Idiotype Vaccination Using Dendritic Cells After Autologous Peripheral Blood Stem Cell Transplantation for Multiple Myeloma—A Feasibility Study

The idiotype (Id) determinant on the multiple myeloma (MM) protein can be regarded as a tumor-specific marker. Immunotherapy directed at the MM Id may stem the progression of this disease. We report here on the first 12 MM patients treated at our institution with high-dose therapy and peripheral blood stem cell transplantation (PBSCT) followed by Id immunizations. MM patients received PBSCT to eradicate the majority of the disease. PBSCT produced a complete response in 2 patients, a partial response in 9 patients and stable disease in 1 patient. Three to 7 months after high-dose therapy, patients received a series of monthly immunizations that consisted of two intravenous infusions of Id-pulsed autologous dendritic cells (DC) followed by five subcutaneous boosts of Id/keyhole limpet hemocyanin (KLH) administered with adjuvant. Between 1 and 11 × 106DC were obtained by leukapheresis in all patients even after PBSCT. The administration of Id-pulsed DC and Id/KLH vaccines were well tolerated with patients experiencing only minor and transient side effects. Two of 12 patients developed an Id-specific, cellular proliferative immune response and one of three patients studied developed a transient but Id-specific cytotoxic T-cell (CTL) response. Eleven of the 12 patients generated strong KLH-specific cellular proliferative immune responses showing the patients' immunocompetence at the time of vaccination. The two patients who developed a cellular Id-specific immune response remain in complete remission. Of the 12 treated patients, 9 are currently alive after autologous transplantation with a minimum follow-up of 16 months, 2 patients died because of recurrent MM and 1 patient succumbed to acute leukemia. These studies show that patients make strong anti-KLH responses despite recent high-dose therapy and that DC-based Id vaccination is feasible after PBSCT and can induce Id-specific T-cell responses. Further vaccine development is necessary to increase the proportion of patients that make Id-specific immune responses. The clinical benefits of Id vaccination in MM remain to be determined.