Nonresistant bifunctional DNA vaccine vector, and construction method and application thereof

The invention discloses a nonresistant bifunctional DNA vaccine vector, and a construction method and an application thereof, and belongs to the technical field of animal gene engineering. A nutrition selection marker is used as the screening marker of the nonresistant bifunctional DNA vaccine vector to substitute antibiotic resistance gene in order to construct a eukaryotic expression plasmid pcD-asd and fundamentally block the diffusion propagation of the antibiotic resistance gene, the safety is good, and the expression efficiency and the copy number are high. The DNA vaccine vector can complement with asd gene defect Gram-negative bacteria to construct a chromosome-plasmid balanced lethal system, and the system can highly and stably express exogenous gene in the eukaryotic cell, and can be used as a nucleic acid vaccine expression vector, for example, attenuated Salmonella typhimunum is used as a vector to construct bivalent and multivalent live bacterial vaccines.