Cassian Yee

Evaluation of the Use of Antigen-specific T Cell Clones for the Treatment of Patients with Metastatic Melanoma:

The application of adoptive cellular immunotherapy for the treatment of malignancies requires the identification of useful tumor target antigens and the development of strategies to efficiently isolate tumor-reactive antigen-specific T cell clones. Studies evaluating the safety, potential toxicity duration of in vivo persistence and anti-tumor efficacy of adoptively transferred tumor-reactive T cells recognizing these antigens will provide critical information for facilitating the design of more effective approaches to adoptive immunotherapy. To this end, we are performing Phase I/II study evaluating the use of tyrosinase-, gp100- and MART-1- specific autologous CD8+ CTL clones for the treatment of patients with metastatic melanoma. The results of this initial study suggest that T cells persist in vivo, traffic to tumor sites and mediate an antigen-specific immune response. Current trials now address potential obstacles to complete tumor eradication and opportunities to improve effector function.

Evaluation of Anti-Tumor Immunity Using MHC-Peptide Tetramers:

Direct analysis of T cells of defined specificity without in vitro manipulation, provides an accurate and highly informative representation of in vivo events. The natural ligand of the TCR, the peptide-MHC complex, can be used to identify T cells of a given specificity. Since the affinity of the peptide-MHC for its TCR ligand is characterized by a very fast dissociation rate, a tetrameric peptide-MHC complex was designed which exhibits sufficient affinity for its TCR ligand to permit its use as a staining reagent in flow cytometry thus enabling simultaneous multiparameter single cell analysis by combined use of fluorescent antibodies staining phenotypic markers or intracellular cytokines. Furthermore, sorting individual tetramer+ cells provides an expeditious means for detailed cellular analysis or in vitro isolation. As a result novel insights into the magnitude, phenotype and functional status of the antigen-specific population can be acquired that were previously not possible using current technologies. We are investigating the use of peptide tetramers to analyze the innate antitumor immune response, and to elucidate mechanisms of T cell differentiation and tumor recognition.

Role of the CD4 T Cell Response in Melanoma:

Current efforts to treat human malignancies by manipulation of the immune system have been directed at augmentation of an antigen-specific CD8 response. However, it is clear from animal studies that a CD8 response alone is insufficient. The importance of CD4 T cells in inducing and maintaining effective CD8 cellular immunity has been well-documented in murine models of immunotherapy but their contribution to the endogenous and induced anti-tumor immune response in humans is poorly defined. The development of novel reagents and methodologies to track the phenotype and function of antigen-specific T cells in vivo now permits a rational examination of the role of CD4 T cells in antigen-specific tumor immunity. Our goals are to characterize the endogenous CD4 response to tumor-associated antigens in patients with melanoma and evaluate the contribution of CD4 helper function to CD8 survival and effector function.

Child-rearing (n=2)

1. Adoptive T cell therapy of melanoma
2. Adoptive T cell therapy of ovarian cancer
3. Murine model of tumor immunity (or lack thereof)
4. Novel methods in immune monitoring
5. Novel methods in isolation and expansion of tumor-specific T cells