Clinical-grade myeloma Ag pre-loaded DC vaccines retain potency after cryopreservation

BACKGROUND: The use of myeloma Ag-loaded mature DC vaccines, cryopreserved in single-use aliquots, is an attractive immunotherapeutic strategy. In this study we investigated the retention of phenotype, viability and potency of DC vaccines after freezing and thawing. METHODS: Plastic-adherent monocytes, derived from a steady-state leukapheresis, were cultured in serum-free media containing GM-CSF and IL-4. DC were loaded on day 6 with myeloma lysate (ML) or idiotype (Id) Ag and keyhole limpet hemocyanin (KLH), induced to mature on day 7 with CD40-ligand and cryopreserved on day 9. Seventeen clinical-scale cultures were evaluated for DC yield, recovery and immunophenotype after potency was validated with allogeneic mixed lymphocyte culture and Ag presentation assays. RESULTS: We produced 88 individual vaccines from 17 clinical-scale cultures. Median DC yield at harvest was 131 x 10(6) (range 37-375 x 10(6)) and median recovery of viable DC after thawing was 69% (range 11-100%). We confirmed viability (7AAD-), phenotype (CD14-, CD83+/CD40+, CD83+/CD80+, CD83+/CD86+, CD83+/CD54+, HLA-DR++) and the ability of the DC to present Ag and stimulate allogeneic T cells post-thawing. DISCUSSION: We have validated a serum-free culture system for the production of DC. Cryopreservation did not interfere with DC activity, allowed time for rigorous quality control (QC) and flexible scheduling of intranodal vaccination, and reduced the time to prepare multiple vaccines.