Thursday, November 20, 2014

Report of the Inefficacy of Eculizumab in Two Cases of Severe Antibody-Mediated Rejection of Renal Grafts

Background : Acute antibody-mediated rejection (AMR) is responsible for up to 20% to 30% of acute rejection after kidney transplantation. New therapeutic agents have recently emerged, such as eculizumab, an anticomplement protein-C5 monoclonal antibody. In the setting of renal transplantation, eculizumab has so far proved effective both for preventive and curative treatments of AMR in sensitized patients and patients diagnosed with severe AMR. Unsuccessful eculizumab treatment has only been reported once in the literature by Stegall et al. (Am J Transplant 2011; 11: 2405).
Methods and Results : We present two cases of AMR resistant to eculizumab after renal transplantation. One patient received the anti-C5 antibody curatively, and the other patient developed AMR while being treated with eculizumab after a relapse of atypical hemolytic uremic syndrome. The peculiarity of these two cases was the absence of C4d deposition in peritubular capillaries as well as the absence of C1q-binding donor-specific anti–human leukocyte antigen alloantibody, as determined retrospectively, suggesting that a complement-independent mechanism underlies the pathogenesis of these AMR.
Conclusion : The use of eculizumab in C4d-negative or C1q-negative AMR does not seem effective (read more).

Pretransplant Immunologic Risk Assessment of Kidney Transplant Recipients With Donor-Specific Anti–Human Leukocyte Antigen Antibodies

Background : Patients with pretransplantation strong donor-specific anti–human leukocyte antigen (HLA) antibodies (DSA) are at higher risk for rejection. We aimed to study the safety of kidney transplantation in patients with lower strength DSAs in a prospective cohort study. 
Methods : Three hundred and seventy-three consecutive adult kidney transplant recipients with (DSA+; n=66) and without (DSA−; n=307) DSA were evaluated. Anti-HLA antibodies with mean fluorescence intensity values over 5,000 for HLA-A, HLA-B, and HLA-DR and more than 10,000 for HLA-DQ were reported as unacceptable antigens. Patients received transplant if flow cytometry T-cell and B-cell cross-match channel shift values were less than 150 and 250, respectively, with antithymocyte globulin and intravenous immunoglobulin induction treatment. 
Results : Patients had a mean number of 1.6±0.8 DSAs with a mean fluorescence intensity value of 2,815±2,550. Twenty-seven percent were flow cytometry cross-match positive with T-cell and B-cell channel shift values of 129±49 and 159±52, respectively. During a median follow-up of 24 months (range, 6–50), there were no statistically significant differences in patient (99% vs. 95%) and graft survival (88% vs. 90%) rates between DSA+ and DSA− groups, respectively. Cumulative acute rejection rates of 11% in the DSA+ group and 12% in the DSA− group were similar. Two DSA+ (3%) and five DSA− (2%) patients developed chronic antibody-mediated rejection (3%). The mean serum creatinine levels were identical between the two groups (1.4±0.6 mg/dL). 
Conclusion : Similar patient and graft survival, and acute rejection rates can be achieved in DSA+ patients compared to DSA− patients with pretransplantation immunologic risk assessment (read more)

Thursday, November 13, 2014

ABO Incompatible Renal Transplantation Without Antibody Removal Using Conventional Immunosuppression Alone

ABO incompatible living donor renal transplantation (ABOi) can achieve outcomes comparable to ABO compatible transplantation (ABOc). However, with the exception of blood group A2 kidneys transplanted into recipients with low titer anti-A antibody, regimens generally include antibody removal, intensified immunosuppression and splenectomy or rituximab. We now report a series of 20 successful renal transplants across a range of blood group incompatibilities using conventional immunosuppression alone in recipients with low baseline anti-blood group antibody (ABGAb) titers. Incompatibilities were A1 to O (3), A1to B (2), A2 to O (2), AB to A (2), AB to B (1), B to A1 (9), B to O (1); titers 1:1 to 1:16 by Ortho. At 36 months, patient and graft survival are 100%. Antibody-mediated rejection (AbMR) occurred in one patient with thrombophilia and low level donor-specific anti-HLA antibody. Four patients experienced cellular rejection (two subclinical), which responded to oral prednisolone. This series demonstrates that selected patients with low titer ABGAb can undergo ABOi with standard immunosuppression alone, suggesting baseline titer as a reliable predictor of AbMR. This reduces morbidity and cost of ABOi for patients with low titer ABGAb and increases the possibility of ABOi from deceased donors (read more)

Saturday, November 8, 2014

Denatured Class I Human Leukocyte Antigen Antibodies in Sensitized Kidney Recipients: Prevalence, Relevance, and Impact on Organ Allocation

Background : Single antigen flow beads assays may overestimate sensitization because of the detection of supposedly irrelevant antibodies recognizing denatured class I human leukocyte antigens (HLAs).
Methods : Sera of 323 HLA-sensitized kidney transplant candidates positive with a class I HLA single antigen flow beads assay were retested after acid treatment of the beads. Denatured HLA antibodies were identified according to ratio between the measured fluorescence intensity for treated and nontreated beads. T-lymphocyte flow cytometry crossmatches were performed to characterize the ability of these antibodies to recognize HLA on normal cells as a surrogate of their potential clinical relevance. Their impact on organ allocation was evaluated through a calculated panel reactive antibody. The utility of single antigen flow beads largely devoid of denatured HLA (iBeads) was also evaluated.
Results : Denatured HLA antibodies were detected in 39% of the patients. They provided much less positive flow cytometry crossmatches than anti-native HLA antibodies (16% vs. 83%, P<0.0001). Removing the HLA-A and HLA-B antigens targeted by denatured HLA antibodies from unacceptable antigens lowered the calculated panel reactive antibody for 90 patients, sometimes dramatically. The iBeads assay demonstrated nearly the same ability to predict crossmatch results than the acid treatment assay.
Conclusion : Denatured class I HLA antibodies are common, but the antigens they target should not be considered as unacceptable in most cases, because they negatively impact access to a transplant while predominantly providing negative sensitive crossmatches. The iBeads assay seems to be a valuable alternative to better define unacceptable antigens (read more)

