Immunotherapy that targets the human papillomavirus (HPV) E6 protein may provide an opportunity to control HPV-associated cervical malignancies. It has been established that T cell-mediated immunity is one of the most crucial components of defense against HPV-associated lesions and that dendritic cells (DCs) are the most potent professional antigen presenting cells (APCs) that prime helper and killer T cells in vivo. Furthermore, it has been shown that intradermal administration of DNA vaccines via gene gun represents an efficient means of delivering DNA vaccines into professional APCs in vivo. We have therefore used the gene gun delivery system to test strategies that require direct delivery of DNA vaccines to professional APCs. We have successfully tested several intracellular targeting strategies that enhance MHC class I and class II processing and presentation and have generated impressive results. Recently, we tested a variety of anti-apoptotic factors for their ability to enhance DC survival and antigen-specific CD8+ T cell immune responses when co-administered with DNA vaccines. Because intracellular targeting and anti-apoptotic strategies modify DCs via different mechanisms, we have been able to combine anti-apoptotic strategies for prolonging DC life with intracellular targeting strategies for enhancing MHC class I and II presentation of antigen by DCs to improve DNA vaccine potency. While coadministration of DNA encoding antigen with DNA encoding anti-apoptotic proteins can significantly enhance DNA vaccine potency, the use of DNA encoding anti-apoptotic proteins raises significant concerns related to oncogenicity. A relatively new technology, RNA interference (RNAi) using small interfering RNA (siRNA) targeting pro-apoptotic proteins may provide similar effects while alleviating concerns for oncogenicity. Thus, in the current proposal we plan to test the hypothesis that intradermal delivery of a DNA vaccine encoding HPV-16 E6 in conjunction with siRNA targeting key pro-apoptotic proteins to antigen-expressing dendritic cells would prolong transfected DC life and lead to enhanced E6-specific T cell-mediated immune responses and antitumor effects in vivo.
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