Specific immune response elicited by a plant based immunogen against Infectious Bursal Disease Virus

GÓMEZ E.; CHIMENO ZOTH S.; CARBALLEDA, J.M.; WIGDOROVITZ. A.; CARRILLO E.; BERINSTEIN A.

Conferencia; Plant-Based Vaccines and Antibodies 2011 Conference; 2011

Introduction-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. The VP2 protein, a structural protein of the virus which contains the major neutralizing epitopes, has been used for the development of subunit vaccines in a variety of heterologous platforms. Escherichia coli, yeast, recombinant viruses (fowlpox, herpesvirus, adenovirus, baculovirus, and Marek?s disease virus) transgenic plants and also DNA vaccines encoding IBDV VP2 gene have been obtained in order to attend to a new generation of vaccines as effective as the traditional virus based ones. Although infection occurs naturally by the oral route and commercial vaccines are based on attenuated live virus, we proposed the vaccination by the parenteral route with an immunogen derived from a Nicotiana benthamiana transient expression assay. This choice of immunogen production and vaccination allowed us to diminish time-consuming, to obtain acceptable yields of the recombinant protein and to evaluate the feasibility of the plant production system itself. Objectives- the objectives of the present work were to transiently express the VP2 protein and to study the immune response elicited by the parenteral administration of the recombinant immunogen in chickens. Materials and Methods- Transient expression was performed by agroinfiltration of Nicotiana benthamiana plants with a suspension of recombinant bacteria harboring the VP2 gene. VP2 protein expression was analyzed by Western blot utilizing an anti-VP2 polyclonal antibody raised in rabbit. SPF Chickens of 18 days old were randomly assigned to experimental groups. Five animals in each group were intramuscularly vaccinated with either a) plant extracts containing VP2, b) plant extracts containing GFP as a non related antigen or c) the commercial vaccine, in a dose/boost scheme. Chickens were vaccinated at days 0, 21 and 35 and they were weekly bled by the wing vein. Serum samples were evaluated for the presence of specific antibodies against IBDV with a commercial ELISA and they were evaluated for virus neutralizing activity using chicken embryo fibroblasts (CEFs). Results- Animals inoculated with the experimental vaccine developed high titres of specific antibodies, clearly superior to the cut off titre (396); while the negative group did not present antibodies against IBDV. As expected, animals vaccinated with the commercial vaccine were all immunized against the virus. Also, the sera from the animals receiving the recombinant VP2 presented virus neutralizing activity reaching the highest antibody titres at 42 dpi. Conclusion and Discussion- The expression, immunogenicity and protective efficacy of an experimental plant-based vaccine against IBDV was investigated. We determined that the agroinfiltration of N. benthamiana leaves, allowed the production of VP2 apparently with the conformational epitopes. We observed that chickens intramuscularly immunized in a dose/boost scheme with crude concentrated extracts developed a specific humoral response with viral neutralizing ability. Given these results, it seems plausible for a plant-based vaccine to have a niche in the veterinary field being the parenteral route the way of inoculation. Plants can be an adequate system of choice to produce immunogens against IBDV.