Impacts of donor‐specific anti‐HLA antibodies and antibody‐mediated rejection on outcomes after intestinal transplantation in children

AMR is a risk factor for graft failure after SBTx. We studied impact of DSAs and AMR in 22 children transplanted between 2008 and 2012 (11 isolated SBTx, 10 liver inclusive Tx, and one modified multivisceral Tx). Three patients never developed DSA, but DSAs were found in seven in the pre‐Tx period and de novo post‐Tx in 19 children. Pathology revealed cellular rejection (15/19), with vascular changes and C4d+. Patients were treated with IV immunoglobulins, plasmapheresis, and steroids. Rescue therapy included antithymocyte globulins, rituximab, eculizumab, and bortezomib. Pathology and graft function normalized in 13 patients, graft loss occurred in two, and death in seven. At the end of the follow‐up, 15 children were alive (68%), 13 with functioning graft (59%). Prognosis factors for poor outcome after Tx were the presence of symptoms at AMR suspicion (P +.033). DSAs were often found following SBTx, mostly de novo. Resistant ACR or severe AMR is still difficult to differentiate, with a high need for immunosuppression in both. DSAs may precede development of severe disease and pathology features on the graft: relationship and correlation need to be better investigated with larger groups before and after Tx.     

Clinical and histopathologic features of antibody‐mediated rejection among pediatric renal transplant recipients with preformed vs de novo donor‐specific antibodies

Preformed and de novo donor specific antibodies (pDSA and dnDSA) are risk factors for ABMR. This study compares the effects of pDSA vs dnDSA in pediatric kidney transplant recipients. Sixteen pediatric patients with biopsy‐proven ABMR were evaluated. Strong DSA (MFI >10 000) was recorded at transplant, rejection, and follow‐up. DSAs with the highest MFI were termed iDSAs. Allograft biopsies were scored according to Banff 2013 criteria. Seven of 16 (44%) patients had pDSA at transplant; 9 (56%) developed dnDSA. Patients with pDSA developed ABMR earlier (median = 63 vs 1344 days, P = .017), while patients with dnDSA were more likely to have strong Class II iDSA (100% vs 28%, P = .009). Viral infection or non‐adherence was more common in patients developing dnDSA (88.8% vs 28.6%, P < .01). Pathology in those with pDSAs demonstrated worse transplant glomerulitis (g score 1.57 ± 0.98 vs 0.56 ± 0.73, P = .031); however, those with dnDSAs exhibited higher C4d+ ABMR (P = .013). Patients developing dnDSAs showed ABMR later post‐transplant with predominance of HLA‐Class II iDSAs. Inadequate immunosuppression likely contributes to dnDSA formation. Patients with no DSA who have unprotocolized decreases in immunosuppression should be screened for dnDSA as it could lead to early intervention and potentially better outcomes.     

Donor‐specific antibodies in a pediatric kidney transplant population—Prevalence and association with antiproliferative drug dosing

Prevalence and implications of anti‐HLA class I and class II antibodies are beginning to be better characterized in pediatric kidney transplant recipients. dnDSA formation is predictive of AMR and downstream diminished graft function and survival. However, risk factors for the development of dnDSA are not well defined in this patient population. After introducing DSA surveillance into our pediatric kidney transplant program, we are reporting the prevalence of class I and class II DSA in 67 otherwise stable recipients. Secondary end‐points included risk factors for DSA development and assessment of graft function. Significantly, lower median daily MMF doses were observed in patients with DSAs compared to patients without DSAs (371 vs 617 mg/m²/d, respectively; P = 0.035). Class II DSA formation was more common, with a prevalence of 17.9%, as compared to 10.4% for class I DSA. Estimated glomerular filtration rate was also decreased in patients with positive DSA vs those with negative titers (71, SD 25 vs 78, SD 29 mL/min/1.73 m², respectively; P = 0.034). We conclude that reduced‐dose MMF is associated with dnDSA and DSA is associated with diminished graft function in stable pediatric kidney transplant recipients.     

