Construction and immunogenicity of recombinant pseudorabies virus expressing the modified GP5m protein of porcine reproduction and respiratory syndrome virus

Abstract

Pseudorabies virus (PRV), an alpha-herpesvirus, has been developed as a live viral vector for animal vaccines. However, the PRV recombinant virus TK^-/gE^-/GP5⁺ expressing GP5 of porcine reproductive and respiratory syndrome virus (PRRSV), based on the PRV genetically depleted vaccine strain TK^-/gE^-/LacZ⁺, scarcely stimulated the vaccinated animals to produce neutralizing antibodies against PRRSV. To develop a booster-specific immune response of such PRV recombinants, the ORF5m gene (the modified ORF5 gene having better immune responses) was substituted for the ORF5 gene and introduced into PRV TK^-/gE^-/LacZ⁺, resulting in a PRV recombinant named TK^-/gE^-/GP5m⁺, which expressed the modified GP5m protein. The recombinant virus was confirmed using PCR, Southern blotting and Western blotting. TK^-/gE^-/GP5m⁺ and TK^-/gE^-/GP5⁺ expressing the authentic GP5 protein were inoculated into Balb/c mice to evaluate their immune responses. The results indicated that the protecting neutralization antibodies (the 3/6 vaccinated mice obtained 1:16) and cell immune responses induced by TK^-/gE^-/GP5m⁺ against PRRSV were higher than that induced by TK^-/gE^-/GP5⁺. Thus, the development of the new PRV recombinant expressing the modified GP5m protein as a candidate vaccine established the basis for the study of bivalent genetic engineering vaccines against PRRSV and PRV.