Utility of Post-Transplant Anti-HLA Antibody Measurements in Pediatric Cardiac Transplant Recipients

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.

Incidence, characterization, and impact of newly detected donor-specific anti-HLA antibody in the first year after pediatric heart transplantation: A report from the CTOTC-04 study

Data on the clinical importance of newly detected donor-specific anti-HLA antibodies (ndDSAs) after pediatric heart transplantation are lacking despite mounting evidence of the detrimental effect of de novo DSAs in solid organ transplantation. We prospectively tested 237 pediatric heart transplant recipients for ndDSAs in the first year posttransplantation to determine their incidence, pattern, and clinical impact. One-third of patients developed ndDSAs; when present, these were mostly detected within the first 6 weeks after transplantation, suggesting that memory responses may predominate over true de novo DSA production in this population. In the absence of preexisting DSAs, patients with ndDSAs had significantly more acute cellular rejection but not antibody-mediated rejection, and there was no impact on graft and patient survival in the first year posttransplantation. Risk factors for ndDSAs included common sensitizing events. Given the early detection of the antibody response, memory responses may be more important in the first year after pediatric heart transplantation and patients with a history of a sensitizing event may be at risk even with a negative pretransplantation antibody screen. The impact on late graft and patient outcomes of first-year ndDSAs is being assessed in an extended cohort of patients.

The use of circulating donor specific antibody to predict biopsy diagnosis of antibody-mediated rejection and to provide prognostic value after heart transplantation in children

BACKGROUND

Antibody-mediated rejection (AMR) is a significant cause of mortality after heart transplantation (HT). Although the presence of donor specific antibody (DSA) is a risk factor for developing AMR, serial DSA testing is not widely performed. We aimed to investigate the predictive values and prognostic implications of circulating DSA using endomyocardial biopsy as the gold standard for AMR diagnosis in pediatric recipients of HT.

METHODS

We performed a retrospective study in pediatric recipients of HT followed during the period 2009-2013 with at least 1 biopsy paired with DSA testing. Positive DSA was defined at mean fluorescent intensity (MFI) ≥2,000 using single antigen bead testing. Statistical analyses included 2 × 2 contingency tables, receiver operating characteristic analysis for optimal MFI cutoffs, Spearman correlation of MFI strength to AMR grade, and Kaplan-Meier analysis of event-free survival.

RESULTS

Of 66 children included, 27 (41%) had ≥1 DSA positive test. DSA testing had a sensitivity of 92.6%, specificity of 62.2%, positive predictive value of 24.0%, and negative predictive value of 98.5% for biopsy diagnosis of AMR at our institution. There was a statistically significant correlation between higher MFI and higher AMR grade. Patients with positive DSA and AMR had similar survival early after DSA detection but trended toward lower cardiovascular event-free survival later compared with patients without DSA and a negative biopsy.

CONCLUSIONS

The results of DSA testing in this cohort showed excellent sensitivity and negative predictive value for biopsy-diagnosed AMR, suggesting that DSA testing may aid in the non-invasive prediction of AMR absence in HT. The correlation of DSA MFI strength with higher AMR biopsy grade and the trend toward differences in longer term cardiovascular outcomes provide evidence for routine DSA monitoring after pediatric HT.

Development and Impact of De Novo Anti-HLA Antibodies in Pediatric Heart Transplant Recipients

There is increasing evidence that de novo anti-HLA antibodies, more specifically de novo donor-specific antibodies (DSA) following solid organ transplantation may be associated with negative outcomes including rejection in the first year and graft loss. Limited data are available in pediatric heart transplant recipients. We sought to prospectively determine the incidence, class and early impact of de novo anti-HLA antibodies in a cohort of pediatric heart transplant recipients. Serial panel reactive antibody testing posttransplant was performed in 25 patients (14 males) transplanted between January 2008 and June 2010. Five patients were sensitized pretransplant; all patients had negative direct crossmatch. Seventy-two percent developed de novo anti-HLA antibodies at a median of 2.6 weeks (IQR 1.2 weeks to 6.2 months) posttransplant; 67% of these were DSA. The majority of recipients in our cohort developed de novo anti-HLA antibodies within the first year posttransplant, with two-thirds being donor-specific. Acute cellular rejection, though frequent, was not different in patients with antibody development regardless of class or specificity, and there was no antibody-mediated rejection, graft loss or early cardiac allograft vasculopathy.

