Factors influencing HLA sensitization in implantable LVAD recipients

Polyinosinic: polycytidylic acid induced inflammation enhances while lipopolysaccharide diminishes alloimmunity to platelet transfusion in mice

Introduction

Alloimmune responses against platelet antigens, which dominantly target the major histocompatibility complex (MHC), can cause adverse reactions to subsequent platelet transfusions, platelet refractoriness, or rejection of future transplants. Platelet transfusion recipients include individuals experiencing severe bacterial or viral infections, and how their underlying health modulates platelet alloimmunity is not well understood.

Methods

This study investigated the effect of underlying inflammation on platelet alloimmunization by modelling viral-like inflammation with polyinosinic-polycytidylic acid (poly(I:C)) or gram-negative bacterial infection with lipopolysaccharide (LPS), hypothesizing that underlying inflammation enhances alloimmunization. Mice were pretreated with poly(I:C), LPS, or nothing, then transfused with non-leukoreduced or leukoreduced platelets. Alloantibodies and allogeneic MHC-specific B cell (allo-B cell) responses were evaluated two weeks later. Rare populations of allo-B cells were identified using MHC tetramers.

Results

Relative to platelet transfusion alone, prior exposure to poly(I:C) increased the alloantibody response to allogeneic platelet transfusion whereas prior exposure to LPS diminished responses. Prior exposure to poly(I:C) had equivalent, if not moderately diminished, allo-B cell responses relative to platelet transfusion alone and exhibited more robust allo-B cell memory development. Conversely, prior exposure to LPS resulted in diminished allo-B cell frequency, activation, antigen experience, and germinal center formation and altered memory B cell responses.

Discussion

In conclusion, not all inflammatory environments enhance bystander responses and prior inflammation mediated by LPS on gram-negative bacteria may in fact curtail platelet alloimmunization.

Enhanced alloresponse to platelet transfusion due to immune dysregulation following ablative chemotherapy in mice

Introduction

Alloimmunization is common following platelet transfusion and can result in negative outcomes for recipients such as refractoriness to subsequent transfusions and rejection of transplants. Healthy people do not receive blood transfusions, and the diseases and therapies that result in a need to transfuse have significant impacts on the immunological environment to which these alloantigens are introduced. Ablative chemotherapies are common among platelet recipients and have potent immunological effects. In this study, we modeled the impact of chemotherapy on the alloresponse to platelet transfusion. As chemotherapies are generally regarded as immunosuppressive, we hypothesized that that they would result in a diminished alloresponse.

Methods

Mice were given a combination chemotherapeutic treatment of cytarabine and doxorubicin followed by transfusion of allogeneic platelets, and compared to controls given no treatment, chemotherapy alone, or transfusion alone. Alloantibody responses were measured 2 weeks after transfusion, and cellular responses and growth factors were monitored over time.

Results

Contrary to our hypothesis, we found that chemotherapy led to increased alloantibody responses to allogeneic platelet transfusion. This enhanced response was antigen-specific and was associated with increased CD4+ and CD8+ T cell responses. Chemotherapy led to rapid lymphocyte depletion followed by reconstitution, non-specific activation of transitional B cells with the highest levels of activation in the least mature subsets, and increased serum levels of B cell activating factor (BAFF).

Conclusion

These data suggest that ablative chemotherapy can increase the risk of alloimmunization and, if confirmed clinically, that additional measures to protect these patient populations may be warranted.

Prospective examination of HLA sensitization after VAD implantation in children and adults

BACKGROUND

Ventricular assist devices (VADs) have improved survival to heart transplantation (HTx). However, VADs have been associated with development of antibodies against human leukocyte antigen (HLA-Ab) which may limit the donor pool and decrease survival post-HTx. Since HLA-Ab development after VAD insertion is poorly understood, the purpose of this prospective single-center study was to quantify the incidence of and evaluate risk factors for HLA-Ab development across the age spectrum following VAD implantation.

METHODS

Adult and pediatric patients undergoing VAD placement as bridge to transplant or transplant candidacy between 5/2016 and 7/2020 were enrolled. HLA-Ab were assessed pre-VAD and at 1-, 3-, and 12-months post-implant. Factors associated with HLA-Ab development post-VAD implant were explored using univariate and multivariate logistic regression.

RESULTS

15/41 (37%) adults and 7/17 (41%) children developed new HLA-Ab post-VAD. The majority of patients (19/22) developed HLA-Ab within two months of implant. New class I HLA-Ab were more common (87% adult, 86% pediatric). Prior pregnancy was strongly associated with HLA-Ab development in adults post-VAD (HR 16.7, 95% CI 1.8-158, p = 0.01). Of the patients who developed new HLA-Ab post-VAD, in 45% (10/22) the HLA-Ab resolved while in 55% (12/22) the HLA-Ab persisted.

CONCLUSION

More than one-third of adult and pediatric VAD patients developed new HLA-Ab early after VAD implant with the majority having class I antibodies. Prior pregnancy was strongly associated with post-VAD HLA-Ab development. Further studies are needed to predict regression or persistence of HLA-Ab developed post-VAD, to understand modulation of individuals' immune responses to sensitizing events, and to determine whether transiently detected HLA-Ab post-VAD recur and have long-term clinical impact post-heart transplantation.

Detection and management of HLA sensitization in candidates for adult heart transplantation

Heart transplantation (HT) remains the preferred therapy for patients with advanced heart failure. However, for sensitized HT candidates who have antibodies to human leukocyte antigens , finding a suitable donor can be challenging and can lead to adverse waitlist outcomes. In recent years, the number of sensitized patients awaiting HT has increased likely due to the use of durable and mechanical circulatory support as well as increasing number of candidates with underlying congenital heart disease. This State-of-the-Art review discusses the assessment of human leukocyte antigens antibodies, potential desensitization strategies including mechanisms of action and specific protocols, the approach to a potential donor including the use of complement-dependent cytotoxicity, flow cytometry, and virtual crossmatches, and peritransplant induction management.

Off-pump implantation of left ventricular assist device via minimally invasive left thoracotomy: Our single-center experience

Background

The aim of this study was to compare our experience of left ventricular assist device implantation via minimally invasive left thoracotomy with off-pump versus on-pump technique.

Methods

Between June 2013 and April 2020, nine patients (8 males, 1 female; mean age: 47±11.9 years; range, 30 to 61 years) who underwent off-pump left ventricular assist device implantation and nine patients (8 males, 1 female; mean age: 47±11.4 years; range, 29 to 60 years) who underwent on-pump minimally invasive left thoracotomy were retrospectively analyzed. Postoperative outcomes and mid-term results of both groups were evaluated.

