Friday, March 29, 2013

Who is the better donor for older hematopoietic transplant recipients: an older-aged sibling or a young, matched unrelated volunteer?

Older patients are increasingly undergoing allogeneic hematopoietic transplantation. A relevant question is whether outcomes can be improved with a younger allele-level 8/8 HLA-matched unrelated donor (MUD) rather than an older HLA-matched sibling (MSD). Accordingly, transplants in leukemia/lymphoma patients age ≥50 years were analyzed comparing outcomes for recipients of MSD ≥50 (n = 1415) versus MUD <50 years (n = 757). Risks of acute graft-versus-host disease (GVHD) grade 2 to 4 (hazard ratio [HR], 1.63; P < .001), 3 to 4 (HR, 1.85; P < .001), and chronic GVHD (HR, 1.48; P < .0001) were higher after MUD compared with MSD transplants. The effect of donor type on nonrelapse mortality (NRM), relapse, and overall mortality was associated with performance score. For patients with scores of 90 or 100, NRM (HR, 1.42; P = .001), relapse (HR, 1.45; P < .001), and overall mortality (HR, 1.28; P = .001) risks were higher after MUD transplants. For patients with scores below 90, NRM (HR, 0.96; P = .76), relapse (HR, 0.86; P = .25), and overall mortality (HR, 0.90; P = .29) were not significantly different after MUD and MSD transplants. These data favor an MSD over a MUD in patients age ≥50 years (read more)

Wednesday, March 27, 2013

Partially Mismatched Transplantation and Human Leukocyte Antigen Donor-Specific Antibodies

The presence of donor human leukocyte antigen (HLA)-specific antibodies (DSA) increases engraftment failure risk in partially HLA-mismatched, or HLA-haploidentical, allogeneic marrow (alloBMT) transplantation. As pre-existing sensitization to HLA antigens is not well characterized among candidates for HLA-haploidentical alloBMT, we retrospectively evaluated both the incidence and relative strength of DSA in this patient population. Based on correlations of solid-phase antibody assays on the Luminex (Luminex, Austin, TX) platform with actual crossmatch tests, DSA were characterized as weak for results that were consistent with negative flow cytometric crossmatch results or as moderate-to-strong for results consistent with positive flow cytometric or cytotoxicity crossmatches. We evaluated 296 alloBMT candidates; 111 (37.5%) were female. DSA were detected in 43 (14.5%) candidates, mostly among female candidates (42.9% female versus 12.5% male). Moderate-to-strong DSA strength was more frequently encountered when directed against haploidentical donors as compared with mismatched unrelated donors. DSA were most commonly detected in female patients directed against their children. Because the presence of DSA has been considered prohibitive for HLA-mismatched alloBMT, we additionally report a desensitization methodology used to reduce DSA to negative or weak levels, ie, levels well below those detectable in a flow cytometric crossmatch. Nine patients without other available donors underwent desensitization. Eight who reduced their DSA to negative or weak levels proceeded to alloBMT and achieved full donor engraftment. These data support routine DSA evaluation in all patients considered for mismatched alloBMT; however, for patients with no other viable options, desensitization to weak or negative DSA levels may afford the opportunity for successful transplantation (read more)

Friday, March 22, 2013

Achieving operational tolerance in transplantation: how can lessons from the clinic inform research directions?

Since the first solid organ transplant between the Herrick twins in 1954, transplantation immunology has sought to move away from harmful immunosuppressive regimens towards tolerogenic strategies that promote long-term graft survival. This has required a concerted multinational effort with scientists and clinicians working towards a common goal. Reports of immunosuppression-free kidney and liver allograft recipients have provided the proof-of-principle, but intentional generation of tolerance in clinical transplantation is still only achieved infrequently. Recently, there have been an increasing number of encouraging developments in the field in both experimental and clinical studies. In this article, we review the latest advances in tolerance research and consider possible future barriers and solutions in achieving reliable graft acceptance in the long term (read more)