HLA molecular epitope mismatching and long-term graft loss in pediatric heart transplant recipients

BACKGROUND

Although evidence links HLA allele mismatching to worse outcomes in pediatric heart transplantation, no studies to our knowledge have applied the quantification of structural HLA differences between donor and recipient to risk evaluation. We examine the association between molecular-level HLA mismatching and long-term graft loss in pediatric recipients of heart transplants.

METHODS

HLA Matchmaker was used to quantify the number of mismatched class-specific HLA eplets among 4,851 heart transplant recipients ≤18 years of age in the Scientific Registry of Transplant Recipients (1987-2012). Survival analysis was used to compare long-term probabilities of graft loss by number of eplet mismatches and allele mismatches stratified by eplet mismatches.

RESULTS

Recipients with 10 to 20 or >20 class I (HLA-A and HLA-B) eplet mismatches experienced increased long-term graft loss compared with recipients with <10 class I eplet mismatches (adjusted hazard ratio = 1.23 [95% confidence interval = 1.06-1.42], adjusted hazard ratio = 1.27 [95% confidence interval = 1.08-1.50], respectively). Recipients with 2 to 4 class I allele mismatches had increased long-term graft loss compared with recipients with 0 to 1 class I allele mismatches. Neither class II (HLA-DR) eplet mismatching nor class II allele mismatching was associated with graft loss. On stratification by allele and structural eplet mismatching, only recipients with 2 to 4 class I allele mismatches and ≥10 class I eplet mismatches had an increased probability of graft loss compared with recipients with 0 to 1 class I allele mismatches (adjusted hazard ratio = 1.42 [95% confidence interval = 1.09-1.57]).

CONCLUSIONS

Molecular-level HLA mismatching may aid in identifying recipients at increased risk of long-term graft loss who could benefit from intensified post-transplant surveillance and management.

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.

Immunologic considerations in heart transplantation for congenital heart disease

Children and adults with congenital heart disease (CHD) can require interventions that result in immunologic alterations that are different than those seen in patients with cardiomyopathies. Patients with CHD can be exposed to heart surgeries, blood products, valved and non-valved allograft tissue, and mechanical circulatory support, all of which can alter the immunologic status of these patients. This change in immunologic status is most commonly manifested as the development of anti-human leukocyte antigen (HLA) antibodies. This review will delineate a) the causes of anti-HLA anti-body production (often referred to as allosensitization); b) preventive strategies for anti-HLA antibody production before transplantation; c) treatment strategies for those patients who develop anti-HLA antibodies before transplantation; d) consequences of HLA allosensitization after transplantation; and e) treatment of HLA allosensitization and antibody-mediated rejection after transplantation.

Rapid reduction in donor-specific anti-human leukocyte antigen antibodies and reversal of antibody-mediated rejection with bortezomib in pediatric heart transplant patients

BACKGROUND

High titer donor-specific antibodies (DSA) and positive crossmatch in cardiac transplant recipients is associated with increased mortality from antibody-mediated rejection (AMR). Although treatment to reduce anti-human leukocyte antigen antibodies using plasmapheresis, intravenous immunoglobulin, and rituximab has been reported to be beneficial, in practice these are often ineffective. Moreover, these interventions do not affect the mature antibody producing plasma cell. Bortezomib, a proteasome inhibitor active against plasma cells, has been shown to reduce DSA in renal transplant patients with AMR. We report here the first use of bortezomib for cardiac transplant recipients in four pediatric heart recipients with biopsy-proven AMR, hemodynamic compromise, positive crossmatch, and high titer class I DSA.

METHODS

Patients received four intravenous dose of bortezomib (1.3 mg/m(2)) over 2 weeks with plasmapheresis and rituximab. DSA specificity and strength (mean fluorescence intensity) was determined with Luminex. All had received previous treatment with plasmapheresis, intravenous immunoglobulin, and rituximab that was ineffective.

RESULTS

AMR resolved in all patients treated with bortezomib with improvement in systolic function, conversion of biopsy to C4d negative in three patients and IgG negative in one patient, and a prompt, precipitous reduction in DSAs. In three patients who received plasmapheresis before bortezomib, plasmapheresis failed to reduce DSA. In one case, DSA increased after bortezomib but decreased after retreatment.