Impaired graft survival in pediatric renal transplant recipients with donor‐specific antibodies detected by solid‐phase assays

Verghese PS, Smith JM, McDonald RA, Schwartz SM, Nelson KA, Warner PR. Impaired graft survival in pediatric renal transplant recipients with donor‐specific antibodies detected by solid‐phase assays. Pediatr Transplantation 2010: 14:730–734. © 2010 John Wiley & Sons A/S. Abstract: SAB assays have increased the sensitivity and specificity to detect HLA alloantibodies, but there is uncertainty about the clinical relevance of SAB‐positive alloantibodies when the FCXM is negative. We performed a retrospective study to evaluate the clinical significance of SAB‐detected DSA in 82 pediatric recipients of a first kidney transplant between January 2000 and December 2005 who had a negative pretransplant FCXM. Pretransplant sera were evaluated by SAB for DSA. Graft loss and rejection between patients with (DSA+) and without DSA (DSA?) were compared. DSA were detected in 13.9%. Eighty percent of DSA+ subjects were DD transplant recipients vs. 56.9% in the DSA? cohort. The RR of graft loss in DSA+ vs. DSA? was 3.3 (95% CI, 1.4–7.9) and in DD was 4.3 (95% CI 1.4–13.1). By Cox regression, the HR of graft loss in DSA+ vs. DSA? was 2.8 (95% CI 0.7–10.9; p = 0.14) and in DD was 5.1 (95% CI 1–25.6; p = 0.05). Acute rejection occurred in 60% in the DSA+ vs. 44.4% in DSA? (p = 0.5). SAB‐detected DSA was associated with impaired renal allograft survival in pediatric renal transplant recipients. Impaired graft survival in pediatric renal transplant recipients with DSA detected by solid‐phase assays.     

Acute antibody‐mediated rejection in ABO‐compatible pediatric liver transplant recipients: case series and review of the literature

Acute AMR is well reported following ABO‐incompatible LTx. However, it remains uncommon in ABO‐compatible LTx. It typically presents with graft dysfunction ≤2 weeks post‐LTx and is often associated with graft loss. We report the clinical presentation, treatment regimen, and outcome of six pediatric LTx recipients diagnosed with early acute AMR based on (i) clinical signs of graft dysfunction, (ii) histopathology indicative of acute injury ± C4d staining, and (iii) presence of HLA DSA. All patients developed elevated ALT and GGT ≤ 45 days post‐LTx. All showed HLA class I (n=4) and/or II (n=6) DSA (peak MFI 6153–11 910). Four had de novo DSA, and two had preformed DSA. Five were initially diagnosed with ACR refractory to steroid therapy. Four exhibited resolution of graft dysfunction with AMR therapy. Two had refractory AMR—one was re‐transplanted; the other was treated with eculizumab and showed improvement in graft function but later died due to a tracheostomy complication. Our case series suggests that AMR following ABO‐compatible LTx may be under‐diagnosed. The presentation can be variable, and treatment should be individualized. Eculizumab may be an option for refractory AMR. Ultimately, future multicenter studies are needed to better define diagnostic criteria, characterize optimal treatment, and assess long‐term outcomes following liver AMR.     

Pediatric kidney recipients may benefit from monitoring for donor‐specific antibodies

There are limited data regarding the presence of DSAs and their effect on graft function in pediatric renal transplantation. The role for serial DSA monitoring in routine clinical practice is unclear. All patients attending a regional transplant clinic were tested for DSAs, measured using Luminex single/mixed antigen beads. Any patient having a positive result subsequently underwent historic testing on samples previously obtained. DSA‐positive patients underwent prospective monitoring of DSAs, and correlation with clinical events was studied. Nine of a total of 50 patients (18%) were DSA‐positive, of whom six had graft dysfunction. The DSA‐positive cohort had significantly increased episodes of AR (p = 0.01). There were two graft losses in the DSA‐positive group and none in the DSA‐negative group. Eight of the DSA‐positive group had potentially reduced exposure to IS because of either adherence issues or clinical indications. DSAs were associated with increased risk of rejection. There appears to be a role for serial monitoring of DSAs in patients where there has been a reduced exposure to IS so that early intervention with optimized IS can be considered.     