Results

Outflow graft was anastomosed to the ascending aorta with J-sternotomy in all patients. The median duration of intubation and intensive care unit stay were one (IQR: 1.5) day and eight (IQR: 6.5) days in the off-pump group, respectively and one (IQR: 0) day and seven (IQR: 7) days in the on-pump group, respectively. Intra-aortic balloon pump was needed during the weaning of cardiopulmonary bypass in one (11%) of the patients in both groups. Postoperative right ventricular failure was observed in two (22%) patients in the offpump group who were treated medically and recovered. There was no need for revision due to bleeding or postoperative extracorporeal membrane oxygenator implantation in either group. In the off-pump group, three patients underwent heart transplantation after median 854 (IQR: 960) days. Three patients died one month, two and four years after implantation. Three patients were still alive with left ventricular assist device and were being uneventfully followed for 365, 400, and 700 days after implantation.

Conclusion

Off-pump technique is safe and feasible option for implantation of left ventricular assist device via minimally invasive left thoracotomy.

Elevated Plasma Immunoglobulin Levels Prior to Heart Transplantation Are Associated with Poor Post-Transplantation Survival

Cardiac allograft vasculopathy (CAV) and antibody-mediated rejection are immune-mediated, long-term complications that jeopardize graft survival after heart transplantation (HTx). Interestingly, increased plasma levels of immunoglobulins have been found in end-stage heart failure (HF) patients prior to HTx. In this study, we aimed to determine whether increased circulating immunoglobulin levels prior to transplantation are associated with poor post-HTx survival. Pre-and post-HTx plasma samples of 36 cardiac transplant recipient patients were used to determine circulating immunoglobulin levels. In addition, epicardial tissue was collected to determine immunoglobulin deposition in cardiac tissue and assess signs and severity of graft rejection. High levels of IgG1 and IgG2 prior to HTx were associated with a shorter survival post-HTx. Immunoglobulin deposition in cardiac tissue was significantly elevated in patients with a survival of less than 3 years. Patients with high plasma IgG levels pre-HTx also had significantly higher plasma levels after HTx. Furthermore, high pre-HTX levels of IgG1 and IgG2 levels were also significantly increased in patients with inflammatory infiltrate in CAV lesions. Altogether the results of this proof-of-concept study suggest that an activated immune response prior to transplantation negatively affects graft survival.

Post-Transplantation Early Blood Transfusion and Kidney Allograft Outcomes: A Single-Center Observational Study

The association between blood transfusion and the occurrence of de novo HLA donor specific antibodies (DSA) after kidney transplantation remains controversial. In this single-center observational study, we examined the association between early blood transfusion, i.e. before 1-month post-transplantation, and the risk of DSA occurrence, using Luminex based-methods. In total, 1,424 patients with a minimum of 1-month follow-up were evaluated between January 2007 and December 2018. During a median time of follow-up of 4.52 years, we observed 258 recipients who had at least one blood transfusion during the first month post-transplantation. At baseline, recipients in the transfused group were significant older, more sensitized against HLA class I and class II antibodies and had a higher 1-month serum creatinine. Cox proportional hazards regression analyses did not show any significant association between blood transfusion and the risk of de novo DSA occurrence (1.35 [0.86–2.11], p = 0.19), the risk of rejection (HR = 1.33 [0.94–1.89], p = 0.11), or the risk of graft loss (HR = 1.04 [0.73–1.50], p = 0.82). These data suggest then that blood transfusion may not be limited when required in the early phase of transplantation, and may not impact long-term outcomes.

De novo human leukocyte antigen allosensitization patterns in patients bridged to heart transplantation using left ventricular assist devices

INTRODUCTION

We examined the impact and time course of de novo human leukocyte antigen (HLA) allosensitization following left ventricular assist device (LVAD) implantation.

METHODS AND RESULTS

Forty patients had a calculated panel reactive antibody (cPRA) prior to LVAD surgery between January 2014 and December 2018. Of these patients, we retrospectively studied 33 patients who had pre-LVAD cPRA <10%. De novo allosensitization was defined as cPRA ≥10% within 3 months following LVAD surgery, and "persistent allosensitization" was defined as cPRA ≥10% at time of heart transplant or death. One-third (11/33) of our cohort developed de novo allosensitization within 3-months post-LVAD. Median duration of follow-up during LVAD support was 588 days (IQR 337-1071 days), or approximately 19 months. In an adjusted, multivariable analysis, female sex remained associated with de novo allosensitization (adjusted odds ratio [95%CI]: 11 (1.4-85), P = 0.026). De novo allosensitization was subsequently associated with persistent allosensitization (P = 0.024). Both axial-flow and centrifugal-flow LVADs had similar rates of allosensitization. Compared to those with no allosensitization, patients with de novo allosensitization did not appear to have inferior post-transplant outcomes of death or treated rejection.

CONCLUSION

In our single-center experience, one-third of patients developed de novo allosensitization which did not appear to associate with inferior post-transplant outcomes. Female sex was associated with de novo allosensitization.

De Novo Human Leukocyte Antigen Allosensitization in Heartmate 3 Versus Heartmate II Left Ventricular Assist Device Recipients

Left ventricular assist devices (LVADs) are associated with the development of antihuman leukocyte antigen (HLA) antibodies, which can create a challenge for future transplantation in these patients. The differential effects of Heartmate 3 (HM3) versus Heartmate II (HMII) on de novo HLA allosensitization remain unknown. Patients who underwent HMII or HM3 implantation and had no prior HLA antibodies by solid-phase assay (Luminex) testing were included in this study. Complement-dependent cytotoxicity (CDC) panel reactive antibody (PRA) levels and Luminex antibody profiles were followed until cardiac transplantation, device explantation, or death. Electronic medical records were reviewed to examine posttransplant outcomes. Thirty-eight HM3 and 34 HMII patients with complete data were followed for 1.5 ± 1.1 years on device support. HM3 and HMII groups had similar age at implant, female gender, ischemic heart failure etiology, bridge strategy at implant, as well as intraoperative and postoperative transfusion requirements. 39.5% of HM3 and 47.1% of HMII patients developed detectable HLA antibodies by Luminex testing (p = 0.516). Development of high-level (mean fluorescence intensity >10,000) antibodies was significantly lower in HM3 than HMII patients (5.3 vs. 20.6%, p = 0.049). CDC PRA testing showed fewer HM3 patients with a positive result (PRA > 0%) than HMII patients (39.4 vs. 70.0%, p = 0.015). Among transplanted patients, those who had developed de novo sensitization on LVAD support showed a trend toward incidence of moderate to severe grade rejection compared with unsensitized patients (23.8 vs. 4.8%, p = 0.078). HM3 is associated with lower risk of de novo HLA sensitization compared with HMII.

