557 - Preformed non-Gal antibodies are highly cytotoxic

557 - Preformed non-Gal antibodies are highly cytotoxic

557 - Preformed non-Gal antibodies are highly cytotoxic even against Galactosyl-transferase knockout, hu
557
Preformed non-Gal antibodies are highly cytotoxic even against Galactosyl-transferase
knockout, human CD55, CD59, CD39 transgenic pig organs in a model of kidney
transplantation into baboons
Stéphanie Le Bas-Bernardet 1 , Nicolas Poirier 1 , Xavier Tillou 1 , Jérémy Hervouet 1 , David
1,
Minault
Karine Renaudin
2
, Nahzli Dilek
1
, Mathias Chatelais
1
, Béatrice Charreau
1
, Julien Branchereau
1
, Peter Cowan
3
, Anthony d’Apice
3
, Cesare Galli
4
, Emanuele Cozzi
5
, Jean-Paul Soulillou
1
,
Gilles Blancho
1
1 Institute
of Transplantation - Urology - Nephrology (ITUN), Nantes, France; 2 Pathology Unit,
University Hospital of Nantes, Nantes, France;
3
Immunology Research Centre, Saint Vincent’s Hospital, Melbourne, Australia;
4
LTR, Laboratorio di Tecnologi della Riproduzione, Cremona, Italy;
1/2
557 - Preformed non-Gal antibodies are highly cytotoxic even against Galactosyl-transferase knockout, hu
5
Consorzio per la Ricerca sul Trapianto d’organi (CORIT), Padova, Italy
Galactosyl-transferase knock-out (GT-KO) pigs could help to solve the problem of pig xenograft
rejection, particularly in the context of additional complement regulatory molecule transgenesis.
Thus, we have performed kidney xenograft transplantations from GT-KO pigs also transgenic
for human CD55, CD59 and CD39 into baboons. Four baboons received a treatment
associating cyclophosphamide, recombinant human C1 inhibitor (rhC1-INH) at 200U/kg every 8
hours for 5 days, in addition to Tacrolimus, Mycophenolate Mofetil and Steroids. Animals
rejected between d12, 13 and 15 with signs of acute humoral xenograft rejection (AHXR) in
comparison to 2 controls who developed AHXR at d3 and 4.
Immuno-histochemistry showed IgM, complement component deposition in microvascular
areas with C3c much higher than C4d, a dense infiltrate of monocyte/macrophages and
moderate infiltrate of T and B cells.
According to these results, the non-Gal antibodies (Ab) were assessed in baboon sera by
donor endothelial cross-match in flow cytometry. Most animals displayed preformed non-Gal Ab
with a complement dependent cytotoxicity (CDC) varying between 30 to 75% of specific lysis.
After a decrease of circulated Ab, presumably trapped inside the graft, elicited Ab increased
from d6 to rejection with a correlating serum CDC increase.
In these preliminary results, we showed a modest graft survival due to AHXR with circulated
XNA and with Ab and complement deposition in graft, suggesting that the transgenes
expression brought only a limited protection to the graft. We showed also the existence of a
pre-immunization with the presence non Gal Ab at a low titer but highly cytotoxic. Thus, despite
donor genetic modifications, one major challenge of xenotransplantation remains
immunosuppression and desensibilization. Other immunosuppressive regimen should be
considered.
2/2