Background: Immunotherapy of cancer with DC vaccines has produced encouraging results in clinical trials. Antigen (Ag)-pulsed DC have elicited CD4+ and CD8+ T-cell immunity and tumor regression in humans. However, there is no standard method of DC production. The DC phenotype, number and Ag-loading process used in these studies have varied, making comparisons between trials difficult.
Methods: In the present report a reproducible method was developed for the production of a DC-based vaccine. Monocytes were enriched by adhesion from healthy donor apheresis products and cultured with growth factors for maturation into DC. The cells were loaded with the tumor Ag idiotype proteins from patients with multiple myeloma. DC culture and Ag loading were performed in an automated and closed system. The DC product was characterized for phenotype by flow cytometry and for function in Ag uptake and Ag presentation.
Results: These monocyte-derived DC expressed high levels of costimulatory molecules (CD80/86). Ag-pulsed DC functioned to induce allogeneic proliferative lymphocyte responses and Ag-specific cytotoxic T lymphocyte (CTL) responses. The DC viability, phenotype and function were well preserved following prolonged frozen storage. Aliquots from the product of a single DC preparation could be used for sequential vaccinations without batch to batch variability.
Discussion: Ag-pulsed DC can be reproducibly generated for clinical use. These standardized methods are now being employed for a clinical trial to evaluate idiotype-pulsed DC vaccine therapy following non-myeloablative transplant for the treatment of multiple myeloma.