Serum cytotoxicity to pig cells and anti-alphaGal antibody level and specificity in humans and baboons.
BACKGROUND
Removal and/or "neutralization" of anti-Gal alpha1-3Gal (alphaGal) antibodies can prevent or delay the hyperacute rejection of pig organs transplanted into primates.


OBJECTIVE
To determine variations in (1) cytotoxicity to pig kidney (PK15) cells, (2) anti-alphaGal antibody level, and (3) specificity in adult human (n=46) and baboon (n=38) sera.


METHODS
Cytotoxicity to PK15 cells was determined by adding rabbit complement to heat-inactivated serum, using a two-color fluorescent dye to distinguish live and dead cells. Anti-alphaGal antibody level was determined by ELISA using alphaGal trisaccharide type 2-BSA glycoconjugate as antigen target. Specificity determined by ELISA using four different alphaGal-BSA glycoconjugates: (disaccharide, trisaccharides type 2 and 6, and pentasaccharide).


RESULTS
Cytotoxicity of human AB sera varied from 30-100% PK15 relative cell damage (%RCD), although that of baboon sera of all blood groups varied from 35-100% RCD. In human AB sera, anti-alphaGal antibody level (at a dilution of 1:80) varied from undetectable to 0.75 (OD at 405 nm), although in baboon sera of all blood groups, anti-alphaGal antibody level varied from undetectable to >2.0. There was no correlation between anti-alphaGal antibody level and serum cytotoxicity in either species. Specificity varied among individuals in both human and baboon sera.


CONCLUSIONS
These studies have demonstrated (1) considerable variation in cytotoxicity and anti-alphaGal antibody level in human and baboon sera, but a lack of correlation between these two parameters; (2) considerable variation in the specificity of anti-alphaGal antibodies; (3) blood group B human and baboon sera have lower levels of anti-alphaGal antibodies; (4) no relation between blood group and specificity of anti-alphaGal antibodies. Although there are minor differences in the parameters measured, baboons would appear to be suitable surrogates for humans in the pig-to-primate xenograft model.
Neethling
F A
FA
Oklahoma Transplantation Institute, Integris Baptist Medical Center, Oklahoma City, USA.
Cooper
D K
DK
D000017:ABO Blood-Group System; D000328:Adult; D000818:Animals; D000918:Antibody Specificity; D002460:Cell Line; D003602:Cytotoxicity, Immunologic; D004187:Disaccharides / Q000276:immunology*; D000939:Epitopes / Q000276:immunology*; D006801:Humans; D010215:Papio; D011817:Rabbits; D013552:Swine
D000017:ABO Blood-Group System; D004187:Disaccharides; D000939:Epitopes; C055075:galactosyl-(1-3)galactose