ABSTRACT
Relapse of hematologic malignancies is the primary cause of treatment failure after allogeneic hematopoietic stem cell transplantation (HCT). Treatment for post-HCT relapse using donor lymphocyte infusion (DLI) has limited utility, particularly in the setting of acute leukemia, and can result in the development of graft-versus-host disease (GVHD). The Wilms' tumor 1 (WT1) gene product is a tumor-associated antigen that is expressed in acute leukemia and other hematologic malignancies, with limited expression in normal tissues. In this pilot trial, we assessed safety and feasibility of a WT1 peptide-loaded donor-derived dendritic cell (DC) vaccine given with DLI designed to enhance and direct the graft-versus-leukemia effect. Secondary objectives were to evaluate immunologic and clinical responses. A total of 5 subjects, median age 17 years (range, 9 to 19 years), with post-HCT relapse were enrolled. Disease subtypes included acute lymphoblastic leukemia (n = 3), acute myelogenous leukemia (n = 1), and Hodgkin lymphoma (n = 1). Successful vaccine production was feasible from all donors. DC vaccination and DLI were well tolerated. One recipient developed grade 1 skin GVHD not requiring systemic therapy. The most common adverse events included grade 1 reversible pain and pruritus at the vaccine injection and delayed-type hypersensitivity (DTH) skin testing sites. There were no grade 3 or higher adverse events related to the research. Immune responses consisted of ELISpot response in 3 recipients and positive DTH tests to WT1 peptide cocktail in 2 subjects. Our study provides 1 of the first attempts to apply tumor-specific vaccine therapy to the allogeneic setting. Preliminary results show the DC-based vaccination is safe and feasible after allogeneic HCT, with a suggestion that this approach can be used to sensitize the repopulated allogeneic-donor immune system to WT1. Future directions may include testing of vaccination strategies in the early post-transplantation setting for relapse prevention.