Differential stem- and progenitor-cell trafficking by prostaglandin E2

To maintain lifelong production of blood cells, haematopoietic stem cells (HSCs) are tightly regulated by inherent programs and extrinsic regulatory signals received from their microenvironmental niche. Long-term repopulating HSCs reside in several, perhaps overlapping, niches that produce regulatory molecules and signals necessary for homeostasis and for increased output after stress or injury. Despite considerable advances in the specific cellular or molecular mechanisms governing HSC–niche interactions, little is known about the regulatory function in the intact mammalian haematopoietic niche. Recently, we and others described a positive regulatory role for prostaglandin E2 (PGE2) on HSC function ex vivo. Here we show that inhibition of endogenous PGE2 by non-steroidal anti-inflammatory drug (NSAID) treatment in mice results in modest HSC egress from the bone marrow. Surprisingly, this was independent of the SDF-1–CXCR4 axis implicated in stem-cell migration. Stem and progenitor cells were found to have differing mechanisms of egress, with HSC transit to the periphery dependent on niche attenuation and reduction in the retentive molecule osteopontin. Haematopoietic grafts mobilized with NSAIDs had superior repopulating ability and long-term engraftment. Treatment of non-human primates and healthy human volunteers confirmed NSAID-mediated egress in other species. PGE2 receptor knockout mice demonstrated that progenitor expansion and stem/progenitor egress resulted from reduced E-prostanoid 4 (EP4) receptor signalling. These results not only uncover unique regulatory roles for EP4 signalling in HSC retention in the niche, but also define a rapidly translatable strategy to enhance transplantation therapeutically (read more)

Allogeneic Bone Marrow Cocultured With Human Islets Significantly Improves Islet Survival and Function In Vivo

imageBackground: A significant barrier to islet transplantation is the rapid loss of human islet function in vivo. The present study evaluates whether bone marrow (BM) could be used to support human islet survival and function in vivo.
Methods: We cocultured human islets and BM for 3 weeks before transplantation into the left subrenal capsule of diabetic severe combined immunodeficient mice.
Results: The cocultured human islets before transplantation demonstrated improved viability, increased size, and migration capacity in vitro. After 4 months, animals transplanted with precultured BM/islets exhibited euglycemia and detectable human insulin levels (157 μU/mL), whereas no human insulin was detected in the islet-only transplantation group. Furthermore, the removal of the transplants on day 126 resulted in hyperglycemia, indicating that the reduction of blood glucose was dependent on the transplants. Diabetic mice transplanted with BM/islets demonstrated the longest survival period (130 vs. 40 days for those with islet-only transplants). The transplanted BM/islets showed signs of vascularization and migration from the renal capsule into medulla.
Conclusions: Our results suggest that BM precultured with human islets may enhance the survival and function of transplanted islets, thus significantly improving the therapeutic efficacy of islet transplantation for type 1 diabetes (read more)

Efficacy, Outcomes, and Cost-Effectiveness of Desensitization Using IVIG and Rituximab

imageBackground: Transplantation rates are very low for the broadly sensitized patient (panel reactive antibody [PRA]>80%; HS). Here, we examine the efficacy, outcomes, and cost-effectiveness of desensitization using high-dose intravenous immunoglobulin (IVIG) and rituximab to improve transplantation rates in HS patients.
Methods: From July 2006 to December 2011, 207 HS (56 living donors/151 deceased donors) patients (donor-specific antibody positive, PRA>80%) were desensitized using IVIG and rituximab. After desensitization, responsive patients proceeded to transplantation with an acceptable crossmatch. Cost and outcomes of desensitization were compared with dialysis.
Results: Of the 207 treated patients, 146 (71%) were transplanted. At 48 months, patient and graft survival by Kaplan–Meier were 95% and 87.5%, respectively. The total 3-year cost for patients treated in the desensitization arm was $219,914 per patient compared with $238,667 per patient treated in the dialysis arm. Thus, each patient treated with desensitization is estimated to save the U.S. healthcare system $18,753 in 2011 USD. Overall, estimated patient survival at the end of 3 years was 96.6% for patients in the desensitization arm of the model (based on Cedars-Sinai survival rate) compared with 79.0% for an age, end-stage renal disease etiology, and PRA matched group of patients remaining on dialysis during the study period.
Conclusions: We conclude that desensitization with IVIG+rituximab is clinically and cost-effective, with both financial savings and an estimated 17.6% greater probability of 3-year survival associated with desensitization versus dialysis alone. However, the benefits of desensitization and transplantation are limited by organ availability and allocation policies (read more)

Thursday, March 21, 2013

Mesenchymal stem cell transfusion for desensitization of positive lymphocyte cross-match before kidney transplantation: outcome of 3 cases

