DNA vaccination against infectious bursal disease
Abstract
The goal of this thesis was to explore the feasibility of using DNA vaccination technology against infectious bursal disease (IBD) virus (IBDV) infection in chickens. The objectives were to (1) construct plasmids as DNA vaccines against homologous challenge with classical standard challenge (STC) strain of IBDV; (2) construct plasmids containing different fragments of IBDV large segment genome to identify the gene essential for protection mediated by DNA vaccination; (3) determine the feasibility of heterologous protection against classical STC or variant E (VE) strain of IBDV by the constructed plasmids as DNA vaccines; (4) evaluate the humoral and cellular immune responses induced upon IBD DNA vaccination. The constructed plasmid (pCR3.1-VP243-STC) carrying VP2-VP4-VP3 genes of classical STC strain of IBDV has achieved homologous protection for 80 to 100% of the chickens against mortality and bursal atrophy. Plasmids containing VP2 gene of IBDV strain STC were able to achieve protection to 80% of chickens against homologous challenge with STC, and chickens receiving plasmids without containing VP2 genes were not protected against infection, suggesting that VP2 gene is essential in achieving protection of chickens from being infected with IBDV mediated by DNA vaccination. Plasmid (pCR3.1-VP2-VE) containing VP2 gene of VE strain protected 40% of chickens against homologous challenge with VE and 30% of chickens against heterologous challenge with STC. The constructed individual plasmid was able to protect yet less effectively against heterologous challenge than against homologous challenge. Vaccination with both plasmids including pCR3.1-VP243-STC and pCR3.1-VP2-VE protected 100% of chickens against challenge with classical STC strain and 55% of chickens against challenge with VE strains of IBDV. Both humoral and cellular immune responses were induced upon IBD DNA vaccination as evidenced by increased IBDV antigen specific antibody responses, increased delayed type hypersensitivity (DTH), and increased lymphocyte proliferation. In conclusion, DNA vaccination technology has the potential to confer protection of chickens against IBDV infection in poultry industry.
Degree
Ph.D.
Advisors
Wu, Purdue University.
Subject Area
Microbiology|Molecular biology|Animal diseases|Veterinary services
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