The overall goal of this project is to develop a method of immunization that induces high titer IgG antibodies against GD3 ganglioside in melanoma patients. GD3 is an attractive target for immunotherapy because it is expressed on virtually all melanoma, it is expressed on few normal tissues, and monoclonal antibodies (MAb) against GD3, such as R24, can induce anti-melanoma effects in animals and in patients. Previous attempts to immunize patients against GD3 have been partially successful using either: a) GD3-lactone conjugated to keyhole limpet hemocyanin and mixed with the adjuvant QS21 (GD3-lactone-KLH+QS21) or b) BEC2 anti-idiotypic MAb mixed with the adjuvant BCG. Using either of these vaccines, low titer antibodies against GD3 can be induced in a subset of patients. In this application, the applicant proposes to test the hypothesis that priming patients with one form of vaccine followed by immunization with the other form of vaccine will be superior in inducing anti-GD3 antibodies compared to either form of vaccine alone and will induce high titer IgG against GD3.
Specific Aim 1 is to conduct a clinical trial involving 24 melanoma patients who are free of disease after surgical resection but who are at high risk for recurrence. They will be randomized to be immunized either with a course of BEC2 + BCG followed by GD3-lactone-KLH+QS21, or GD3-lactone-KLH+QS21 followed by BEC2+BCG. The applicant will assess and compare the anti-GD3 antibody response induced in each arm, both quantitatively and qualitatively, after immunization with the """"""""priming"""""""" vaccine and after the second course of vaccination. A secondary goal of this project is to make an initial attempt to identify T cells that recognize GD3 ganglioside. Several recent publications have indicated that, in some circumstances, T cells can recognize carbohydrates and other non-protein molecules.
Under Specific Aim 2, the applicant will test peripheral blood T cells from the patients immunized to look at T cells against GD3. T cell reactivity will be assessed using both a proliferation assay and by ELISPOT. It is possible that such T cells play an important role in the low recurrence rates observed in adjuvant immunotherapy trials previously conducted using BEC2.
