BackgroundDespite chemo-induction therapy and autologous stem cell transplantation (ASCT), the vast majority of patients with Multiple Myeloma (MM) relapse within 7 years and the disease remains incurable. Adoptive Allogeneic T-cell therapy (ATCT) might be curative for MM, however current ATCT protocols often lead to graft versus host disease (GvHD). Transplanting only tumor reactive donor T cells that mediate a graft-versus-myeloma (GvM) but not GvHD may overcome this problem.MethodsWe used an MHC-matched/miHA-disparate B10.D2 → Balb/c bone marrow transplantation (BMT) murine model and MOPC315.BM MM cells to develop an ATCT protocol consisting of total body irradiation, autologous-BMT and infusion of selective, myeloma-reactive lymphocytes of T cell receptor (TCR) Vβ 2, 3 and 8.3 families (MM-auto BMT ATCT).ResultsPre-stimulation ex vivo of allogeneic T cells by exposure to MOPC315.BM MM cells in the presence of IL-2, anti-CD3 and anti-CD28 resulted in expansion of the myeloma-reactive T cell TCRVβ 2, 3 and 8.3 subfamilies. Their isolation and infusion into MM-bearing mice resulted in a vigorous GvM response without induction GvHD and long-term survival. Repeated infusion of naïve myeloma-reactive T cell TCRVβ 2, 3 and 8.3 subfamilies was also effective.ConclusionsThese data demonstrate that a transplantation protocol involving only selective tumor-reactive donor T cell families is an effective immunotherapy and results in long-term survival in a mouse model of human MM. The results highlight the need to develop similar ATCT strategies for MM patients that result in enhanced survival without symptoms of GvHD.

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Multiple myeloma (MM) is a malignant plasma cell disorder that accounts for approximately 10% of all hematological cancers. Despite recent advances, long-term survival is rare after autologous bone marrow transplantation (auto-BMT) and/or treatment with recently introduced anti-myeloma agents and disease recurs in virtually all patients. Allogeneic bone marrow transplantation (allo-BMT) is an effective treatment that can provide partial or complete remission in patients with MM. The therapeutic potential of allo-BMT is attributed to the "graft-versus-myeloma" (GvM) effect that aims to destroy residual tumor cells that survived an induction protocol of chemotherapy/radiotherapy and to maintain immune surveillance to prevent relapse. However, allo-BMT remains a controversial treatment, since the donor T cells that mediate the GvM effect are also the source of the cells that react to other tissue alloantigens and induce graft versus-host disease (GvHD), a major cause of morbidity and mortality in allo-BMT recipients. Nonetheless, allo-BMT remains the only potentially curable treatment for MM. Recently TCR Vβ CDR3-size spectratype analyses in an animal model of MM identified T cells subfamilies involved in the anti-host and anti-tumor reactivity. We have now carried this work further and tested the potential of integrating auto-BMT with a donor lymphocyte infusion (DLI) composed only of anti-MM reactive Vβ 2, 3 and 8.3 T cell subfamilies. The results demonstrate that these T cell subsets are indeed involved in the generation of a potent GvM response in MM bearing mice and is associated with enhanced survival. Importantly, the GvM response was not accompanied by the development of GvHD. Nonetheless, the GvM response was not sufficient to completely inhibit relapse. We then pre-stimulated donor T cells with MM cells in vitro in the presence of co-stimulatory factors and found that our selective DLI protocol induced a vigorous and long-lasting GvM which translated into long-term survival, again in the complete absence of GvHD. Interestingly, quite similar results were obtained by treating MM-bearing mice with repeat doses of naïve donor Vβ 2, 3 and 8.3 T cell subfamilies. The treated mice showed significantly lower serum paraprotein levels and myeloma infiltration in bone marrow and spleen. Taken together, the results suggest that a transplantation protocol involving only tumor cell-reactive donor T cell subfamilies might be devised for MM patients that results in a potent GvM with enhanced survival but without symptoms of GvHD. Disclosures No relevant conflicts of interest to declare.