The effect of paracorporeal pulsatile biventricular assist devices on allosensitization in adults: A comparison with left ventricular assist devices

Ventricular assist devices (VADs) have been associated with the development of anti-HLA antibodies ('allosensitization'), but data on devices providing biventricular support in adults are limited. We sought to characterize differences in anti-HLA antibody formation in adult patients receiving left- (LVAD) versus biventricular- (BiVAD) assist devices as bridge to transplantation (BTT) by retrospectively reviewing the records of adult patients who have undergone VAD implantation at our institution. We assessed 82 patients supported with a pulsatile-flow paracorporeal BiVAD and compared them with 40 patients receiving LVAD till 2018. Forty-eight (58.5%) of the BiVAD and 23 (57.5%) of the LVAD patients were eventually transplanted (p = 0.91) with an average time to transplantation 559 and 598 days, respectively (p = 0.73). Evidence of sensitization pre-VAD was found in 11.0% of the BiVAD patients and 15.0% of the LVAD ones (p = 0.53); these percentages rose to 43.9% (p < 0.001) and 40.0% (p = 0.01), respectively. The post-VAD sensitization status was not significantly different between the BiVAD and the LVAD group (p = 0.68). De novo sensitization was comparable between the two groups (p = 0.55). Post-transplantation outcomes regarding rejections and cardiac allograft vasculopathy were also similar. Conclusively, BiVAD- and LVAD- induced allosensitization do not appear to differ significantly.

Treatment of donor-specific antibody-mediated rejection after heart transplantation by IgM-enriched human immunoglobulin

Antibody‐mediated graft rejection caused by donor‐specific antibodies (DSA‐MR) remains a serious problem after heart transplantation (HTx). IgM‐enriched human intravenous immunoglobulin (IGM‐IVIG) consists of 76% IgG, 12% IgM, and 12% IgA and provides a new multifactorial approach for DSA‐MR. Between 2017 and 2020, four (P1–4) of 102 patients developed DSA‐MR after HTx in our department and were repetitively treated with IGM‐IVIG in combination with anti‐thymocyte globulin. While in P1 and P4, DSA‐MR occurred within the early post‐operative interval, P2 and P3 developed DSA‐MR approximately 1 year after transplantation. An impairment of ventricular function was observed in three of four patients. Furthermore, P1 and P4 suffered from malign ventricular arrhythmias. After the application of IGM‐IVIG, the ventricular function recovered, and all patients could be discharged from the hospital. As part of a multifactorial therapeutic approach, treatment with IGM‐IVIG seems to be a safe and effective strategy to address DSA‐MR.

Outcome of desensitization in human leukocyte antigen and ABO incompatible living donor kidney transplantation: Single center experience of first 200 incompatible transplants

BACKGROUND AND AIMS

Although desensitization is well established, concerns about graft outcome, patient survival and rejection still exist. The present study aims at comparing outcomes of renal transplant recipients across simultaneous ABO and human leukocyte antigen (HLA) incompatibility barriers to those with ABO or HLA incompatibility alone.

MATERIALS AND METHODS

This was a retrospective study conducted from October 2015 to December 2018. All patients with a clinical diagnosis of chronic kidney disease, who were prospective HLA incompatible (HLAi) and/or ABO incompatible (ABOi) renal transplant recipients were included. A total of 400 cases including 36 ABOi transplants, 154 HLAi transplants, 10 simultaneously ABO and HLA incompatible transplants, and 200 ABO (ABOc) and HLA (HLAc) compatible kidney transplants from living donors were included.

RESULTS

There were significantly more number of blood transfusions, previous transplants and pregnancies in HLAi transplant recipients relative to the ABOi or the control group. Mean number of therapeutic plasma exchange procedures per patient and mean plasma volume processed per procedure were slightly higher in the ABOi + HLAi category. The incidence of graft dysfunction due to suspected antibody-mediated rejection during first year was highest in the ABOi + HLAi group, followed by ABOc + HLAi and ABOi + HLAc, lowest in the ABOc + HLAc category. Mean time to first episode of graft dysfunction was significantly shorter with incompatible transplants. There were no kidney transplant recipient deaths in the study.

CONCLUSION

Patient outcome and graft outcomes observed with incompatible transplants were not worse than those observed with compatible transplants.

Noninvasive biomarkers for prediction and diagnosis of heart transplantation rejection

For most patients with end-stage heart failure, heart transplantation is the treatment of choice. Allograft rejection is one of the major post-transplantation complications affecting graft outcome and survival. Recent advancements in science and technology offer an opportunity to integrate genomic and other omics-based biomarkers into clinical practice, facilitating noninvasive evaluation of allograft for diagnostic and prognostic purposes. Omics, including gene expression profiling (GEP) of blood immune cell components and donor-derived cell-free DNA (dd-cfDNA) are of special interest to researchers. Several studies have investigated levels of dd-cfDNA and miroRNAs in blood as potential markers for early detection of allograft rejection. One of the achievements in the field of transcriptomics is AlloMap, GEP of peripheral blood mononuclear cells (PBMC), which can identify 11 differentially expressed genes and help with detection of moderate and severe acute cellular rejection in stable heart transplant recipients. In recent years, the utilization of GEP of PBMC for identifying differentially expressed genes to diagnose acute antibody-mediated rejection and cardiac allograft vasculopathy has yielded promising results. Advancements in the field of metabolomics and proteomics as well as their potential implications have been further discussed in this paper.

The meaning of donor-specific antibodies after heart transplant

PURPOSE OF REVIEW

Antibody-mediated rejection (AMR) is a major contributor of impaired long-term survival after heart transplantation (HTx). The presence of circulating donor-specific antihuman leukocyte antigen (HLA) antibodies (DSAs) is considered as a mandatory criterion for AMR after HTx. DSA are known prognostic biomarkers of outcome, for example, recipients with de-novo DSA have a three-fold increased risk of mortality.

RECENT FINDINGS

Although the awareness of the impact and prognosis of DSA on the survival has been increased in the HTx community over the last decade, the management of DSA pre and posttransplant varies among centers and is mainly based on the experience of transplant physicians. Thus, firm consensus strategies for each HTx recipient should be established by a center advisory board of experts in the field of HLA genetics, transplantation immunology, and HTx to evaluate the immunological risk preoperatively and also continuously during the posttransplant course. Consequently, the recent advances of invasive and noninvasive diagnostic tools should be applied, according to the risk, laboratory findings, and clinical events of the recipient. Such individual strategy will result in tailored therapeutic options.

