DNA-mediated vaccination against infectious bursal disease in chickens

The objective of the present study was to investigate the feasibility of a DNA vaccine to protect chickens against infectious bursal disease virus (IB DV) infection, A plasmid DNA carrying VP2, VP4, and VP3 genes of the standa rd challenge (STC) strain of IBDV was constructed and designated as pCR3.1- VP243-STC. One-day-old chickens were intramuscularly injected with the plas mid pCR3.1-VP243-STC once (group D1). twice (group D2), or three times (gro up D3) at weekly intervals. Chickens at 3 weeks old were orally inoculated with IBDV strain STC and observed for 10 days after challenge. Immunization twice (group D2) or three times (group 133) with the plasmid pCR3.1-VP243- STC conferred protection for 50-100 or 80-100% of chickens, respectively, a s evidenced by the absence of clinical signs, mortality. and bursal atrophy . Although chickens vaccinated once (group D1) with the plasmid pCR3.1-VP24 3-STC did not have clinical signs. they exhibited varying degree of bursal atrophy after challenge. Enzyme-linked immunosorbent assay (ELISA) antibody titers in chickens protected by the plasmid pCR3.1-VP243-STC were signific antly lower (P < 0.05) than those not protected 10 days after challenge. IB DV antigen was not detected in the bursae of chickens that were protected b y receiving the plasmid pCR3.1-VP243-STC twice or three times. The results indicate that the constructed plasmid pCR3.1-VP243-STC as a DNA vaccine pro vided efficacious protection for chickens against IBDV infection. (C) 2001 Elsevier Science Ltd. All rights reserved.