Abstract
Infectious bursal disease virus (IBDV) is the etiological agent of an immunosuppressive and highly contagious disease that affects young birds causing important economic losses in the poultry industry worldwide. We have previously developed a plant-based vaccine candidate for infectious bursal disease (IBD) that is able to protect against infection with IBDV when administered through intramuscular (im) route. Given that oral vaccination is non-invasive and stimulates the immunity of the mucosal gastrointestinal surface, the initial site of contact and entry of IBDV, the aim of this work was to study if our immunogen was also able to elicit a protective immune response when orally administered. We demonstrated that 85% of the animals that received two oral doses of the vaccine formulation and all animals that were orally boosted after an im prime scheme developed virus neutralizing antibodies and were protected against IBDV infection, evidenced by the bursa/body weight (BB) ratio, absence of T-cell infiltration, and low viral load in bursa. Although mild to moderate bursal damage was observed in some of these animals, these lesions were not as severe as the ones observed in challenged control groups, which also presented signs of acute inflammation, bursal atrophy, T-cell infiltration, and absence of viral clearance. These results show that two immunizations with our recombinant immunogen are able to induce a specific and protective immune response in chicken against IBDV when orally administered in a prime/boost scheme or when the oral boost follows an im prime scheme. In conclusion, our oral plant-based vaccine candidate could represent a viable alternative to conventional vaccines and is of great interest to the poultry industry.
Highlights
Infectious bursal disease virus (IBDV) is a non-enveloped icosahedral bisegmented doublestranded RNA virus, which is a member of the Birnaviridae family (Dobos et al, 1979; Müller et al, 1979)
After blocking with 4% skimmed milk in phosphate-buffered saline (PBS)-T (0.05% Tween 20), the plates were subsequently incubated with a 1:400 dilution of sample sera, washed and incubated again with a 1:4000 dilution of goat antichicken IgG antibodies coupled to horseradish peroxidase (Bethyl Laboratories, United States)
The expression of recombinant VP2 in a concentrated plant extract was confirmed by Western blot and quantified by SDS-PAGE followed by Coomassie Brilliant Blue staining
Summary
Infectious bursal disease virus (IBDV) is a non-enveloped icosahedral bisegmented doublestranded RNA virus, which is a member of the Birnaviridae family (Dobos et al, 1979; Müller et al, 1979). It is the etiological agent of infectious bursal disease (IBD), an acute highly contagious immunosuppressive disease that affects young birds, causing important economic losses in the. Oral Plant-Based Vaccine Against IBDV poultry industry worldwide both directly, through clinical signs and mortality, and indirectly, due to incremented susceptibility to other pathogens and failure in vaccination programs (Chanie and Kegne, 2014; Rautenschlein and Alkie, 2016). Mucosal vaccination usually requires a larger amount of antigen to compensate the degradation by gastric acid and proteases present in the GIT, multiple boosts, and/or the coadministration of adjuvants (Streatfield, 2006; Vela Ramirez et al, 2017)
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