SUMMARY

Novel standards for the management of DSA in HTx recipients on the basis of an interdisciplinary approach of experts will improve diagnostics for personalized medicine.

Factors influencing transfusion-associated HLA sensitization in patients bridged to heart transplantation using ventricular assist device

BACKGROUND

Bridging heart failure patients with mechanical ventricular assist devices (VAD) enables access to transplantation. However, VAD is associated with increased risk for anti-HLA antibodies associated with rejection of subsequent allografts. Factors determining alloantibody formation in these patients remain undefined.

METHODS

We performed a single-center retrospective cohort study of 164 patients undergoing heart transplantation from 2014 to 2017. Medical records including use of VAD, transfused blood products, anti-HLA antibody testing, crossmatch, and time to transplant were evaluated.

RESULTS

Patients received an average of 13.8 red blood cell and 1.9 single-donor platelet units associated with VAD. There was a 28.7% increase in the incidence of anti-HLA antibodies after VAD. Development of anti-HLA antibodies did not correlate with volume or type of blood products, but with pre-VAD HLA sensitization status; relative risk of new alloantibodies in patients with pre-VAD antibodies was 3.5-fold higher than those without prior antibodies (P = .008). Development of new anti-HLA antibodies was associated with an increased time to transplant (169 vs 330 days, P = .013).

CONCLUSIONS

Our findings indicate that the presence of anti-HLA antibodies pre-VAD was the most significant risk factor for developing additional antibodies post-VAD, suggesting that a subset of patients may be predisposed to alloantibody formation.

Pathogen reduction with riboflavin and ultraviolet light induces a quasi-apoptotic state in blood leukocytes

BACKGROUND

Alloimmunization to platelet-rich plasma (PRP) transfusions can cause adverse reactions such as platelet refractoriness or transplant rejection. Pathogen reduction treatment with ultraviolet light and riboflavin (UV + R) of allogeneic PRP was shown to reduce allogeneic antibody responses and confer partial antigen-specific immune tolerance to subsequent transfusions in mice. Studies have shown that UV + R was effective at both rapidly killing donor white blood cells (WBCs) and reducing their ability to stimulate an allogeneic response in vitro. However, the manner in which UV + R induces WBC death and its associated role in the immune response to treated PRP is unknown.

METHODS AND MATERIALS

This study evaluates whether UV + R causes WBC apoptosis by examining phosphatidylserine exposure on the plasma membrane, membrane asymmetry, caspase activity, and chromatin condensation by flow cytometry. The immunogenicity of WBCs killed with UV + R versus apoptotic or necrotic pathways was also examined in vivo.

RESULTS

WBCs after UV + R exhibited early apoptotic-like characteristics including phosphatidylserine exposure on the outer leaflet of the plasma membrane and loss of membrane asymmetry, but unlike canonical apoptotic cells, caspase activity and chromatin condensation were not apparent. However, in vivo studies demonstrated, unlike untreated or necrotic WBCs, both apoptotic WBCs and UV + R-treated WBCs failed to prime alloantibody responses to subsequent untreated transfusions.

CONCLUSION

Overall, the mechanism of WBC death following UV + R treatment shares some membrane characteristics of early apoptosis but is distinct from classic apoptosis. Despite these differences, UV + R-treated and apoptotic WBCs both offer some protection from alloimmunization.

Excellent outcome after desensitization in high immunologic risk kidney transplantation

Introduction

HLA-incompatible (HLAi) and ABO-incompatible (ABOi) kidney transplantation (KT) has been on the increase over the last decade. However, there are wide variations in outcomes from these procedures. In this study we evaluated the graft and patient outcomes in incompatible KT and non-sensitized KT.

Methods

Patients who underwent KT between January 2012 and April 2018 were enrolled and reviewed. We divided kidney transplant recipients (KTRs) into five groups as follows: HLAi (n = 50); ABOi (n = 65); HLAi+ABOi (n = 5); control (n = 428); and living-donor control (LD control, n = 218). We compared the risk of rejection, graft function, graft survival, and patient survival between incompatible KTRs and control/LD control KTRs.

Results

Although the incidence of active antibody-mediated rejection in HLAi group tends to be higher than in control and LD control groups (6.0% vs. 2.8%, P = 0.20; 6.0% vs. 3.7%, P = 0.44, respectively), the rejection-free survival, graft survival, and patient survival were not significantly different from those of the control and LD control groups in all three incompatible KT groups (all P>0.05). Graft function during the study period was also not different between incompatible KTRs and control/LD control groups (both P>0.05). Using Cox regression analysis, neither HLAi nor ABOi were risk factors for graft failure. Some infectious diseases such as urinary tract infection and cytomegalovirus infection were more common in the HLAi group than in the control/LD control group (both P<0.05), but only one infection-related death occurred in HLAi KTRs. Infection risks were similar in the ABOi and HLAi+ABOi groups compared to controls.

Conclusion

Our results showed favorable outcomes for incompatible KT after desensitization. Although desensitization therapy for incompatible KT has improved access to transplantation for KT candidates with high immunological risk, more clinical data are clearly needed.

Predicting Transfusions During Left Ventricular Assist Device Implant

Perioperative bleeding and transfusion cause morbidity and mortality in patients receiving left ventricular assist devices (LVADs). We assessed factors associated with transfusions within 30 days of durable LVAD implantation and the clinical outcomes associated with transfusions. A retrospective cohort study of patients undergoing initial durable LVAD implantation between 2014 and 2016 was performed. Rates of packed red blood cell (PRBC) or other blood product transfusions (platelets or fresh frozen plasma) were assessed. Ordinal multivariable regression analysis was performed to determine factors independently associated with transfusion. Analysis included 156 patients, mean age 54.6 years and 74.4% male, who received a mean of 11.7 units of PRBC and 10.0 units of other products within 30 days. Preimplant mechanical ventilation, dialysis, higher INR, previous sternotomy, higher model for end-stage liver disease score, and lower hemoglobin were associated with increased PRBC transfusion rates. Higher preoperative central venous pressure, mechanical ventilation, concomitant surgical procedures, previous sternotomy, and lower hemoglobin were associated with increased PRBC transfusion rates within 48 hours of implant (adjusted odds ratio [OR] 1.46, P = 0.013 per 5 mm Hg). There were no significant associations with ferritin (adjusted OR 1.00, P = 0.236) or transferrin saturation (adjusted OR 1.17, P = 0.068). Transfusions were associated with an increase in ventilation duration, intensive care unit length of stay, reoperation for bleeding, and all-cause mortality. In patients undergoing LVAD implantation, perioperative blood product exposure is common and associated with increased morbidity and mortality. Elevated central venous pressure and anemia are potentially modifiable factors associated with increased early PRBC transfusion rates.