Antibody‐mediated rejection with the presence of glomerular crescents in a pediatric kidney transplant recipient: A case report

Glomerular crescents in kidney transplantation are indicative of severe glomerular injury and constitute a hallmark of RPGN. Their concurrence with ABMR has been rarely described only in adult patients. We report a case of 10‐year‐old boy with compound heterozygous Fin‐major Finnish‐type congenital nephrotic syndrome, who had received a deceased‐donor kidney transplant 5 years before onset of acute kidney injury and nephrotic range proteinuria without hematuria. Kidney allograft biopsy illustrated 6 glomeruli with global sclerosis and 6 with remarkable circumferential or segmental cellular crescents. Negative glomerular immunofluorescence for immune‐complex deposits and the absence of serum ANCA eliminated the presence of immune‐mediated and ANCA‐positive pauci‐immune crescentic glomerulonephritis. Diagnosis of ABMR was based on the high levels of HLA class II DSA and the histological evidence of glomerulitis, peritubular capillaritis, and acute tubular injury with positive linear peritubular capillary C4d staining. The patient despite plasmapheresis and enhanced immunosuppressive treatment progressed to end‐stage renal disease. We conclude that glomerular crescents may represent a finding of AMBR and possibly a marker of poor allograft prognosis in pediatric patients.     

The utility of comprehensive assessment of donor specific anti-HLA antibodies in the clinical management of pediatric kidney transplant recipients

Advances in anti-HLA antibody characterization have had a major impact on kidney transplantation. Comprehensive characterization of DSA has improved protocols for allosensitized transplant candidates, increasing access to acceptable donors. Sensitive and specific solid phase antibody detection assays have given important insight into the clinical characteristics of antibody-mediated allograft injury, resulting in the development of a classification system for acute AMR. In addition, important insights into the nature of chronic antibody-mediated allograft rejection have been achieved as a result of improvements in DSA characterization. Finally, assays initially developed as tools to detect DSA in the clinical setting have been employed in innovative research protocols, allowing the investigation of new therapeutic approaches.     

Results of early treatment for de novo donor‐specific antibodies in pediatric kidney transplant recipients in a cross‐sectional and longitudinal cohort

The development of dnDSA anti‐HLA antibodies has been shown to be a significant risk factor for graft failure. In 2008, we instituted a routine protocol of standardized monitoring and treatment of dnDSA in pediatric kidney transplant recipients. Of 67 first‐time pediatric kidney transplant recipients, 26 (38%) developed dnDSA after 1.36 (IQ 1‐2.14) years. Coefficient of variance of tacrolimus, a surrogate marker of non‐adherence, was found to be the single most important risk factor for dnDSA development. Overall, there was a significant reduction in dnDSA with treatment in 19 (76%) children. No difference in graft survival and estimated glomerular filtration rate was noted between dnDSA negative and those treated for dnDSA. There was an increased risk of hospitalization in those treated for dnDSA. This study suggests that early detection and treatment of dnDSA can help to prevent graft failure and preserve graft function in the short term. Future studies and longer follow‐up are needed to fully elucidate the effect of early detection and treatment of dnDSA in pediatric kidney transplant recipients.     

Donor‐specific anti‐HLA antibodies in pediatric renal transplant recipients with creeping creatinine: Prevalence,histological correlations,and impact on patient and graft survival

Donor‐specific anti‐HLA antibodies (DSA) causing CAMR are responsible for a high proportion of long‐term graft failures after RTX. We studied the prevalence of DSA in RTX children biopsied for creeping Cr, its relationship with NA, and patient and graft survival according to histopathology. Between 2008 and 2013, 92 children were biopsied at a median of 38 months post‐RTX. At biopsy, the prevalence of DSA was 49% and C4d 70%. NA rate was 45%, higher in adolescents (60%). Most frequent diagnoses were CAMR (72%) and interstitial fibrosis with tubular atrophy (IFTA) (28%). Forty‐five of 66 patients with CAMR (68%) had detectable DSA. Twenty‐one DSA‐negative patients with CAMR had histological damage (IFTA + C4d positivity). C4d was detected in 64 of 66 biopsies with CAMR. Recipients with IFTA alone had neither C4d, nor detectable DSA, and were adherent. Graft survival at five yr was 89% in patients with CAMR, 79% in those with CAMR + TCMR Banff I, 33% in those with CAMR + TCMR Banff II, and 96% in those with IFTA. ABMR and complement activation were frequent in children biopsied for creeping Cr. Recipients with DSA were more likely to be non‐adherent and have CAMR or CAMR + TCMR and worse graft survival.     

