Thursday, August 30, 2012

HLA-C–Dependent Prevention of Leukemia Relapse by Donor Activating KIR2DS1

Background : Of the cancers treated with allogeneic hematopoietic stem-cell transplantation (HSCT), acute myeloid leukemia (AML) is most sensitive to natural killer (NK)–cell reactivity. The activating killer-cell immunoglobulin-like receptor (KIR) 2DS1 has ligand specificity for HLA-C2 antigens and activates NK cells in an HLA-dependent manner. Donor-derived NK reactivity controlled by KIR2DS1 and HLA could have beneficial effects in patients with AML who undergo allogeneic HSCT.
Methods : We assessed clinical data, HLA genotyping results, and donor cell lines or genomic DNA for 1277 patients with AML who had received hematopoietic stem-cell transplants from unrelated donors matched for HLA-A, B, C, DR, and DQ or with a single mismatch. We performed donor KIR genotyping and evaluated the clinical effect of donor KIR genotype and donor and recipient HLA genotypes.
Results : Patients with AML who received allografts from donors who were positive for KIR2DS1 had a lower rate of relapse than those with allografts from donors who were negative for KIR2DS1 (26.5% vs. 32.5%; hazard ratio, 0.76; 95% confidence interval [CI], 0.61 to 0.96; P=0.02). Of allografts from donors with KIR2DS1, those from donors who were homozygous or heterozygous for HLA-C1 antigens could mediate this antileukemic effect, whereas those from donors who were homozygous for HLA-C2 did not provide any advantage (24.9% with homozygosity or heterozygosity for HLA-C1 vs. 37.3% with homozygosity for HLA-C2; hazard ratio, 0.46; 95% CI, 0.28 to 0.75; P=0.002). Recipients of KIR2DS1-positive allografts mismatched for a single HLA-C locus had a lower relapse rate than recipients of KIR2DS1-negative allografts with a mismatch at the same locus (17.1% vs. 35.6%; hazard ratio, 0.40; 95% CI, 0.20 to 0.78; P=0.007). KIR3DS1, in positive genetic linkage disequilibrium with KIR2DS1, had no effect on leukemia relapse but was associated with decreased mortality (60.1%, vs. 66.9% without KIR3DS1; hazard ratio, 0.83; 95% CI, 0.71 to 0.96; P=0.01).
Conclusions : Activating KIR genes from donors were associated with distinct outcomes of allogeneic HSCT for AML. Donor KIR2DS1 appeared to provide protection against relapse in an HLA-C–dependent manner, and donor KIR3DS1 was associated with reduced mortality (read more)

Saturday, August 25, 2012

Fecal calprotectin and alpha-1 antitrypsin predict severity and response to corticosteroids in gastrointestinal graft-versus-host disease

Diagnosis of gastrointestinal GVHD (GI-GVHD) is based on clinical symptoms and histologic findings. No biomarkers predicting responses to treatment are routinely available even though 30% to 50% of patients will not respond to corticosteroids. In this study, we aimed to evaluate fecal calprotectin, α-1-antitrypsin (α(1)-AT), and elastase at the time of first symptoms as diagnostic and prognostic tools for GI-GVHD in 72 consecutive patients, of whom 51 developed GI-GVHD. The prognostic value of markers was evaluated by their association with complete response (CR) and steroid-resistant (SR) GVHD. Calprotectin and α(1)-AT concentrations increased with GI-GVHD initial stages but patients with initial stage 1 GI-GVHD had similar marker levels to patients without GI-GVHD, so sensitivity to diagnose GI-GVHD was weak. In contrast, calprotectin and α(1)-AT were predictors for SR-GVHD and CR. Multiple regression modeling identified calprotectin and α(1)-AT concentration as independently predicting SR-GVHD together with initial stage > 2 GI-GVHD. Our results showed that fecal calprotectin and α(1)-AT levels at the time of diagnosis are predictive for responses to treatment but are not diagnostic markers for initial stage 1 to 3 GI-GVHD (read more).

