Approach to kidney transplant in sensitized potential transplant recipients

Nanoparticle targeting to the endothelium during normothermic machine perfusion of human kidneys

Ex vivo normothermic machine perfusion (NMP) is a new clinical strategy to assess and resuscitate organs likely to be declined for transplantation, thereby increasing the number of viable organs available. Short periods of NMP provide a window of opportunity to deliver therapeutics directly to the organ and, in particular, to the vascular endothelial cells (ECs) that constitute the first point of contact with the recipient's immune system. ECs are the primary targets of both ischemia-reperfusion injury and damage from preformed antidonor antibodies, and reduction of perioperative EC injury could have long-term benefits by reducing the intensity of the host's alloimmune response. Using NMP to administer therapeutics directly to the graft avoids many of the limitations associated with systemic drug delivery. We have previously shown that polymeric nanoparticles (NPs) can serve as depots for long-term drug release, but ensuring robust NP accumulation within a target cell type (graft ECs in this case) remains a fundamental challenge of nanomedicine. We show that surface conjugation of an anti-CD31 antibody enhances targeting of NPs to graft ECs of human kidneys undergoing NMP. Using a two-color quantitative microscopy approach, we demonstrate that targeting can enhance EC accumulation by about 5- to 10-fold or higher in discrete regions of the renal vasculature. In addition, our studies reveal that NPs can also nonspecifically accumulate within obstructed regions of the vasculature that are poorly perfused. These quantitative preclinical human studies demonstrate the therapeutic potential for targeted nanomedicines delivered during ex vivo NMP.

Pre- and Posttransplant Refractory Idiopathic Membranous Glomerulonephritis: The Forgotten Potential Culprit

Idiopathic membranous nephropathy has been recently recognized as an autoimmune disease that may recur or develop de novo posttransplant, whereby specific auto- or alloantibodies are directed against recently recognized podocyte structures such as the phospholipase receptor PLAR2 and the thrombospondin receptor THSD7A. The observed inconsistencies in therapeutic responses with all presently recognized therapies irrespective of immunosuppressive regimen used and the superiority of complete and sustained remission rates in recurrent disease after kidney transplant compared with native disease imply the existence of different immunopathogenic signatures that may be operational, either isolated or combined, in the pathogenesis of membranous nephropathy. These pathogenic mechanisms involve primarily B-cell-mediated pathways with a T-cell help component and distinct auto- and alloantibody-secreting mechanisms involving different B cells. These pathways are present in separate compartments such as in CD20+-activated B cells found in spleen and lymph nodes, CD19+/CD20- plasmablasts and short-lived plasma cells in the blood, and CD19-/CD20-/CD38+/CD138+ long-lived memory plasma cells niched naturally in the bone marrow and ectopically in the native or grafted inflamed kidney. These latter nonproliferating plasma cells lacking CD19 and CD20 markers would be resistant to in vivo B-cell depletion by anti-CD20 monoclonal therapies. They produce considerable amounts of immunoglobulin G (IgG) autoantibodies and alloantibodies and provide the basis for humoral memory and refractory autoimmune diseases. This may explain the limited rate of sustained complete remission, which, as observed in most studies, does not exceed a rate of 20% in all rituximab-treated patients despite total B-cell eradication. There is an important need for the development of new biomarkers to help identify and predict therapeutic responses. Potential new therapeutic targets against plasma cells such as proteasome inhibitors, anti-CD38 monoclonal antibodies, and autoreactive pathogenic B-cell-specific depleting regimens, as well as new anti-CD20 monoclonal antibodies, may help tailor therapy to the individual need for optimal outcome.

Bortezomib as a Novel Approach to Early Recurrent Membranous Glomerulonephritis After Kidney Transplant Refractory to Combined Conventional Rituximab Therapy

We report a case of early recurrent membranous glomerulonephritis after kidney transplant from a deceased donor. The patient received induction therapy and was discharged with a serum creatinine level of 0.78 mg/dL on triple maintenance immunosuppressive therapy, which included tacrolimus, mycophenolate mofetil, and prednisone. At 7 months after transplant, a graft biopsy for new-onset isolated proteinuria (2.7 g/day) revealed stage 2 recurrent membranous glomerulonephritis. In the face of persistent proteinuria despite combined conservative rituximab therapy over several months and the total eradication of CD20-positive cells, bortezomib was introduced. This resulted in a substantial decline in proteinuria within 2 months and its subsequent disappearance several months later. This was paralleled by a considerable drop in plasma CD34-positive and CD138-positive cell counts. These preliminary observations indicate that recurrent posttransplant membranous glomerulonephritis is associated in part with a B-cell- mediated immunologic process that may involve both CD20-positive and plasma cells. Rituximab-resistant or partially responsive recurrent posttransplant membranous glomerulonephritis may benefit from a proteasome inhibitor-based therapy.