Risk factors for the development of donor‐specific antibodies after pediatric heart transplantation

DSA after HTx may have adverse effects on patient survival. The aim of this study was to assess risk factors for the development of DSA after pediatric HTx. All HTx recipients at our center with serial monitoring of DSA were identified. Cox proportional hazards model was used to estimate donor and recipient characteristics associated with the development of DSA. De novo DSA were detected in 40 (33%) of 121 HTx recipients. Characteristics associated with de novo DSA included older age, African American race, prior operations, prior ECMO, PRA > 10%, longer bypass time, mechanical support at transplant, and donor death from GSW. In a multivariable model, mechanical support (HR 3.23, 95% CI [1.02, 8.87]), African American race (HR 3.36, 95% CI [1.68, 7.32]), and donor death from GSW (HR 4.76, 95% CI [1.62, 14.01]) were significantly associated with DSA. Multiple factors appear to play a role in the development of DSA, knowledge of which may guide the frequency of post‐transplant monitoring. DSA develop more frequently in those with prior sensitizing events, suggesting the possibility that these exposures predispose the immune system to respond to donor antigens, even in the presence of a negative cross‐match.     

Efficacy of bortezomib for reducing donor‐specific antibodies in children and adolescents on a steroid minimization regimen

AMR is increasingly being recognized as an important cause of renal allograft injury, contributing to significant morbidity and graft loss. There are few controlled trials and no well‐established treatment guidelines for AMR in renal transplant recipients. We retrospectively reviewed the outcome of four pediatric renal transplant recipients on a steroid minimization immunosuppression protocol treated with bortezomib for elevated DSA and acute AMR from 2012 to 2013. All patients received four doses of bortezomib 1.3 mg/m² given on days one, four, eight, and 11. All patients also received other treatments prior to bortezomib, which may have included rituximab, methylprednisolone, plasmapheresis, and/or IVIg. While bortezomib in addition to other therapies significantly decreased DSA titers, DSA remained very elevated months after treatment. All four patients had immediate improvement or stabilization of renal function but one eventually lost her graft. There were no adverse events related to bortezomib six months after treatment.     

Donor‐specific HLA antibodies and graft function in kidney‐transplanted children – the Vienna cohort

In the pediatric population, little is known on de novo DSA development, its impact on graft function, and association with suboptimal IS. We assessed the prevalence of de novo DSA in the Vienna cohort of 40 renal transplanted children and adolescents and prospectively followed its association with clinical parameters, graft function, and proteinuria for one yr. At the cross‐sectional analysis (median post‐transplant time of five yr), 17% of the patients had developed de novo DSA. All HLA‐Ab were anti‐HLA class II antibodies and persisted in 85% of the cases until the follow‐up screening performed within one yr. Basic clinical and laboratory parameters did not differ between DSA‐negative and DSA‐positive patients at the time of HLA‐Ab screening. Suboptimal IS due to reduced medication or non‐adherence could not be proven in DSA‐positive patients. The changes in eGFR did not differ during the prospective study period, but there was a significantly higher proteinuria in the DSA‐positive patients during the follow‐up. Our data demonstrate an overall prevalence of 17% of de novo DSA in a pediatric renal transplant cohort. During 12 months of prospective follow‐up time, we could demonstrate a significant impact of de novo DSA presence on proteinuria.     

JC polyomavirus‐specific antibody responses in pediatric kidney transplant recipients