CONCLUSIONS

Bortezomib reduces DSA and may be an important adjunct to treatment of AMR in cardiac transplant recipients. Bortezomib may also be useful in desensitization protocols and in prevention of AMR in sensitized patients with positive crossmatch and elevated DSA.

Outcomes in pediatric cardiac transplantation with a positive HLA cross-match

Previous studies have shown poor outcomes in pediatric heart transplant recipients with a high PRA or a positive direct donor-recipient cross-match. This study describes outcomes in patients with a positive cross-match at a large pediatric program. Pediatric heart transplant patients at a large single center between January 1993 and July 2009 were reviewed; those with cross-match data were analyzed. Cross-match data were available in 242/262 (92.4%) patients. Indications for transplant were cardiomyopathy (58%), CHD (32%), and retransplant (7%). PRA was ≥10% in 31/213 (14.6%) patients. A retrospective cross-match was positive in 17/31 (55%) patients with PRA ≥10% and 0/182 with PRA <10%. In positive cross-match patients, rejection frequency in the first year post-transplant was higher than negative cross-match patients (1.69 vs. 0.96 episodes/pt year, p = 0.014). There was no difference in rejection frequency after the first year post-transplant (0.18 vs. 0.12 episodes/pt year, p = 0.14). Overall survival was not significantly different between the groups with a median follow-up time of 4.5 yr. Heart transplantation in patients with a positive cross-match may result in good medium-term survival but a higher frequency of early rejection. Further investigation is warranted to define which patients with a positive cross-match will do poorly.

Management of children undergoing cardiac transplantation with high Panel Reactive Antibodies

Highly sensitised children in need of cardiac transplantation have overall poor outcomes because of increased risk for dysfunction of the cardiac allograft, acute cellular and antibody-mediated rejection, and vasculopathy of the cardiac allograft. Cardiopulmonary bypass and the frequent use of blood products in the operating room and cardiac intensive care unit, as well as the frequent use of homografts, have predisposed potential recipients of transplants to allosensitisation. The expansion in the use of ventricular assist devices and extracorporeal membrane oxygenation has also contributed to increasing rates of allosensitisation in candidates for cardiac transplantation. Antibodies to Human Leukocyte Antigen can be detected before transplantation using several different techniques, the most common being the "complement-dependent lymphocytotoxicity assays". "Solid-phase assays", particularly the "Luminex® single antigen bead method", offer improved specificity and more detailed information regarding specificities of antibodies, leading to improved matching of donors with recipients. Allosensitisation prolongs the time on the waiting list for potential recipients of transplantation and increases the risk of complications and death after transplantation. Aggressive reduction of antibodies to Human Leukocyte Antigen in these high-risk patients is therefore of vital importance for long-term survival of the patient and cardiac allograft. Strategies to decrease Panel Reactive Antibody or percent reactive antibody before transplantation include plasmapheresis, intravenous administration of immunoglobulin, and specific treatment to reduce B-cells, particularly Rituximab. These strategies have resulted in varying degrees of success. Antibody-mediated rejection and cardiac allograft vasculopathy are two of the most important complications of transplantation in patients with high Panel Reactive Antibody. The treatment of antibody-mediated rejection in recipients of cardiac transplants is largely empirical and includes the use of high-dose corticosteroids, plasmapheresis, intravenous administration of immunoglobulins, anti-thymocyte globulin, and Rituximab. Cardiac allograft vasculopathy is believed to be secondary to chronic complement-mediated endothelial injury and chronic vascular rejection. The use of proliferation signal inhibitors, such as sirolimus and everolimus, has been shown to delay the progression of cardiac allograft vasculopathy. In some non-sensitised recipients of cardiac transplants, the de novo formation of antibodies to Human Leukocyte Antigen after transplantation may increase the likelihood of adverse clinical outcomes. The use of serial testing for donor-specific antibodies after cardiac transplantation may be advisable in patients with frequent episodes of rejection and patients with history of sensitisation. Allosensitisation before transplantation can negatively influence outcomes after transplantation. A high incidence of antibody-mediated rejection and graft vasculopathy can result in graft failure and decreased survival. Current strategies to decrease allosensitisation have helped to expand the pool of donors, improve times on the waiting list, and decrease mortality. Centres of transplantation offering desensitisation are currently using plasmapheresis to remove circulating antibodies; intravenous immunoglobulin to inactivate antibodies; cyclophosphamide to suppress B-cell proliferation; and Rituximab to deplete B-lymphocytes. Similar approaches are also used to treat antibody-mediated rejection after transplantation with promising results.

