Minimal effect of bortezomib in reducing anti‐pig antibodies in human leukocyte antigen‐sensitized patients: a pilot study

Abstract

Background Bortezomib, a proteosome inhibitor used to treat multiple myeloma, has been administered (+/- plasma exchange +/- intravenous immunoglobulin [IVIg]) in attempts to reduce antibodies against human leukocyte antigens (HLA) in sensitized patients undergoing organ transplantation. To our knowledge, bortezomib has not been investigated for its effect on natural anti-pig antibodies. If bortezomib could reduce the production of anti-pig antibodies, this would likely be beneficial to the outcome of pig organ grafts in primates. Methods Nine patients received bortezomib either to reduce anti-HLA antibody levels before organ allotransplantation or to treat antibody-mediated rejection. Patients at the Mayo Clinic (Group 1; n=4) received bortezomib alone, whereas at the UPMC (Group 2; n=5) this was combined with plasmaphereses +/- IVIg in some cases. Anti-pig IgM and IgG levels against wild-type (WT) and α1,3-galactosyltransferase gene-knockout (GTKO) pig aortic endothelial cells (flow cytometry – relative MFI) and anti-Gal IgM and IgG (ELISA – OD480nm) were measured pre- and post-bortezomib therapy. Results Mean anti-pig IgM levels were 11.2 (WT) and 1.9 (GTKO) pre-bortezomib and 9.4 (WT: P=0.02) and 1.7 (GTKO: P=0.33) post-bortezomib. Mean anti-pig IgG levels were 4.3 (WT) and 1.5 (GTKO) pre-bortezomib and 3.6 (WT: P=0.21) and 1.4 (GTKO: P=0.20) post-bortezomib. Mean anti-Gal IgM and IgG levels were 0.7 and 1.1, respectively, pre-treatment, and 0.6 (P=0.03) and 1.1 (NS), respectively, post-treatment. When the data were analyzed in Groups 1 and 2 separately, there were no significant differences between the pre- and post-bortezomib levels of anti-pig, anti-nonGal, or anti-Gal IgM or IgG. Conclusion From this limited study, we conclude that bortezomib might reduce anti-Gal IgM levels in primates, but, in this respect alone, is unlikely to have any significant effect on the outcome of GTKO pig organ transplantation.

Xenotransplantation: immunological hurdles and progress toward tolerance

“…The results may also reflect a major role for B cells in presenting antigen to T cells that promote non‐Gal antibody production. Attempts at targeted plasma cell depletion with anti‐CD38 or bortezomib were ineffective in reducing anti‐Gal antibody levels . In addition, the effects of antibodies such as belimumab that target B‐cell survival factors on the production of non‐Gal antibodies have not been reported.…”

Antibody‐mediated rejection in xenotransplantation: Can it be prevented or reversed?

“…221 Of direct relevance to xenotransplantation, in patients who had received prolonged courses of bortezomib in an effort to reduce the levels of anti-HLA antibodies, little reduction in anti-pig antibody was documented. 224 In contrast to bortezomib, carfilzomib is a proteasome inhibitor that irreversibly inhibits activity of the 20S proteasome and is associated with fewer neuropathic side-effects. 225,226 Following lung allotransplantation, Pham et al observed that the addition of carfilzomib to plasmapheresis and IVIg resulted in greater DSA depletion, clearance of de novo DSA, and conversion to non-complement-activating antibodies.…”

Xenotransplantation tolerance: applications for recent advances in modified swine

“…However, attempts to decrease natural antibody production this way have been only somewhat effective. Bortezomib, a proteasome inhibitor resulting in apoptosis of plasma cells, had no significant effect when serum antiswine antibody levels (non-Gal and anti-Gal IgM or IgG) were measured in patients undergoing organ transplantation (15,16). IdeS (imlifidase) is an endopeptidase derived from Streptococcus pyogenes that targets and cleaves human IgG (but not IgM).…”