In Kidney Transplant Recipients With a Positive Virtual Crossmatch, High PRA was Associated With Lower Incidence of Viral Infections

BACKGROUND

There is little information on the incidence, risk factors, and outcomes associated with CMV and BK infections in sensitized patients.

METHODS

We examined 254 consecutive kidney transplant recipients with positive virtual crossmatch and negative flow crossmatch.

RESULTS

A total of 111 patients (43%) developed CMV disease or BK infection or nephropathy (BKVN). Specifically, 78 patients (30.7%) developed BK infection, 19 (7.5%) had BKVN, and 33 (12.9%) presented with CMV disease. Four patients (1.5%) developed both infections. Mean time from transplant to diagnosis for BK and CMV was 4.07 ± 3.10 and 8.35 ± 5.20 months, respectively. African American (HR, 2.64; 95% CI, 1.37-5.07; P = 0.003), thymoglobulin induction (HR, 2.18; 95% CI, 1.38-3.43; P = 0.0008), DSA greater than 500 MFI at transplant (HR, 1.64; 95% CI, 1.05-2.57; P = 0.03), history of diabetes (HR, 1.62; 95% CI, 1.01-2.60; P = 0.04), CMV D+/R- (HR, 2.30; 95% CI, 1.06-5.01; P = 0.03), and acute rejection (HR, 1.49; 95% CI, 0.99-2.24; P = 0.05) were associated with increase incident of BK/CMV, whereas rituximab (HR, 0.47; 95% CI, 0.24-0.91; P = 0.02), peak PRA greater than 80% (HR, 0.48; 95% CI, 0.27-0.84; P = 0.01), and living donor transplant (HR, 0.57; 95% CI, 0.36-0.87; P = 0.01) were associated with a lower likelihood of infection. Thymoglobulin induction (HR, 2.50; 95% CI, 1.02-6.13; P = 0.04), and peak PRA greater than 80% (HR, 0.45; 95% CI, 0.23-0.86; P = 0.02) remained significant predictors of infection after multivariate adjustment.

CONCLUSIONS

Although more than 40% of patients with a positive virtual crossmatch presented with BK infection/CMV disease, high PRA greater than 80% seemed to be protective.

Evaluating the Use of Bortezomib and Eculizumab in Desensitization of Transplant Patients

Objective: To systematically review the existing literature concerning the utilization of bortezomib and eculizumab to determine if there is enough evidence to warrant their routine use in desensitization protocols for high-risk transplant candidates. Data Sources: PubMed, Google Scholar, and ClinicalTrials.gov were searched using the terms bortezomib, eculizumab, desensitization, transplant, highly-sensitized, pre-sensitized, and antibody-mediated rejection (AMR). The articles included were published between January 2009 and August 2012. Study Selection and Data Extraction: All English-language articles involving human subjects were assessed for inclusion. The search included articles evaluating the use of these agents in desensitization and the prevention of AMR, but excluded articles investigating these drugs in the treatment of established AMR. Data Synthesis: Highly sensitized transplant candidates are at an increased risk of developing AMR after transplant; desensitization potentially reduces this risk. The addition of bortezomib and eculizumab to current desensitization protocols may enhance outcomes. The bortezomib search produced 3 efficacy trials, 1 safety trial, 2 in-progress trials, 14 patient cases from 8 published case reports, and 3 efficacy study abstracts. Conclusions: Much of the available literature assessing the efficacy of bortezomib and eculizumab for use in desensitization exists as restricted clinical trials and incomplete case reports. Bortezomib and eculizumab appear to be potentially effective additions to current desensitization protocols. However, we are unable to determine at this time whether these agents improve the most clinically relevant outcome of successful transplantation. Further well-designed clinical trials are needed to determine their true clinical efficacy in highly sensitized transplant candidates.