Active specific and adoptive immunotherapy for cancer centering on cytolytic T lymphocyte (CTL) response have shown encouraging results. These treatment modalities, however, would benefit from the involvement of cognate CD4+ T helper (Th) cells. We have found that CD4+ T cells -- engineered to express a MHC class I- restricted melanoma epitope specific T cell receptor (TCR) that is also used by CTL to recognize the epitope -- synthesize Th1 type cytokines and exhibit cytolytic potential against melanoma cells and surrogate target cells in an epitope specific manner. We propose a comprehensive study of the biology of such MHC class I-restricted TCR engineered CD4 T cells in an anti-melanoma immune response focusing on their role as effector cells and as helper T cells. The central hypothesis is that considering that help and suppression are two mutually opposed conditions, if one could engage CTL and helper cells recognizing a tumor associated epitope of interest simultaneously through an identical TCR and on the same MHC restricting molecules, the CD4+ T cells would facilitate the generation of a robust and long-lasting CTL response and mitigate Treg activation. Additionally, by exhibiting anti-tumor effector function of their own, they would expand the anti-tumor repertoire. We propose to test this hypothesis through several specific aims designed with CD4+ T cells engineered to express melanoma epitope (MART-127-35 and Tyrosinase368-376)-specific TCR in in vitro assays, and in HLA- A2.1/Kb transgenic mice employing a chimeric human-mouse TCR consisting of mouse constant regions and human variable regions, in vivo. The biology of the CD4+ Th cells will be assessed through a comprehensive phenotypic and functional characterization in in vitro CTL generation assay, in vitro Treg activation assay, and in adoptive transfers of chimeric TCR engineered T cells into HLA-A2.1/Kb mice bearing A2.1/Kb transgenic B-16 melanoma cells. The proposed research will lead to the development of a new and complementary strategy to active specific and adoptive immunotherapy for cancer. Lay Summary: The proposed research is designed to develop a novel way to engage killer T cells and helper T cells (two important players in the immune system) to work in a collaborative and synergistic manner so as to orchestrate a robust and long-lived cellular immune attack against human cancers - a major cause of death. PUBLIC HEALTH RELEVANCE: Cancer vaccines and adoptive cell therapy for cancer have shown promising results but the two basic approaches need new strategies addressing two major impediments -- the lack of an effective way that would engage cognate CD4 T helper (Th) cells in the treatment and T regulatory (Treg) cell activities. We propose a novel strategy that could address both constraints through the employment of CD4 T cells engineered to express an MHC class I-restricted and tumor epitope specific T cell receptor (TCR) that are also used by cytolytic T cells (CTL) to recognize the tumor antigen. The TCR-engineered CD4 Th cells, therefore, could provide help towards the generation of a robust and long-lived CTL response as well as expand the therapeutic repertoire by mitigating Treg activities (as help and suppression are mutually opposed conditions) and through their own cytolytic potential.