Miae Kim

Antibody‐Mediated Rejection in Kidney Transplantation: A Review of Pathophysiology, Diagnosis, and Treatment Options

Antibody‐mediated rejection (AMR), also known as B‐cell–mediated or humoral rejection, is a significant complication after kidney transplantation that carries a poor prognosis. Although fewer than 10% of kidney transplant patients experience AMR, as many as 30% of these patients experience graft loss as a consequence. Although AMR is mediated by antibodies against an allograft and results in histologic changes in allograft vasculature that differ from cellular rejection, it has not been recognized as a separate disease process until recently. With an improved understanding about the importance of the development of antibodies against allografts as well as complement activation, significant advances have occurred in the treatment of AMR. The standard of care for AMR includes plasmapheresis and intravenous immunoglobulin that remove and neutralize antibodies, respectively. Agents targeting B cells (rituximab and alemtuzumab), plasma cells (bortezomib), and the complement system (eculizumab) have also been used successfully to treat AMR in kidney transplant recipients. However, the high cost of these medications, their use for unlabeled indications, and a lack of prospective studies evaluating their efficacy and safety limit the routine use of these agents in the treatment of AMR in kidney transplant recipients.

Impact of Pretransplant Anti-HLA Antibodies on Outcomes in Lung Transplant Candidates

RATIONALE The prevalence of anti-HLA antibodies in lung transplant candidates and their impact on waitlist and transplant outcomes is not known. OBJECTIVES We examined the prevalence of pretransplant anti-HLA antibodies at varying thresholds and evaluated their impact on outcomes before and after lung transplantation. METHODS We performed a single-center retrospective cohort study including all patients listed for lung transplantation between January 2008 and August 2012. Per protocol, transplant candidates were assessed by solid phase LABscreen mixed Class I and II and LABscreen Single Antigen assays. MEASUREMENTS AND MAIN RESULTS Among 224 patients, 34% had anti-HLA antibodies at mean fluorescent intensity (MFI) greater than or equal to 3,000 (group III), and 24% had antibodies at MFI 1,000 to 3,000 (group II). Ninety percent of the patients with pretransplant anti-HLA antibodies had class I antibodies, whereas only seven patients developed class II alone. Patients in group III were less likely to receive transplants than patients without any anti-HLA antibodies (group I) (45.5 vs. 67.7%, P = 0.005). Wait time to transplant was longer in group III than group I, although this difference did not meet statistical significance, and waitlist mortality was similar. Among transplant recipients, antibody-mediated rejection (AMR) was more frequent in group III than in group II (20% vs. 0%, P = 0.01) or group I (6.3%, P = 0.05). CONCLUSIONS The presence of anti-HLA antibodies at the high MFI threshold (>3,000) was associated with lower transplant rate and higher rates of AMR. Screening for anti-HLA antibodies using the 3,000 MFI threshold may be important in managing transplant candidates and recipients.

Early aspirin use and the development of cardiac allograft vasculopathy

BACKGROUND Cardiac allograft vasculopathy (CAV) remains a leading cause of morbidity and mortality after orthotopic heart transplantation (OHT). Little is known about the influence of aspirin on clinical expression of CAV. METHODS We followed 120 patients with OHT at a single center for a median of 7 years and categorized them by the presence or absence of early aspirin therapy post-transplant (aspirin treatment ≥6 months in the first year). The association between aspirin use and time to the primary end-point of angiographic moderate or severe CAV (International Society for Heart and Lung Transplantation grade ≥2) was investigated. Propensity scores for aspirin treatment were estimated using boosting models and applied by inverse probability of treatment weighting (IPTW). RESULTS Despite a preponderance of risk factors for CAV among patients receiving aspirin (male sex, ischemic heart disease as the etiology of heart failure, and smoking), aspirin therapy was associated with a lower rate of moderate or severe CAV at 5 years. Event-free survival was 95.9% for patients exposed to aspirin compared with 79.6% for patients without aspirin exposure (log-rank p = 0.005). IPTW-weighted Cox regression revealed a powerful inverse association between aspirin use and moderate to severe CAV (adjusted hazard ratio 0.13; 95% confidence interval 0.03-0.59), which was directionally consistent for CAV of any severity (adjusted hazard ratio 0.50; 95% confidence interval 0.23-1.08). CONCLUSIONS This propensity score-based comparative observational analysis suggests that early aspirin exposure may be associated with a reduced risk of development of moderate to severe CAV. These findings warrant prospective validation in controlled investigations.

Multicenter evaluation of efficacy and safety of low-dose versus high-dose valganciclovir for prevention of cytomegalovirus disease in donor and recipient positive (D+/R+) renal transplant recipients

The cytomegalovirus (CMV) donor‐positive/recipient‐positive (D+/R+) population is the largest proportion of renal transplant recipients (RTR). Guidelines for prevention of CMV in the intermediate‐risk D+/R+ population include prophylaxis with valganciclovir (VGCV) 900 mg/day for 3 months. This study is the first head‐to‐head analysis, to our knowledge, comparing the efficacy and safety CMV prophylaxis of VGCV 450 vs 900 mg/day for 3 months in D+/R+ RTR.

