Vaccine to Treat Melanoma
Wistar scientists have developed novel peptides that mimic a BRAF mutation (BRAFV600E) which is expressed in a majority of melanomas. These mutated BRAF peptides stimulate T cell proliferation in melanoma patients who express HLA-2; this HLA type is expressed by about 50% of melanoma patients. Vaccines against BRAFV600E may induce both Class I and Class II-restricted lymphocyte responses and, as such, would be a useful tool for immunotherapy of melanoma.
In pre-clinical studies, 4 of 5 melanoma patients with BRAFV600E-positive lesions mounted a significant immune response (T cell proliferation) to stimulation with BRAFV600E peptide, thus demonstrating the feasibility of this immunotherapy in melanoma patients.
Method for Identifying Novel Cancer Antigens for Vaccine Development
A novel method for cloning MHC class II-dependent antigens from cancer cells has been developed for use in creating new cancer vaccines. Cancer antigens bound to MHC molecules on the surface of specialized antigen presenting cells (APCs) are recognized by CD4+ T-helper (Th) lymphocytes, which play a central role in providing protective immunity against cancer. New MHC class II-dependent cancer antigens therefore have significant promise as vaccine immunogens. They have previously been identified by artificially fusing libraries of cancer peptides with MHC molecules, expressing them in standard cell lines, and screening them for activation of CD4+ Th cells in culture. However, this method fails to recapitulate the complexity of antigen-MHC processing and presentation by APCs; requires prior knowledge of the MHC restriction element used by the Th cell and is very laborious. Wistar scientists have developed a phage method for expressing tumor cDNA libraries directly in APCs, without prior fusion to MHC. The APCs naturally process and present these tumor peptides on their surface, where they can be readily screened for CD4+ Th cell activation. The method has been used at Wistar to identify a novel Th cell antigen that is shared by melanomas and gliomas, and may be useful for the identification of other antigens for cancer vaccine development.
Three-Dimensional System to Measure Lymphocyte Migration
There is a need for model systems that can be used to identify clinically relevant behaviors of cytotoxic T lymphocytes (CTL), including tumor cell lysis and active migration, as well as systems that can be used to identify chemokines and tumor antigens that influence active migration of CTL towards tumor cells. Traditionally, CTL are raised and studied in two-dimensional mixed lymphocyte tumor cell culture (MLTC) that includes either (1) long-term cultured tumor cells to stimulate peripheral blood mononuclear cells (PBMC) for CTL induction or (2) disaggregated tumor tissue with tumor infiltrating lymphocytes (TIL) where both types of cultures are two dimensional and are grown directly on plastic surfaces. Studies in melanoma and colon cancer patients have shown that characterization of CTL responses using such two-dimensional cultures do not reflect the CTL’s in vivo behavior and specifically, CTL-exerted anti-tumoral activity.
Wistar scientists have developed a three-dimensional reconstruct model containing solid layers of collagen, tumor cells and CTL that closely mimic the condition of patients in vivo, preserving in vivo semi-phenotypic and functional characteristics of the cells. This model closely mimics CTL behavior in cancer patients and allows the detection of CTL migration and identification of tumor antigens and cytokines/chemokines involved in CTL migration.
Monoclonal Antibody Against Melanotransferrin (ME D63)