An ongoing study at the Massachusetts General Hospital has demonstrated that mixed hematopoietic chimerism can be achieved with HLA-identical and HLA-mismatched related donor allogeneic bone marrow transplantation using non-myeloablative, relatively non-toxic conditioning in patients with advanced hematologic malignancies.
Striking anti-tumor responses have been observed in this group of patients with advanced malignancies, particularly in association with donor leukocyte infusions given on day 35. Bone marrow transplantation and induction of mixed chimerism has been shown in animal studies to be associated with specific tolerance to organ grafts from the donor.
In two patients with renal failure secondary to multiple myeloma, a simultaneous kidney and marrow transplant was performed from the same HLA-identical sibling donor. The first patient is in clinical remission from her myeloma and has been accepting her kidney allograft without immunosuppression for more than 40 months, and the second is in partial remission, with kidney graft tolerance for more than 16 months.
This non-myeloablative allogeneic BMT protocol will be evaluated for the induction of mixed chimerism and renal allograft tolerance in patients with multiple myeloma and renal failure. Patients with end-stage renal failure secondary to multiple myeloma are not eligible for conventional bone marrow transplantation, the only known potentially curative therapy for their disease, and are not usually considered eligible for renal transplantation. We will make use of a relatively non-toxic, non-myeloablative conditioning regimen for allogeneic BMT in an attempt to simultaneously correct the underlying hematologic disorder and induce specific tolerance to a renal allograft from the same donor. Patients will receive 60 mg/kg cyclophosphamide i.v. on days –5 and –4, ATG (Upjohn) 20 mg/kg on days –1, +1, +3 and +5, and 7 Gy thymic irradiation on day –1. Donor bone marrow and a kidney graft from an HLA-identical (or one HLA antigen-mismatched) related donor will be given on day 0. Cyclosporine will be given from day –1 and tapered early (starting at 36-60 days) if renal function is normal and no GVHD occurs. If no GVHD occurs, a DLI will be administered on day 44 to patients with multiple myeloma.
Mechanistics Studies: Chimerism will be monitored by VNTR and STR analysis of separated CD3+, CD19+ and CD33+ cells. Erythroid chimerism will be analyzed via hemoglobin electrophoresis in patients with sickle cell disease. Naïve and memory-type CD4 and CD8 T cell recovery and TREC will be monitored. Pre-transplant donor and host EBV-LCL lines will be established and post-transplant patient PBMC will be analyzed for tolerance in MLR, CML and limiting dilution analyses, and using ELISpot and intracelllular cytokine staining assays. Donor renal epithelial cell lines will be established and compared to lymphocytes as stimulators and targets of anti-donor immune responses. These studies will help to elucidate mechanisms of tolerance. Protocol biopsies will be performed at defined times and analyzed by histological appearance, immunohistochemical and immunofluorescent staining, and PCR for cytokine mRNA. These studies will help to define intragraft parameters that distinguish tolerance from rejection.