Construction And Immunobiological Properties Of Attenuated Salmonella Typhimurium Harbouring DNA Vaccine Against H5 Subtype Of Avian Influenza Virus

Highly pathogenic avian influenza (HPAI), a highly contagious disease with worldwide distribution, can cause severe economic losses to the poultry industry with its high percent of disease and death. The killed vaccine has been verified that they are important for controlling the infection and epidemic of this disease, but several disadvantages are unable to be avoided, e.g. potential dangerous of virus distribution and unable to induce cellular and mucosal immune responses. Thus, developing a safe and high protective vaccine is necessary.Attenuated Salmonella typhimurium can be used as vectors to directly deliver DNA vaccine into immune system from mucosal approach, then the heterologous antigen can be expressed in vivo and induces the protective humoral, cellular and local mucosal immune response. Using attenuated Salmonella typhimurium as vectors to deliver DNA vaccines is a novel promising method to control avian influenza.The high-copy-number plasmid is unstable within Salmonella, which restrict the development of recombinant Salmonella vaccine vector. A novel plasmid pmcDNA3.1+ was constructed based on plasmid pcDNA3.1+ and its stability is improved. Then the AIV DNA vaccine delivered by attenuated Salmonella typhimurium was constructed, and the immunobiological properties of the recombinant bacteria was evaluated in mice and chickens.1. Improve stability of plamid pcDNA3.1+ within Salmonella typhimurium by downregulation of the ampicillin resistance gene expressionA novel plasmid pmcDNA3.1+ was constructed by removing the promoter sequence of ampicillin resistance gene (bla gene) in plasmid pcDNA3.1+. In contrast to pcDNA3.1+, pmcDNA3.1+ was stable within attenuated Salmonella typhimurium SL7207 in LB medium with or without ampicillin. The recombinant plasmids...