Detection of Anti-Non-α-Gal Xenoreactive Antibodies in Human Blood Products

Surgical bleeding is a risk in any solid organ transplant, and is commonly addressed with the transfusion of human blood products to replace or supplement coagulation factors. It is unknown if these blood products would harm xenotransplanted pig organs in human recipients demonstrating coagulopathy. The aim of this study was to investigate in vitro if blood products such as fresh frozen plasma (FFP) or cryoprecipitate (cryo) contain xenoantibodies capable of cytotoxicity to GTKO pig cells.

We obtained 12 individual single-donor (7 FFP and 5 cryo) blood products from our institution's blood bank for testing. Peripheral blood mononuclear cells (PBMCs) were obtained from a GTKO/hCD55 pig for use as target cells. We performed a series of flow cytometry crossmatch (FCXM) and complement-dependent cytotoxicity (CDC) assays.

We found that all the tested blood products contained some degree of IgM and IgG xenoantibody. Tests using a 1:50 dilution revealed a significant decrease in IgM xenoantibody binding, but an increase in the detection of IgG binding. Multiple preparations were capable of GTKO PBMC cytotoxicity but the level of antibody binding and cell death varied by preparation.

Both FFP and cryo contain IgM and IgG non-galactose-α-1,3-galactose (αGal) xenoantibodies capable of killing GTKO PBMCs, though the level varies by preparation. Although some centers utilize a genetic background with mutations in the three enzymes responsible for the known xenoantigens, others are investigating the GTKO pig as a potential option. These results suggest that a center pursuing a human xenotransplantation study with a GTKO genetic background should pre-screen blood products prior to administration.