Friday, August 24, 2012

High anti-HLA response in women exposed to intrauterine transfusions for severe alloimmune hemolytic disease is associated with mother–child HLA triplet mismatches, high anti-D titer, and new red blood cell antibody formation

BACKGROUND: Women whose fetuses were treated with intrauterine transfusions (IUTs) for alloimmune hemolytic disease are high responders to red blood cell (RBC) antigens. We investigated the risk for HLA alloimmunization.
STUDY DESIGN AND METHODS: Women and their children treated with IUT between 1987 and 2008 were included. Participants were HLA antigen typed and studied for the prevalence of HLA antibodies compared to age-matched parous nontransfused blood donors. Anti-D titer, the formation of new RBC antibodies after IUT, and the degree of fetomaternal HLA mismatches on HLA antibody formation and/or persistence were analyzed.
RESULTS: A higher prevalence of HLA Class I antibodies was observed in these women compared to controls (41% vs. 23%). Both a higher anti-D titer (>8000) and formation of new RBC antibodies after IUT were associated with increased HLA immunization. HLA antibody formation was associated with the number of fetomaternal triplet epitope mismatches. Antigens within HLA-Bw4, HLA-B35/51/52/53/18/78-complex and A1/A9, were higher and mismatches within HLA-C were less immunogenic than expected. HLA antibodies against the IUT-treated fetus were more persistent than other antibodies.
CONCLUSION: Women whose fetuses were treated with IUT had a high risk of developing and maintain fetal-specific HLA Class I antibodies. Factors associated with increased HLA immunization were a higher amount of fetomaternal HLA triplet mismatches, higher anti-D titer, and additional RBC antibody formation. We presume that the induction of HLA Class I antibodies is the result of increased fetomaternal hemorrhage during IUT, eliciting antibodies in women with an increased susceptibility to alloimmunization (read more).

Economics of hematopoietic cell transplantation

Given the rapidly rising healthcare costs, it is important to understand the economic costs of hematopoietic cell transplantation (HCT), a procedure that is being used more frequently in the treatment of various hematologic disorders. Studies have reported a wide range of costs for HCT, from $36 000 to $88 000 (USD) for a single autologous transplantation for the initial hospitalization, to $200 000 (USD) or more for a myeloablative allogeneic procedure involving an unrelated donor. Common posttransplantation complications, such as infections and GVHD, have been shown to be significant cost drivers. Comparisons across studies are limited by differences in patient populations, cost ascertainment methods, and length of follow-up. This article summarizes the current state of knowledge about costs and cost-effectiveness of HCT, highlighting the challenges in conducting these studies and identifying important areas for future research. We discuss the need for more value-based assessments of HCT using high-quality approaches to measuring costs and outcomes so that potential future efforts to contain costs are well informed and appropriate (read more).

Mapping of novel peptides of WT-1 and presenting HLA alleles that induce epitope-specific HLA-restricted T cells with cytotoxic activity against WT-1+ leukemias

The Wilms tumor protein (WT-1) is widely recognized as a tumor antigen that is expressed differentially by several malignancies. However, WT-1 peptides known to induce tumoricidal T cells are few. In the present study, we evaluated T-cell responses of 56 healthy donors to in vitro sensitization with autologous APCs loaded with a pool of overlapping 15-mer peptides spanning the sequence of WT-1. Thereafter, we mapped the WT-1 peptides eliciting responses in each individual, defined the immunogenic peptides, and identified their presenting HLA alleles. We report 41 previously unreported epitopes of WT-1: 5 presented by class II and 36 by class I alleles, including 10 that could be presented by more than 1 class I allele. IFN+ T cells responding to 98% of the class I and 60% of the class II epitopes exhibited HLA-restricted cytotoxicity against peptide-loaded targets. T cells specific for 36 WT-1 peptides were evaluable for leukemocidal activity, of which 27 (75%) lysed WT-1+ leukemic targets sharing their restricting HLA allele. Each epitope identified induced T-cell responses in most donors sharing the epitopes' presenting allele; these responses often exceeded responses to flanking peptides predicted to be more immunogenic. This series of immunogenic epitopes of WT-1 should prove useful for immunotherapies targeting WT-1+ malignancies (read more).

De Novo Donor-Specific HLA Antibody Development and Peripheral CD4+CD25high Cells in Kidney Transplant Recipients: A Place for Interaction?

