Renal xenografts from triple-transgenic pigs are not hyperacutely rejected but cause coagulopathy in non-immunosuppressed baboons.
BACKGROUND
The genetic modification of pigs is a powerful strategy that may ultimately enable successful xenotransplantation of porcine organs into humans.


METHODS
Transgenic pigs were produced by microinjection of gene constructs for human complement regulatory proteins CD55 and CD59 and the enzyme alpha1,2-fucosyltransferase (H-transferase, HT), which reduces expression of the major xenoepitope galactose-alpha1,3-galactose (alphaGal). Kidneys from CD55/HT and CD55/CD59/HT transgenic pigs were transplanted into nephrectomised, nonimmunosuppressed adult baboons.


RESULTS
In several lines of transgenic pigs, CD55 and CD59 were expressed strongly in all tissues examined, whereas HT expression was relatively weak and did not significantly reduce alphaGal. Control nontransgenic kidneys (n=4) grafted into baboons were hyperacutely rejected within 1 hr. In contrast, kidneys from CD55/HT pigs (n=2) were rejected after 30 hr, although kidneys from CD55/CD59/HT pigs (n=6) maintained function for up to 5 days. In the latter grafts, infiltration by macrophages, T cells, and B cells was observed at days 3 and 5 posttransplantation. The recipients developed thrombocytopenia and abnormalities in coagulation, manifested in increased clotting times and an elevation in the plasma level of the fibrin degradation product D-dimer, within 2 days of transplantation. Treatment with low molecular weight heparin prevented profound thrombocytopenia but not the other aspects of coagulopathy.


CONCLUSIONS
Strong expression of CD55 and CD59 completely protected porcine kidneys from hyperacute rejection and allowed a detailed analysis of xenograft rejection in the absence of immunosuppression. Coagulopathy appears to be a common feature of pig-to-baboon renal transplantation and represents yet another major barrier to its clinical application.
Immunology Research Centre, St Vincent's Hospital, Fitzroy, Victoria, Australia.
P J
PJ
Cowan
A
A
Aminian
H
H
Barlow
A A
AA
Brown
C G
CG
Chen
N
N
Fisicaro
D M
DM
Francis
D J
DJ
Goodman
W
W
Han
M
M
Kurek
M B
MB
Nottle
M J
MJ
Pearse
E
E
Salvaris
T A
TA
Shinkel
G V
GV
Stainsby
A B
AB
Stewart
A J
AJ
d'Apice
D000818:Animals; D001778:Blood Coagulation Disorders / Q000209:etiology*; D018957:CD59 Antigens / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D005647:Fucosyltransferases / Q000235:genetics / Q000502:physiology*; D006084:Graft Rejection; D007150:Immunohistochemistry; D007165:Immunosuppression Therapy; D007668:Kidney / Q000473:pathology; D016030:Kidney Transplantation / Q000009:adverse effects / Q000276:immunology*; D051379:Mice; D010215:Papio; D013552:Swine; D014183:Transplantation, Heterologous / Q000276:immunology*; D000097631:Galactoside 2-alpha-L-fucosyltransferase
D018957:CD59 Antigens; D005647:Fucosyltransferases; D000097631:Galactoside 2-alpha-L-fucosyltransferase