The Presence of Pretransplant HLA Antibodies Does Not Impact the Development of Chronic Lung Allograft Dysfunction or CLAD Related Death.

Background Development of donor-specific antibodies (DSA) after lung transplantation is associated with antibody mediated rejection, acute cellular rejection, and bronchiolitis obliterans syndrome; however, the significance of circulating antibodies before transplant remains unclear. Methods We performed a retrospective cohort study including recipients of primary lung transplants between 2008 and 2012. We assessed the impact of circulating HLA and noncytotoxic DSA detected before transplant on development of Chronic Lung Allograft Dysfunction (CLAD) or CLAD-related death. Results 30% of subjects had circulating class I antibodies alone, 4% Class II, and 14.4% class I and class II at mean fluorescent intensity greater than 1000. Nine percent of the subjects had DSA class I, 9% class II, and 2.4% both DSA classes 1 and 2. Neither the presence of circulating antibodies (adjusted hazard ratio, 0.87; 95% confidence interval, 0.50-1.54) nor the presence of DSA (adjusted hazard ratio, 1.56; 95% confidence interval, 0.77-3.18) before transplant at mean fluorescent intensity greater than 1000 was associated with the development of CLAD or CLAD-related death. Conclusions Although in previous studies we have shown an increased incidence of antibody-mediated rejection in patients with pretransplant DSA, neither the presence of HLA antibodies nor DSA translated to an increased risk of allograft dysfunction or death if prospective crossmatch testing was negative. Prospective studies are needed to define the impact of pretransplant sensitization on lung transplant recipients.

Risk evaluation and mitigation strategies: a focus on the mycophenolic acid preparations.

Objective To review risks associated with mycophenolic acid (MPA) preparations and evaluate their required risk evaluation and mitigation strategies (REMS) elements. Data Sources and Extraction Articles were identified through a non–date-limited MEDLINE and EMBASE search using the terms fetal toxicity, teratogenicity, risk evaluation and mitigation strategies, REMS, MPA, mycophenolate mofetil, enteric-coated MPA, and organ transplant. Information from the Food and Drug Administration (FDA) and the manufacturers of the MPA preparations was also evaluated. Data Synthesis The MPA preparations are associated with several potential risks, including gastrointestinal disturbances and myelosuppression; however, their impact on the fetus in pregnant patients taking 1 of these agents poses the greatest risk. The FDA approved REMS programs for all MPA products, both innovator and generic preparations, in September 2012. With evidence of increased risk of miscarriage and birth defects associated with MPA use, the FDA instituted a REMS program that contains both a medication guide and elements to assure safe use (ETASU). Conclusion The medication guides for the MPA products, which were previously FDA approved, should continue to be distributed to patients who get either an initial prescription filled or a refill. The ETASU requires prescribers to complete training and obtain patient signatures on the Patient-Prescriber Acknowledgment Form. A single, national, voluntary pregnancy registry specific to this medication has been established, and pregnant patients should be encouraged to participate. Although the impact of the MPA REMS on clinical practice is not clear, it is a step toward increasing the understanding of fetal risks with MPA.

Impact of HMG-CoA reductase inhibitors on the incidence of polyomavirus-associated nephropathy in renal transplant recipients with human BK polyomavirus viremia

Up to 20% of renal transplant recipients (RTR) will develop human BK polyomavirus (BKPyV) viremia. BKPyV viremia is a pre‐requisite of polyomavirus‐associated nephropathy (PyVAN). Risk of BKPyV infections increases with immunosuppression. Currently, the only effective therapy against PyVAN is reductions in immunosuppression, but this may increase the risk of rejection. In vitro data have shown that pravastatin dramatically decreased caveolin‐1 expression in human renal proximal tubular epithelial cells (HRPTEC) and suppressed BKPyV infection in these cells. Based on these data, we postulated that statin therapy may prevent the progression of BKPyV viremia to PyVAN.

Generic immunosuppression in transplantation: current evidence and controversial issues

The overall success of organ transplantation in the 21st century has been predicated, in part, on the use of newer, more potent, and selective immunosuppressive agents. However, the high cost of lifelong immunosuppression represents a financial burden for many patients. In the past 15 years, regulatory agencies in Europe and America have approved several generic immunosuppressants. One concern is whether the conversion between innovator and generic immunosuppressants will prove to be problematic. This manuscript aims to compare and contrast the bioequivalence requirements among regulatory authorities in the USA, Europe, and Canada, evaluate published studies of generic immunosuppressants in transplant recipients, summarize consensus statements made by transplant organizations and discuss how to engage patients in discussion regarding the choice between innovator and generic immunosuppressants.