The aim of this study was to determine whether the abundance of regulatory T cells (Tregs) (CD4+CD25high) affects the de novo development of anti-HLA donor-specific antibodies (DSAs) in kidney transplant recipients (KTRs). Methods. Unsensitized (PRA ≤ 10%, no DSA) adult primary KTRs who received a living (83%) or deceased (17%) KT in our Institution during 2004/2005 were included. DSA testing was performed monthly, and Tregs were quantified by flow cytometry every 3 months, during the 1st year after KT. All patients received triple drug immunosuppressive therapy (CNI + MMF or AZA + PDN); 83% received anti-CD25. Results. 53 KTRs were included; 32% developed DSA during the 1st year after KT. Significantly lower 7-year graft survival was observed in those who developed DSA. No difference was observed in Treg numbers up to 9 months after KT, between DSA positive and negative. However, at 12 months after KT, DSA-negative patients had significantly higher numbers of Treg. Conclusions. Early development of DSA was not associated to variations in Treg abundance. The differences in Treg numbers observed at the late time point may reflect better immune acceptance of the graft and may be associated to long-term effects. Additional inhibitory mechanisms participating earlier in DSA development after KT deserve to be sought (read more).

The complement-mediated prozone effect in the Luminex single-antigen bead assay and its impact on HLA antibody determination in patient sera

The Luminex xMAP system has become an important tool for HLA antibody screening and identification in sera of transplant patients. Recently, the Luminex single antigen bead assay was shown to be prone to an artefact, the so called prozone phenomenon: Sera with high titer HLA antibodies gave negative results when tested neat, but reacted strongly positive after 1:10 dilution. We also observed such a phenomenon and found that it was most likely caused by the complement component 1 (C1) by competitively displacing the detection antibodies. In this article we review the complement-mediated prozone effect and other mechanisms of interference with solid phase assays, and we discuss possible consequences for HLA antibody testing with the Luminex SAB assay (read more).

Thursday, August 23, 2012

Kidney Transplantation With and Without Simultaneous Bilateral Native Nephrectomy in Patients With Polycystic Kidney Disease: A Comparative Retrospective Study

imageBackground: Patients with autosomal dominant polycystic kidney disease (ADPKD) often need to undergo native nephrectomy and are candidates for kidney transplantation. The necessity and timing of nephrectomy are controversial. Some authors recommend simultaneous bilateral native nephrectomy (SBN) as the preferred option in living-donor kidney transplantation (LDKT). These recommendations are based on small study populations. We therefore set out to study outcomes of LDKT with SBN, compared with LDKT alone in a larger single-center cohort.
Methods: A consecutive series of 159 patients with ADPKD undergoing LDKT were included in the study. Of the 159 patients, 2 were excluded because of missing data, 79 underwent LDKT alone (group A), and 78 underwent LDKT with SBN (group B). Demographic data and intraoperative and postoperative data were collected from patient charts and the national kidney registry.
Results: There were no differences regarding background data. Group B experienced significantly longer operating times (183.7 vs. 319.3 min, P<0.001), a greater need for blood transfusions (0.1 vs. 1.6 units, P<0.001) and plasma products (35.1 vs. 438.3 mL, P<0.001), and longer hospital stays (11.8 vs. 15.4 days, P<0.001). It also experienced more intraoperative events and postoperative complications but fewer reoperations/reinterventions. There were no differences in patient and graft survival rates.
Conclusions: SBN in patients undergoing LDKT for ADPKD does not have a significant negative impact on patient and graft survival rates. It obviates a separate surgical procedure but requires longer hospital stay. It may be associated with more postoperative complications and risk of graft loss. These considerations should be communicated to the recipient and the donor (read more).

The Implications of Acute Rejection for Allograft Survival in Contemporary U.S. Kidney Transplantation