OBJECTIVES: Donor specific antibodies (DSA) and a positive cross-match are contraindications for kidney transplantation. Trials of allograft transplantation across the HLA barrier have employed desensitization strategies, including the use of plasmapheresis, intravenous immunoglobulins, anti-B-cell monoclonal antibodies and splenectomy, associated with high-intensity immunosuppressive regimens. Our case 1 report suffered from repeatedly positive lymphocyte cross match after 1st renal transplantation. Graft nephrectomy could not correct the state of sensitization. Splenectomy was done in a trial to get rid of the antibody producing clone. Furthermore plasmapheresis with low dose IVIG could not as well revert the state of sensitization for the patient. MATERIAL AND METHODS: About 50 millions donor specific MSCs were injected to the patient. RESULTS: MSCs transfusion proved to be the only procedure which could achieve successful desensitization before performing the second transplantation owing to their immunosuppressive properties. CONCLUSION: This case indicates that DS-MSCs is a potential option for anti-HLA desensitization. In cases 2 and 3 IV DS-MSCs transfusion was selected from the start as a successful line of treatment for pre renal transplantation desensitization to save other unnecessary lines of treatment that were tried in case 1 (read more)

Saturday, March 16, 2013

Therapeutic preparations of IVIg contain naturally occurring anti-HLA-E antibodies that react with HLA-Ia (HLA-A/-B/-Cw) alleles

The US Food and Drug Administration approved intravenous immunoglobulin (IVIg), extracted from the plasma of thousands of blood donors, for removing HLA antibodies (Abs) in highly sensitized patients awaiting organ transplants. Since the blood of healthy individuals has HLA Abs, we tested different IVIg preparations for reactivity to HLA single antigen Luminex beads. All preparations showed high levels of HLA-Ia and -Ib reactivity. Since normal nonalloimmunized males have natural antibodies to the heavy chains (HCs) of HLA antigens, the preparations were then tested against iBeads coated only with intact HLA antigens. All IVIg preparations varied in level of antibody reactivity to intact HLA antigens. We raised monoclonal Abs against HLA-E that mimicked IVIg’s HLA-Ia and HLA-Ib reactivity but reacted only to HLA-I HCs. Inhibition experiments with synthetic peptides showed that HLA-E shares epitopes with HLA-Ia alleles. Importantly, depleting anti–HLA-E Abs from IVIg totally eliminated the HLA-Ia reactivity of IVIg. Since anti–HLA-E mAbs react with HLA-Ia, they might be useful in suppressing HLA antibody production, similar to the way anti-RhD Abs suppress production. At the same time, anti–HLA-E mAb, which reacts only to HLA-I HCs, is unlikely to produce transfusion-related acute lung injury, in contrast to antibodies reacting to intact-HLA (read more)

Friday, March 15, 2013

Transvenous Renal Transplant Biopsy via a Transfemoral Approach

Percutaneous renal biopsy (PRB) of kidney transplants might be prevented by an elevated risk of bleeding or limited access to the allograft. In the following, we describe our initial experience with 71 transvenous renal transplant biopsies in 53 consecutive patients with unexplained reduced graft function who were considered unsuitable candidates for PRB (4.2% of all renal transplant biopsies at our institution). Biopsies were performed via the ipsilateral femoral vein with a renal biopsy set designed for transjugular renal biopsy (TJRB) of native kidneys. Positioning of the biopsy system within the transplant vein was achievable in 58 of 71 (81.7%) procedures. The specimen contained a median of 10 glomeruli (range 0–38). Tissue was considered as adequate for diagnosis in 56 of 57 (98.2%) biopsies. With respect to BANFF 50.9% of the specimen were adequate (>10 glomeruli), 47.4% marginally adequate (1–9 glomeruli) and 1.8% inadequate (no glomeruli). After implementation of real-time assessment all specimen contained glomeruli. One of the fifty-eight (1.8%) procedure-related major complications occurred (hydronephrosis requiring nephrostomy due to gross hematuria). Transfemoral renal transplant biopsy (TFRTB) is feasible and appears to be safe compared to PRB. It offers a useful new alternative for histological evaluation of graft dysfunction in selected patients with contraindications to PRB (read more)

Tuesday, March 12, 2013

Cancer risk with alemtuzumab following kidney transplantation

Alemtuzumab has been employed for induction therapy in kidney transplantation with low rates of acute rejection and excellent graft and patient survival. Antibody induction therapy has been linked to increased vulnerability to cancer. Data regarding malignancy rates with alemtuzumab are limited. We studied 1350 kidney transplant recipients (between 2001 and 2009) at the University of Pittsburgh Starzl Transplant Institute, for post-transplant de novo and recurrent malignancy, excluding non-melanoma skin cancer, among patients receiving alemtuzumab, thymoglobulin, and no induction therapies. Of the 1350 patients, 1002 (74.2%) received alemtuzumab, 205 (15.2%) received thymoglobulin, and 122 (9%) received no induction therapy. After excluding cancers occurring within 60 d post-transplantation, 43 (3.25%) malignancies were observed during a median follow-up time of 4.0 yr. The incidence of malignancy was 5.4% (1.09 per 100 patient-years [PY]) with thymoglobulin, 2.8% (0.74 per 100 PY) with alemtuzumab, and 3.3% (0.66 per 100 PY) with no induction (across all groups; p = 0.2342, thymoglobulin vs. alemtuzumab; p = 0.008). Thus, with the exception of non-melanoma skin cancer which we did not evaluate, alemtuzumab induction was not associated with increased cancer incidence post-kidney transplantation when compared to no induction therapy and was associated with lower cancer incidence when compared to thymoglobulin (read more)