BKPyV is widely recognized in KTRs, but little is known about rates of primary and secondary JCPyV exposure in pediatric KTRs. We evaluated JCPyV exposure in pediatric KTRs using antibody responses in the first 12 months post‐transplant. Of 46 children transplanted between 2009 and 2014, 6 lacked any samples for serologic testing, leaving 40 KTRs for study. JCPyV‐specific IgG and IgM antibodies were measured using a normalized VLP ELISA. Significant JCPyV exposure was defined as IgG seroconversion, increasing IgG levels of >0.5 nOD units, or IgM detection. Of 40 recipients (median age 3.2 years), 11 (27.5%) were seropositive, 20 (50%) seronegative for JCPyV‐IgG, while 9 (22.5%) had no specimen at the time of transplantation, but were confirmed as seronegative in post‐transplant samples. Of 29 (72.5%) at risk, JCPyV‐IgG seroconversion occurred in 15/29 (51.7%) including JCPyV‐IgM in 6 patients (20.7%). Two patients (6.9%) developed only JCPyV‐IgM. Among JCPyV‐IgG‐positive KTRs, six (12.5%) had significant IgG increases. Altogether 23 of 40 patients (57.5%) had serological evidence of primary or secondary JCPyV exposure. In these patients, kidney function tended to be lower during the 2 years of follow‐up, but only one patient lost the graft due to JCPyV nephropathy. Thus, JCPyV exposure is common in pediatric KTR and may present serologically as primary or secondary infection. Although only one case of JC‐PyVAN occurred, a trend toward lower renal function was seen. Dedicated studies of larger cohorts are warranted to define impact of JCPyV in pediatric KTR.     

Bortezomib in the treatment of antibody‐mediated rejection in pediatric kidney transplant recipients: A multicenter Midwest Pediatric Nephrology Consortium study

Antibody‐mediated rejection leads to allograft loss after kidney transplantation. Bortezomib has been used in adults for the reversal of antibody‐mediated rejection; however, pediatric data are limited. This retrospective study was conducted in collaboration with the Midwest Pediatric Nephrology Consortium. Pediatric kidney transplant recipients who received bortezomib for biopsy‐proven antibody‐mediated rejection between 2008 and 2015 were included. The objective was to characterize the use of bortezomib in pediatric kidney transplant recipients. Thirty‐three patients received bortezomib for antibody‐mediated rejection at nine pediatric kidney transplant centers. Ninety percent of patients received intravenous immunoglobulin, 78% received plasmapheresis, and 78% received rituximab. After a median follow‐up of 15 months, 65% of patients had a functioning graft. The estimated glomerular filtration rate improved or stabilized in 61% and 36% of patients at 3 and 12 months post‐bortezomib, respectively. The estimated glomerular filtration rate at diagnosis significantly predicted estimated glomerular filtration rate at 12 months after adjusting for chronic histologic changes (P .001). Fifty‐six percent of patients showed an at least 25% reduction in the mean fluorescence intensity of the immune‐dominant donor‐specific antibody, 1‐3 months after the first dose of bortezomib. Non‐life‐threatening side effects were documented in 21 of 33 patients. Pediatric kidney transplant recipients tolerated bortezomib without life‐threatening side effects. Bortezomib may stabilize estimated glomerular filtration rate for 3‐6 months in pediatric kidney transplant recipients with antibody‐mediated rejection.     

Three‐yr safety and efficacy of everolimus and low‐dose cyclosporine in de novo pediatric kidney transplant patients

The three yr results of a multicenter trial in de novo pediatric KT treated with a proliferative signal inhibitor and low dose CNI are presented. Thirty‐seven children (9.1 ± 5 yr old) received basiliximab, cyclosporine A (CyA C2:1400 ng/mL), (MMF C0:1.5–3 μg/mL), and prednisone. Three wk later everolimus was started (C0:5–10 ng/mL), CyA was reduced (C2:600 ng/mL after 90 days 300 ng/mL), and MMF discontinued. During the three‐yr period patient and graft survivals were 96%. One patient died for causes unrelated to the immunosuppression. Cumulative acute rejection rate including protocol and indication biopsies was 21.9%. None of the patients had signs of chronic humoral rejection. Incidence of dnDSA was 5%, 11%, and 22% at one, two, and three yr post‐transplant, respectively. Mean glomerular filtration rate measured at one yr and three yr post‐transplant was 105.5 ± 31 and 110.7 ± 27 mL/min/1.73 m², respectively. A growth velocity of 7.7 ± 6.7 cm/yr was achieved with positive catch‐up growth. No malignancy or post‐transplant lymphoproliferative diseases were diagnosed. In conclusion, the treatment based on basiliximab induction, everolimus, low‐dose cyclosporine, and low‐dose prednisone leads to good long‐term efficacy in de novo pediatric KT recipients.     