imageBackground: We examined the frequency and clinical impact of acute rejection (AR) in contemporary U.S. kidney transplantation.
Methods: Data for Medicare-insured kidney transplant recipients in 2000 to 2007 (n=48,179) were drawn from the United States Renal Data System. AR events were ascertained from Organ Procurement and Transplantation Network reports. AR was subclassified as antibody (Ab)-treated AR or other management (non–Ab-treated AR). Associations of AR with subsequent all-cause graft loss were estimated with time-varying Cox regression. Covariates included recipient, donor, and transplant factors in the United Network for Organ Sharing Kidney Allocation Review Committee survival model.
Results: The frequencies of non–Ab-treated AR per 100 graft-years at risk among standard criteria donor recipients over the first 6, 12, 24, and 36 months after transplantation were 9.93, 8.43, 5.71, and 4.70, respectively. Non–Ab-treated AR was consistently more than twice as common as Ab-treated AR by risk period and donor type. Development of Ab-treated AR predicted a greater risk of graft loss than non–Ab-treated AR. The relative risk for graft loss from Ab-treated AR continuously increased with later timing of AR after transplantation, whereas risk associated with non–Ab-treated AR peaked for events reported in months 13 to 24 after kidney transplantation. Regardless of the diagnosis time, the relative risk of graft loss was higher in the first 89 days after a given AR report compared with 90 days and beyond.
Conclusions: AR events recognized later after transplantation have more serious graft loss implications, especially within the first 89 days after AR reporting. This observation may reflect reduced intensity of monitoring, delays in diagnosis, or clinicopathologic features of late AR (read more).

An Isolated Venous Sac as a Novel Site for Cell Therapy in Diabetes Mellitus

imageBackground: Transplanting pancreatic islets is of significant interest for type 1 diabetes mellitus. After intraportal injection of islets, inferior engraftment and eventual loss of transplanted islets constitute major limitations. Therefore, alternative approaches will be helpful. Here, we evaluated in animals whether an isolated venous sac would support survival of transplanted islets, along with correction of hyperglycemia.
Methods: Pancreatic islets isolated from adult Lewis rats were transplanted either into an isolated venous sac made from lumbar vein or into the portal vein of syngeneic rats. The integrity and vascular organization of the venous sac was determined by studies of the local microcirculation. The engraftment, survival, and function of transplanted islets were analyzed by histology, including endocrine function in situ and by glycemic control in rats with streptozotocin-induced diabetes.
Results: Transplanted islets showed normal morphology with insulin expression in isolated venous sac during the long term. Transplanted islets received blood supply from vasa vasorum and had access to drainage through venous tributaries in the venous sac. This resulted in restoration of euglycemia in diabetic rats. Removal of islet graft-bearing venous sac in diabetic rats led to recurrence of hyperglycemia. By contrast, euglycemia was not restored in rats treated by intraportal transplantation of islets.
Conclusions: We demonstrated that pancreatic islets successfully engrafted and functioned in the isolated venous sac with ability to restore euglycemia in diabetic rats. Therefore, the isolated venous sac offers a new site for transplantation of pancreatic islets. This would be clinically beneficial as an alternative to intrahepatic islet transplantation (read more)

Wednesday, August 22, 2012

Alpha-Gal detectors in xenotransplantation research: a word of caution

Xenogeneic tissues are currently employed in clinical practice to create biological substitutes (bioprosthetic heart valves) and in the repair of various damaged tissues (pericardium, gastric-mucosa, nerves, cartilage). Many studies have shown that xenogeneic tissues express superficial epitopes as alpha-Gal, capable of triggering hyperacute and acute vascular rejection phenomena. Currently, no tissue treatment has proven able to completely mask or inactivate such epitopes. In fact, neither glutaraldehyde fixation nor decellularisation procedures ensure a definitive solution because of the persistence of reactive xenoantigen residues. The ability to ascertain alpha-Gal epitope removal from a xenogeneic tissue is closely related to the possibility of its quantitative determination. In the past, detection of the alpha-Gal epitope relied on the use of alpha-Gal reactive isolectin molecules and was limited to isolated cells. Recently, the quantitative evaluation of this antigen has been carried out in whole connective tissue through the use of the monoclonal antibody M86. This article provides an overview of the implications of the alpha-Gal epitope in the current clinical scenario and a definitive comparison between the reliability and specificity of isolectines vs. M86 in alpha-Gal determination (read more).

Tuesday, August 21, 2012

What is the significance of HLA-DR antigen expression in the extraglomerular mesangium in glomerulonephritis.

