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Gal Kock-out pig islets can modulate the humoral response after the transplantation of macroencapsulated pig islets in diabetic primates

Yasuhiro Igarashi, Sophie Veriter, Pierre Gianello, Denis Dufrane

Université catholique de Louvain, Brussels, Belgium

Objective: This work investigated the use of alpha,1,3galactosyl transferase-knockout (Gal-KO) pig as a source of islets for “Macroencapsulated pig islets xenotransplantation in diabetic primates”.

Methods: Streptozotocin-induced diabetic Cynomolgus primates (n=6) were transplanted (without any immunosuppression) with (i) free-pig islets (Gal-KO, n=1 and native Gal+ islets, n=1) transplanted under the kidney capsule/muscle and (ii) macroencapsulated pig islets (Gal-KO, n=2 and native Gal+ islets, n=2) transplanted in the subcutaneous tissue. Blood glucose metabolism was weekly followed. Immunohistochemistry for Insulin/CD3/CD68/C3d was performed at day 7/14 and 30/60 post-transplantation for free-/ and macroencapsulated pig islets, respectively. Flow cytometry analysis (for anti-pig antibodies and cytotoxicity) and ELISA assays (for Gal-antibody specificity) were also performed on the primate sera at day 0/30/60/90 post-transplantation.

Results: IsolatedGal-KOpig islets did not stained by Isolectin B4 in contrast to native Gal+ islets (beta and endothelial cells). The transplantation of free- Gal KO pig islets did not elicit an increase of preformed anti-pig IgG antibodies in contrast to Gal+ islets (MFI: 1336.3 vs. 50.1 at day 30 post-transplantation, respectively) associated with no specificity against Gal epitope. Viable pig islets with insulin staining and no CD3/CD68 infiltration/C3d deposition was found, at day 7 post-implantation, for free Gal-KO pig islets in contrast to massive cellular infiltration, complement deposition without living Gal+ pig islets. Free Gal-KO pig islets destruction was observed, at day 14 post-transplantation, by mainly CD3 infiltration. A significant lower increase of preformed anti-pig IgG antibodies was found for primates transplanted with macroencapsulated Gal-KO pig islets in comparison to Gal+ islets (MFI: 99.7± 6.3 vs. 509.9 ± 130.3 at day 30, respectively) with a lower specificity for the Gal epitope (absorbance at 0.15 ± 0.09 vs. 0.45 ± 0.11, respectively).

Conclusions: The use of Gal-KO pig islet can significantly reduce the humoral response elicited by encapsulated pig islets.