Medhat Askar

Nonpermissive HLA-DPB1 mismatch increases mortality after myeloablative unrelated allogeneic hematopoietic cell transplantation

We examined current outcomes of unrelated donor allogeneic hematopoietic cell transplantation (HCT) to determine the clinical implications of donor-recipient HLA matching. Adult and pediatric patients who had first undergone myeloablative-unrelated bone marrow or peripheral blood HCT for acute myelogenous leukemia, acute lymphoblastic leukemia, chronic myelogenous leukemia, and myelodysplastic syndrome between 1999 and 2011 were included. All had high-resolution typing for HLA-A, -B, -C, and -DRB1. Of the total (n = 8003), cases were 8/8 (n = 5449), 7/8 (n = 2071), or 6/8 (n = 483) matched. HLA mismatch (6-7/8) conferred significantly increased risk for grades II to IV and III to IV acute graft vs host disease (GVHD), chronic GVHD, transplant-related mortality (TRM), and overall mortality compared with HLA-matched cases (8/8). Type (allele/antigen) and locus (HLA-A, -B, -C, and -DRB1) of mismatch were not associated with overall mortality. Among 8/8 matched cases, HLA-DPB1 and -DQB1 mismatch resulted in increased acute GVHD, and HLA-DPB1 mismatch had decreased relapse. Nonpermissive HLA-DPB1 allele mismatch was associated with higher TRM compared with permissive HLA-DPB1 mismatch or HLA-DPB1 match and increased overall mortality compared with permissive HLA-DPB1 mismatch in 8/8 (and 10/10) matched cases. Full matching at HLA-A, -B, -C, and -DRB1 is required for optimal unrelated donor HCT survival, and avoidance of nonpermissive HLA-DPB1 mismatches in otherwise HLA-matched pairs is indicated.

The Role of Proteasome Inhibition With Bortezomib in the Treatment of Antibody-Mediated Rejection After Kidney-Only or Kidney-Combined Organ Transplantation

Background. We report our initial experience in using the proteasome inhibitor, bortezomib, to treat established antibody-mediated rejection (AMR) in 20 patients. Methods. There were 16 kidney-only and 4 kidney-combined organ recipients with de novo donor-specific antibody (DSA) and histologic evidence of AMR with peritubular capillaries C4d deposition. AMR was diagnosed 19.8 months (range 1-71 months) posttransplant. Patients received intravenous corticosteroids followed by a 2-week cycle on days 1-4-8-11 of plasmapheresis and 1.3 mg/m2 bortezomib; then 0.5 mg/kg intravenous immunoglobulin four times. Results. De novo class I DSA was detected in 11 (55%) and class II DSA in 18 (90%) recipients. The absolute mean difference between peak-nadir dominant DSA was 68,171 molecules of equivalent soluble fluorochrome (P<0.0001), representing 55%±22%. Only two patients (10%) had undetectable DSA after treatment. Patient survival is 100%, and graft survival is 85% with a mean follow-up of 9.8 months (range 2-20 months). The treatment was generally well tolerated but caused fatigue, gastrointestinal complaints, fluid retention, and thrombocytopenia in a number of patients. The last follow-up estimated glomerular filtration rate was 41.9±16.8 mL/min (range 20.6-72.2 mL/min). However, only 25% returned to their baseline renal function before AMR, and many have proteinuria with urine protein/creatinine more than 0.5 in 41% and more than 1.0 in 18%. Conclusions. The bortezomib-containing regimen demonstrated activity in AMR but seems to be most effective before the onset of significant renal dysfunction (serum creatinine <3 mg/dL) or proteinuria (<1 g/day). The best use of bortezomib to treat AMR should be evaluated in controlled trials using dosing strategies that include longer courses or retreatment schedules.