Thursday, March 7, 2013

Center-Level Utilization of Kidney Paired Donation

With many multicenter consortia and a United Network for Organ Sharing program, participation in kidney paired donation (KPD) has become mainstream in the United States and should be feasible for any center that performs live donor kidney transplantation (LDKT). Lack of participation in KPD may significantly disadvantage patients with incompatible donors. To explore utilization of this modality, we analyzed adjusted center-specific KPD rates based on casemix of adult LDKT-eligible patients at 207 centers between 2006 and 2011 using SRTR data. From 2006 to 2008, KPD transplants became more evenly distributed across centers, but from 2008 to 2011 the distribution remained unchanged (Gini coefficient = 0.91 for 2006, 0.76 for 2008 and 0.77 for 2011), showing an unfortunate stall in dissemination. At the 10% of centers with the highest KPD rates, 9.9–38.5% of LDKTs occurred through KPD during 2009–2011; if all centers adopted KPD at rates observed in the very high-KPD centers, the number of KPD transplants per year would increase by a factor of 3.2 (from 494 to 1593). Broader implementation of KPD across a wide number of centers is crucial to properly serve transplant candidates with healthy but incompatible live donors (read more)

Wednesday, March 6, 2013

Epstein-Barr Virus DNAemia Is an Early Surrogate Marker of the Net State of Immunosuppresion in Solid Organ Transplant Recipients

imageBackground: Epstein-Barr virus (EBV) DNAemia (EBVd) may be a surrogate marker of the net state of immunosuppression after solid organ transplantation (SOT).
Methods: A sample of 81 SOT recipients (53 renal, 21 liver, and 7 cardiac) from our institution (2003–2004) surviving more than 180 days was analyzed. EBVd was monitored in whole blood within the first 6 months using a real-time polymerase chain reaction assay. Using a Cox proportional hazards model, duration and magnitude of EBVd were assessed as potential surrogate markers for the occurrence of late adverse events (>6 months): graft dysfunction, graft loss, death, and immunosuppression-related adverse events (IRAE), defined by the occurrence of solid organ tumor and opportunistic and severe infections.
Results: A median of 10 blood samples per patient was screened. A total of 68 (84%) patients had detectable EBVd. Persistent EBVd (>30 days) was found in 40 (49.4%) and high EBVd (>1500 copies/mL) in 35 (43.3%). Multivariate analyses showed that persistent EVBd and high EBVd levels were independently related to the development of IRAE (hazard ratio, 2.95 and 4.32, respectively), whereas no significant associations were observed with late graft dysfunction or graft loss.
Conclusions: Persistent and high levels of EBVd within the first 6 months after SOT are surrogate markers of increased risk of IRAE (read more)

Systematic Comparison of Four Cell- and Luminex-Based Methods for Assessment of Complement-Activating HLA Antibodies

imageBackground: Efforts to increase the specificity and sensitivity of human leukocyte antigen (HLA) antibody detection assays recently led to the establishment of two novel Luminex bead-based assays to detect complement-activating antibodies by the assessment of complement products C1q or C4d. Here, we present a systematic comparison of the four methods, complement-dependent lymphocytotoxicity (CDC) and C1q-, C4d-, and IgG-Luminex, to assess or predict the complement-binding capability of HLA IgG antibodies.
Methods: Forty-five sera of highly immunized patients have been assessed by in-house modified C1q- and C4d-Luminex assays and compared with standard CDC and IgG-Luminex.
Results: Antibody specificities assigned by the C1q- and C4d-Luminex assay revealed an excellent concordance of 94% and 97% for HLA class I and II, respectively. Complement-fixing HLA class II antibodies were found less frequently among IgG antibodies compared with class I. Both C1q- and C4d-Luminex detected, on average, three times more specificities than CDC. Although we found a high correlation of mean fluorescence intensity values between C1q- and C4d-Luminex assays, IgG mean fluorescence intensity was not a suitable surrogate marker for the prediction of complement binding.
Conclusions: C1q- and C4d-Luminex assays are characterized by an increased sensitivity and specificity compared with CDC, the current standard in detecting complement-fixing HLA antibodies. Pretransplantation risk assessment for transplantation but also posttransplantation monitoring are important applications for both assays to improve overall allograft survival (read more)