Sex differences in preformed panel-reactive antibody levels and outcomes in patients undergoing heart transplantation

BACKGROUND

Sex differences in panel-reactive antibody (PRA) levels in heart transplant recipients and their association with transplant-related outcomes are mostly unknown.

METHODS

In 20 181 (24.7% women) first-time heart transplant recipients included from July 2004 to March 2015 in the prospective Organ Procurement and Transplantation Network (OPTN), we studied sex differences in most recent (mr) and peak (p)PRA and outcomes (graft failure, rejection, cardiac allograft vasculopathy [CAV], retransplantation, and mortality). Median follow-up (all-cause mortality) was 6 years. Analyses are based on OPTN data (March 6, 2017).

RESULTS

MrPRA levels were associated with all-cause mortality (hazard ratio, 95% confidence interval: class I 1.03, 1.01-1.04, P < 0.001) and acute rejection (class II 1.08, 1.03-1.14, P = 0.0044). PPRA levels were associated with all-cause mortality (class I 1.02, 1.00-1.04, P = 0.015) and CAV (class II 1.03, 1.01-1.06, P = 0.020). Sex interactions were seen for the association of pPRA and graft failure with a higher risk in women, and for pPRA and CAV with a higher risk in men.

CONCLUSIONS

PRA were associated with different transplant-related outcomes in both sexes. However, women with elevated pPRA were shown to be at higher risk for graft failure, whereas higher levels of pPRA were more hazardous for men in developing CAV.

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.

New insights on innate B-cell immunity in transplantation

Innate B cells and natural antibodies (Nabs) have been extensively studied in normal physiological conditions as well as in several diseases. However, their significance in the context of ABO-compatible solid organ transplantation is only emerging. This review summarizes recent studies exploring these often neglected innate immune elements in situations related to sensitization and clinical graft rejection. A focus is placed on class-switched IgG Nabs that develop amidst inflammation, rather than IgM Nabs abundant at the steady state, as new evidence point to their implication in serum reactivity to HLA and kidney graft failure. The involvement of innate B cells in the pathophysiology of CAV is also presented. Lastly, we discuss key questions that need answering to understand whether and how innate B-cell immunity contributes to the outcome of solid organ transplantation.

Clinical outcomes of ABO- and HLA-incompatible kidney transplantation: a nationwide cohort study

This was a nationwide cohort study to investigate the impact of anti-A/B and donor-specific anti-HLA (HLA-DSA) antibodies on the clinical outcomes in kidney transplant recipients (KTRs). We classified a total of 1964 KTRs into four groups: transplants from ABO-incompatible donors (ABOi, n = 248); transplants in recipients with HLA-DSA (HLAi, n = 144); transplants from combined ABOi and HLAi donors (ABOi + HLAi, n = 31); and a control group for whom neither ABOi nor HLAi was applicable (CONT, n = 1541). We compared the incidence of biopsy-proven acute rejection (BPAR), allograft and patient survival rates. The incidence of BPAR was higher in the HLAi and ABOi + HLAi groups relative to the CONT group; in contrast, it was not higher in the ABOi group. Death-censored graft survival rates did not differ across the four groups. However, relative to the CONT group, patient survival rate was reduced in the ABOi and ABOi + HLAi groups, and with infection being the most common cause of death. Further, multivariable analysis revealed that desensitization therapy because of ABOi or HLAi was independent risk factors for patient mortality. HLAi was a more important risk factor for BPAR compared with ABOi. However, pretransplant desensitization therapy for either ABOi or HLAi significantly increased the risk of infection-related mortality.

Do Prior Driveline Infections Increase the Risk of Infection in Heart Transplant Patients Treated With Rabbit Antithymocyte Globulin Induction Therapy?

BACKGROUND

The use of mechanical circulatory support devices (MCSDs) has been increasing over the past several years. Driveline infections (DLIs) are one of the most common complications seen in these patients; reportedly, up to 50% of patients with MCSDs can develop this complication. It is believed that the removal of the driveline results in treatment of the localized infection area. MCSD patients are also known to develop circulating antibodies. These circulating antibodies have been associated with poor outcomes after heart transplantation. The use of rabbit antithymocyte globulin (ATG) as induction therapy reportedly decreases the development of circulating antibodies; it is now commonly used in sensitized patients undergoing heart transplantation. It is unknown whether ATG induction therapy immediate posttransplant will increase the risk of infection of those MCSD patients with DLIs.

METHODS

Between 2003 and 2013, we evaluated 57 MCSD patients who subsequently underwent heart transplantation and received ATG induction therapy. Patients were divided into those with previous MCSD DLI and those without, and they were assessed for 1-year freedom from infection (specifically, sternal wound infections). One-year survival and freedom from treated rejection, both cellular and antibody mediated, were also assessed.

RESULTS

MCSD patients with DLIs who received ATG induction did not have a lower freedom from any treated infection and from sternal wound infection posttransplant compared with those MCSD patients without DLIs and not treated with ATG induction. There were also no significant differences between the 2 groups in terms of 1-year posttransplant survival and freedom from treated rejection.

CONCLUSIONS

The use of ATG induction in patients with prior DLIs did not seem to increase the risk for posttransplant infection (eg, sternal wound infection). ATG induction can therefore be safely used in this population.

Ventricular assist device elicits serum natural IgG that correlates with the development of primary graft dysfunction following heart transplantation

BACKGROUND

Pre-transplant sensitization is a limiting factor in solid-organ transplantation. In heart transplants, ventricular assist device (VAD) implantation has been associated with sensitization to human leukocyte antigens (HLA). The effect of VAD on non-HLA antibodies is unclear. We have previously shown that polyreactive natural antibodies (Nabs) contribute to pre-sensitization in kidney allograft recipients. Here we assessed generation of Nabs after VAD implantation in pre-transplant sera and examined their contribution to cardiac allograft outcome.

METHODS

IgM and IgG Nabs were tested in pre-transplant serum samples collected from 206 orthotopic heart transplant recipients, including 128 patients with VAD (VAD patients) and 78 patients without VAD (no-VAD patients). Nabs were assessed by testing serum reactivity to apoptotic cells by flow cytometry and to the generic oxidized epitope, malondialdehyde, by enzyme-linked immunosorbent assay.

RESULTS

No difference was observed in serum levels of IgM Nabs between VAD and no-VAD patients. However, serum IgG Nabs levels were significantly increased in VAD compared with no-VAD patients. This increase was likely due to the presence of the VAD, as revealed by lower serum IgG Nabs levels before implantation. Elevated pre-transplant IgG Nabs level was associated with development of primary graft dysfunction (PGD).

