Session Time: 3:15pm-4:45pm
Presentation Time: 3:39pm-3:51pm
*Purpose: Knock-out (KO) of porcine carbohydrates (CHO), including Gal 1,3αGal, inhibits antibody-mediated xenograft rejection. The β4Gal epitope was discovered using serum from xenograft-sensitized baboons, but whether humans (and baboons) have detectable titers of preformed antibody (as humans do for Neu5Gc), and whether anti-β4Gal antibody modulates lung xenograft injury, remains controversial.
*Methods: Pre-lung transplant and post-op day1 anti-pig Ab binding against GalTKO versus double KO (DKO) porcine aortic endothelial cells (PAECs) was measured in sera from 14 baboons that had received a lung from a GalTKO pig and compared to those in which the donor animal had also β4Gal KO, with (TKO) or without (DKO) additional Neu5GcKO. In addition, lung biopsies from wildtype, GalTKO, DKO and TKO pigs after 30min of ex vivo xeno-perfusion with human blood were stained for IgG and IgM binding to evaluate Ab binding to pig tissue. In one case Ab binding to GalTKO and DKO cells was also measured at 1 and 31d in a long-surviving xenolung recipient.
*Results: In naïve baboons, IgM Ab binding was consistently lower on GalTKO.β4GalKO relative to GalTKO PAECs (Fig.1). When compared to single KO lungs, decline in anti-non-Gal Ab levels on post-op d1 in vivo was consistently less using GalTKO.β4GalKO lungs (58%±16% vs. 31%±16%, n=7 and 3, respectively). In a long-surviving LTX recipient animal, sensitized anti-non Gal antibody binding in a long-survivor was almost completely abrogated when using TKO cells. By IHC, lungs with multiple CHO KOs appear to show decreased IgM tissue deposition relative to GalTKO lungs.
*Conclusions: These results show decreased preformed IgM antibody binding to TKO vs. GalTKO PAECs in pre-transplant baboon sera and suggest that sensitized anti-non Gal antibody predominantly recognized β4Gal antigen post xenolung transplantation. This confirms that β4Gal is a “non-Gal” antigen, recognized by antibodies in naïve baboons, which presumably contributes to pig lung xenograft injury. The KO of β4Gal in donor pigs will likely help to better control Ab-mediated xenorejection pathways and advance xenotransplantation of the lung and other organs towards the clinic.
To cite this abstract in AMA style:Burdorf L, Abady Z, Cerel B, Petitpas K, Laird C, Pratts S, Cheng X, Phelps CJ, Eyestone W, Ayares DL, III RNPierson, Azimzadeh AM. Overcoming Ab-Mediated Xenolung Rejection: Beta4Gal is an Important Pre- and Post-Transplant Ab Target, Relevant to Xenograft Injury in Baboons [abstract]. Am J Transplant. 2020; 20 (suppl 3). https://atcmeetingabstracts.com/abstract/overcoming-ab-mediated-xenolung-rejection-beta4gal-is-an-important-pre-and-post-transplant-ab-target-relevant-to-xenograft-injury-in-baboons/. Accessed October 26, 2020.
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