Impact of active antibody‐mediated rejection treatment on donor‐specific antibodies in pediatric kidney transplant recipients

AMR is a major cause of graft loss after kidney transplantation. We evaluated a retrospective cohort of 13 pediatric kidney transplant patients diagnosed with active AMR. All 13 patients were treated with plasmapheresis (PP), IVIg, and rituximab. Anti‐HLA DSAs were measured at the time of transplantation, AMR diagnosis, 30 days post‐rejection treatment, 90 days post‐rejection treatment, and 24 ± 12 months post‐AMR. A total of 68 DSAs were identified from 13 patients at the time of active AMR diagnosis. The primary objective of this study was to differentiate treatment response rates between class I and class II anti‐HLA DSA post‐AMR treatment. Overall, DSAs were significantly reduced at 30 days, and the reduction was sustained at 90 days post‐treatment, even for class II anti‐HLA and strongly positive DSAs. A significant difference between class I and class II anti‐HLA DSA was observed at 30 days; however, between class significance was lost at 90‐day follow‐up due to continued class II anti‐HLA DSA treatment response. Low DSA strength was predictive of treatment response. eGFR demonstrated significant improvement 90 days after AMR diagnosis compared to the initial value at the time of AMR, and the effect was sustained for 12 months. These results suggest that the AMR treatment is effective in pediatric kidney transplant recipients with an early diagnosis of active AMR across both class I and class II anti‐HLA DSAs.     

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

Management of late humoral rejection remains challenging, and DSA may persist. A case report illustrates how individual DSA titers using solid‐phase‐based assays may help to assess for accommodation. A male cystinosis patient received a cadaveric renal transplant at the age of 12 yr with a daclizumab, tacrolimus, MMF, and steroids‐based immunosuppression. After three acute rejection episodes over the first eight months, interstitial fibrosis/tubular atrophy (IF/TA) was diagnosed on biopsy, while the immunosuppression was left unchanged with a high target exposure for both tacrolimus and MPA. One yr later, AMR type III (C4d and DSA positive) was treated with daily plasmapheresis, IVIG 100 mg/kg and pulse steroids 5 mg/kg. DSA (DR 53, DQ4, and DQ 2) were not responding until the plasma volume was increased to 2.5 plasma volumes. A second rise of creatinine confirmed worse humoral rejection; daily plasma exchange was resumed, and two doses of rituximab (375 mg/m²) were given. Subsequently, all DSA dropped, but only DR53 DSA remained unchanged, whereas the DQ antibodies rebounded to very strong titers. With a follow‐up of over 120 days after recovery of the CD19 count, off all additional treatment and on identical immunosuppression with tacrolimus and MMF and prednisone, the patient's creatinine remained stable between 45 and 50 um while DQ DSA remain strong to very strong. We conclude that the patient is in a state of accommodation. DSA titers should be monitored when managing late humoral rejection.     

Donor specific antibodies after transplantation

The detection of donor-specific antibodies after organ transplantation might provide an incisive way to monitor allo-specific immunity and predict graft outcome. Still, the availability of new assays for these antibodies prompts us to pose some questions about results that might be observed. These questions include whether the antibodies detected in the blood are a sensitive measure of alloimmunity, whether the detected antibodies are truly specific for the donor and whether they are noxious for the graft. Here, we explain why answers to these questions might interest the basic scientist and clinician.     

HLA antibodies in pediatric heart transplantation

We have analyzed the impact of anti-HLA antibodies present in the patients' circulation prior and/or following heart transplantation in a population of 108 pediatric recipients. Anti-HLA class I and class II antibodies were monitored by traditional CDC using donor and panel T and B lymphocytes and by SPA for detection of DSA. There was a highly significant correlation between the development of AMR and presence of CDC- or SPA-detected DSA. However, the fraction of the transplant population which remained AMR-free was much higher among patients with SPA-detected compared to CDC-detected DSA. Furthermore, long-term graft survival was negatively affected only by cytotoxic, complement-fixing anti-HLA class I antibodies developing following transplantation. Anti-HLA class I or class II antibodies detected by SPA had no effect on long-term survival rates.