Background. Despite significant side effects, chronic systemic immunosuppression remains the backbone of clinical transplantation. We investigated the feasibility of preventing early allorecognition in canine renal allografts using a nonsystemic pretreatment. Methods. The renal vasculature was treated with a bioengineered interface consisting of a nano-barrier membrane during 3 hr of ex vivo warm perfusion. Results. Preliminary feasibility of the immunocloaking technology was established by the following criteria: it is possible to achieve approximately 90% coverage of the vasculature with nano-barrier membrane after 3 hr of ex vivo warm perfusion; covering the luminal surfaces prevents allorecognition as determined by mixed lymphocyte-vascular endothelial reaction; covering the luminal surfaces does not negatively affect renal function as determined by auto-transplant outcomes; and graft rejection is significantly postponed in canine kidneys treated with the immunocloaking technology. In the absence of systemic immunosuppression, untreated control dogs experienced a mean onset of rejection on day 6, whereas in the treated dogs with modified renal vascular luminal surfaces, the mean onset of rejection was significantly delayed until day 30. Conclusions. The ability to postpone, or eventually eliminate, the allorecognition that occurs immediately on reper-fusion could provide a new window of opportunity to introduce adjunct therapies to support tolerance induction. To our knowledge, this is the first time significantly prolonged canine renal allograft survival has been achieved in the absence of systemic immunosuppression or immunologic manipulation of the recipient.

We previously reported that a bioengineered interface consisting of a nano-barrier membrane (NB-LVF4) used as an artificial interface between skin allografts and wound surfaces significantly prolonged graft survival without immunosuppression. We now evaluated whether NB-LVF4 could serve as a targeted drug delivery system to further improve outcomes. Fibroblast growth factor-1 (FGF-1) was selected for its known function as a wound hormone. Full-thickness 8-mm skin grafts were cross-transplanted between out-bred mice. Controls were transplanted without treatment. In test groups, the NB-LVF4, with or without FGF-1, was applied to both basolateral skin and wound surfaces with polymerization resulting in a tridimensional transparent membrane. The mice were evaluated for T-cell activation and development of donor-specific antibody. Rejection occurred in controls by 7 days. NB-LVF4 treatment, with or without FGF-1, was found to significantly prolong allograft survival (27 and 28 days, respectively [p < 0.05]). Untreated controls stimulated 10-fold shift in the number of circulating CD4+ cells while test groups exhibited substantially reduced shifts in CD4+ cells. The group treated with FGF-1 did not develop donor-specific antibody. Treatment with the NB-LVF4 membrane delays the onset of allograft rejection in the absence of systemic immunosuppression. FGF-1 appears to prevent the development of a humoral response by preventing B cell activation.

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