Measuring the Impact of Targeting FcRn-Mediated IgG Recycling on Donor-Specific Alloantibodies in a Sensitized NHP Model

Abstract

BackgroundIn transplantation, plasmapheresis and IVIg provide the mainstay of treatment directed at reducing or removing circulating donor-specific antibody (DSA), yet both have limitations. We sought to test the efficacy of targeting the IgG recycling mechanism of the neonatal Fc receptor (FcRn) using anti-FcRn mAb therapy in a sensitized non-human primate (NHP) model, as a pharmacological means of lowering DSA.MethodsSix (6) rhesus macaque monkeys, previously sensitized by skin transplantation, received a single dose of 30mg/kg anti-RhFcRn IV, and effects on total IgG, as well as DSA IgG, were measured, in addition to IgM and protective immunity. Subsequently, 60mg/kg IV was given in the setting of kidney transplantation from skin graft donors. Kidney transplant recipients received RhATG, and tacrolimus, MMF, and steroid for maintenance immunosuppression.ResultsCirculating total IgG was reduced from a baseline 100% on D0 to 32.0% (mean, SD ± 10.6) on d4 post infusion (p<0.05), while using a DSA assay. T-cell flow cross match (TFXM) was reduced to 40.6±12.5% of baseline, and B-cell FXCM to 52.2±19.3%. Circulating total IgM and DSA IgM were unaffected by treatment. Pathogen-specific antibodies (anti-gB and anti-tetanus toxin IgG) were significantly reduced for 14d post infusion. Post-transplant, circulating IgG responded to anti-FcRn mAb treatment, but DSA increased rapidly.ConclusionTargeting the FcRn-mediated recycling of IgG is an effective means of lowering circulating donor-specific IgG in the sensitized recipient, although in the setting of organ transplantation mechanisms of rapid antibody rise post-transplant remains unaffected.

Desensitization and belatacept-based maintenance therapy in pregnancy-sensitized monkeys receiving a kidney transplant

“…1A and table S4). Compared to a previously reported male model (18,19), in which two serial skin transplants are undertaken with a 6-week interval, females were significantly older at the time of transplant (5.08 ± 1.1 years old versus 13.24 ± 2.5 years old) and had greater number of sensitizing events (2 events versus 6.2 ± 2.2 events) and a greater distance of time between sensitizing event to kidney transplant (from the first event: 185.2 ± 8.7 days versus 3033.5 ± 1190.6 days; from the last event: 131.8 ± 2.25 days versus 1111.5 ± 819.9 days; Fig. 1B and table S4).…”

Addition of interleukin-6 receptor blockade to carfilzomib-based desensitization in a highly sensitized nonhuman primate model

“…Axillary lymph node (LN) biopsy, bone marrow aspiration from the iliac crest, and blood draws were performed prior to desensitization and after completion of therapy to monitor these immune compartments. Heterotopic renal allotransplantation was performed as previously described in the same donor/recipient pairs (kidney swap) 28,29 . After life‐sustaining kidney transplantation, peripheral blood was obtained at least once a week for complete blood counts, serum chemistry, and tacrolimus trough levels.…”

“…Washed cells were stained for live/dead cell using Aqua dead cell stain kit (Life Technologies) and then stained with the following antibodies: CD3, CD4, CD8, CD20, CD25, CD27, CD28, CD56, CD95, PD‐1, CXCR5, ICOS, IgD, IgG, IgM, Ki67, and CD127. DSA was assessed by B and T cell flow crossmatch from serially collected recipient serum samples with donor peripheral blood mononuclear cells (PBMCs) as previously described 29,30 . The DSA levels were expressed as mean fluorescence intensity (MFI) value.…”

“…Heterotopic renal allotransplantation was performed as previously described in the same donor/recipient pairs (kidney swap). 28,29 After lifesustaining kidney transplantation, peripheral blood was obtained at least once a week for complete blood counts, serum chemistry, and tacrolimus trough levels. Real-time PCR was performed to measure rhesus cytomegalovirus (RhCMV) reactivation.…”

“…DSA was assessed by B and T cell flow crossmatch from serially collected recipient serum samples with donor peripheral blood mononuclear cells (PBMCs) as previously described. 29,30 The DSA levels were expressed as mean fluorescence intensity (MFI) value. Samples were collected with an LSRII flow cytometer (BD Biosciences) and analyzed using FlowJo software 9.2 and 10.8 (Tree Star).…”