Session Time: 3:15pm-4:00pm
Presentation Time: 3:30pm-4:00pm
*Purpose: Immunosuppression avoidance by induction of immune tolerance represents a primary goal in the field of transplantation. Yet, success of this concept relies on extensive pre-transplant recipient preconditioning which is not feasible in VCA. In this study we therefore explored a novel approach to induce cyclophosphamide-based delayed immune tolerance.
*Methods: Orthotopic hindlimb transplantation from Balb/c to C57BL6 was performed. Allografts were maintained with Rapamycin until POD29. The induction regimen comprised non-myeloablative total body irradiation, anti-thymocyte immune globulin (ATG) on POD30 and high-dose cyclophosphamide on POD34. Additional modification included donor bone marrow transplantation (dBMT) on POD31 with or without combination of post-induction ATG (POD40) and pre-induction fludarabine (POD 27 and 29). Graft survival, chimerism level, and frequency of CD8 memory T cells (Tmem, CD44hiCD62Llow) were monitored. Multiple 14-color flow panel and subsequent t-SNE analysis were performed in long-term survivor (>200d).
*Results: The induction regimen applied on POD0 led to indefinite graft survival (>200d) in all VCA recipients (n=13) with stable chimerism levels. In contrast, with delayed induction regimen on POD30(n=9), graft survival was 70.1±22.9d with a chimerism level of 2.5±2.3%. With the addition of dBMT alone (n=5), graft survival and chimerism level increased to 83.6±15.9d and 3.4±1.4%, respectively. A significant elevation of post-induction CD8 Tmem was detected in those groups (39.8±25.9% and 51%±14.4%, compared with naïve control 4.5%±0.6%). With further optimization by adding pre-induction fludarabine and post-induction ATG, graft survival increased to 136±58d with a stable chimerism level of 27.2±28.8% (n=6). Long-term survivors (n=3) accepted donor matched secondary skin grafts (>50d) while acutely rejecting skin grafts from FVBN/J (<7d) confirming donor specific tolerance. Post-induction CD8 Tmem levels in those long-term survivors decreased to 7.9%±2.6%. In addition, t-SNE analysis revealed an elevation of exhaustion markers (PD-1 and Tim-3 on CD4 and CD8 T cells).
*Conclusions: Successful delayed tolerance induction can be achieved in a murine model of hindlimb transplantation with intensified conditioning regimens.
To cite this abstract in AMA style:Guo Y, Messner F, Oh B, Furtmüller G, Lee W, Cooney D, Luznik L, Brandacher G. Induction of Delayed Immune Tolerance after Reconstructive Transplantation by Combining Donor Bone Marrow Transplantation and High-Dose Cyclophosphamide Treatment [abstract]. Am J Transplant. 2020; 20 (suppl 3). https://atcmeetingabstracts.com/abstract/induction-of-delayed-immune-tolerance-after-reconstructive-transplantation-by-combining-donor-bone-marrow-transplantation-and-high-dose-cyclophosphamide-treatment/. Accessed July 23, 2021.
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