Identification of a permissible HLA mismatch in hematopoietic stem cell transplantation

In subjects mismatched in the HLA alleles C*03:03/C*03:04 no allogeneic cytotoxic T-lymphocyte responses are detected in vitro. Hematopoietic stem cell transplantation (HSCT) with unrelated donors (UDs) showed no association between the HLA-C allele mismatches (CAMMs) and adverse outcomes; antigen mismatches at this and mismatches other HLA loci are deleterious. The absence of effect of the CAMM may have resulted from the predominance of the mismatch C*03:03/C*03:04. Patients with hematologic malignancies receiving UD HSCT matched in 8/8 and 7/8 HLA alleles were examined. Transplants mismatched in HLA-C antigens or mismatched in HLA-A, -B, or -DRB1 presented significant differences (P < .0001) in mortality (hazard ratio [HR] = 1.37, 1.30), disease-free survival (HR = 1.33, 1.27), treatment-related mortality (HR = 1.54, 1.54), and grade 3-4 acute graft-versus-host disease (HR = 1.49, 1.77) compared with the 8/8 group; transplants mismatched in other CAMMs had similar outcomes with HR ranging from 1.34 to 172 for these endpoints. The C*03:03/C*03:04 mismatched and the 8/8 matched groups had identical outcomes (HR ranging from 0.96-1.05). The previous finding that CAMMs do not associate with adverse outcomes is explained by the predominance (69%) of the mismatch C*03:03/03:04 in this group that is better tolerated than other HLA mismatches.

Amino acid substitution at peptide-binding pockets of HLA class I molecules increases risk of severe acute GVHD and mortality

HLA disparity has a negative impact on the outcomes of hematopoietic cell transplantation (HCT). We studied the independent impact of amino acid substitution (AAS) at peptide-binding positions 9, 99, 116, and 156, and killer immunoglobulin-like receptor binding position 77 of HLA-A, B, or C, on the risks for grade 3-4 acute graft-versus-host disease (GVHD), chronic GVHD, treatment-related mortality (TRM), relapse, and overall survival. In multivariate analysis, a mismatch at HLA-C position 116 was associated with increased risk for severe acute GVHD (hazard ratio [HR] = 1.45, 95% confidence interval [CI] = 1.15-1.82, P = .0016). Mismatch at HLA-C position 99 was associated with increased transplant-related mortality (HR = 1.37, 95% CI = 1.1-1.69, P = .0038). Mismatch at HLA-B position 9 was associated with increased chronic GVHD (HR = 2.28, 95% CI = 1.36-3.82, P = .0018). No AAS were significantly associated with outcome at HLA-A. Specific AAS pair combinations with a frequency >30 were tested for association with HCT outcomes. Cysteine to tyrosine substitution at position 99 of HLA-C was associated with increased TRM (HR = 1.78, 95% = CI 1.27-2.51, P = .0009). These results demonstrate that donor-recipient mismatch for certain peptide-binding residues of the HLA class I molecule is associated with increased risk for acute and chronic GVHD and death.

Pre-transplant antibodies to Kα1 tubulin and collagen-V in lung transplantation: Clinical correlations

BACKGROUND Immune responses to lung-associated self-antigens (SAgs) have been implicated in chronic lung allograft rejection. The goals of this study were to determine the prevalence of pre-existing antibodies (Abs) to the SAgs in pulmonary diseases and the association between pre-existing Abs to SAgs and the development of primary graft dysfunction (PGD), donor-specific antibodies (DSA), and chronic rejection. METHODS Pre- and post-transplant sera were analyzed from 317 lung transplant (LTx) recipients between 2000 and 2011 with diagnosis of chronic obstructive disease (n = 161), idiopathic pulmonary fibrosis (IPF; n = 50), cystic fibrosis (CF; n = 55), and others (n = 51). Samples were analyzed for Abs to SAgs by enzyme-linked immunosorbent assay, and DSA and cytokines by Luminex. The clinical diagnosis of PGD and bronchiolitis obliterans syndrome (BOS) was based on International Society for Heart and Lung Transplantation guidelines. RESULTS The overall prevalence of Abs to SAgs was 22.71%, including 18% in chronic obstructive pulmonary disease (p = 0.033), 34% in IPF (p = 0.0006), 29% in CF (p = 0.0023), and 19.6% in other diagnoses (p = 0.044). The incidence of PGD (88% vs 54%, p < 0.05), DSA (70% vs 45%, p < 0.01), and BOS (90% vs 38% (p < 0.001) after LTx was significantly higher in patients with pre-LTx Abs to SAgs than without. Pro-inflammatory cytokines (interleukin-1β, interleukin-17, and interferon-γ) were elevated in patients who had pre-LTx Abs to SAgs, along with a reduction in anti-inflammatory interleukin-10. CONCLUSIONS Patients with IPF and CF have the highest prevalence of Abs to SAgs. Patients with pre-existing Abs to SAgs are at increased risk for development of PGD, DSA, and BOS. Strategies to remove pre-existing Abs to SAgs should be considered to improve lung allograft outcome.

