The present disclosure provides dual viruses capable of producing a primary virus and a secondary virus, and dual oncolytic viruses capable of producing a primary oncolytic virus and a secondary oncolytic virus.

A viral vector delivery system for both respiratory and digestive tracts of pigs and an application thereof are provided. The viral vector delivery system includes a backbone plasmid and a helper plasmid. The backbone plasmid is produced by inserting a full-length cDNA of porcine enterovirus B (PEVB) into a pUC57 plasmid. The helper plasmid is produced by inserting a green fluorescent protein-coding gene into a plasmid pCAG-T7-polymerase. The viral vector delivery system can be constructed with high efficiency, can quickly cause a cytopathic effect (CPE) after infecting cells, has a viral titer up to 10.sup.7.75 TCID.sub.50/mL, and can maintain high stability. A pathogenic epitope for the respiratory and digestive tracts of pigs is inserted into the backbone plasmid to produce a vaccine antigen, which is non-pathogenic, has high stability and a high viral titer, and allows a prominent immunization effect after being inoculated in pigs.

A viral vector delivery system for both respiratory and digestive tracts of pigs and an application thereof are provided. The viral vector delivery system includes a backbone plasmid and a helper plasmid. The backbone plasmid is produced by inserting a full-length cDNA of porcine enterovirus B (PEVB) into a pUC57 plasmid. The helper plasmid is produced by inserting a green fluorescent protein-coding gene into a plasmid pCAG-T7-polymerase. The viral vector delivery system can be constructed with high efficiency, can quickly cause a cytopathic effect (CPE) after infecting cells, has a viral titer up to 10.sup.7.75 TCID.sub.50/mL, and can maintain high stability. A pathogenic epitope for the respiratory and digestive tracts of pigs is inserted into the backbone plasmid to produce a vaccine antigen, which is non-pathogenic, has high stability and a high viral titer, and allows a prominent immunization effect after being inoculated in pigs.