Study On The Immune Enhancement Mechanism Of DDAB-PLGA Adjuvant

Lactic acid-glycolic acid copolymer(PLGA)is a biologically safe and FDA-approved pharmaceutical excipient,as a vaccine delivery and adjuvant system,which is a very hopeful vaccine adjuvant.In this paper,we study the mechanism of DDAB-PLGA as a vaccine adjuvant induced by immune enhancement.In detail,this research contents mainly includes the following aspects:(1)Preparation of particles.DDAB-PLGA particles with different size(100 nm and 1?m)were prepared by O/W double emulsion method and nano-precipitation method using OVA as model antigen.And its physical and chemical properties were characterized.The results show that the DDAB-PLGA particles with smooth surface,uniform particle size and favorable dispersibility are successfully prepared.(2)Evaluation of the immune effect of particles.Nanoparticles in the immune system through the regulation of particle size can regulate the release of antigen behavior,significantly enhanced its immune effect,100 nm DDAB-PLGA nanoparticles have the potential to enhance cellular and humoral immune responses,while microparticles tend to humoral immune responses.100 nm DDAB-PLGA nanoparticles can induce higher levels of CTL responses,induce T cells to polarize to Thl and higher levels of memory T cell responses,and stimulate the effective immune response.(3)Biodistribution of particles in animals.Combining DDAB-PLGA particles with 89Zr-labeled OVA was prepared successfully,involved in Letabolic activities in the body and dynamic distribution in the organ or tissue.The PET/CT imaging technique was used to monitor and trace the antigen transport process effectively in vivo.The biological behavior of the nanoparticles vaccine in the body after its reinfusion was discussed,especially the homing ability to lymphoid tissues.(4)The effect of nanoparticles on lymphoid organs and dendritic cells.Particles can induce more APC cells that are loaded with more antigen partly through the passive lymphatic drainage,and some of them are processed by antigen-presenting cells,which are delivered and transported to the lymph nodes.Particles were ingested by DCs and survived by lysosome to the cytoplasm,which significantly increased the cross-presenting level of the antigen.At the same time,it can induce the maturation and activation of DCs through the secretion of a large number of inflammatory cytokines.(5)Mechanisms of dendritic cell maturation induced by particles.The in vitro and in vivo experiments confirmed that p38 MAPK signaling pathway plays an important role in the regulation of dendritic cell maturation induced by DDAB-PLGA particles,and p38 signaling pathway up-regulates the expression of cytokines.