Rapamycin Combined with Anti-CD45RB mAb and IL-10 or with G-CSF Induces Tolerance in a Stringent Mouse Model of Islet Transplantation

Background: A large pool of preexisting alloreactive effector T cells can cause allogeneic graft rejection following transplantation. However, it is possible to induce transplant tolerance by altering the balance between effector and regulatory T (Treg) cells. Among the various Treg-cell types, Foxp3 +Treg and IL-10-producing T regulatory type 1 (Tr1) cells have frequently been associated with tolerance following transplantation in both mice and humans. Previously, we demonstrated that rapamycin+IL-10 promotes Tr1-cell-associated tolerance in Balb/c mice transplanted with C57BL/6 pancreatic islets. However, this same treatment was unsuccessful in C57BL/6 mice transplanted with Balb/c islets (classified as a stringent transplant model). We accordingly designed a protocol that would be effective in the latter transplant model by simultaneously depleting effector T cells and fostering production of Treg cells. We additionally developed and tested a clinically translatable protocol that used no depleting agent. Methodology/Principal Findings: Diabetic C57BL/6 mice were transplanted with Balb/c pancreatic islets. Recipient mice transiently treated with anti-CD45RB mAb+rapamycin+IL-10 developed antigen-specific tolerance. During treatment, Foxp3 +Treg cells were momentarily enriched in the blood, followed by accumulation in the graft and draining lymph node, whereas CD4 +IL-10 +IL-4 - T (i.e., Tr1) cells localized in the spleen. In long-term tolerant mice, only CD4 +IL-10 +IL-4 - T cells remained enriched in the spleen and IL-10 was key in the maintenance of tolerance. Alternatively, recipient mice were treated with two compounds routinely used in the clinic (namely, rapamycin and G-CSF); this drug combination promoted tolerance associated with CD4 +IL-10 +IL-4 - T cells. Conclusions/Significance: The anti-CD45RB mAb+rapamycin+IL-10 combined protocol promotes a state of tolerance that is IL-10 dependent. Moreover, the combination of rapamycin+G-CSF induces tolerance and such treatment could be readily translatable into the clinic. © 2011 Gagliani et al

Cyclosporine inhibits long-term survival in cardiac allografts treated with monoclonal antibody against CD45RB

Background: We have previously reported that a monoclonal antibody to CD45RB is a novel immunosuppressive agent; however, the optimal regimen in cardiac allografts remains unknown. The present study was undertaken to determine the optimal protocol of this therapy and its interaction with cyclosporine. Methods: A heterotopic heart allograft model was used in C57BL/6 to BALB/c mice. The following studies were conducted: 1) dose response study (low, intermediate, and high doses at 1, 3, and 9 mg/kg/day respectively), 2) short course (2 days) therapy vs long course (9 days) therapy, 3) pretreatment (starting on day -1) vs no pretreatment, 4) daily therapy vs alternative day therapy, and 5) monoclonal antibody treatment with and without cyclosporine. Results: The efficacy of the CD45RB monoclonal antibody was dose and duration dependent (p <0.01). Pretreatment significantly improved the efficacy of this therapy (74.5 +/- 13.4 days vs 30.6 +/- 1.5 days, p <0.01). Daily therapy was superior to alternate day therapy (74.5 +/- 13.4 days vs 30.4 +/- 1.5 days, p <0.03). Interestingly, we found that administration of cyclosporine prior to, at the same time as, or after administration of the CD45RB monoclonal antibody had a detrimental effect on graft survival compared to mAb treated alone (16.6 +/- 0.4 days, 25 +/- 2.3 days, and 35.3 +/- 0.9 days respectively vs 74.5 days, p <0.01). Conclusions: Immunosuppression with CD45RB monoclonal antibody is dose and duration dependent. Pretreatment and daily therapy improves results. Addition of cyclosporine inhibits long-term graft survival achieved by the monoclonal antibody alone. J Heart Lung Transplant 1999;18:441-447

Prevention and reversal of renal allograft rejection by antibody against CD45RB

REJECTION continues to be the single largest impediment to successful organ transplantation(1). Antilymphocyte globulin, which contains antibodies that react with the leukocyte common antigen known as CD45 (refs 2-6), has proved to be one of the most effective agents for preventing rejection. We have shown earlier that a monoclonal antibody directed against the RB isoform of CD45 substantially inhibits the alloreactivity of human CD4(+) lymphocytes in vitro(7). Here we investigate whether CD45RB could be an appropriate target for preventing renal allograft rejection in mice. Mice treated with two injections of a monoclonal antibody (MB23G2) (ref. 8) raised against CD45RB protein all survived and had normal renal function. Furthermore, this antibody reversed acute rejection when therapy was delayed until day 4, and the mice survived for their natural lifespan. The immunosuppression achieved may find application in the prevention and treatment of transplant rejection in man