  Recent clinical xenotransplantation and human decedent studies demonstrate
that clinical hyperacute rejection of genetically engineered porcine organs can
be reliably avoided but that antibody mediated rejection continues to limit
graft survival. We previously identified porcine glycans and proteins which are
immunogenic after cardiac xenotransplantation in nonhuman primates, but the
clinical immune response to antigens present in glycan depleted triple knockout
(TKO) donor pigs is poorly understood. In this study we use fluorescence
barcoded HEK cells and HEK cell lines expressing porcine glycans (Gal and SDa)
or proteins (CD9, CD46, CD59, PROCR and ANXA2) to screen antibody reactivity in
human serum from 160 swine veterinarians, a serum source with potential
occupational immune challenge from porcine tissues and pathogens. High levels
of anti-Gal IgM were present in all samples and lower levels of anti-SDa IgM
were present in 41% of samples. IgM binding to porcine proteins, primarily CD9
and CD46, previously identified as immunogenic in pig to non-human primate
cardiac xenograft recipients, was detected in 28 of the 160 swine veterinarian
samples. These results suggest that barcoded HEK cell lines expressing porcine
protein antigens can be useful for screening human patient serum. A
comprehensive analysis of sera from clinical xenotransplant recipients to
define a panel of commonly immunogenic porcine antigens will likely be
necessary to establish an array of porcine non-Gal antigens for effective
monitoring of patient immune responses and allow earlier therapies to reverse
antibody mediated rejection.
