Development Of Therapeutic DNA Vaccine And Protein Vaccine Using Orally Delivered Antigen Presentation System Mediated By Attenuated Salmonella Typhimurium

Therapeutic vaccines of cancer are attractive for their capacity of breaking the immune tolerance and invoking long-term immune response targeting cancer cells without autoimmunity. An efficient antigen delivery system is the key issue of developing an effective cancer vaccine. Attenuated Salmonella typhimurium as the carrier of cancer vaccine are able to transfer DNA from the prokaryote to the eukaryote and preferentially replicate within the tumor tissue. Heat shock protein 70 delivers the tumor-associated antigens to antigen presenting cells via its polypeptide-binding domain and breaks immune tolerance of the cancer cells. Here in the first part of this thesis, we described a novel low-copy-number DNA vaccine based on the Hsp70-TAA complex and carried by the attenuated Salmonella typhimurium strain SL3261. Orally administration of this vaccine elicited specific CTL-mediated lysis of the melanoma tumor cells and marked activation of the T cells. The therapeutic vaccine effectively protected 57.1% C57BL/6J mice from lethal challenge with B16F10 melanoma tumor cells in prophylactic settings and eradicated 62.5% tumor growth in therapeutic settings.Location of the invasive bacteria in solid tumor after orally administration can also be utilized in development of targeted cancer therapy. Though the intracellular location of Salmonella may hamper their entrance into the antigen presentation pathway, the typeâ…¢secretion system circumvents this problem by transferring the protein they encoded directly into the cytosol of APCs. In the form of Hsp70-TAA complex, heat shock protein 70 facilitates the presentation of tumor-associated antigens through its receptor on APCs. In the second part of this thesis, we designed a novel therapeutic vaccine using typeâ…¢secretion system to deliver Hsp70-TRP2 by fusing with typeâ…¢secretion protein SopE. This live recombinant bacteria vaccine, when orally administrated, successfully presented the tumor antigen, broke the immune tolerance, induced specific cytotoxicity against tumor cells, and therefore revealed protective (75%) and therapeutic (62.5%) effect against generation and growth of B16F10 melanoma in C57BL/6J mice. The construction of the two antigen delivery system, mediated by attenuated Salmonella typhimurium, provides promising methods for development of therapeutic DNA vaccine and protein vaccine against various type of cancer.