CONCLUSIONS

Our study demonstrates that VAD support elicits IgG Nabs reactive to apoptotic cells and oxidized epitopes. These findings further support broad and non-specific B-cell activation by VAD, resulting in IgG sensitization. Moreover, the association of serum IgG Nabs levels with development of PGD suggests a possible role for these antibodies in the inflammatory reaction accompanying this complication.

Reduced MHC alloimmunization and partial tolerance protection with pathogen reduction of whole blood

BACKGROUND

Allogeneic blood transfusion can result in an immune response against major histocompatibility complex (MHC) antigens, potentially complicating future transfusions or transplants. We previously demonstrated that pathogen reduction of platelet-rich plasma (PRP) with riboflavin and ultraviolet light (UV+R) can prevent alloimmunization in mice. A similar pathogen-reduction treatment is currently under development for the treatment of whole blood using riboflavin and a higher dose of UV light. We sought to determine the effectiveness of this treatment in the prevention of alloimmunization.

STUDY DESIGN AND METHODS

BALB/cJ mice were transfused with untreated or UV+R-treated, allogeneic C57Bl/6J whole blood with or without leukoreduction. Mice were evaluated for donor-specific antibodies, ex vivo splenocyte cytokine responses, and changes in the frequency of regulatory T (T_reg ) cells.

RESULTS

UV+R treatment blocked cytokine priming and reduced anti-MHC alloantibody responses to transfused whole blood. Leukoreduction reduced alloantibody levels in both the untreated and UV+R-treated groups. Mice transfused with UV+R-treated whole blood had reduced alloantibody and cytokine responses when subsequently transfused with untreated blood from the same donor type. This reduction in responses was not associated with increased T_reg cells.

CONCLUSIONS

Pathogen reduction of whole blood with UV+R significantly reduces, but does not eliminate, the alloimmune response. Exposure to UV+R-treated whole blood transfusion does appear to induce tolerance to alloantigens, resulting in reduced anti-MHC alloantibody and cytokine responses to subsequent exposures to the same alloantigens. This tolerance does not appear to be driven by an increase in T_reg cells.

Current Expectations for Cardiac Transplantation in Patients With Congenital Heart Disease

Congenital heart disease accounts for 40% of pediatric heart transplants and presents unique challenges to the transplant team. Suitability for transplantation is defined in part by degree of sensitization, pulmonary vascular resistance, and hepatic reserves. The incremental transplant risk for patients with congenital heart disease occurs within the first 3 months, after which survival is equivalent to transplantation for cardiomyopathy. Single ventricle with prior palliation, and especially the failing Fontan, carry the highest risk for transplantation and are least amenable to bridging with mechanical circulatory support. More effective bridging to transplant with mechanical circulatory support will require improvements in the adverse event profile of available pumps and the introduction of miniaturized continuous flow technology. The major barriers to routine long-term survival are chronic allograft failure and allograft vasculopathy. Despite these many challenges, continuing improvements in the care of pediatric heart transplant patients have pushed the median posttransplant survival past 15 years for children and to 20 years for infants.

Mechanical Circulatory Support in Children

The field of pediatric mechanical circulatory support has undergone a significant evolution with the advent of devices designed for children and the implementation of new strategies for deployment. With the ongoing shortage of organs the demand for new devices specifically designed for children will only increase. This review discusses the evolution of mechanical circulatory support, available devices, and the implementation of new strategies for their deployment.

Heart Transplantation

Although the number of available donor hearts severely limits the epidemiologic impact of heart transplantation on patients with heart failure, patients with end-stage heart failure unresponsive to medical management currently have no other viable alternatives. Destination therapy with a ventricular assist device is the closest toward approaching clinical reality but has been plagued with problems of infection and stroke. The purpose of this review is to summarize recent developments in the field that may broaden the clinical impact of heart transplantation. For example, novel methods of cardiac preservation are being designed to safely evaluate and utilize “extended criteria” donors. Surgical techniques and medical management have reduced the incidence of postoperative right heart failure, and immunosuppressive regimens promise to limit chronic graft vascular disease.

The impact of Angiotensin II Type 1 Receptor antibodies on morbidity and mortality in Heart Mate II supported recipients

AIMS

One of the proposed limitations of left ventricular assist device (LVAD) therapy is high degree of sensitization. Apart from human leukocyte antigen (HLA), antibodies against Angiotensin II Type 1 Receptor (AT1R) have been associated with adverse outcomes. The purpose of this study was to compare complications and survival of anti - AT1R positive versus negative Heart Mate II (HMII) recipients.

METHODS

Altogether 96 patients received HMII at our institution between 2008 and 2012. These were stratified into three groups: antibody positive before implantation (AT1R+), antibody conversion during support (AT1R-/+) and patients who remained antibody negative (AT1R-). Survival, major on-device adverse events and post-transplant rejections were assessed with Kaplan-Meier and log-rank tests.

RESULTS

Two year on-device and overall survival was 78 ± 12% and 75 ± 10% in AT1R-, 60 ± 23% and 60 ± 15% in AT1R+ and 92 ± 6% and 87 ± 5% in AT1R-/+ group (P = 0.409, P = 0.185). Freedom from major adverse event at two years for AT1R-, AT1R+ and AT1R-/+ was 49 ± 14%, 53 ± 16% and 41 ± 11% (P = 0.875). Freedom from rejection was 63 ± 17% in patients who were both anti-AT1R and HLA negative and 65 ± 13% in those who were antibody positive (P = 0.788).

CONCLUSION

Patients who were anti-AT1R antibody positive had similar on-device survival and rate of complications in comparison to those who were antibody negative. In transplanted patients, there were no differences in the overall survival and rejection between the groups.

C1q-binding anti-HLA antibodies do not predict platelet transfusion failure in Trial to Reduce Alloimmunization to Platelets study participants

BACKGROUND

In the Trial to Reduce Alloimmunization to Platelets (TRAP) study, 101 of 530 subjects became clinically refractory (CR) to platelets (PLTs) without lymphocytotoxicity assay (LCA)-detectable anti-HLA antibodies. The LCA only detects complement-binding antibodies and is less sensitive than newer assays. Utilizing a more sensitive bead-based assay that does not distinguish between complement-binding versus non-complement-binding antibodies, we have previously shown that while many LCA-negative (LCA-) patients do have anti-HLA antibodies, these low- to moderate-level antibodies do not predict refractoriness. As complement can contribute to PLT rejection, we assessed if previously undetected complement-binding antibodies account for refractoriness among LCA- patients.

