The goal of this project is to develop a synthetic peptide vaccine for inducing cytolytic T-lymphocytes (CTL) specific for v-region peptides (idiopeptides) that arise from processing of endogenous, clonally expressed Ig molecules of the malignant B-cells in patients with chronic lymphocytic leukemia (CLL).These peptides, which are presented on the MHC molecules of the malignant cells, are a desirable target for T-cell-based immunotherapy since, like idiotypic determinants of native Ig molecules, they tend to be clonally restricted. Recent evidence suggests that patients' immune Systems are unlikely to be tolerant to all of the v- region peptides presented by malignant CLL cells. Peripheral blood mononuclear cells of the patient will be immunized in vitro with synthetic v-region peptides derivatized with an adjuvant that enhances CTL responses. The resulting T-cell clones will initially be tested for cytolytic activity using EBV transformed normal B-cells pulsed with the synthetic peptides used for immunization. EBV B-cells are a convenient source of cultured cells expressing MHC antigens of the patient. Positive clones will be characterized for antigen sensitivity and MHC restriction and then tested for cytolytic activity using the malignant B-cells from the patient. A basic goal is the identification of synthetic v-region peptides that are capable of inducing cytolytic responses that can kill malignant B-cells. In addition to testing the feasibility of T-cell immunotherapy for CLL, in vitro induction of CTL specific for malignant B-cells may lead to the establishment of T-cell clones useful for adoptive immunotherapy. In this proposal, we study CLL because of its unique practical advantages. CLL is often an indolent disease that is not treated for more than 5 years after diagnosis. Large numbers of malignant B-cells, as well as non- malignant cells, can be obtained from peripheral blood and cryopreserved. Establishment of malignant B-cell lines is unnecessary. The occurrence of malignant cells in peripheral blood is also an advantage since even minimal residual disease could likely be monitored with PCR methodology if our procedure were to be used with patients.
