One of the main challenges facing tumor immunologists is to develop strategies that would effectively stimulate Type-1 anti-tumor T cell responses, which have been correlated with better clinical outcome and prolonged survival of cancer patients. As CD4+ T cells were shown to play a critical role in mediating these responses, it was of interest to examine novel ways of effectively stimulating and enhancing Type-1 CD4+ T cell responses. For these studies I used MAGE-A6, a tumor associated antigen (TAA) expressed by a broad range of human cancer types. Two novel MAGE-A6 T-helper epitopes were identified and were shown to be recognized by CD4+ T cells isolated from the majority of normal donors or patients with melanoma, regardless of their HLA genotype (i.e. poly-DR presented epitopes). Furthermore, peptide-specific T cells also recognized autologous monocytes pulsed with recombinant MAGE-A6 protein, supporting the natural processing and MHC presentation of these epitopes. Interestingly, one of the novel MAGE-A6 epitopes possesses a high-degree of homology with a microbial peptide. CD4+ T cells stimulated in vitro with this microbial peptide cross-reacted against the MAGE-A6 homologue peptide, and could recognize naturally-processed MAGE-A6 epitopes more effectively than T cells stimulated with MAGE-A6 peptides. This study showed that it is possible to stimulate, and even enhance tumor-specific T cell responses using microbial epitopes that are homologous to TAA-derived peptides. In the final study, human dendritic cells (DC) were engineered to secrete high levels of IFN-×-inducing cytokines IL-12p70 and IL-18 via recombinant adenoviral infection to generate an in vitro stimulus capable of promoting previously deficient patient Th1-type responses. DC engineered to secrete both of these cytokines simultaneously (DC.IL-12/18) were highly effective at stimulating MAGE-A6-specific Th1-type CD4+ T cell responses from patients with melanoma, particularly when loaded with MAGE-A6 protein. Poly-DR presented epitopes and MAGE-A6 protein defined in this thesis, if loaded onto DC.IL-12/18, could prove clinically useful as a vaccine modality capable of promoting the recovery and/or enhancement of tumor antigen-specific, Th1-type CD4+ T cell responses in the majority of patients harboring MAGE-A6+ cancers.
| Identifer | oai:union.ndltd.org:PITT/oai:PITTETD:etd-06222006-141321 |
| Date | 29 June 2006 |
| Creators | Vujanovic, Lazar Nikola |
| Contributors | William Chambers, Hannah Rabinowich, Louis Falo, Russell Salter, Ora A. Weisz, Walter J. Storkus, Angus Thomson |
| Publisher | University of Pittsburgh |
| Source Sets | University of Pittsburgh |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.pitt.edu/ETD/available/etd-06222006-141321/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Pittsburgh or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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