STUDY DESIGN AND METHODS

Samples from 169 LCA- (69 CR, 100 non-CR) and 20 LCA-positive (LCA+; 10 CR, 10 non-CR) subjects were selected from the TRAP study serum repository. Anti-Class I HLA immunoglobulin (Ig)G and C1q-binding antibodies were measured in serum or plasma with bead-based detection assays. Levels of C1q-binding antibodies were compared between CR and non-CR subjects and correlated with corrected count increments (CCIs).

RESULTS

While some of the LCA- subjects had detectable C1q-binding anti-Class I HLA antibodies, and some LCA+ subjects did not, levels were significantly higher among LCA+ subjects. C1q-binding anti-Class I HLA antibody levels did not differ significantly between CR and non-CR among either the LCA- or the LCA+ subjects. Furthermore, there was no significant correlation observed between CCIs and either C1q-binding or any anti-HLA IgG antibodies.

CONCLUSIONS

This work confirms that low- to moderate-level anti-Class I antibodies do not drive PLT rejection, suggesting a role for antibody-independent mechanisms.

Reduced alloimmunization in mice following repeated transfusion with pathogen-reduced platelets

BACKGROUND

Allogeneic transfusion can result in alloimmunization, leading to platelet (PLT) refractoriness and rejection of solid organ transplants. Previously we demonstrated that pathogen reduction using UV light and riboflavin (UV + R) eliminates the immunogenicity of white blood cells (WBCs) in vitro, blocks alloimmunization from transfusion in mice, and results in reduced ex vivo cytokine responses to subsequent untreated transfusions. We sought to determine if repeated transfusion with pathogen-reduced PLT-rich plasma (PRP) would eventually cause breakthrough alloimmunization or enhanced tolerance.

STUDY DESIGN AND METHODS

BALB/cJ mice were transfused weekly for 2, 4, or 8 weeks with C57Bl/6J PRP that was either untreated or pathogen reduced with UV + R and leukoreduced or not. Alloimmunization was determined by measuring donor antibody levels, ex vivo cytokine responses, and 24-hour donor PLT recovery. The role of donor antibodies in PLT refractoriness was also assessed by transfer of diluted immune sera into naïve recipients.

RESULTS

Donor antibody levels increased with the number of transfusions, but levels were significantly reduced using either UV + R or leukoreduction, and combining UV + R and leukoreduction gave the best protection. Priming of ex vivo cytokine responses required WBCs and remained suppressed with repeated UV + R-treated transfusion. PLT recovery was reduced with UV + R in naïve mice, and multiply transfused mice had poor PLT recovery even when antibody levels were relatively low. Approximately 1/100 dose of serum from a multiply transfused mouse was sufficient for complete rejection of donor PLTs.

CONCLUSIONS

Pathogen reduction significantly reduces alloimmunization in repeatedly transfused mice and combined with leukoreduction provides a high level of protection from alloimmunization.

Pediatric mechanical circulatory support: available devices and outcomes as bridge-to-transplant therapy

PURPOSE OF REVIEW

The use of mechanical circulatory support in children has increased dramatically over the current decade. A review of the pediatric ventricular assist device (VAD) literature is timely and relevant in order to improve outcomes and refine patient selection as new devices become available and current VADs are used in smaller patients.

RECENT FINDINGS

Outcomes of pediatric patients bridged to transplant with VAD therapy continue to improve. Patient selection in children continues to be complex as size and anatomy make decision-making unique from the adult practice. In addition, device selection and surgical planning are evolving in children. The use of temporary devices for long-term use is an example of an innovative application of current technology. Sensitization and adverse events are important issues that are necessary to understand in order to improve outcomes. The importance of a national registry to help monitor patient outcomes is critical to assessing this highly technological therapy.

SUMMARY

There are many implications of improving and expanding durable device use in children. VAD therapy is evolving as a standard of care as a bridge to transplant in children. Continued surveillance of outcomes is critical to improving patient selection and decreasing adverse events in children with advanced heart failure.

False-positive hepatitis C virus serology after placement of a ventricular assistance device

BACKGROUND

Ventricular assist devices (VADs) have been associated with immune activation and sensitization. We observed several cases of false-positive (FP) hepatitis C virus (HCV) antibody (Ab) tests in patients being evaluated for orthotopic heart transplant (OHT), prompting us to investigate this further.

METHODS

We reviewed all VAD and OHT cases at Johns Hopkins from 2005 to 2012. FP HCV serology was defined as an equivocal or low-positive HCV Ab, plus either (i) a negative recombinant immunoblot (RIBA) and/or HCV nucleic acid test (NAT), or (ii) an indeterminate RIBA and negative NAT.

RESULTS

In 53 patients with available HCV testing, nearly 40% of patients (21/53: 39.6%) developed FP HCV Ab tests after VAD placement: 4 patients had negative NAT, 12 had negative RIBA, and 5 had an indeterminate RIBA and negative NAT. All patients with indeterminate RIBA tests had isolated reactivity to the same HCV protein, c100p/5-1-1p (NS4b protein). In 3 of 4 VAD patients who had OHT and repeat HCV Ab testing after VAD removal, repeat HCV Ab was negative (699-947 days after OHT); in 1 case, FP HCV serology persisted (5 days after OHT). Thirteen patients had OHT alone and none developed a FP HCV Ab.

CONCLUSIONS

FP HCV Ab results following VAD placement are very common. Reversal of FP serology in several patients after VAD removal is suggestive of a possible association with the VAD hardware. Clinicians should be aware of this phenomenon, as it could lead to delays in determining eligibility for OHT and increased costs.

Ventricular assist devices and increased blood product utilization for cardiac transplantation

BACKGROUND AND AIM OF STUDY

The purpose of this study was to examine whether blood product utilization, one-year cell-mediated rejection rates, and mid-term survival significantly differ for ventricular assist device (VAD patients compared to non-VAD (NVAD) patients following cardiac transplantation.

METHODS

From July 2004 to August 2011, 79 patients underwent cardiac transplantation at a single institution. Following exclusion of patients bridged to transplantation with VADs other than the HeartMate II® LVAD (n = 10), patients were stratified by VAD presence at transplantation: VAD patients (n = 35, age: 54.0 [48.0-59.0] years) vs. NVAD patients (n = 34, age: 52.5 [42.8-59.3] years). The primary outcomes of interest were blood product transfusion requirements, one-year cell-mediated rejection rates, and mid-term survival post-transplantation.

