Abstract
Although there are many similarities between the mammalian and avian immune systems, comparatively little is known about how the avian immune system is modulated in response to changes in other physiological processes or infectious diseases. In this thesis I report on various topics on avian immunology. In the first study we tested for simultaneous changes in the digestive physiology and mucosal immune function of the guts of White Leghorn cockerel chicks undergoing food restriction and realimentation. The results of this study indicate that during restriction-realimentation some features of gut immune function are maintained unchanged in the face of regulatory changes that influence digestive functions. WNV causes morbidity and mortality in humans, horses and more than 300 bird species in North America. In the second study, the protective abilities of recombinant WNV envelope (E) protein as both an oral and intramuscular (IM)-delivered vaccine were investigated in white leghorn cockerels. Following a post-vaccination WNV challenge, viremias were significantly lower in the IM-vaccinated group compared to orally vaccinated and non-vaccinated groups (P< 0.001). The results of this study indicate that IM, but not oral, vaccination of chickens with E protein is protective against WNV infection. In the third study, the WNV susceptibility of 5-6 week old juvenile pigeons and 12 month old adult pigeons was investigated. Adult pigeons given a high dose of WNV (10 super(5) PFU) had significantly higher viremias compared to adult pigeons given a low dose of WNV (10 super(3) PFU) and all juvenile groups. The results of this study indicate a possible age-related decline in immunocompetence in pigeons when WNV is used as the challenge agent. The reasons for the wide range of WNV susceptibility that exists in the bird community are largely unknown, although it has been hypothesized that the ability to mount a robust neutralizing antibody response to West Nile virus infection is likely correlated with disease resistance. In the final chapter we review previous work done in mammalian and avian species on immune responses to WNV, and propose future studies on avian immune responses to WNV infection, with particular focus on highly susceptible corvid birds to WNV infection.