The HLA-DR antigen is a HLA class II molecule involved in the presentation of antigenic peptides to the T cell receptor, thus regulating the immune response. Renal expression of the HLA-DR antigen may indicate specific sites of immunologically-mediated kidney injury in glomerulonephritis (GN). The aim of our study was to assess the presence of the HLA-DR antigen along the nephron including the extraglomerular mesangium in GN. A cross-sectional study of 22 patients with glomerulonephritis, mean age: 46.59±10.77 years, 14 male and 8 female, was conducted. Conventional stains, as well as immunohistochemistry for the HLA-DR Antigen Alpha-Chain were employed on kidney biopsies. Immunohistochemistry was assessed using a semi-quantitative score: 0-absent, 1-mild, 2-moderate, 3-intense. Statistical analysis was performed using SPSS17. Four patients presented Focal and Segmental Glomerulosclerosis (FSGS), 5 patients: membranoproliferative GN, 7 patients: membranous nephropathy, 3 patients: mesangial proliferative GN, 2 patients: minimal change disease (MCD), and 1 patient: crescentic GN. Regarding the percentage of cases with HLA-DR positive cells along the nephron out of 22 patients: glomerular endothelial cells were 100% positive, intraglomerular mesangium cells were 81.8% positive, podocytes were 36.4% positive, extraglomerular mesangium cells were 31.8% positive, proximal tubule cells were 95.5% positive, distal tubule cells were 68.2% positive, interstitial capillaries were 77.3% positive, and cells of interstitial infiltrates were 27.3% positive. The percentage of cases staining positively for the HLA-DR antigen in the extraglomerular mesangium was 25% in FSGS, 60% in membranoproliferative GN, 0% in membranous nephropathy, 33.3% in mesangial proliferative GN, 100% in minimal change disease and 0% in crescentic GN.A prominent HLA-DR antigen distribution was found on glomerular endothelial cells, intraglomerular mesangium cells and proximal and distal tubular cells. Extraglomerular mesangium cells and podocytes stained variably for the HLA-DR antigen, as did the cells of the interstitial infiltrates. The extraglomerular mesangium which serves as a portal of entry into the intraglomerular mesangium is endowed with antigen-presenting capabilities and is a region where induction of immune reactions could take place (read more)

Saturday, August 18, 2012

Association of HLA Mismatch With Death With a Functioning Graft After Kidney Transplantation: A Collaborative Transplant Study Report

HLA mismatches may correlate with risk of death with a functioning graft (DWFG) because of requirement for higher immunosuppression doses and more antirejection therapy. Deceased-donor kidney transplants (n = 177 584) performed 1990–2009 and reported to the Collaborative Transplant Study were analyzed. The incidence of DWFG was found to be 4.8% during year 1 posttransplant and 7.7% during years 2–5 (Kaplan–Meier estimates). Most frequent causes of DWFG were infection, cardiovascular disease and malignancy (32.2%, 30.9% and 3.6% in year 1; 16.4%, 29.6% and 15.9% in years 2–5). HLA-A + B + DR mismatches were significantly associated with DWFG during year 1 (p < 0.001), a correlation that diminished but persisted during years 2–5 (p < 0.001). HLA mismatch was associated with DWFG because of infection (p < 0.001 during year 1, p = 0.043 during years 2–5) or cardiovascular disease (p < 0.001 during year 1, p = 0.030 during years 2–5) but not malignancy. There was also a significant association between HLA mismatch and hospitalization for viral (p < 0.001) or bacterial (p = 0.002) infection. Multivariable analysis showed that mismatches for HLA class II were more strongly associated with both hospitalization and DWFG than mismatches for HLA class I (read more).

IVIg and rituximab for treatment of chronic antibody-mediated rejection: a prospective study in paediatric renal transplantation with a 2-year follow-up

Chronic antibody-mediated rejection (AMR) is the major cause of late renal allograft loss. There is, however, no established treatment for this condition. We report the results of a prospective pilot study on an antihumoral therapy (AHT) consisting of high-dose intravenous immunoglobulin G (IVIG) and rituximab in 20 paediatric renal transplant recipients. Donor-specific HLA antibodies (HLA DSA) were quantified by Luminex-based bead array technology. Loss of eGFR decreased significantly from 7.6 ml/min/1.73 m² during 6 months prior to AHT to 2.1 ml/min/1.73 m² (= 0.0013) during 6 months after AHT. Fourteen patients (70%) responded: nine of nine patients (100%) without and five of 11 (45%) with transplant glomerulopathy (= 0.014). C4d positivity in PTC decreased from 40 ± 18.5% in the index biopsy to 11.6 ± 12.2% (= 0.002) in the follow-up biopsy. In four of nine biopsies (44%) C4d staining turned negative. During 2 years of follow-up, the median loss of eGFR in each of the four 6-month periods remained significantly lower compared with prior to AHT. Class I DSA declined in response to AHT by 61% (= 0.044), class II DSA by 63% (= 0.033) 12 months after intervention. AHT with IVIG and rituximab significantly reduces or stabilizes the progressive loss of transplant function in paediatric patients with chronic AMR over an observation period of 2 years, apparently by lowering circulating DSA and reducing intrarenal complement activation (read more).