RESULTS

Preoperative patient characteristics were similar for VAD and NVAD patients. NVAD patients presented with higher median preoperative creatinine levels compared to VAD patients (1.3 [1.1-1.6] vs. 1.1 [0.9-1.4], p = 0.004). VAD patients accrued higher intraoperative transfusion of all blood products (all p ≤ 0.001) compared to NVAD patients. The incidence of clinically significant cell-mediated rejection within the first posttransplant year was higher in VAD compared to NVAD patients (66.7% vs. 33.3%, p = 0.02). During a median follow-up period of 3.2 (2.0, 6.3) years, VAD patients demonstrated an increased postoperative mortality that did not reach statistical significance (20.0% vs. 8.8%, p = 0.20).

CONCLUSIONS

During the initial era as a bridge to transplantation, the HeartMate II® LVAD significantly increased blood product utilization and one-year cell-mediated rejection rates for cardiac transplantation. Further study is warranted to optimize anticoagulation strategies and to define causal relationships between these factors for the current era of cardiac transplantation.

How do we manage cardiopulmonary bypass coagulopathy?

BACKGROUND

Patients who undergo cardiopulmonary bypass (CPB) are at risk for coagulopathy. Suboptimal turnaround time (TAT) of laboratory coagulation testing results in empiric administration of blood products to treat massive bleeding. We describe our initiative in establishing the coagulation-based hemotherapy (CBH) service, a clinical pathology consultation service that uses rapid TAT coagulation testing and provides comprehensive assessment of bleeding in patients undergoing CPB. A transfusion algorithm that treats the underlying cause of coagulopathy was developed.

STUDY DESIGN AND METHODS

The coagulation testing menu includes all aspects of coagulopathy with close proximity of the laboratory to the operating room to allow for rapid test results. The hemotherapy pathologist monitors laboratory results at several stages in surgery and uses a comprehensive algorithm to monitor a patient's hemostasis. The optimal number and type of blood products are selected when the patient is taken off CPB.

RESULTS

The CBH service was consulted for 44 ventricular assist device implants, 30 heart transplants, and 31 other cardiovascular surgeries from May 2012 through November 2013. The TAT for laboratory tests was 15 minutes for complete blood count, antithrombin, and coagulation panel and 30 minutes for VerifyNow and thromboelastography, in comparison to 45 to 60 minutes in normal settings. The transfusion algorithms were used with optimal administration of blood components with preliminary data suggestive of reduced blood product usage and better patient outcomes.

CONCLUSION

We described the successful introduction of a novel pathology consultation service that uses a rapid TAT coagulation testing menu with transfusion algorithms for improved management of CPB patients.

Intravenous human immunoglobulin treatment of serum from HLA-sensitized patients in kidney transplantation

OBJECTIVE

Intravenous immunoglobulin (IVIG) products are known to have beneficial immunomodulatory effects on several inflammatory and autoimmune disorders. These effects could be attributed to a different inhibitory action on complement factors, but other mechanisms could be implicated, e.g., immunocomplexes development and/or anti-idiotypic antibodies. Positive results on the reduction of anti-Human Leukocyte Antigens (HLA) antibodies in highly sensitized patients have also been found. The present study focuses on the effect of IVIG on the reduction of Panel Reactive Antibody level and crossmatch positivity in sensitized patients awaiting kidney transplantation.

METHODS

The study was performed adapting an in vitro assay on sensitized patients' sera in waiting list for kidney transplantation. Sera of twelve highly sensitized patients were evaluated for the cytotoxicity inhibition after 10% IVIG treatment.

RESULTS

A reduction of anti- HLA antibody levels was observed in 75% (9/12) of treated patients in vitro, while 25% (3/12) resulted unresponsiveness. Particularly, our data showed a significantly higher Panel Reactive Antibody reduction for T lymphocytes (p<0.010) than B lymphocytes (p<0.032).

CONCLUSIONS

In this study, we have used an in vitro assay to investigate susceptibility to desensitization with IVIG treatment of sensitized patient sera. These findings reveal that the variable effect of IVIG on reducing Panel Reactive Antibody in our immunized patients could be attributed to a different inhibitory action on complement, likely due to the type and the titre of anti-HLA antibodies.

Antibody depletion for the treatment of crossmatch-positive pediatric heart transplant recipients

Sensitization to HLA is a risk factor for adverse outcomes after heart transplantation. Requiring a negative prospective CM results in longer waiting times and increased waitlist mortality. We report outcomes in a cohort of sensitized children who underwent transplant despite a positive CDC CM+ using a protocol of antibody depletion at time of transplant, followed by serial IVIG administration. All patients <21 yrs old who underwent heart transplantation at Boston Children's Hospital from 1/1998 to 1/2011 were included. We compared freedom from allograft loss, allograft rejection, and serious infection between CM+ and CM- recipients. Of 134 patients in the cohort, 33 (25%) were sensitized prior to transplantation and 12 (9%) received a CM+ heart transplant. Serious infection in the first post-transplant year was more prevalent in the CM+ patients compared with CM- patients (50% vs. 16%; p = 0.005), as was HD-AMR (50% vs. 2%; p < 0.001). There was no difference in freedom from allograft loss or any rejection. At our center, children transplanted despite a positive CM had acceptable allograft survival and risk of any rejection, but a higher risk of HD-AMR and serious infection.

Quantification, identification, and relevance of anti-human leukocyte antigen antibodies formed in association with the berlin heart ventricular assist device in children

BACKGROUND

Ventricular assist devices (VADs) are increasingly being used in pediatric patients to provide long-term cardiac support. One potential complication of VAD therapy is the development of antibodies directed against human leukocyte antigens (HLA). This phenomenon has not been well described with the Berlin Heart EXCOR VAD, the most commonly used VAD in pediatric patients.

METHODS

The records of all pediatric patients undergoing VAD support using the Berlin Heart device at our institution between April 2005 and August 2011 were reviewed retrospectively. Demographic and clinical data regarding the VAD course were collected. Assessment of anti-HLA antibodies was performed using Luminex, and antibodies were quantified using mean fluorescence intensity (MFI). Assessment for anti-HLA antibodies was performed before VAD implantation and in serial fashion after VAD implantation. Clinically significant anti-HLA antibodies (sensitization) were defined by an MFI of more than 1000.

RESULTS

Thirty-six patients were supported with the Berlin Heart VAD; 13 met inclusion criteria. The majority (85%) carried the diagnosis of dilated cardiomyopathy. Evidence of sensitization pre-VAD was found in 69%; new-onset sensitization (the development of new antibodies on VAD) occurred in 69%. All patients survived to transplantation. In two patients, the retrospective crossmatch was positive, but only in one patient was the crossmatch positive for antibodies formed while on VAD.

CONCLUSIONS

Using Luminex and MFI quantification, anti-HLA antibodies are common before VAD implantation in pediatric patients. While on VAD support, new anti-HLA antibodies formed in a majority, but the immediate impact of these antibodies appears to be limited.