Glomerular filtration rate slopes have significantly improved among renal transplants in the United States

Introduction. In recent years, the use of higher risk donor organs and steroid avoidance regimens with potential increased acute rejection risk have increased. We hypothesized that these patterns adversely affect changes in posttransplant renal function. Methods. By using Scientific Registry of Transplant Recipients data and multivariable generalized linear models, we examined factors associated with slopes of estimated glomerular filtration rate (GFR; modification of diet in renal disease) from 6 to 12 months and 6 to 24 months posttransplant in solitary adult renal transplant recipients transplanted between 2003 and 2008 (n=91,241). We estimated GFR at each interval, analyzed changes within patients between follow-up intervals, and evaluated changes in 1-year graft and patient survival during the study period. Results. GFR intercept at 6 months averaged 54.3 mL/min/1.73 m2 (standard deviation [SD] 18.2 mL/min/1.73 m2). Decline in GFR between 6 and 12 months posttransplant averaged 0.69 mL/min/1.73 m2 (SD 10.9 mL/min/1.73 m2) and between 6 and 24 months averaged 2.45 mL/min/1.73 m2 (SD 15.7 mL/min/1.73 m2). However, the GFR decline was significantly attenuated during the study period among both deceased and living donor transplant recipients. Factors significantly associated with steeper GFR decline were increased pretransplant dialysis time, older donor age, diabetes as a primary diagnosis, low body mass index, African American race, retransplants, nonprivate insurance, and increased panel reactive antibody percent. Baseline or slope in renal function did not differ substantially by immunosuppressive regimen. One-year overall graft survival increased during the study period from 92.3% to 93.9%. Conclusions. GFR slopes and 1-year survival rates have improved in the United States independent of donor quality and immunosuppressive regimen. Findings may reflect increased skill in medical management and need further evaluation to determine whether short-term improvements translate to improved long-term survival.

HLA and MICA allosensitization patterns among patients supported by ventricular assist devices

BACKGROUND Ventricular assist devices (VADs) are increasingly being used as a bridge to transplantation and have been implicated as a risk factor for allosensitization to human leukocyte antigens (HLA). We investigate the association between VAD and allosensitization to human leukocyte antigens (HLA) and major-histocompatibility-complex (MHC) class I-related Chain A (MICA) antigens. METHODS We considered all patients who received a VAD at our institution between 2000 and 2009; 89 of them had pre-VAD and post-VAD (≤6 months after implant) HLA antibody screening. A control group of non-VAD heart transplant candidates was constructed with at least 2 pre-transplant panel-reactive antibody (PRA) tests within 8 months. Two controls were randomly selected/VAD patient matched for year (n = 178). Patients and controls with available sera from these time-points were tested by Luminex/flow PRA single-antigen beads and by MICA antibody Luminex single-antigen beads. Medical records were reviewed for comparison of pre-transplant immunologic risk factors and post-transplant outcomes between the 2 groups. RESULTS Compared with controls, VAD patients had greater Class I differences between peak and initial PRA (18% vs. 0%, p < 0.0001) and higher peak PRA (24% vs. 6%, p < 0.0001). The differences between the 2 groups in Class II were less pronounced than in Class I. Of patients who had single-antigen testing, VAD implantation was significantly associated with development of new HLA antibody specificities (Class I and/or Class II) post-VAD with an increase in calculated PRA (cPRA) post-VAD compared with controls (16% vs. 0%, p < 0.0001). This risk was still present after adjusting for age, gender, pre-VAD PRA, transfusion and duration of follow-up in a multivariate analysis (p < 0.0001 and 0.02, respectively). There were no differences in development of MICA antibodies between the 2 groups (14% in both). There was no significant difference in the incidence of pre-transplant positive T-cell crossmatch, pre-transplant donor-specific HLA antibodies, rejection episodes or graft survival between the 2 groups. CONCLUSION Our results suggest that VAD is associated with significant HLA allosensitization independent of common risk factors.

