Occurrence of Fatal and Nonfatal Adverse Outcomes after Heart Transplantation in Patients with Pretransplant Noncytotoxic HLA Antibodies

Heart transplantation and anti-HLA antibodY: myocardial dysfunction and prognosis - HeartLAy study

AIMS

The presence of anti-human leucocyte antigen (HLA) antibodies has been implicated in a higher incidence of complications as well as mortality rate in heart transplantation. The aim of the study was to identify through non-invasive parameters early signs of myocardial dysfunction in the presence of anti-HLA antibodies but without evidence of antibody-mediated rejection (AMR) and its possible prognostic impact.

METHODS AND RESULTS

A total of 113 heart-transplanted patients without acute cellular rejection (ACR) and AMR or cardiac allograft vasculopathy (CAV) were prospectively enrolled and divided into two groups ['HLA+' (50 patients) and 'HLA-' (63 patients)], based on the presence of anti-HLA antibodies. Each patient was followed for 2 years after the enrolment, recording episodes of AMR, ACR, CAV, and mortality. Clinical characteristics were similar between the two groups. Among laboratory data, N-terminal pro-B-type natriuretic peptide and high-sensitivity cardiac troponin values were significantly higher in the presence of anti-HLA antibodies (P < 0.001 and P = 0.003, respectively). The echocardiographic parameters that showed a statistically significant difference between the two groups were deceleration time of E wave (DecT E, P < 0.001), left ventricular global longitudinal strain (P < 0.001), tricuspid annular plane systolic excursion (P = 0.011), tricuspid S' wave (P = 0.002), and free wall right ventricular longitudinal strain (fwRVLS, P = 0.027), whereas left atrial strain did not differ significantly (P = 0.408). Univariate analysis showed that anti-HLA antibodies were associated with the development of CAV at both 1 and 2 year follow-up [odds ratio (OR) 11.90, 95% confidence interval (CI) 1.43-90.79, P = 0.022 and OR 3.37, 95% CI 1.78-9.67, P = 0.024, respectively]. Bivariate analysis demonstrated that both fwRVLS and DecT E were predictors of CAV development independently from HLA status.

CONCLUSIONS

The presence of circulating anti-HLA antibodies is correlated with a mild cardiac dysfunction, even in the absence of AMR, and CAV development. Interestingly, reduced values of DecT E and fwRVLS were predictors of future development of CAV, independently from anti-HLA antibody.

Current Desensitization Strategies in Heart Transplantation

Heart transplant candidates sensitized to HLA antigens wait longer for transplant, are at increased risk of dying while waiting, and may not be listed at all. The increasing prevalence of HLA sensitization and limitations of current desensitization strategies underscore the urgent need for a more effective approach. In addition to pregnancy, prior transplant, and transfusions, patients with end-stage heart failure are burdened with unique factors placing them at risk for HLA sensitization. These include homograft material used for congenital heart disease repair and left ventricular assist devices (LVADs). Moreover, these risks are often stacked, forming a seemingly insurmountable barrier in some cases. While desensitization protocols are typically implemented uniformly, irrespective of the mode of sensitization, the heterogeneity in success and post-transplant outcomes argues for a more tailored approach. Achieving this will require progress in our understanding of the immunobiology underlying the innate and adaptive immune response to these varied allosensitizing exposures. Further attention to B cell activation, memory, and plasma cell differentiation is required to establish methods that durably abrogate the anti-HLA antibody response before and after transplant. The contribution of non-HLA antibodies to the net state of sensitization and the potential implications for graft longevity also remain to be comprehensively defined. The aim of this review is to first bring forth select issues unique to the sensitized heart transplant candidate. The current literature on desensitization in heart transplantation will then be summarized providing context within the immune response. Building on this, newer approaches with therapeutic potential will be discussed emphasizing the importance of not only addressing the short-term pathogenic consequences of circulating HLA antibodies, but also the need to modulate alloimmune memory.

Impact of pretransplant antibodies on outcomes after heart transplantation

Purpose of review

Since the discovery of human leukocyte antigen (HLA) in the 1950s, there has been great interest in the role of antibodies in posttransplant rejection. The development of the lymphocyte toxicity test by Terasaki et al. in the 1960s was the first step toward understanding the role of antibodies in posttransplant rejection.

Recent findings

Subsequently, various organs have been transplanted and improving posttransplant outcomes have become a focus of research. In particular, methods to measure antibodies that affect posttransplant outcomes, including anti-HLA antibodies, and methods to desensitize patients from specific antibodies have been explored. One recent method for measuring antibodies is called the solid-phase assay, which uses purified HLA fixed to microbeads. This assay does not use donor lymphocytes and allows clinicians to test the reactivity of patient serum against a panel of antibodies. It has also enabled the identification of specific anti-HLA antibodies using a single HLA.

Summary

In addition to advances in methods to measure and analyze anti-HLA antibodies, the clinical impact of non-HLA antibodies has also received much attention recently.

Sensitization in Heart Transplantation: Emerging Knowledge: A Scientific Statement From the American Heart Association

Sensitization, defined as the presence of circulating antibodies, presents challenges for heart transplant recipients and physicians. When present, sensitization can limit a transplantation candidate’s access to organs, prolong wait time, and, in some cases, exclude the candidate from heart transplantation altogether. The management of sensitization is not yet standardized, and current therapies have not yielded consistent results. Although current strategies involve antibody suppression and removal with intravenous immunoglobulin, plasmapheresis, and antibody therapy, newer strategies with more specific targets are being investigated.

Antibody-mediated rejection in heart transplantation: new developments and old uncertainties

PURPOSE OF REVIEW

Antibody-mediated rejection (AMR) currently represents one of the main problems for clinical management of heart transplant because of its diagnostic complexity and poor evidences supporting treatments.

RECENT FINDINGS

Disorder-based diagnosis is a cornerstone in defining AMR. The limitations of the current classification have been partially overcome by novel studies improving the description of the immune-pathological graft abnormalities, and by new molecular approaches allowing a better understanding of the mechanisms behind AMR and of its relationship with cellular rejection and chronic vasculopathy. In-depth characterization of donor-specific antibodies showed to provide additional prognostic information and guide for treatment. Clinical relevance of AMR is bound to appropriate detection of graft dysfunction. In addition to traditional longitudinal evaluation by echocardiogram, cardiac magnetic resonance and detection of cell-free DNA may represent novel sensitive markers for graft injury that could prompt treatment before dysfunction becomes clinically manifest.

SUMMARY

Despite improvements in the diagnostic process, therapeutic strategies made little progress in addition to the consolidation of practices supported by limited evidences. Novel complement inhibitors appear promising in changing this scenario. Nevertheless, collaborative multicenter studies are needed to develop standardized approaches tailored to the highly variable clinical and laboratory features of AMR.

Human Leukocyte Antigen Sensitization in Solid Organ Transplantation: A Primer on Terminology, Testing, and Clinical Significance for the Apheresis Practitioner

The human leukocyte antigen (HLA) system is an important immunologic barrier that must be considered for successful solid organ transplantation. Formation of donor-specific HLA antibodies in solid organ transplantation is an important cause of allograft injury and may contribute to recipient morbidity and mortality. Therapeutic plasma exchange is often requested to lower HLA antibody levels prior to or after transplantation and for management of HLA antibodies in the context of organ rejection. In this review, we summarize the current terminology, laboratory testing, and clinical significance of HLA sensitization in the solid organ transplant population. Furthermore, to illustrate applications of HLA testing in clinical practice, we summarize our own lung and kidney institutional protocols for managing HLA antibodies in the peri-transplant setting.

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.