Peptidoglycan Adjuvant Facilitates In Vitro And In Vivo Performance Studies Of BSA And PCV2 Under Different Delivery Systems

As oral vaccine has the disadvantages of low immune effect and poor stability through the gastrointestinal tract,injection is the main inoculation route for the porcine circovirus type 2 vaccine(PCV2)up to now,which increases the cost and causes stress response.Mucosal immunity is still the most important protection way for vaccination.In order to improve the immunogenicity and reactivity of oral vaccine,the PCV2virus-like particle(PCV2-VLP)was protected through encapsulation and exert its effects in the intestinal tract.The Lactobacillus plantarum peptidoglycan(LPG)was used as adjuvant to stimulate the protection capability of the vaccine.In this experiment,Lactobacillus plantarum 1.157 was used to extract peptidoglycan(PG)as adjuvant by trichloroacetic acid method.The chitosan and pectin alone or in combination was used as wall material to prepare LPG microspheres,and the encapsulation efficiency and LPG loading capacity were measured.The microspheres were structurally characterized by infrared spectrum and thermogravimetric analysis;The toxicity and in vitro immune effects were determined through cytotoxicity test and phagocytosis test.The immune effect was verified by animal experiments.Then using bovine serum albumin(BSA)as model antigen,LPG+BSA pectin microspheres and LPG+BSA pectin compounding chitosan microspheres were prepared,which were characterized for encapsulation efficiency,drug loading capacity,gastrointestinal simulation,structural characterization,as well as cellular and animal experiments.Finally,LPG+PCV2-VLP pectin microspheres and LPG+PCV2-VLP pectin compounding chitosan microspheres were prepared from PCV2-VLP.The in vitro and in vivo properties of these microspheres were investigated as before.The results showed that chitosan microspheres and pectin microspheres loading LPG had no toxicity to cells.These microspheres could increase the phagocytic ability of cells(P<0.05),and enhance the immunity of mice(P<0.05),verifying the immune effect of LPG as an adjuvant.LPG+BSA pectin microspheres and LPG+BSA pectin compounding chitosan microspheres showed sustained release effect and no toxicity to cells,thus enhancing the immune effect of the body.These results verified the feasibility of preparing oral vaccine with BSA as model antigen.PCV2-VLP pectin microspheres showed good stability and sustained-release effect,with no toxicity to cells,and could increase the phagocytic ability of cells(P<0.05).These microspheres were nontoxic to mice,and increased the production of IgG(15.67±0.90 mg/m L)and sIgA(36.68±2.38?g/m L,P<0.05)in peripheral blood and small intestine,respectively.The study provides some basis for the development of the novel PCV2 oral vaccine.