Depletion of anti-gal antibodies in baboons by intravenous therapy with bovine serum albumin conjugated to gal oligosaccharides.
BACKGROUND
Anti-Galalpha 1-3Gal (Gal) antibodies (Ab) play a key role in the rejection of pig cells or organs transplanted into primates. A course of extracorporeal immunoadsorption (EIA) of anti-Gal Ab using an immunoaffinity column of a Gal type 6 oligosaccharide depletes Ab successfully, but Ab returns during the next few days. Although therapy with an anti-CD154 monoclonal antibody (mAb) prevents an induced Ab response to Gal or non-Gal epitopes, T cell-independent natural anti-Gal IgM and IgG return to baseline (pretransplant) levels. We have investigated the capacity of continuous i.v. infusion of bovine serum albumin conjugated to Gal type 6 oligosaccharide (BSA-Gal) to deplete or maintain depletion of circulating anti-Gal Ab.


METHODS
Porcine peripheral blood mobilized progenitor cells (PBPC) obtained by leukapheresis from MHC-inbred miniature swine (n=6) were transplanted into baboons. Group 1 baboons (n=4) underwent whole body (300 cGy) and thymic (700 cGy) irradiation, T cell depletion with antithymocyte globulin, complement depletion with cobra venom factor, short courses of anti-CD154 mAb therapy (20 mg/kg i.v. on alternate days), cyclosporine (CyA) (in two baboons only), mycophenolate mofetil, and porcine hematopoietic growth factors. Anti-Gal Ab depletion by EIA was carried out before transplantation of high doses (2-4x 1010 cells/kg) of PBPC. Group 2 baboons (n=3) received the group 1 regimen (including CyA) plus a continuous i.v. infusion of BSA-Gal. To prevent sensitization to BSA, anti-CD154 mAb therapy was continued until BSA-Gal administration was discontinued.


RESULTS
In group 1, Gal-reactive Ab returned to pre-PBPC transplant levels within 15-21 days, but no induced Ab to Gal or non-Gal determinants developed while anti-CD154 mAb therapy was being administered. In group 2, anti-Gal Ab was either not measurable or minimally measurable while BSA-Gal was being administered. After discontinuation of BSA-Gal, Ab did not return to pre-PBPC transplant level for more than 40-60 days, and no sensitization developed even when all therapy was discontinued. In one baboon, however, Ab to Gal type 2, but not type 6, returned during BSA-Gal therapy.


CONCLUSIONS
Prevention of the induced humoral response to Gal and non-Gal epitopes by anti-CD154 mAb therapy has been reported previously by our group, but our studies are the first to demonstrate a therapy that resulted in an absence of natural anti-Gal Ab for a prolonged period. The combination of BSA-Gal and T cell costimulatory blockade may facilitate survival of pig cells and organs transplanted into primates. The return in one baboon of Ab reactive with the Gal type 2 oligosaccharide, but not type 6, indicates some polymorphism of anti-Gal Ab and suggests that, to be effective in all cases, the infusion of a combination of type 6 and type 2 BSA-Gal may be required.
Teranishi
K
K
Transplantation Biology Research Center, Massachusetts General Hospital, MGH East, Building 149-9019, 13th Street, Boston, MA 02129, USA.
Gollackner
B
B
Bühler
L
L
Knosalla
C
C
Correa
L
L
Down
J D
JD
White-Scharf
M E
ME
Sachs
D H
DH
Awwad
M
M
Cooper
D K C
DK
D000818:Animals; D000911:Antibodies, Monoclonal / Q000008:administration & dosage / Q000627:therapeutic use; D000917:Antibody Formation; D023201:CD40 Ligand / Q000276:immunology; D002240:Carbohydrate Sequence; D004187:Disaccharides / Q000276:immunology*; D005690:Galactose / Q000008:administration & dosage / Q000627:therapeutic use*; D006084:Graft Rejection / Q000276:immunology; D006085:Graft Survival / Q000187:drug effects / Q000276:immunology; D016298:Hematopoietic Cell Growth Factors / Q000627:therapeutic use; D019650:Hematopoietic Stem Cell Mobilization; D018380:Hematopoietic Stem Cell Transplantation; D007163:Immunosorbent Techniques; D007165:Immunosuppression Therapy / Q000379:methods; D007262:Infusions, Intravenous; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000008:administration & dosage / Q000737:chemistry / Q000627:therapeutic use*; D010215:Papio; D011323:Primates; D012710:Serum Albumin, Bovine / Q000008:administration & dosage / Q000627:therapeutic use*; D013552:Swine; D013556:Swine, Miniature; D013997:Time Factors; D014183:Transplantation, Heterologous / Q000276:immunology*; D014916:Whole-Body Irradiation
D000911:Antibodies, Monoclonal; D004187:Disaccharides; D016298:Hematopoietic Cell Growth Factors; D009844:Oligosaccharides; C055075:galactosyl-(1-3)galactose; D023201:CD40 Ligand; D012710:Serum Albumin, Bovine; D005690:Galactose