimulatory properties of TLR ligands, it was also demonstrated that the prophylactic administration of either poly I:C (a TLR3 ligand), LPS or CpG ODN may confer immunity to a low pathogenic avian influenza virus, as determined by a reduction in both oropharyngeal and cloacal virus shedding in infected birds. Furthermore, transcriptional analysis of genes in the spleen and lungs identified interleukin (IL)-8, interferon (IFN)-α and IFN-γ as correlates of immunity. In conclusion, TLR ligands may modulate several aspects of the chicken immune system to induce an anti-viral state, thereby conferring immunity to AIV.
Date: 2012-08-23

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