Design And Application Of Novel Tumor Vaccines Based On A Cell-penetratin Peptide And Bacterial Outer Membrane Vesicles

Human beings have been fighting against cancer for hundreds of years,and more and more cancer therapeutic strategies have been developed.The traditional methods of tumor treatment include surgery,radiotherapy and chemotherapy.Tumor immunotherapy is a new type of tumor therapy,which can eliminate tumor by promoting the patient's anti-tumor immune response.Tumor vaccine is a type of tumor immunotherapy,which has been developed rapidly in recent years,but the ideal tumor vaccine with high antitumor efficacy still needs further development.In order to induce effective antitumor immune response and achieve better antitumor effect,an ideal tumor vaccine needs to contain at least three elements:antigens with high immunogenicity,an effective delivery strategy,and efficient immune adjuvants.In this dissertation,two types of tumor vaccines were designed and evaluated.First of all,the antigen in tumor vaccine,as an exogenous antigen,cannot effectively induce the immune response mediated by CD8+T cells that can directly kill tumors.In order to solve this problem,our first design took ovalbumin(OVA)as the model antigen,and used the new cell-penetrating peptide cytosol localizing internalization peptide 6(CLIP6)as the delivery system to alter the cellular entry pattern of OVA.Our results showed that the CLIP6 coupling can significantly enhance the antigen cross presentation in bone marrow derived dendritic cells(BMDCs).In addition,as a tumor preventive vaccine,CLIP6-OVA could inhibit tumor growth to a certain extent in a melanoma model.Secondly,multiple injection of bacterial outer membrane vesicle(OMV)with the ability to stimulate immune responses were needed to inhibit tumor growth,which has a high risk of side effects.In the previous work,we found that a single injection of OMV derived from Salmonella typhimurium S.t ?pG can made tumor blank.So the mechanism of this phenomenon was studied and the results showed that,owing to the lipopolysaccharide(LPS)on their surface,single injection of S.t ?pG-OMV could lead to enrichment of red blood cells(heme)at the tumor site,causing an increase of light absorption in the near-infrared region.Then,based on the clotting caused by OMV,we proposed the strategy of in situ tumor vaccine.In this strategy,firstly,OMV was used for causing heme concentrating in tumors,and then followed by heme-mediated photothermal therapy(PTT).Secondly,the immune responses induced by PTT could realize the in situ tumor vaccine,while OMV could further promote the immune responses.The results showed that there was no significant biological toxicity in vivo after single injection of OMV,and this in situ vaccine strategy could completely eliminate the subcutaneous tumor in the 4T1 mouse breast cancer model,while in another CT26 mouse colon cancer model,this in situ vaccine strategy not only cured the mice,but also completely inhibited the recurrence of CT26 tumors after treatment,showing excellent anti-tumor effectIn conclusion,two types of tumor vaccines were designed to effectively promote the antitumor effects.Both vaccines were easy to prepare,with low cost and high biocompatibility,showing certain development potential and might providing new ideas for the development of different forms of tumor vaccines.