Donor-specific HLA antibodies in paediatric cardiac transplant recipients are associated with poor graft survival

There is increasing evidence that DSA are associated with poor graft survival, although there are little data in children. We aimed to describe the incidence of DSA in this group and to determine correlation with graft survival. HLA antibodies were analysed in 59 paediatric cardiac transplant recipients. Mean age 10.4 (0.7-18.5) yr, mean time post-transplant 5.1 (0.3-17.3) yr. Antibody detection/identification was performed on the Luminex platform with subsequent identification using Lifescreen Identification kits/One-Lambda Single antigen kits. Forty patients (69%) had no HLA antibodies. DSA were found in four (7%). One had transient Class I antibodies and normal cardiac function. The other three had persistent Class II antibodies (two subsequently required re-transplantation, the third had cardiac failure due to CAV). Non-DSA were found in 15 (25%), all with normal graft function and without rejection. There was no difference in function or CAV prevalence between those with non-DSA and those without antibodies. HLA DSA is uncommon in paediatric cardiac allograft recipients but, if persistent, suggests poorer prognosis. In our series, antibodies to HLA class II on donor tissue were associated with increased graft loss. Routine screening and regular testing are recommended.

Human leukocyte antigen antibodies and chronic rejection: from association to causation

Considerable research has established an association between human leukocyte antigen antibodies and chronic rejection. Two new major developments now provide evidence that this relationship is in fact causative. First, recent studies of serial serum samples of 346 kidney transplant patients from four transplant centers show that de novo antibodies, can be detected before rejection. Moreover, serial testing revealed that when antibodies were not present, 528 patient years of good function was demonstrable in 149 patients. Second, among 90 patients whose grafts chronically failed, 86% developed antibodies before failure. To assess the likelihood of a causal link, we applied the nine widely accepted Bradford Hill criteria and conclude that the evidence supports a causal connection between human leukocyte antigen antibodies and chronic rejection. The clinical implication is significant because we hope this review will stimulate centers to begin the one remaining task of showing that antibody removal will indeed prevent chronic failure.

Myocardial HLA-G reliably indicates a low risk of acute cellular rejection in heart transplant recipients

BACKGROUND

Human leukocyte antigen-G (HLA-G), a non-classical MHC I protein with restricted tissue expression, plays an essential role in immune tolerance and has been negatively associated with acute and chronic rejection after heart transplantation. We assessed myocardial HLA-G expression in adult heart transplant patients in an attempt to determine the value of this protein in identifying patients with a low risk of acute cellular rejection.

METHODS

Two groups of patients were included in this study. Group A (non-rejecting) included 29 patients who had no moderate or severe rejection episodes (ISHLT Grade <2R) post-transplant. Group B (rejecting) included 38 patients with at least two moderate or severe rejection episodes (Grade >or=2R) within a 1-year period. Expression of HLA-G in three myocardial biopsies post-transplant from each patient was determined through immunohistochemical staining.

RESULTS

In Group A, 86% of patients had HLA-G(+) biopsies compared with 11% of patients in Group B (p < 0.001; sensitivity 86%, specificity 87%). Whereas 60% of non-rejecting HLA-G(+) patients had at least two positive biopsies, all rejecting HLA-G(+) patients had only one positive biopsy.

CONCLUSIONS

There is a significant negative association between myocardial HLA-G expression and acute cellular rejection after cardiac transplantation. Detection of HLA-G appears to reliably indicate a low risk of developing moderate or severe allograft rejection and may, subsequently, allow for a reduced immunosuppressive regimen.

Experience with bovine pericardium for the reconstruction of the aortic arch in patients undergoing a Norwood procedure

BACKGROUND

The incidence of recurrent aortic arch obstruction after the Norwood procedure is between 0% and 36%. Allograft material is frequently used to enlarge the aorta; its use has been associated with the development of significant allosensitization. We report our experience using bovine pericardium for the reconstruction of the aortic arch in patients undergoing a Norwood procedure.

