INTRAPULMONARY DELIVERY OF OLIGODEOXYNUCLEOTIDES CONTAINING CYTOSINE PHOSPHODIESTER GUANINE MOTIFS (CPG-ODN) TO NEONATAL BROILER CHICKENS
Oligodeoxynucleotides containing CpG motifs (CpG-ODN) are known for their ability to stimulate the vertebral immune system and provide protection against pathogens. We have demonstrated the effect of CpG-ODN against Escherichia coli and Salmonella infections by in ovo and parenteral delivery. This study's objective was to discover the efficacy of immunomodulatory effects of CpG-ODN by the intrapulmonary (IPL) route as micro droplets. In the second chapter, we demonstrated immunoprotection of neonatal broiler chickens against a lethal challenge of E. coli following IPL delivery of CpG-ODN. Immunoprotection was observed 6 hours following CpG-ODN and lasted for five days post treatment. CpG-ODN treated birds showed significantly lower clinical scores and lower bacterial load in the body. In the third chapter, we demonstrated the efficacy of IPL delivery of CpG-ODN under field conditions by developing a commercial-scale prototype nebulizer (CSPN). The CSPN was able to deliver CpG-ODN to 8,000 birds at a time. We were able to deliver CpG-ODN by the IPL route to protect neonatal broiler chicks against lethal E. coli septicemia at a significant level when the humidex was at or below 28 and relative humidity was 40-60% (P<0.05) in the CSPN. Results of this study confirmed that IPL delivery of CpG-ODN against septicemia in neonatal broiler chickens was industrially feasible and effective under different weather conditions. In the fourth chapter, we explored the antibacterial mechanisms of CpG-ODN by IPL delivery. We observed T helper (Th)1 and Th2 type cytokine upregulation together with interleukin (IL) 1β and lipopolysaccharide-induced tumor necrosis factor (LITAF) in spleen and lungs following CpG-ODN delivery. It was also evident that the spleen and lungs had increased infiltration of antigen presenting cells (APCs) and cluster of differentiation (CD) 4+ and CD8+ T cells. Costimulatory molecule CD40 upregulation and distinct major histocompatibility class II expression in lung APCs indicated the cells were maturing and presenting antigens actively. In the fifth chapter, we utilized the novel metabolomics analysis tool and investigated the changes in the metabolome of broiler chicks upon CpG-ODN administration. The metabolites that contributed to the distinct difference belonged to various pathways of energy metabolism. Our work on IPL delivery of CpG-ODN against E. coli septicemia demonstrated the potential utilization of CpG-ODN in the poultry industry as an alternative to antibiotics to prevent losses due to bacterial infections of neonatal chickens.
CpG-ODN, intrapulmonary, neonatal broiler chickens, E. coli, immunoprotection, commercial, mucosal, immune stimulation, innate immunity
Doctor of Philosophy (Ph.D.)