Protection of chicken against very virulent IBDV provided by in ovo priming with DNA vaccine and boosting with killed vaccine and the adjuvant effects of plasmid-encoded chicken interleukin-2 and interferon-γ

Abstract

The aim of this study was to examine the efficacy of in ovo prime-boost vaccination against infectious bursal disease virus (IBDV) using a DNA vaccine to prime in ovo followed by a killed-vaccine boost post hatching. In addition, the adjuvant effects of plasmid-encoded chicken interleukin-2 and chicken interferon-γ were tested in conjunction with the vaccine. A plasmid DNA vaccine (pcDNA-VP243) encoding the VP2, VP4, and VP3 proteins of the very virulent IBDV (vvIBDV) SH/92 strain was injected into the amniotic sac alone or in combination with a plasmid encoding chicken IL-2 (ChIL-2) or chicken IFN-γ (ChIFN-γ) at embryonation day 18, followed by an intramuscular injection of a commercial killed IBD vaccine at 1 week of age. The chickens were orally challenged with the vvIBDV SH/92 strain at 3 weeks of age and observed for 10 days. In ovo DNA immunization followed by a killed-vaccine boost provided significantly better immunity than the other options. No mortality was observed in this group after a challenge with the vvIBDV. The prime-boost strategy was moderately effective against bursal damage, which was measured by the bursa weight/body weight ratio, the presence of IBDV RNA, and the bursal lesion score. In ovo DNA vaccination with no boost did not provide sufficient immunity, and the addition of ChIL-2 or ChIFN-γ did not enhance protective immunity. In the ConA-induced lymphocyte proliferation assay of peripheral blood lymphocyte collected 10 days post-challenge, there was greater proliferation responses in the DNA vaccine plus boost and DNA vaccine with ChIL-2 plus boost groups compared to the other groups. These findings suggest that priming with DNA vaccine and boosting with killed vaccine is an effective strategy for protecting chickens against vvIBDV.

The Effect of Methionine and Threonine Supplementations on Immune Responses of Broiler Chickens Challenged with Infectious Bursal Disease

“…Bursa of Fabricius is responsible for the development of humoral immunity. The bursal lesions were characterized by lymphoid depletion and edema in the follicles, fibroplasias in the interfollicular connective tissues and proliferation of the reticular epithelial cells (Park et al, 2009). A possible explanation of these results might be that dietary methionine and threonine may have interfered with apoptotic or necrotic process of bursal lymphocytes during infection of IBDV because the use of IBD vaccine can cause a varying degree of bursal lymphocytolysis (Amakye-Anim et al, 2000).…”

Current status of vaccines against infectious bursal disease

“…A potential use of DNA vaccine for priming in ovo or at 1 day old followed by boosting with inactivated vaccine or vectored vaccine has been described (Haygreen et al, 2006;Hsieh et al, 2007) and induced protection from a virulent challenge infection. The use of DNA vaccination via the in ovo route was also described (Oshop et al, 2003;Haygreen et al, 2006;Park et al, 2009). The results showed that the in ovo delivery without a boost vaccination was not sufficient to induce protective immunity.…”

In ovodelivery of various biological supplements, vaccines and drugs in poultry: current knowledge

“…Thus, priming it with a DNA vaccine will ensure satisfactory results. The in ovo vaccination method in chicks prevents frequent trouble of multiple vaccine administration . Turkey herpesvirus and fowlpox IBDV vector vaccines via the in ovo route have shown an increased safety profile compared with live IBDV vaccine .…”