Renal transplantation in sensitized recipients with positive luminex and negative CDC (complement-dependent cytotoxicity) crossmatches

Recently, Luminex-crossmatch (LumXm) was introduced. The aim of this study was to evaluate clinical outcomes in sensitized recipients with a positive Luminex-crossmatch (LumXm (+)) and a negative complement-dependent cytotoxicity crossmatch (CDCXm (−)) after renal transplantation. Fifty-five renal transplant recipients with a CDCXm (−) and PRA class I or II ≥20% were enrolled in this study between February 2008 and December 2010 at Severance Hospital. Eighteen patients displayed LumXm (+) defined as LumXm positive class I or II and 37 patients displayed LumXm (−). Mean duration of follow-up was 18.9 ± 8.3 months. During this period, no patient death or graft loss occurred. The incidence of biopsy-proven or clinically presumed rejection was higher in the LumXm (+) group (= 12, 66.7%) than in the LumXm (−) group (= 6, 18.2%) (= 0.001). All biopsy-proven acute rejections (= 12) were diagnosed as acute cellular rejection. No significant difference in mean serum creatinine level or eGFR was observed between the groups at 18 months post-transplantation. The short-term outcome of renal transplantation in sensitized patients with a LumXm (+) and a CDCXm (−) may be considered to be acceptable. However, patients with a LumXm (+) have a substantially higher immunological risk for the development of acute cellular rejection (read more).

Friday, August 17, 2012

Immunogenetics & Transplantation goes mobile !

If you own an Android (e.g. Samsung Galaxy) or Windows Phone 7 (WP7) (e.g. Nokia Lumia or Samsung Focus), you can download the official blog app by clicking here (Google Play) or here (Windows Phone Marketplace) for just € 3,99. See screenshots below. iPhone app will be available as soon as enough revenues will be collected from Android and WP7 marketing.

Just put your phone camera in front of this tag to download the app :

Wednesday, August 15, 2012

Impact of Pretransplant Human Leukocyte Antigen-C and -DP Antibodies on Kidney Graft Outcome

The aim of our study was to determine whether the presence of specific human leukocyte antigen (HLA)-C and -DP antibodies before transplantation influenced graft outcomes in immunized recipients. Two groups of pretransplant immunized recipients were studied: patients with only classical HLA-A, -B, -DR, -DQ antibodies (n = 176) and those with classical plus HLA-C and/or -DP antibodies (n = 27). Acute antibody-mediated rejection was preferentially associated with the presence of pretransplant anti-HLA-C and -DP antibodies (5/6 cases). In four cases, acute rejection episodes were followed by graft loss within 15 months after transplantation. There was a significant increase in the number of acute rejection episodes especially antibody-mediated acute rejections (P = .036) and in the number of graft losses for immunologic reasons (P < .001) among the group with pretransplant anti-C and -DP antibodies. Pretransplant anti-DP antibodies seemed to be involved more frequently in poor graft outcomes as shown in several recent published cases. We need to investigate their specific role among a larger cohort, taking into account an epitope analysis (read more).

Donor-specific HLA-DQ antibodies may contribute to poor graft outcome after renal transplantation