One-Unit versus Two-Unit Cord-Blood Transplantation for Hematologic Cancers

BACKGROUND : Umbilical-cord blood has been used as the source of hematopoietic stem cells in an estimated 30,000 transplants. The limited number of hematopoietic cells in a single cord-blood unit prevents its use in recipients with larger body mass and results in delayed hematopoietic recovery and higher mortality. Therefore, we hypothesized that the greater numbers of hematopoietic cells in two units of cord blood would be associated with improved outcomes after transplantation.
METHODS : Between December 1, 2006, and February 24, 2012, a total of 224 patients 1 to 21 years of age with hematologic cancer were randomly assigned to undergo double-unit (111 patients) or single-unit (113 patients) cord-blood transplantation after a uniform myeloablative conditioning regimen and immunoprophylaxis for graft-versus-host disease (GVHD). The primary end point was 1-year overall survival.
RESULTS : Treatment groups were matched for age, sex, self-reported race (white vs. nonwhite), performance status, degree of donor–recipient HLA matching, and disease type and status at transplantation. The 1-year overall survival rate was 65% (95% confidence interval [CI], 56 to 74) and 73% (95% CI, 63 to 80) among recipients of double and single cord-blood units, respectively (P=0.17). Similar outcomes in the two groups were also observed with respect to the rates of disease-free survival, neutrophil recovery, transplantation-related death, relapse, infections, immunologic reconstitution, and grade II–IV acute GVHD. However, improved platelet recovery and lower incidences of grade III and IV acute and extensive chronic GVHD were observed among recipients of a single cord-blood unit.
CONCLUSIONS : We found that among children and adolescents with hematologic cancer, survival rates were similar after single-unit and double-unit cord-blood transplantation; however, a single-unit cord-blood transplant was associated with better platelet recovery and a lower risk of GVHD (read more)

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 (read more)

Impact of donor mismatches at individual HLA-A, -B, -C, -DR, and -DQ loci on the development of HLA-specific antibodies in patients listed for repeat renal transplantation

We have analyzed the relationship between donor mismatches at each HLA locus and development of HLA locus–specific antibodies in patients listed for repeat transplantation. HLA antibody screening was undertaken using single-antigen beads in 131 kidney transplant recipients returning to the transplant waiting list following first graft failure. The number of HLA mismatches and the calculated reaction frequency of antibody reactivity against 10,000 consecutive deceased organ donors were determined for each HLA locus. Two-thirds of patients awaiting repeat transplantation were sensitized (calculated reaction frequency over 15%) and half were highly sensitized (calculated reaction frequency of 85% and greater). Antibody levels peaked after re-listing for repeat transplantation, were independent of graft nephrectomy and were associated with length of time on the waiting list (odds ratio 8.4) and with maintenance on dual immunosuppression (odds ratio 0.2). Sensitization was independently associated with increasing number of donor HLA mismatches (odds ratio 1.4). All mismatched HLA loci contributed to the development of HLA locus–specific antibodies (HLA-A: odds ratio 3.2, HLA-B: odds ratio 3.4, HLA-C: odds ratio 2.5, HLA-DRB1: odds ratio 3.5, HLA-DRB3/4/5: odds ratio 3.9, and HLA-DQ: odds ratio 3.0 (all significant)). Thus, the risk of allosensitization following failure of a first renal transplant increases incrementally with the number of mismatches at all HLA loci assessed. Maintenance of re-listed patients on dual immunosuppression was associated with a reduced risk of sensitization (read more)

Thursday, November 6, 2014

Postoperative Rebound of Anti-Blood Type Antibodies and Antibody-Mediated Rejection after ABO-Incompatible Living Related Kidney Transplantation.

The purpose of this study is to examine whether postoperative anti-blood type antibody rebound is attributed to kidney allograft rejection in ABO blood type-incompatible (ABO-I) living related kidney transplantation (KTx). A total of 191 ABO-I recipients who received ABO-I living related KTx between 2001 and 2013 were divided into two groups: Group 1 consisted of low rebound (≦1:32), N=170, and Group 2 of high rebound (≧1:64), N=21, according to the levels of the rebounded anti-blood type antibodies within one year after transplantation. No prophylactic treatment for rejection was administered for elevated anti-blood type antibodies, regardless of the levels of the rebounded antibodies. Within one year after transplantation, T cell-mediated rejection was observed in 13 of 170 recipients (13/170, 8%) in Group 1, and in 2 of 21 recipients (2/21, 10%) in Group 2 (Groups 1 vs. 2, P=0.432). Antibody-mediated rejection was observed in 15 of 170 recipients (15/170, 9%) and 2 of 21 recipients (2/21, 10%) in Groups 1 and 2, respectively (P=0.898). In this study, we found no correlation between the postoperative anti-blood type antibody rebound and the incidence of acute rejection. We concluded that no treatment is necessary for rebounded anti-blood type antibodies (read more)