Cardiac antibody-mediated rejection

Pediatric heart transplantation: how to manage problems affecting long-term outcomes?

Since the initial International Society of Heart Lung Transplantation registry was published in 1982, the number of pediatric heart transplantations has increased markedly, reaching a steady state of 500-550 transplantation annually and occupying up to 10% of total heart transplantations. Heart transplantation is considered an established therapeutic option for patients with end-stage heart disease. The long-term outcomes of pediatric heart transplantations were comparable to those of adults. Issues affecting long-term outcomes include acute cellular rejection, antibody-mediated rejection, cardiac allograft vasculopathy, infection, prolonged renal dysfunction, and malignancies such as posttransplant lymphoproliferative disorder. This article focuses on medical issues before pediatric heart transplantation, according to the Korean Network of Organ Sharing registry and as well as major problems such as graft rejection and cardiac allograft vasculopathy. To reduce graft failure rate and improve long-term outcomes, meticulous monitoring for rejection and medication compliance are also important, especially in adolescents.

Identifiable Risk Factors and Miscalculations During Listing for Pediatric Heart Transplantation

The objective of this study is to describe identifiable risk factors, complications, and pitfalls while listing pediatric patients for heart transplantation, which is the standard of care for end-stage heart disease in children. Since the introduction of cyclosporine in the 1980s, the management in pediatric heart transplantation has shown consistent improvement, mainly because of technological advances and the integration of multidisciplinary teams in the field. However, the complexity of this patient population makes medical providers vulnerable to complications as a result of undesirable mistakes. Transplant survival is impacted negatively when mistakes from health-care providers compound the high-risk status of the patient. The identification of multiple risk factors and undesirable miscalculations may help transplant teams make decisions before allocating organs, intervene or minimize morbidity, and provide the best quality of life to recipients.

Outcome of antibody-mediated rejection compared to acute cellular rejection after pediatric heart transplantation

Outcomes of ACR after pediatric HTx have been well described, but less has been reported on outcomes of AMR. We compared the clinical characteristics and cardiovascular outcomes (composite end-point of death, retransplantation, or allograft vasculopathy) of pediatric HTx recipients with AMR, ACR, and no rejection in a retrospective single-center study of 104 recipients. Twenty were treated for AMR; 15 were treated for ACR. Recipients with AMR had an increased frequency of congenital heart disease (90% vs ACR 67% vs no rejection 59%, P = .03), homograft (68% vs 7% vs 18%, P < .001), HLA sensitization (45% vs 13% vs 13%, P = .008), and positive cross-match (30% vs 7% vs 9%, P = .046). AMR caused hemodynamic compromise more often than ACR (39% vs 4%, P = .02). AMR recipients had worse cardiovascular outcome than recipients with ACR or no rejection (40% vs 20% vs 8.6%, P = .003). In bivariate Cox analysis, AMR (HR 4.1, CI 1.4-12.0, P = .009) and ischemic time (HR 1.6, CI 1.1-2.3, P = .02) were associated with worse cardiovascular outcome; ACR was not. In summary, pediatric HTx recipients who develop AMR have worse cardiovascular outcome than recipients who develop only ACR or experience no rejection at all.

Significance of Anti-HLA Antibodies on Adult and Pediatric Heart Allograft Outcomes

As methods for human leukocyte antigens (HLA) antibody detection have evolved and newer solid phase assays are much more sensitive, the last 15 years has seen a renewed focus on the importance of HLA antibodies in solid organ transplant rejection. However, there is still much controversy regarding the clinical significance of antibody level as depicted by the mean fluorescence intensity of a patient’s neat serum. Emerging techniques, including those that identify antibody level and function, show promise for the detection of individuals at risk of allograft rejection, determination of the effectiveness of desensitization prior to transplant, and for monitoring treatment of rejection. Here, we review current publications regarding the relevance of donor-specific HLA antibodies (DSA) in adult and pediatric heart transplantation (HT) with graft survival, development of antibody-mediated rejection and cardiac allograft vasculopathy (CAV). The negative impact of DSA on patient and allograft survival is evident in adult and pediatric HT recipients. Many questions remain regarding the most appropriate frequency of assessment of pre- and posttransplant DSA as well as the phenotype of DSA memory vs. true de novo antibody using large multicenter adult and pediatric cohorts and state-of-the-art methodologies for DSA detection and characterization.

Eosinophil count, allergies, and rejection in pediatric heart transplant recipients

BACKGROUND

Allograft rejection and long-term immunosuppression remain significant challenges in pediatric heart transplantation. Pediatric recipients are known to have fewer rejection episodes and to develop more allergic conditions than adults. A T-helper 2 cell dominant phenotype, manifested clinically by allergies and an elevated eosinophil count, may be associated with immunologic quiescence in transplant recipients. This study assessed whether the longitudinal eosinophil count and an allergic phenotype were associated with freedom from rejection.

METHODS

This single-center, longitudinal, observational study included 86 heart transplant patients monitored from 1994 to 2011. Post-transplant biannual complete blood counts, allergic conditions, and clinical characteristics related to rejection risk were examined.

