Recombinant adenovirus co-expressing capsid proteins of two serotypes of foot-and-mouth disease virus (FMDV): in vitro characterization and induction of neutralizing antibodies against FMDV in swine.

Human adenovirus type 5 (Ad5) has been evaluated as a novel gene delivery vector for the development of live-viral vaccines for foot-and-mouth disease (FMD). In this study, we constructed an Ad5 vector co-expressing the capsid precursor proteins, P1, of FMD virus (FMDV) field strains A24 Cruzeiro and O1 Campos and examined the neutralizing antibody responses in swine after inoculation with the vector. To construct the Ad5 vector, a bicistronic expression cassette containing a cytomegalovirus promoter, the P1 coding sequence of FMDV A24, the internal ribosomal entry site (IRES) of FMDV A12, the P1 coding sequence of FMDV O1 Campos and the coding region of A12 3C protease was inserted into the E1 region of an E1/E3-deleted Ad5. The recombinant adenovirus, Ad5A24+O1, was generated by transfection of 293 cells with full-length pAd5A24+O1 recombinant plasmid DNA. The recombinant Ad5 co-expressed P1 of both A24 and O1 in infected 293 cells and P1 of both serotypes was processed to produce VP0, VP3, and VP1. We further demonstrated the formation of capsid protein complexes by co-precipitation of VP0, VP3, and VP1 with monoclonal antibodies against viral capsid proteins. Swine inoculated with Ad5A24+O1 generated neutralizing antibodies against both A24 and O1. However, the overall neutralizing antibody response was considerably lower than that induced by a commercial FMD vaccine or a monovalent Ad5-A24 vaccine.