Pretransplant Desensitization with Costimulation Blockade and Proteasome Inhibitor Reduces DSA and Delays Antibody-Mediated Rejection in Highly Sensitized Nonhuman Primate Kidney Transplant Recipients

Abstract

BackgroundPatients with broad HLA sensitization have poor access to donor organs, high mortality while waiting for kidney transplant, and inferior graft survival. Although desensitization strategies permit transplantation via lowering of donor-specific antibodies, the B cell–response axis from germinal center activation to plasma cell differentiation remains intact.MethodsTo investigate targeting the germinal center response and plasma cells as a desensitization strategy, we sensitized maximally MHC-mismatched rhesus pairs with two sequential skin transplants. We administered a proteasome inhibitor (carfilzomib) and costimulation blockade agent (belatacept) to six animals weekly for 1 month; four controls received no treatment. We analyzed blood, lymph node, bone marrow cells, and serum before desensitization, after desensitization, and after kidney transplantation.ResultsThe group receiving carfilzomib and belatacept exhibited significantly reduced levels of donor-specific antibodies (P=0.05) and bone marrow plasma cells (P=0.02) compared with controls, with a trend toward reduced lymph node T follicular helper cells (P=0.06). Compared with controls, carfilzomib- and belatacept-treated animals had significantly prolonged graft survival (P=0.02), and renal biopsy at 1 month showed significantly reduced antibody-mediated rejection scores (P=0.02). However, four of five animals with long-term graft survival showed gradual rebound of donor-specific antibodies and antibody-mediated rejection.ConclusionsDesensitization using proteasome inhibition and costimulation blockade reduces bone marrow plasma cells, disorganizes germinal center responses, reduces donor-specific antibody levels, and prolongs allograft survival in highly sensitized nonhuman primates. Most animals experienced antibody-mediated rejection with humoral-response rebound, suggesting desensitization must be maintained after transplantation using ongoing suppression of the B cell response.

Preoperative carfilzomib and lulizumab based desensitization prolongs graft survival in a sensitized non-human primate model

“…It is difficult to state whether lulizumab induced more complete suppression of Tfh or B cell proliferation since we did not directly compare it to carfilzomib and belatacept-treated animals. We observed a higher frequency of naïve T (CCR7 + CD45RA + ) and B (CD27 -IgD + ) cells after lulizumab treatment ( Figure 3B and 3C), which was similar to belatacept treatment 15 (Figure 2A).…”

“…To evaluate the efficacy of carfilzomib and lulizumab treatment for desensitization, we sensitized rhesus monkeys as previously described 15,24 . Briefly, naive fully MHC-mismatched rhesus macaque pairs exchanged skin transplantations twice from the same donor (swapping).…”

“…Our attempts to reduce this burden by using a single costimulation blocker (belatacept) with proteasome inhibition showed dramatic improvement with respect to morbidity 15 . However, while prolonging graft survival, belatacept-based treatment did not prevent later chronic antibody-mediated rejection (AMR).…”

“…However, while significantly prolonging graft survival, treatment with carfilzomib and belatacept failed to achieve durable desensitization and resulted in rebound of donor-specific antibody (DSA) post kidney transplantation that was associated with graft loss 15 . Thus, our attention turned toward novel costimulation blockade agents with the potential to improve the efficacy and durability of our 'dual targeting' desensitization approach.…”

Costimulation Blockade in Vascularized Composite Allotransplantation

“…As it has been shown by us and others, the use of belatacept resulted in inhibition of DSA formation (39,93). As anticipated and similar to other organ transplants graft vasculopathy and antibody mediated rejection in VCA are associated with the presence of DSA or C4d deposits (106)(107)(108)(109)(110). The incidence of acute rejection in VCA has been reported to 85% within the first year (39, 76), which is higher than other solid organ transplants (111)(112)(113).…”