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Abstract
Infectious laryngotracheitis (ILT) is an acute upper respiratory tract infection causes by Gallid alpha herpesvirus type 1 (GaHV-1) given the common name - Infectious laryngotracheitis virus (ILTV). Currently vaccination, with either live-attenuated and/or recombinant viral vector vaccines, is the main tool used to control the disease. Both live attenuated vaccines, (of chicken embryo origin (CEO) and of tissue culture origin (TCO)) are administered by the mucosal route. Vaccines given on mucosal tissues in the head induce effective protection against infection. The head-associated lymphoid tissue (HALT) is comprised of nasal-associated lymphoid tissue (NALT), conjunctiva-associated lymphoid tissue (CALT) and the Harderian gland (HG). These are located in the anatomical site of ILTV entry, and are important for the initiation of immunity by interaction of virus with local organized lymphoid tissues after ocular vaccination of chickens. The focus of this dissertation was to demonstrate the dynamics of B and T cells (but not T cells), and mononuclear phagocytes in the CALT and HG following vaccine or exposure to virulent ILTV. In summary, this study showed that entry of the virus onto mucosal tissues of the head dictated the level ILTV replication in the upper and lower respiratory tract, and consequently influenced the outcome of infection. Further, the results of these experiments revealed important dynamic changes in the number of B cells, T cells and macrophages in HALT and HG following vaccination or exposure to virulent ILTV virus. Furthermore, this study underscored distinctive roles for CALT and HG during viral replication associated with CEO vaccination or virulent virus, and provided an indication that ILTV can circumvent the local immune activation, by delaying innate responses and downregulating MHC class II cellular expression. This knowledge will be critical to the future development of live attenuated vaccines and viral vector, or subunits vaccines that effectively trigger virus specific T cell responses after mucosal vaccination via eye-drop, in drinking water or by aerosol spray