The expression in plants of an engineered VP2 protein of Infectious Bursal Disease Virus induces formation of structurally heterogeneous particles that protect from a very virulent viral strain

Abstract

Infectious Bursal Disease Virus (IBDV), the etiological agent of Gumboro disease, causes mortality and immunosuppression in chickens and major losses to poultry industry worldwide. The IBDV major capsid protein VP2 is considered the best candidate for the production of novel subunit vaccines. This structural protein contains the major conformational epitopes responsible for the induction of IBDV neutralizing antibodies in chickens and has been demonstrated able to form supramolecular structures in yeast and insect cells. The aim of this study was to express an engineered version of the VP2 protein (His-pVP2) to verify its ability to self-assemble into virus-like particles in plants. The recombinant VP2 was transiently expressed by agroinfiltration in Nicotiana benthamiana and transmission electron microscopy of sucrose density gradient fractions revealed the presence of a mixed population of differently shaped particles ranging from spherical capsids, with a diameter between ~25 and ~70 nm, to tubular structures, with variable length (from 100 to 400 nm). The recombinant VP2-based particles when used for the intramuscular immunization of specific-pathogen-free chicks resulted able to induce the production of anti-IBDV specific antibodies at titers comparable to those induced by a commercial vaccine. Moreover, all the immunized birds survived to the challenge with a Moroccan very virulent IBDV strain with no major histomorphological alterations of the Bursa of Fabricius, similarly to what obtained with the commercial inactivated vaccine.

Adjuvanticity of sliver nanoparticles with Infectious bursal disease virus VP2 protein and its effect on humoral immune response in chickens

“…In the placebo group, the titers remained non-immune throughout the experiment. Recently, a 40 kDa IBDV rVP2 expressed in Nicotiana benthamiana demonstrated IBDV speci c neutralizing antibody titers in chicken comparable to those induced by the commercial vaccine [14].…”

“…These epitopes are responsible for the induction of virus-neutralizing antibodies. Therefore, the IBDV major capsid protein VP2 is utilized for developing diagnostics and novel subunit vaccines [12,14]. Recent studies used Escherichia coli [7,33], Lactococcus lactis [34], and plant [14] expression systems to express IBDV rVP2 based virus-like particles and had a molecular mass of more than 40 kDa.…”

“…Therefore, the IBDV major capsid protein VP2 is utilized for developing diagnostics and novel subunit vaccines [12,14]. Recent studies used Escherichia coli [7,33], Lactococcus lactis [34], and plant [14] expression systems to express IBDV rVP2 based virus-like particles and had a molecular mass of more than 40 kDa. This study elaborated the diagnostic and immunogenic potential of a truncated 19 kDa rVP2 protein.…”

“…The structural VP2 protein is considered the best candidate for developing diagnostics and subunit vaccines as it induces a protective immune response in chickens [10][11][12][13][14]. The virus neutralizing humoral immune response is generated against this protein [15].…”

“…The adjuvanted nanoparticle vaccines open the avenues for controlled antigen delivery to immune cells [19]. Recent studies showed the adjuvanticity of silver, gold, polylactide-co-glycolide, and calcium phosphate nanoparticles in enhancing the immunogenicity of antigens [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]. Despite other applications of nanoparticles, they are used as immune potentiators.…”