Successful tolerance induction under CD40 ligation in a rodent small bowel transplant model: first report of a study with the novel antibody AH.F5.
BACKGROUND
Intestinal transplantation has been hampered by high rates of intestinal allograft rejection. One mechanism of altering rejection in other organ transplant models has been blockade of second set T-cell costimulatory signals. AH.F5, a novel hamster anti-rat monoclonal antibody to CD154, blocks CD40-dependent T-cell costimulation. We hypothesized that blockade of this pathway might abrogate rejection in a rodent orthotopic survival model of intestinal transplantation.


METHODS
Eight groups were studied with different dosing schema, including syngeneic transplants (group 1), untreated allogeneic transplants (group 2), allogeneic transplants plus multiple doses of AH.F5 alone given IV or s.c. (groups 3 and 4), allogeneic transplants plus donor splenocyte preconditioning with and without single dose AH.F5 (groups 5 and 6), and donor splenocyte preconditioning followed by multiple doses of AH.F5 with and without thymectomy (groups 7 and 8).


RESULTS
Control animals all died within 12 days of transplantation, whereas antibody-alone and splenocytes-alone resulted in modest prolongation of survival to 16 days. Only animals treated with splenocytes before transplantation and AH.F5 survived long-term (>60 days, group 8). These animals tolerated donor-specific skin grafts, rejected third-party grafts, and fed normally. However, their weight gain was subnormal and they demonstrated intestinal muscular thickening, which might represent chronic rejection. Thymectomy prevented the induction of tolerance.


CONCLUSIONS
AH.F5 prevents acute intestinal allograft rejection in combination with donor-specific splenocyte preconditioning. We achieved long-term survival and the animals appeared tolerant. Central conditioning is essential for success with this antibody when used alone. Further studies with different dosing regimens or second agents seem warranted.
Recanati/Miller Transplantation Institute and Department of Pathology, The Mount Sinai School of Medicine, New York, New York, USA. thomas.fishbein@mountsinai.org
Thomas M
TM
Fishbein
Liqing
L
Wang
Chris
C
Benjamin
Jianhua
J
Liu
Adel
A
Tarcsafalvi
Anatoly
A
Leytin
Charles M
CM
Miller
Peter
P
Boros
D000818:Animals; D000911:Antibodies, Monoclonal / Q000627:therapeutic use*; D023201:CD40 Ligand / Q000276:immunology / Q000502:physiology*; D006224:Cricetinae; D006084:Graft Rejection; D007108:Immune Tolerance; D007421:Intestine, Small / Q000637:transplantation*; D008297:Male; D051381:Rats; D011914:Rats, Inbred BN; D011917:Rats, Inbred Lew; D019172:Transplantation Conditioning; D014184:Transplantation, Homologous
D000911:Antibodies, Monoclonal; D023201:CD40 Ligand