Generation of SLA-DQ Knockout Pigs and Screening for Anti-SLA-DQ Antibodies in Sera From Naïve and HLA Class II-sensitized Patients.

Background: The most common cause of late graft failure in renal allotransplantation is chronic antibody-mediated rejection caused by donor-specific antibodies against class II human leukocyte antigen (HLA), particularly HLA-DQ. In preclinical renal xenotransplantation, graft failure 1-mo posttransplant is characterized by glomerulopathy and immunoglobulin G (IgG) staining in the glomerulus. Rhesus renal xenograft recipients with late graft failure also have anti-swine leukocyte antigen (SLA)-DQ antibodies present in their serum suggesting that, like allotransplantation, late xenograft failure may be driven by antidonor major histocompatibility complex class II antibodies, particularly SLA-DQ. Some patients have anti-SLA-DQ antibodies, but the magnitude of this problem is unclear.

Methods: We evaluated patient sera for the presence of anti-SLA-DQ antibodies in engineered immortalized cells, to determine patients' reactivity toward 7 different SLA-DQ molecules. Next, we created glycoprotein, alpha-galactosyltransferase 1/beta-1,4-N-acetyl-galactosaminyltransferase 2/SLA-DQ knockout (KO) pigs so that we could evaluate the impact of SLA-DQ on the level of antipig antibodies by performing crossmatches with serum from naïve and HLA class II-sensitized patients and SLA-DQ KO peripheral blood mononuclear cells.

Results: Naïve and HLA class II-sensitized patients had anti-SLA-DQ immunoglobulin M and IgG that were pan-specific rather than SLA-DQ allele-specific. Crossmatching patient sera with peripheral blood mononuclear cells from the SLA-DQ KO pigs revealed that many patients had anti-SLA-DQ antibodies. Eliminating SLA-DQ reduced human immunoglobulin M and IgG binding to primary pig cells.

Conclusions: SLA-DQ is a xenoantigen for most patients. SLA-DQ KO pigs may help address this problem.