The impact of HLA unidirectional mismatches on the outcome of myeloablative hematopoietic stem cell transplantation with unrelated donors

The impact of HLA homozygosity at mismatched (MM) loci on the outcome of 2687 myeloablative unrelated donor hematopoietic cell transplantations performed for malignant disease was evaluated among 4 groups: 7/8 bidirectional MM transplants (donor and recipient heterozygous MM, n = 1393), 7/8 host-versus-graft (HVG) vector MM (recipient homozygous, n = 112), 7/8 graft-versus-host (GVH) vector MM (donor homozygous, n = 119), and 8/8 matches (n = 1063). Multivariate analyses found 7/8 GVH (P = .001) and bidirectional MM groups (P < .0001) had significantly worse transplant-related mortality and overall and disease-free survival than the 8/8 match group, a difference not observed with the 7/8 HVG MM group (P > .01). The 3 7/8 groups differed only for grades III-IV acute GVH disease (GVHD), where HVG MM had less GVHD than the 7/8 bidirectional MM (hazard ratio [HR] 0.52, P = .0016) and GVH MM (HR 0.43, P = .0009) groups but not the 8/8 group (HR 0.83, P = .39). There were no differences between the 7/8 groups for relapse, chronic GVHD, neutrophil engraftment, or graft failure. GVH MM have the same risk as 7/8 bidirectional MM. 7/8 HVG MM confer a reduced risk of acute GVHD without an increased risk of disease relapse or graft failure compared with a 7/8 bidirectional MM.

Scoring HLA Class I Mismatches by HistoCheck Does Not Predict Clinical Outcome in Unrelated Hematopoietic Stem Cell Transplantation

Currently, there is no well-accepted rating system for reliably predicting which HLA-mismatched (MM) unrelated donor should be selected for a patient without an HLA allele-matched donor. We evaluated the ability of an MM ranking system, HistoCheck, to predict the risk associated with HLA class I disparity in a population of 744 single allele or antigen HLA-A, -B, or -C MM myeloablative unrelated donor hematopoietic stem cell transplantation recipients with acute myelogenous leukemia, acute lymphoblastic leukemia, chronic myelogenous leukemia, or myelodysplastic syndrome, facilitated through the National Marrow Donor Program between 1988 and 2003. Multivariate models were used to adjust for other significant clinical risk factors. HLA MMs were scored using the HistoCheck Web-based tool, and the patients were divided into 4 quartiles: dissimilarity score (DSS) 1.04-2.84 (allele MM), DSS >2.84-13.75 (allele and antigen MM), DSS >13.75-19.39 (antigen MM), and DSS >19.39-36.62 (antigen MM). Using the lowest scoring quartile as the reference, the DSS groups were evaluated for associations with relapse, treatment-related mortality, acute and chronic graft-versus-host disease, leukemia-free survival, and overall survival in the entire cohort and also in subset analyses by disease and disease stage. No significant associations were found between DSS and any outcomes in the overall cohort using the quartile categories or treating DSS as a continuous variable. Higher DSS scores were associated with decreased engraftment in early-stage disease (P = .0003), but not in other disease stages. In summary, DSS does not correlate with transplantation outcomes, and the HistoCheck scoring system does not provide an effective technique for ranking HLA class I MM. The dataset used in this study is available to evaluate new algorithms proposed for donor selection.

Combined liver-kidney transplants: allosensitization and recipient outcomes.

Background. A pretransplant positive crossmatch in combined liver kidney transplants (CLK) is not considered a contraindication based on the reported immunoprotection conferred by the liver allograft. However, antibody-mediated rejection of the kidney in CLK has been reported recently. This prompted our study to investigate the impact of presensitization on CLK recipient outcomes. Methods. We examined kidney allograft and patient survival by indication of sensitization using Scientific Registry of Transplant Recipients data on CLK performed from 1995 to 2008. We defined sensitization as panel reactive antibody (PRA) more than 10% or a positive T-cell crossmatch (TXM). Results. Among 2484 CLK recipients with available PRA or TXM information, 30% had positive TXM or PRA more than 10%. Among those with TXM information, 12% had a positive crossmatch (n=234). In univariate analyses, patient (P=0.002) and overall kidney graft survival (P=0.015) were significantly diminished among sensitized patients. Differences in patient survival translated to estimated half-lives of 10.3 years among nonsensitized recipients versus 7.8 years among sensitized recipients, In multivariable Cox models, allosensitization was independently associated with patient death (adjusted hazard ratio=1.22, 95% CI, 1.04–1.43) and overall kidney graft loss (adjusted hazard ratio=1.16, 95% CI, 1.00–1.36). Conclusions. These results suggest a negative impact of presensitization on patient and overall renal allograft survival in CLK. Accordingly, presensitization may need to be considered in risk stratification and clinical management of CLK.