RESULTS

At least 1 episode of acute cellular rejection (ACR) occurred in 38 patients (44%), antibody-mediated rejection (AMR) occurred in 11 (13%), and 49 patients (57%) were diagnosed with an allergic condition. Patients with ACR or AMR had a lower eosinophil count compared with non-rejectors (p = 0.011 and p = 0.022, respectively). In the multivariable regression analysis, the presence of panel reactive antibodies to human leukocyte antigen I (p = 0.014) and the median eosinophil count (p = 0.011) were the only independent covariates associated with AMR. Eosinophil count (p = 0.010) and female sex (p = 0.009) were independent risk factors for ACR. Allergic conditions or young age at transplant were not protective from rejection.

CONCLUSIONS

This study demonstrates a novel association between a high eosinophil count and freedom from rejection. Identifying a biomarker for low rejection risk may allow a reduction in immunosuppression. Further investigation into the role of the T-helper 2 cell phenotype and eosinophils in rejection quiescence is warranted.

Tandem hemodialysis and plasma exchange

The combination of hemodialysis and plasma exchange as one tandem procedure was first described in 1999 by Siami et al. (ASAIO J 45:229-233), but larger pediatric case series were not described until 2012. Even in adults, there are only limited case series. If performed in sequence, up to 8 h of treatment time may be required. With the use of the tandem procedure in stable patients, the same procedures can be completed during the same time as a routine hemodialysis, which is more convenient for patients and may reduce healthcare costs. Little is known about the utilization of the combination of hemodialysis and plasma exchange in children. The purpose of this review is to summarize the adult and scarce pediatric experience. The results of a survey carried out by the authors using the Internet listserver "PedNeph" to obtain an overview of the current practice patterns of pediatric nephrologists are also presented.

Bortezomib use in a pediatric cardiac transplant center

Data are limited on the efficacy and safety of bortezomib for the treatment of AMR following OHT for pediatric acquired or CHD. Retrospective chart review identified patients who received bortezomib for acute (n = 3, within two wk of diagnosis) and chronic (n = 1, three months after diagnosis) AMR or as part of a desensitization regimen (n = 1). Bortezomib was associated with a 3-66% reduction in class I DSA and a 7-82% reduction in class II DSA. Two of the three acute AMR cases resolved by the first follow-up biopsy. Two patients with AMR resolution are currently well. One patient developed a second episode of AMR, which was unresponsive to bortezomib therapy and required retransplantation for progressive coronary allograft vasculopathy. One patient died shortly after the third cycle from multi-organ failure. The desensitization patient showed transient HLA reduction with two cycles, but died five months after transplant from sepsis. Complications included infection (3/5), peripheral neuropathy (2/5), AKI (2/5), and thrombocytopenia (3/5). Adverse events appear more common in critically ill patients. Bortezomib therapy resulted in variable DSA reduction and AMR resolution in AMR in OHT secondary to pediatric acquired or CHD.

Using individual DSA titers to assess for accommodation after late humoral rejection

Management of late humoral rejection remains challenging, and DSA may persist. A case report illustrates how individual DSA titers using solid-phase-based assays may help to assess for accommodation. A male cystinosis patient received a cadaveric renal transplant at the age of 12 yr with a daclizumab, tacrolimus, MMF, and steroids-based immunosuppression. After three acute rejection episodes over the first eight months, interstitial fibrosis/tubular atrophy (IF/TA) was diagnosed on biopsy, while the immunosuppression was left unchanged with a high target exposure for both tacrolimus and MPA. One yr later, AMR type III (C4d and DSA positive) was treated with daily plasmapheresis, IVIG 100 mg/kg and pulse steroids 5 mg/kg. DSA (DR 53, DQ4, and DQ 2) were not responding until the plasma volume was increased to 2.5 plasma volumes. A second rise of creatinine confirmed worse humoral rejection; daily plasma exchange was resumed, and two doses of rituximab (375 mg/m(2)) were given. Subsequently, all DSA dropped, but only DR53 DSA remained unchanged, whereas the DQ antibodies rebounded to very strong titers. With a follow-up of over 120 days after recovery of the CD19 count, off all additional treatment and on identical immunosuppression with tacrolimus and MMF and prednisone, the patient's creatinine remained stable between 45 and 50 um while DQ DSA remain strong to very strong. We conclude that the patient is in a state of accommodation. DSA titers should be monitored when managing late humoral rejection.

Successful treatment of hemodynamic compromise caused by antibody-mediated and cellular rejection in a recipient 12 years after heart transplantation

Heart transplantation (HTx) is an established therapy for stage D heart failure due to recent advances in immunosuppressive regimens. However, antibody-mediated rejection remains an unsolved problem because of its refractoriness to standard immunosuppressive therapy with high mortality and graft loss. We experienced a 16-year old patient with hemodynamic compromise caused by both cellular and antibody-mediated rejection 12 years after HTx. The rejection was refractory to repeated steroid pulse treatment, intravenous immunoglobulin administration, and intensifying immunosuppression including addition of everolimus. Eventually, she was successfully treated with repeated plasma exchange accompanied by a single administration of the anti-CD20 monoclonal antibody rituximab.