METHODS

A retrospective analysis of 33 consecutive patients evaluated for a second-stage procedure after an initial Norwood repair was performed. All patients underwent a cardiac catheterization. The presence of recurrent arch obstruction (gradient > 10 mm Hg) and its management were noted. Three consecutive patients were tested for anti-HLA antibodies at the time of their Fontan procedure.

RESULTS

The mean age at the time of the cardiac catheterization was 4.12 months (range, 2 to 7 months). The incidence of recurrent arch obstruction was 18.2% (6 patients). Four patients (12.1%) had distal obstruction, 1 patient (3%) had proximal obstruction, and 1 patient (3%) had mid-transverse arch obstruction. Five of the 6 patients underwent aortic arch reintervention consisting of four balloon dilatations and two surgical patch aortoplasties. Thirty-one patients advanced to a second-stage procedure, including 30 bidirectional Glenn anastomoses, and 1 Rastelli repair. No significant allosensitization was present in the patients tested.

CONCLUSIONS

The use of bovine pericardium in the Norwood procedure is associated with an acceptable incidence of recurrent arch obstruction. Its availability, lower cost, and possible immunologic advantages make it an attractive alternative to allograft material.

Cardiac transplant outcomes in pediatric patients with pre-formed anti-human leukocyte antigen antibodies and/or positive retrospective crossmatch

BACKGROUND

Children undergoing heart transplantation who have preformed anti-human leucocyte antigen (HLA) panel reactive antibodies (PRA) or positive retrospective crossmatch (XM) may be at increased risk for rejection and graft failure. We assessed outcomes of transplant recipients with either positive PRA before transplant or positive retrospective XM.

METHODS

A review of 148 heart transplant patients between 1990 and 2006 was undertaken, identifying transplants in patients with pre-transplant PRA > 1% and/or a positive XM. Demographic information and detailed post-transplant outcomes including episodes of rejection, infection, and graft failure were recorded.

RESULTS

There were 11 PRA positive (PRA+) transplants, 135 PRA negative (PRA-) transplants, and no PRA data on 2. There were 14 XM+ transplants, 115 XM- transplants, and no XM data on 19. Kaplan-Meier graft survival was better in XM- than XM+ patients (p < 0.015), but not different between PRA+ and PRA- Groups. Timing of first rejection and number of rejection episodes were not different between XM+ and XM- Groups or between PRA+ and PRA- Groups. Infections were not different between PRA or XM Groups. Four patients were PRA+/XM- (all PRA, 1%-10%), 7 were PRA-/XM+, and 7 were PRA+/XM+ (6 of 7 PRA >10%).

CONCLUSIONS

Pediatric heart transplant patients whose retrospective XM is positive are at significantly increased risk for graft failure. Elevated pre-transplant PRA may not predict increased risk of graft failure, although markedly positive PRA (>10%) predicts a positive retrospective XM. Improved treatment for pediatric transplant patients with a positive retrospective XM is needed.

Pediatric Heart Transplantation in Human Leukocyte Antigen–Sensitized Patients

Background— There is an elevated risk for poor outcomes after heart transplant (HTx) in patients sensitized to human leukocyte antigens including graft dysfunction, acute cellular and antibody-mediated (AMR) rejection, and cardiac allograft vasculopathy. We report our experience with human leukocyte antigens–sensitized pediatric HTx recipients.

Methods and Results— We identified pediatric HTx patients with elevated pre-HTx Panel Reactive Antibody (Class I/II; >10%), or a positive T- or B-cell crossmatch. Thirteen patients met criteria (5 female, 39%). The median age at HTx was 7 months (3.5 months to 15.5 years). Nine were infants who had prior palliation for congenital heart disease. Four were older patients (median 7.3 years; 4.8 to 15.5 years): 2 had congenital heart disease (Fontan), 2 were re-HTx. B-cell therapies were used in all patients, guided by assessment of CD19+ and CD20+ cells. Immunosuppression included thymoglobulin induction, and tacrolimus, mycophenolate mofetil, and steroids. Daily plasmapheresis ± intravenous immunoglobulin G was used if there was a positive crossmatch on day 1, with a gradual, biopsy-guided weaning schedule. Rituximab was used when AMR was detected on biopsy: more recently (n=3), used empirically perioperatively. AMR was confirmed in 9 patients within median 0.9 months post-HTx. Seven had early acute cellular rejection (≥ ISHLT Grade 2 R) with no hemodynamic compromise or graft dysfunction. There were 4 deaths post-HTx (range, 11 days to 9 months). The median follow-up of 9 survivors was 1.7 years (0.3 to 3.7 years). Of 7 patients >6 months post-HTx, no AMR or cardiac allograft vasculopathy was observed at a mean of 1.9+1.1 years post-HTx and no cardiac allograft vasculopathy.

