Construction and immune response characterization of a recombinant pseudorabies virus co-expressing capsid precursor protein (P1) and a multiepitope peptide of foot-and-mouth disease virus in swine.

Foot-and-mouth disease (FMD) is the most contagious and devastating disease of livestock. Our previous studies demonstrated that TK(-)/gG(-)/P1(+), a recombinant expressing the FMDV capsid precursor protein (P1) based on attenuated pseudorabies virus (PRV) TK(-)/gG(-), could be used as a recombinant vaccine to protect pigs against both pseudorabies and FMD. However, because the P1 expression cassette is inserted into the gG locus of the genome of PRV TK(-)/gG(-), this bivalent vaccine cannot be used in conjunction with the PRV gE-ELISA, an extensively used discriminatory serological test in eradication programs for pseudorabies, which limits the clinical use of this bivalent vaccine. To circumvent this shortcoming, in this study, an expression cassette containing synthetic multiepitope gene "FHG" consisting of six potential B cell epitopes and two potential T cell epitopes of FMDV, under the control of CMV promoter, was further inserted into the gE/gI locus of genome of TK(-)/gG(-)/P1(+), resulting in a new recombinant FHG/P1/PRV. The immunogenicity of FHG/P1/PRV was evaluated and compared with TK(-)/gG(-)/P1(+) in piglets. Our results clearly showed that FHG/P1/PRV performed better than or comparable with TK(-)/gG(-)/P1(+), as demonstrated by comparable PRV-specific neutralizing antibodies, enhanced FMDV-specific neutralizing antibodies, and cellular immune responses. More importantly, no gE- and gG-specific antibodies could be detected in pigs immunized with FHG/P1/PRV. These data indicate that FHG/P1/PRV is a promising bivalent vaccine candidate with more extensive potential application than TK(-)/gG(-)/P1(+) against both pseudorabies and FMD.