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Brief Definitive Reports |








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Cancer Immunotherapy and Gene Therapy Program, and the
Laboratory of Molecular Tissue Typing and || Immunochemistry Unit, Department of Biology and Technology (DIBIT), Scientific Institute H. San Raffaele, 20132 Milan, Italy; ¶ Roche Milano Ricerche, 20132 Milan, Italy; ** Roche Discovery Technologies, Hoffman-La Roche, Inc., Nutley, New Jersey 07110; and 
Departement Chirurgie, Kantonsspital, CH-4031 Basel, Switzerland
In this study we used TEPITOPE, a new epitope prediction software, to identify sequence segments on the MAGE-3 protein with promiscuous binding to histocompatibility leukocyte antigen (HLA)-DR molecules. Synthetic peptides corresponding to the identified sequences were synthesized and used to propagate CD4+ T cells from the blood of a healthy donor. CD4+ T cells strongly recognized MAGE-3281–295 and, to a lesser extent, MAGE-3141–155 and MAGE-3146–160. Moreover, CD4+ T cells proliferated in the presence of recombinant MAGE-3 after processing and presentation by autologous antigen presenting cells, demonstrating that the MAGE-3 epitopes recognized are naturally processed. CD4+ T cells, mostly of the T helper 1 type, showed specific lytic activity against HLA-DR11/MAGE-3–positive melanoma cells. Cold target inhibition experiments demonstrated indeed that the CD4+ T cells recognized MAGE-3281–295 in association with HLA-DR11 on melanoma cells. This is the first evidence that a tumor-specific shared antigen forms CD4+ T cell epitopes. Furthermore, we validated the use of algorithms for the prediction of promiscuous CD4+ T cell epitopes, thus opening the possibility of wide application to other tumor-associated antigens. These results have direct implications for cancer immunotherapy in the design of peptide-based vaccines with tumor-specific CD4+ T cell epitopes.
Key Words: MAGE-3 CD4+ epitopes melanoma tumor vaccines adoptive immunotherapy
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