Conclusions— Despite aggressive management, acute cellular rejection and AMR occurred frequently early post-HTx. An algorithm of B cell–directed strategies can be effective in managing these patients with reasonable intermediate-term outcomes.

Pathophysiology and diagnosis of allograft rejection in pediatric heart transplantation

PURPOSE OF REVIEW

Attempts at improving diagnostic monitoring of allograft rejection continue at a steady pace. The main issue remains whether these methods will replace the standard method of tissue histology from endomyocardial biopsy.

RECENT FINDINGS

The aim in the development of novel techniques to diagnose rejection is the application of noninvasive methods. These range from echocardiography, biomarkers, and genomic profiling to more sensitive antibody detection systems. No single method has the accuracy to be a stand-alone test. Methods of assessing graft dysfunction alone may not be accurate enough in this population. Nonetheless, these and other clinical descriptive studies help us better understand the rejection process in pediatric recipients.

SUMMARY

Solid organ transplantation creates the ideal medium where basic science meets clinical science. Clinical cardiology continues to improve on ways to assess organ dysfunction, but to correlate these methods to early graft rejection, immunobiologic techniques will probably need to be incorporated.

Survival in Allosensitized Children After Listing for Cardiac Transplantation

BACKGROUND

Little is known about the effect of pre-transplant alloantibody in the pediatric cardiac transplant population.

METHODS

All cardiac listings (n = 298) at Children's Hospital of Pittsburgh from January 1990 through February 2006 were reviewed to determine the impact of allosensitization on transplantation outcomes. Analysis focused on: (1) wait list outcomes; (2) survival from the time of listing, regardless of subsequent transplantation; (3) post-transplant graft and patient survival; and (4) post-transplant freedom from graft vasculopathy. Institutional policy required a negative, prospective crossmatch for candidates with panel-reactive antibody >20%.

RESULTS

Alloantibody data were available for 252 (85%) listings. Median time to transplantation was greater for sensitized vs non-sensitized subjects (2.7 months vs 1.3 months; p = 0.02). At 1 year after listing, sensitized subjects had a higher incidence of death (22% vs 8.4%; p = 0.055). Survival at all time-points after listing (regardless of transplantation) was worse for sensitized subjects (p = 0.04). Although no statistically significant differences in post-transplant graft or patient survival were noted, pre-transplant allosensitization was associated with decreased freedom from graft vasculopathy (hazard ratio [HR] 2.76, 95% confidence interval [CI] 1.18 to 6.45; p = 0.019).

CONCLUSIONS

A policy requiring a negative, prospective crossmatch for highly sensitized candidates is associated with longer wait list time and higher mortality after listing. The development of graft vasculopathy appears to be influenced by the presence of pre-transplant alloantibody.

Extremely high association between appearance of HLA antibodies and failure of kidney grafts in a five-year longitudinal study

Longitudinal studies were conducted over a five-year period for HLA antibodies on 493 sera tested from 54 kidney transplant patients. HLA single antigen beads were employed to establish donor specificity of the antibodies. Only 3 of 22 patients without antibodies rejected a graft in contrast to 17 out of 32 patients with posttransplant antibodies (p = 0.003). Using a serum creatinine value of 4.0 mg/dL as the cut-off for a failed graft, 4 of 22 patients without antibodies failed compared to 21 of 32 with antibodies (p = 0.0006). Among patients with donor-specific antibodies (DSA) 13 of 15 failed (p = 0.000004). Even among patients with non-donor specific antibodies (NDSA), 8 of 17 failed (p = 0.05). Among patients who could be identified as making de novo antibodies (since they developed antibodies while not having antibodies for more than six months after transplantation), 6 of 11 failed (p = 0.03). Sequential testing for HLA antibodies shows that antibodies appear prior to a rise in serum creatinine and subsequent graft failure. The very strong association between the production of HLA antibodies after transplantation and graft failure indicates the importance of monitoring for posttransplant HLA antibodies.