Preliminary Research On Protein-DNA Nano-particle Anticancer Vaccine

DNA vaccine has made a remarkable progress in the recent years. As a novel type of vaccine, the most attractive feature is the potential of DNA immunization to elicit both cell-induced immune response and antibody response. Meantime, other advantages of DNA vaccine as product include stable, easy transformation and production. Therefore, there are broad values of DNA vaccine research and application. However, the immunogenicity of DNA is usually significantly low and couldn't elicit enough immune response,which has increasingly become the main blockade to DNA application.In responding to this somewhat unexpected setback following new strategies have been developed to improve the immunogenicity of DNA vaccine: protein-DNA nano-particle vaccine. Protein vaccine and DNA vaccine can condense into nano-particle through the electrostatic interaction, which may elicit T-cell induced response by DNA vaccine and elicit antibody response by protein vaccine. In addition,the nano-particle could improve APCs'functions of phagocytosis and presenting antigens, and enhance DNA immune response.Firstly, human inhibition apoptosis protein survivin and chorionic gonadotropinβchain- CTP37 gene were used as targeting antigens. By methods of gene engineering, a series of recombinant specific tumor antigens were expressed and purified in E.coli. Including: SLC-survivin-IM, (survivin)1-IM, (survivin)2-IM and CTP37-IM.Since a cationic peptide has been fused with above recombinant protein, so these protein could combine with DNA through electrostatic interaction. Meanwhile, in protein vaccine, Cellthatular penetration peptide and endosome releasing peptide could protect DNA against digestion and may increase the expression of exogenous gene.Then,the above protein vaccine combine with DNA vaccine which encoding the same antigen, both of which condense into a protein-DNA nano-particle. Assay of agarose gel electrophoretic retardation has been proved that protein could combine with DNA through electrostatic interactions. Assay of DnaseⅠdigest protection has confirmed that nano-particle protect DNA against DnaseⅠdigestion. Observed with Atomic force microscope (AFM) has confirmed that protein vaccine and DNA vaccine condense into a stable nano-particle with diameter from 50nm to 500nm. In fact, this particle is easy to be endocytosis by APC. Last, DNA vaccine combining with protein could transfect into eukaryotic cell 293T by transient transfection and protein never affects the expression of DNA vaccine.In conclusion, this combinant nano-particle vaccine, as a new delivery model of DNA vaccines, could improve the immunogenicity of DNA vaccine. It maybe has potential advantages of safety and immune stimulating function, these values of application need be research deeply.