Carbohydrate antigen expression and anti‐pig antibodies in New World capuchin monkeys: Relevance to studies of xenotransplantation

Abstract

Background: Old World non-human primates (OWNHPs) are used for preclinical pigto-NHP studies. However, like pigs, OWNHPs express Neu5Gc, and therefore do not develop natural anti-Neu5Gc antibodies. New World NHPs (NWNHPs) have been reported not to express Neu5Gc. We investigated the potential of NWNHPs in xenotransplantation research. Methods:We investigated expression of Gal, Neu5Gc, and Sd a antigens on RBCs and PBMCs from humans, selected OWNHPs, and capuchin monkeys (a NWNHP). Serum anti-Gal and anti-Neu5Gc IgM and IgG levels were measured by ELISA. Binding of primate serum IgM and IgG to pig RBCs was measured by flow cytometry.

Justification of specific genetic modifications in pigs for clinical organ xenotransplantation

“…Testing in vivo has not yet been reported, in part because Old World NHPs express Neu5Gc and appear to have antibodies against a new target epitope exposed by TKO in the pig (sometimes referred to as the “4th xenoantigen”; Figure A) . In this respect, New World monkeys would prove better surrogates for humans (Figure B), but the limited size of the majority of the available New World monkeys largely prohibits pig organ transplantation in these species. Nevertheless, there is evidence from experiments in which human blood has been perfused through pig lungs or livers ex vivo that deletion of expression of Neu5Gc reduces human anti‐pig antibody binding and is beneficial to organ survival …”

“…(A) Baboon (n = 14) and (B) capuchin monkey (a New World monkey) (n = 10) IgM and IgG antibody binding to WT, GTKO, DKO (KO of Gal and Sda), and TKO pig RBCs. Serum antibody binding to pig RBCs was performed, as previously described (ref). (Note that CMAHKO in pig cells appears to expose a fourth xenoantigen against which Old World NHPs, but not New World monkeys, have natural antibodies.…”

Xenotransplantation literature update, May/June 2019

“…Ex vivo perfusion models using porcine hepatic perfusion with human blood can be a cost‐efficient substitute to evaluate antigenicity, albeit with significant limitations over NHP models . Zhang, Xuan et al used the example of human antibodies against N‐glycolylneuraminic acid (Neu5Gc), which are not present in NHPs; however, Li et al suggest the use of New World capuchin monkey in response to the problem of New5Gc expression in preclinical models to make NHP studies more translatable . They investigated expression of Gal, Neu5Gc, and Sda antigens on RBCs and PBMCs from humans, selected Old World non‐human primates (OW NHPs), and capuchin monkeys (a New World NHP) using ELISA and flow cytometry .…”

“…Humans and capuchin RBCs and PBMCs did not express Neu5GC, which is expressed in both types of cell in OWNHPs. However, capuchins did have some Gal expression in PBMCs which may be a problematic trade‐off in using capuchins as an NHP model . Despite this, the anti‐Neu5Gc antibody response does need to be assessed and prevented in porcine xenotransplant unless CMAH gene knockout is used to remediate Neu5Gc expression .…”

“…Additionally, success in preclinical studies improves both public and professional perception. In the previous issue of Xenotransplantation, Zhang et al made a comprehensive review of porcine hepatic xenotransplantation, Li et al asses the use of New World capuchin monkey as NHP models, Zhao et al evaluate xenoimplications of IL‐6, TNF‐alpha, and IL‐17 signaling, Wang et al explored porcine renal development through SIX1 and SIX4 gene knockout studies, and Masuhiro et al studied clinical grade neonatal porcine bone marrow‐derived mesenchymal stem cells (npBM‐MSCs). Additionally, Terlecki et al researched bovine pericardial xenografts, Roderjan et al studied porcine semilunar heart valves, and Grebenik et al looked deeper into xenopericardial biomeshes.…”