Rituximab Prevents an Anamnestic Response in Patients With Cryptic Sensitization to HLA

imageBackground: Some patients sensitized to HLA antigens do not have antibody present in serum specimens that are available before transplantation. However, such patients are at risk for an anamnestic response resulting from a proinflammatory response to the trauma of transplant surgery. Quantifying HLA-specific B cells provides a way to identify these patients and provide treatment to prevent an anamnestic response.
Methods: B cells were isolated before transplantation from 59 patients, 20 of whom were treated with rituximab at the time of transplantation. Ninety-nine tests were performed to quantify HLA-specific B cells by staining with HLA tetramers. Patients were considered sensitized or nonsensitized based on the frequencies of HLA-specific B cells. Pretransplantation and posttransplantation sera were tested for the detection of antibody specific for the tetramer antigen.
Results: Of the 24 cases where patients were considered sensitized to HLA antigens but did not have antibody before transplantation, no posttransplantation antibody to the tetramer antigen was detected in 10 cases when patients were treated with rituximab, but antibody was detected in 13 of 16 cases when there was no rituximab treatment (P=0.00006). The mean frequencies of B cells specific for HLA-B7 were the same in rituximab-treated patients who did not make antibody and in nontreated patients who did make antibody (6.0% vs. 5.7%; P=0.8).
Conclusions: Elimination of peripheral HLA-specific B cells in patients who are sensitized to HLA antigens but lacking detectable antibody abrogates an anamnestic response (read more)

Cotransplantation of Umbilical Cord–Derived Mesenchymal Stem Cells Promote Hematopoietic Engraftment in Cord Blood Transplantation: A Pilot Study

imageBackground: Delayed hematopoietic reconstitution after cord blood transplantation (CBT) may lead to increased risk of complications and longer hospitalization. Bone marrow–derived mesenchymal stem cells (MSCs) have been found to promote engraftment after hematopoietic stem cell transplantation. However, harvesting MSCs from bone marrow involves an invasive procedure. Then again, MSCs can be easily obtained from umbilical cords without harm to the donors.
Methods: Umbilical cord–derived MSCs (UCMSCs) were isolated from Wharton’s jelly and then ex vivo cultured. After showing normal karyotype and negative for infectious contamination, culture-expanded UCMSCs were intravenously infused into the recipients on the day of CBT. The control patients were those receiving CBT alone. Adverse effects and efficacy of intravenous UCMSCs were evaluated.
Results: A total of five patients received cotransplantation of UCMSCs at the time of CBT. No serious adverse events were observed. The time to achieve neutrophil engraftment ranged from 7 to 13 days (median, 11 days) and platelet engraftment ranged from 22 to 41 days (median, 32 days). Compared with the nine patients receiving CBT alone, patients receiving cotransplantation of UCMSCs had significantly faster hematopoietic recovery of neutrophils and platelets (P=0.02 and 0.01, respectively).
Conclusions: This pilot study is the first report of cotransplantation of UCMSCs in CBT. Intravenous infusion of UCMSCs appeared to be a feasible and safe modality to enhance hematopoietic engraftment in patients receiving CBT. Further studies were warranted (read more)

Saturday, March 2, 2013

Increased C4d in post-reperfusion biopsies and increased donor specific antibodies at one-week post transplant are risk factors for acute rejection in mild to moderately sensitized kidney transplant recipients.

In order to define the intensity of immunosuppression, we examined risk factors for acute rejection in desensitization protocols that use baseline donor-specific antibody levels measured as mean fluorescence intensity (MFImax). The study included 146 patients transplanted with a negative flow crossmatch and a mean follow-up of 18 months with the majority (83%) followed for at least 1 year. At the time of transplant, mean-calculated panel-reactive antibody and MFImax ranged from 10.3-57.2% and 262-1691, respectively, between low- and high-risk protocols. Mean MFImax increased significantly from transplant to 1 week and 1 year. The incidence of acute rejection (mean 1.65 months) as a combination of clinical and subclinical rejection was 32%, including 14% cellular, 12% antibody-mediated, and 6% mixed rejection. In regression analyses, only C4d staining in post-reperfusion biopsies (hazard ratio 3.3, confidence interval 1.71-6.45) and increased specific antibodies at 1-week post transplant were significant predictors of rejection. A rise in MFImax by 500 was associated with a 2.8-fold risk of rejection. Thus, C4d staining in post-reperfusion biopsies and an early rise in donor specific antibodies after transplantation are risk factors for rejection in moderately sensitized patients (read more)