T-cell depletion and graft survival induced by anti-human CD3 immunotoxins in human CD3epsilon transgenic mice.
BACKGROUND
Anti-CD3 immunotoxins are broad-spectrum immunosuppressive agents in a wide range of organ transplantation animal models with potential use in eliciting antigen-specific tolerance. However, the anti-CD3 immunotoxins used in animal studies do not cross-react with human T cells, limiting extrapolation to humans and hindering clinical development.


METHODS
Three anti-human CD3-directed immunotoxins, DT389-scFv(UCHT1), scFv(UCHT1)-PE38, and UCHT1-CRM9, were compared in vitro and in transgenic mice, tg(epsilon)600+/-, that have T cells expressing both human and murine CD3epsilon antigens.


RESULTS
These immunotoxins were extraordinarily potent in vitro against human or transgenic mouse T cells, with IC50 values in cellular assays ranging from pM to fM. Systemic administration of these immunotoxins dose-dependently depleted >99% of tg(epsilon)600+/- lymph node and spleen T cells in vivo. Depletion was specific for T cells. The loss of the concanavalin A-induced, but not the lipopolysaccharide-induced, splenic proliferative response from immunotoxin-treated animals further demonstrated specific loss of T-cell function. Immunotoxin treatment prolonged fully allogeneic skin graft survival in tg(epsilon)600+/- recipients to 25 days from 10 days in untreated animals. T-cells recovered to approximately 50% of normal levels after approximately 22 days in animals with or without skin grafts; T-cell recovery correlated with skin graft rejection. All three immunotoxins elicited >100 day median survival of fully allogeneic heterotopic heart grafts. By 100 days, T cells recovered to normal numbers in these animals, but the grafts showed chronic rejection.


CONCLUSIONS
These immunotoxins profoundly deplete T cells in vivo and effectively prolong allogeneic graft survival.
Weetall
Marla
M
Novartis Pharmaceuticals, Summit, New Jersey 07901, USA. marla.weetall@pharma.novartis.com
Digan
Mary Ellen
ME
Hugo
Ronald
R
Mathew
Sheba
S
Hopf
Christine
C
Tart-Risher
Nicole
N
Zhang
Jin
J
Shi
Victor
V
Fu
Fumin
F
Hammond-McKibben
Denise
D
West
Susan
S
Brack
Richard
R
Brinkmann
Volker
V
Bergman
Reinhard
R
Neville
David
D
Lake
Philip
P
D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D017252:CD3 Complex / Q000235:genetics / Q000276:immunology*; D003208:Concanavalin A / Q000494:pharmacology; D004167:Diphtheria Toxin / Q000494:pharmacology*; D006085:Graft Survival / Q000276:immunology*; D016027:Heart Transplantation / Q000276:immunology*; D006801:Humans; D000922:Immunotoxins / Q000494:pharmacology*; D008070:Lipopolysaccharides / Q000494:pharmacology; D008213:Lymphocyte Activation; D007959:Lymphocyte Culture Test, Mixed; D008212:Lymphocyte Depletion / Q000379:methods*; D051379:Mice; D008822:Mice, Transgenic; D011993:Recombinant Fusion Proteins / Q000494:pharmacology*; D016038:Skin Transplantation / Q000276:immunology*; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology*
D000911:Antibodies, Monoclonal; D017252:CD3 Complex; D004167:Diphtheria Toxin; C114317:FN18-CRM9; D000922:Immunotoxins; D008070:Lipopolysaccharides; D011993:Recombinant Fusion Proteins; D003208:Concanavalin A