Introduction

Membrane cofactor protein (CD46) is known to attenuate the complement cascade by facilitating cleavage of C3b and C4b. In solid organ xenotransplantation, organs expressing CD46 has been shown to resist hyperacute rejection; however, the value of CD46 expression for islet xenotransplantation remains poorly defined. Here we attempt to delineate the role of CD46 in early neonatal porcine islet engraftment by comparing Gal-knocked out (GKO) and hCD46-knocked in (hCD46/GKO) islets in a dual transplant model.

Methods

Neonatal GKO and hCD46/GKO piglets were obtained from Revivicor Inc., the pancreata were recovered and neonatal porcine islets (NPIs) were isolated using a modified Korbutt technique. Rhesus macaques were used as recipients. An islet preparations for each genotype was made for each recipient and infused into separate hemilivers. Seven animals underwent dual transplant without immunosuppression and were sacrificed at 1 hour (n=4) or 24 hours (n=3). Both hemilivers were recovered and fixed for immunohistochemistry (CD46, insulin, neutrophil elastase, platelet, IgM, IgG, C3d, C4d, CD68, Caspase 3). Quantitative immunohistochemical analysis was performed using the Aperio Imagescope.

Results

The weight of pancreas at recovery (p=0.41) and NPI yield (p=0.69) were comparable between two genotypes (3.23±0.09 g/piglet and 11829±2164 IEQs/g for GKO, 3.02±0.23 g/piglet and 12976±1866 IEQs/g for hCD46/GKO). Within 1 hour of intraportal infusion of xenografts, no differences were observed between the two types of islets in terms of platelet, antibody or complement deposition. Cellular infiltration and islet apoptotic activity were similar at 1 hour too. At 24 hours, hCD46/GKO islets demonstrated significantly less platelet deposition (p=0.0129) and neutrophil infiltration (p=0.0136) compared to GKO islets. In contrast, C3d (p=0.38) and C4d (p=0.45) deposition was equal between the two genotypes.

Conclusions

In summary, hCD46/GKO islets experienced less platelet deposition and neutrophil infiltration compared to GKO islets, even though complement deposition on islets was similar between two types of NPIs. Our findings suggest that expression of hCD46 on NPIs potentially provides a survival advantage in vivo by reducing early thrombo-inflammatory events associated with instant blood mediated inflammatory reaction (IBMIR) following intraportal islet infusion.

CITATION INFORMATION: Gao Q., Samy K., Davis R., Song M., MacDonald A., Leopardi F., How T., Williams K., Devi G., Collins B., Kirk A. The Role of CD46 in Early Islet Engraftment in a Dual Transplant Model Am J Transplant. 2017;17 (suppl 3).

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