Removal of blood group A/B antigen in organs by ex vivo and in vivo administration of endo-beta-galactosidase (ABase) for ABO-incompatible transplantation.
BACKGROUND
ABO incompatibility in organ transplantation is still a high risk factor for antibody-mediated rejection, despite the progress in effective treatments. We have explored the possibility of using the enzyme to remove the blood type A/B antigen in organs.


METHODS
Recombinant endo-beta-galactosidase (ABase), which releases A/B antigen, was produced in E. coli BL-21. Human A/B red blood cells (RBC) were digested with ABase, and subjected to flow cytometric analysis after incubation with human sera. Purified recombinant ABase was intravenously administered to a baboon. Biopsies were taken from kidney and liver before and 1, 4 and 24 h after in vivo administration. Excised baboon kidneys were perfused with cold UW solution+/-purified recombinant ABase and preserved at 4 degrees C. Biopsies were taken before and 1 and 4 h after ex vivo perfusion. The change in A/B antigen expression was analyzed by immunohistochemical study.


RESULTS
ABase removed 82% of A antigen and 95% of B antigen in human A/B red blood cells, and suppressed anti-A/B antibody binding and complement activation effectively. ABase was also found to remain active at 4 degrees C. In vivo infusion of ABase into a blood type A baboon demonstrated a marked reduction of A antigen expression in the glomeruli of kidney (85% at 1 h, 9% at 4 h and 13% at 24 h) and the sinusoids of liver (47% at 1 h, 1% at 4 h and 3% at 24 h) without serious adverse effects. After ex vivo perfusion and cold storage of excised baboon kidney (blood type B) with ABase, the expression levels of B antigen in glomeruli were reduced to 49% at 1 h and 6% at 4 h.


CONCLUSIONS
This alternative approach might be useful for minimizing antibody removal and anti-B cell immunosuppression as an adjuvant therapy in ABO-incompatible kidney, liver and possibly heart transplantation.
Department of Applied Immunology, Nagoya University School of Medicine, Nagoya, Japan. takakoba@med.nagoya-u.ac.jp
Takaaki
T
Kobayashi
Dage
D
Liu
Haruko
H
Ogawa
Yuko
Y
Miwa
Takaharu
T
Nagasaka
Shoichi
S
Maruyama
Yu-Teh
YT
Li
Akira
A
Onishi
Masaki
M
Iwamoto
Takafumi
T
Kuzuya
Kenji
K
Kadomatsu
Kazuharu
K
Uchida
Akimasa
A
Nakao
D000017:ABO Blood-Group System; D000818:Animals; D001787:Blood Group Incompatibility; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D007150:Immunohistochemistry; D007668:Kidney / Q000166:cytology / Q000276:immunology*; D016030:Kidney Transplantation / Q000276:immunology; D008099:Liver / Q000166:cytology / Q000276:immunology*; D016031:Liver Transplantation / Q000276:immunology; D048530:Papio anubis; D011994:Recombinant Proteins / Q000008:administration & dosage / Q000494:pharmacology; D001616:beta-Galactosidase / Q000008:administration & dosage / Q000494:pharmacology*
D000017:ABO Blood-Group System; D011994:Recombinant Proteins; D001616:beta-Galactosidase