DDAB/PLA Nanoparticles As Adjuvants For Anthrax Vaccine

Bacillus anthracis is a Gram-positive bacillus that can cause anthrax which is a zoonotic disease.Anthrax is mainly infected by the gastrointestinal,skin or inhalation.Human infected almost by skin or inhalation with mortality rates of 20%and 100%,respectively.Adjuvants of the anthrax vaccines are mainly aluminum salts.However,aluminum adjuvants as anthrax vaccine adjuvants have serious local reactions such as erythema swollen and induration at the injection site.Therefore,we need to develop new types of adjuvants.Biodegradable polymer particles have the ability to carry a large number of antigens,can continue to provide antigens,modified with targeted delivery function and biodegradability and good biocompatibility,and therefore they are employed as a novel vaccine adjuvant.Polylactide nanospheres promote the antigen uptake by antigen presenting cells(APCs)and are presented via the MHC I pathway,leading to higher levels of humoral and cellular immune responses.Factors The particle size of biodegradable polymeric particle adjuvants is one of the immune effect factors except the surface properties.Therefore,this thesis designed nano-particles with different particle sizes and compared their immune effects,and then optimized the formulation of the vaccine with nanoparticle as adjuvant,and the enhanced immune mechanism was also studied.The detailed research contents are as follows:(1)Microparticles and nanoparticles were prepared by rapid emulsification and nanoprecipitation method,respectively.The diameters of DDAB/PLA particles were 1 μm and 170 nm,respectively.The uptake of antigens loaded on nanoparticles were significantly higher than those of microparticles.Compared with the immune effects at animal level,the nanoparticle-adjuvanted vaccines are superior to microparticle-adjuvanted vaccines.(2)The nanoparticle-adjuvanted vaccine at the animal level and cellular level showed that the nanoparticle had good biosafety.The optimum dosage of the vaccine was 5 μg,and the nanoparticle adjuvant concentration was 3 mg/mL,and the immunization volume was 100 μL.When compared with the aluminum-adjuvanted vaccine,the best formulation of the vaccine was found that the antigen loaded on naonparticles could be greatly uptake by the DC cells;which further improved activation of DC cells.Comparing immune effects at animal levels,it was found that the immune effect of nanoparticle-adjuvated vaccines is superior to that of aluminum-adjuvanted vaccines,and the immune persistence was also far better than aluminum-adjuvanted vaccines.(3)The immune enhancement mechanism mechanism of nanoparticle adjuvant was also studied.It was found that nanoparticles could activate DCs and B cells in lymph nodes,and further improve formation of germinal center B cells.The results of the histochemistry also showed that the nanoparticle could enhance proliferation of germinal center cells,which further promote the formation of follicular helper T cells and activate the T cells in the lymph node.It was also showed that the nanoparticles could enhance antigen crosspresentation in vitro.In summary,this DDAB/PLA nanoparticle vaccine adjuvant exhbit good immunological effect,which has the potential to become a new type of vaccine adjuvant.