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Long term survival of PEGylated murine allogenic islets using short course immunomodulation

Jaime A. Giraldo^1,2, R. Damaris Molano^1,3, Hernan R. Rengifo¹, Carmen Fotino¹, Camillo Ricordi^1,2,3,4,5, Antonello Pileggi^1,2,3,4, Cherie L. Stabler^1,2,3

¹Diabetes Research Institute; ²Biomedical Engineering; ³Department of Surgery; ⁴Department of Microbiology & Immunology; ⁵Department of Medicine, University of Miami, Miami, FL, United States

Clinical islet transplantation has shown promise for Type 1 diabetes treatment. Nonetheless, inflammatory and immunological host responses to the implant lead to islet dysfunction and destruction, in spite of systemic immunosuppression. Cellular PEGylation, the addition of a single coating of poly(ethylene glycol) (PEG) to the cell/ tissue surface, has been shown to reduce inflammation and mitigate immune recognition via generation of a steric barrier. We sought to evaluate the potential of PEGylation, alone and in combination with a short-course immunomodulatory regimen, on the survival of fully-MHC mismatched islet allografts. Lymphocyte Function-associated Antigen 1 (LFA-1) plays a key role both in lymphocyte trafficking and co-stimulation and has demonstrated success in partially preventing murine allograft rejection.

PEGylated or unmanipulated DBA/2 islets (H2d) were transplanted under the renal subcapsular space of chemically-induced diabetic C57BL/6J mice (H2b). Control animals received untreated islets and saline (n=20) or anti-LFA-1 antibody (KBA, 100ug/day, i.p.) on days 0-6 (n=10). Islets were coated with a single layer of PEG (SVA-PEG, MW 5000) prior to transplantation into untreated (n=10) or anti-LFA-1 treated mice (n=9).

Ninety percent of the control islet transplants rejected within 60 days. Either the short course of LFA-1 blockade or PEGylation of islets resulted in long term (>100 days) function of the allograft in 50% or 60% of cases, respectively. Combination of islet PEGylation with LFA-1 blockade resulted in 78% of the transplants functioning long-term. Nephrectomy of the graft bearing kidney resulted in prompt return to hyperglycemia for all transplants.

Islet PEGylation represents a simple, highly cell compatible procedure to prevent allograft rejection. In combination with a short course immunotherapy, murine allograft rejection is prevented in a majority of the transplants. This study demonstrates the potency found with the combination of these two mild strategies, indicating a synergistic effect.

Authors acknowledge support from NIH (DP2-DK083096-01) and DRIF.