A Critical Role for TGF-ß/Fc and Nonlytic IL-2/Fc Fusion Proteins in Promoting Chimerism and Donor-Specific Tolerance.

BACKGROUND: Immunoglobulin-cytokine fusion molecules have been shown to be the new generation of immunomodulating agents in transplantation tolerance induction. In the present study, we tested whether immunoregulatory cytokine fusion proteins of IL-10/Fc, TGF-ß/Fc, or IL-2/Fc would enhance allogeneic bone marrow cell (BMC) engraftment and promote tolerance induction. METHODS: B6 (H2) mice were conditioned with anti-CD154 (MR1) and rapamycin (Rapa) plus 100 cGy total body irradiation (MR1/Rapa/100 cGy) and transplanted with allogeneic B10.D2 (H2) BMC. Recipients were treated with lytic IL-2/Fc, nonlytic IL-2/Fc, TGF-ß/Fc, or IL-10/Fc fusion proteins to promote chimerism to induce tolerance. RESULTS: Donor chimerism was achieved in 20% of recipients conditioned with MR1/Rapa/100 cGy. The addition of TGF-ß/Fc (5- or 10-day treatment) or nonlytic IL-2/Fc (10-day treatment) fusion proteins to the conditioning resulted in engraftment in nearly 100% of recipients. In contrast, lytic IL-2/Fc or IL-10/Fc had no effect. The combination of nonlytic IL-2/Fc and TGF-ß/Fc had a synergistic effect to promote engraftment and resulted in significantly higher donor chimerism compared with recipients conditioned with TGF-ß/MR1/Rapa/100 cGy. Engraftment was durable in the majority of chimeras and increased over time. The chimeras accepted donor skin grafts and promptly rejected third-party skin grafts. Moreover, specific T cell receptor-Vß5.½ and TCR-Vß11 clonal deletion was detected in host T cells in chimeras, suggesting central tolerance to donor alloantigens. CONCLUSIONS: Allogeneic BMC engraftment is enhanced with TGF-ß/Fc fusion protein treatment. TGF-ß/Fc and nonlytic IL-2/Fc exert a synergistic effect in promotion of alloengraftment and donor-specific transplant tolerance, significantly decreasing the minimum total body irradiation dose required.

Biopatterned CTLA4/Fc Matrices Facilitate Local Immunomodulation, Engraftment, and Glucose Homeostasis After Pancreatic Islet Transplantation.

Pancreatic islet transplantation (PIT) represents a potential therapy to circumvent the need for exogenous insulin in type 1 diabetes. However, PIT remains limited by lack of donor islets and the need for long-term multidrug immunosuppression to prevent alloimmune islet rejection. Our goal was to evaluate a local immunoregulatory strategy that sustains islet allograft survival and restores glucose homeostasis in the absence of systemic immunosuppression. Nanogram quantities of murine CTLA4/Fc fusion protein were controllably delivered within human acellular dermal matrix scaffolds using an inkjet-based biopatterning technology and cotransplanted with allogeneic islets under the renal capsule to create an immunoregulatory microenvironment around the islet allograft. We achieved long-term engraftment of small loads of allogeneic islet cells with 40% of MHC-mismatched mouse recipients maintaining sustained normoglycemia following pancreatic ß-cell ablation by streptozotocin. Biopatterned CTLA4/Fc local therapy was associated with expansion of Foxp3+ regulatory T cells and shifts in cytokine production and gene expression from proinflammatory to regulatory profiles, thus substantially benefiting islet allografts survival and function. This study is a new paradigm for targeted therapies in PIT that demonstrates the favorable effects of immune alterations in the transplant milieu and suggests a unique strategy for minimizing systemic immunosuppression and promoting islet allograft survival.