Approaches to enhance protection against infectious bursal disease in chickens conferred by DNA -mediated vaccination
Abstract
Two approaches were explored for improving and/or enhancing immune response and protection efficacy against infectious bursal disease (IBD) by DNA vaccination in chickens. One approach was to co-administer chicken interferon-γ (cIFN-γ) expressing plasmid (P/cIFN-γ) or chicken interleukin-2 (cIL-2) expressing plasmid (P/cIL-2) as a molecular adjuvant in conjunction with DNA vaccination and the other approach was to employ the prime-boost strategy by priming specific-pathogen-free (SPF) or broiler chickens with infectious bursal disease virus (IBDV) large segment protein (VP243) expressing plasmid (P/VP243/E) and subsequently boosting them with conventional killed IBD vaccine. Co-administration of plasmid P/cIFN-γ with plasmid P/VP243/E 2 times at weekly intervals did not enhance the immune response and protection (33 to 50%) against challenge by IBDV in SPF chickens. Co-administration of plasmid P/cIL-2 2 times at weekly interval in DNA vaccination enhanced protection (86%) against challenge by IBDV in SPF chickens, similar to that in SPF chickens vaccinated with P/VP243/E weekly for 3 times. Priming with plasmid P/VP243/E (400 μg for SPF chickens, 10 mg for broiler chickens) 1 time and boosting with killed IBD vaccine 1 or 2 times reached 100% protection against challenge by IBDV in SPF or broiler chickens with maternally derived antibody to IBDV. Broiler chickens protected by priming with 10 mg of plasmid P/VP243/E had significantly lower (P<0.05) enzyme-linked immunosorbent assay (ELISA) and virus neutralization (VN) titers to IBDV than those in the challenge control group after challenge. In DNA-mediated vaccination, broiler chickens with maternally derived antibody to IBDV intramuscularly inoculated with at least 7.5 mg of plasmid P/VP243/E 3 times at weekly interval conferred 100% protection against challenge by IBDV and had significantly higher (P<0.05) stimulation indices for IBDV-stimulated lymphocyte proliferation response than those in the control group, indicating the induction of cellular immune response. In conclusion, DNA vaccination with high dose of plasmid P/VP243/E can avoid the inhibitory effect by maternal antibody to IBDV and both approaches including co-administration of molecular adjuvant and DNA prime-killed vaccine boost, prove to enhance immune response and/or protection efficacy against challenge by IBDV to a certain level.
Degree
Ph.D.
Advisors
Lin, Purdue University.
Subject Area
Veterinary services|Anatomy & physiology|Animals
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