Increasing evidence suggests a detrimental effect of donor-specific antibodies directed against the human leukocyte antigen (HLA)-A, -B, and -DR loci on renal allograft outcomes. Limited data exist on the impact of de novo HLA-DQ antibodies. Over a 3-year period, we prospectively monitored 347 renal transplant recipients without pre-transplant donor-specific antibodies for their development de novo. After 26 months of follow-up, 62 patients developed donor-specific antibodies, of which 48 had a HLA-DQ antibody either alone (33 patients) or in combination with an HLA-A, -B, or -DR antibody (15 patients). Only 14 patients developed a donor-specific HLA-A, -B, or -DR antibody without a HLA-DQ antibody present. Acute rejection occurred in 21% of the HLA-DQ–only patients, insignificant when compared with 11% of patients without donor-specific antibodies. At the last follow-up, the mean serum creatinine and the fraction of patients with proteinuria were significantly higher in those that developed only HLA-DQ than those without antibodies. The 3-year graft survival was significantly worse when HLA-DQ antibodies were combined with non-DQ antibodies (52%) compared with HLA-DQ alone, non-DQ antibodies alone, or no antibodies (92–94%). Thus, our prospective monitoring study found that donor-specific HLA-DQ antibodies were the most common type detected and these antibodies may contribute to inferior graft outcomes. Ongoing surveillance is necessary to determine the long-term outcome of patients developing HLA-DQ donor-specific antibodies (read more).

Tuesday, August 14, 2012

Comparison of time on the deceased donor kidney waitlist versus time on the kidney paired donation registry in the Australian program

In the Australian kidney paired donation (KPD) program matching is based on acceptable mismatches, whereas deceased donor waitlist (DDWL) patients are allocated kidneys based on HLA antigen matching rules. Herein, we compared waiting time for a KPD match to the waiting time on the DDWL and the occurrence of matching in the DDWL for patients who were registered in both programs. Data on first dialysis, matches on the DDWL, KPD program entry, matches and transplant dates were assessed in 26 KPD recipients of the Australian program. There were 22 recipients who were listed in the DDWL and received kidney transplants by KPD. Time on dialysis until KPD transplantation was 808 ± 646 days. Eleven patients had never been matched with a deceased donor (waiting time 345 ± 237 days) and 11 had been matched on average 3 ± 5 times (waiting time 1227 ± 615 days, < 0.0001 vs. never matched), but did not progress to transplantation because of positive crossmatch or class II donor-specific antibody. Mean time from registration in the KPD program until kidney transplantation was 153 ± 92 days (< 0.0001 vs. DDWL). KPD allocation using the acceptable mismatch approach is effective in identifying suitable live donors for some recipients within a relatively short time-frame (read more).

Thursday, August 9, 2012

Hepatitis B–Positive Donors in Renal Transplantation: Increasing the Deceased Donor Pool

It is reasonable to transplant HbsAg-positive kidneys into recipients who are themselves hepatitis B surface antigen (HbsAg) positive with appropriate antiviral treatment after transplantation. Although there are limited data regarding the hepatitis B virus (HBV) transmission risk following transplantation of kidneys from HbsAg-positive donors into HBV-immune recipients, current literature suggests that the risk of chronic infection in the recipient can be prevented by using antiviral agents or by boosting protective anti-HBs titers. The risk of chronic HBV infection following transplantation of kidneys from HbsAg-positive donors for HBV-naive recipients is high but can be minimized by administering lifelong antiviral therapy. Such a policy could be considered in an urgent situation. The most cost-effective antiviral prophylaxis strategy is lifelong lamivudine. Kidneys from HBsAg neg/anti-HBcore pos recipients are associated with a low rate of chronic HBV infection in the recipient and therefore can no longer be regarded as marginal donors. Booster vaccination to achieve protective HBV immunity or lifelong lamivudine therapy should prevent posttransplant HBV infection. Hence, we believe that strategies allowing transplantation of kidneys from donors with HBV can be undertaken safely with careful selection and matching of donors and recipients increasing access to kidney transplantation. (read more)

The EuroChimerism concept for a standardized approach to chimerism analysis after allogeneic stem cell transplantation

Hematopoietic stem cell transplantation is becoming an increasingly important approach to treatment of different malignant and non-malignant disorders. There is thus growing demand for diagnostic assays permitting the surveillance of donor/recipient chimerism posttransplant. Current techniques are heterogeneous, rendering uniform evaluation and comparison of diagnostic results between centers difficult. Leading laboratories from 10 European countries have therefore performed a collaborative study supported by a European grant, the EuroChimerism Concerted Action, with the aim to develop a standardized diagnostic methodology for the detection and monitoring of chimerism in patients undergoing allogeneic stem cell transplantation. Following extensive analysis of a large set of microsatellite/short tandem repeat (STR) loci, the EuroChimerism (EUC) panel comprising 13 STR markers was established with the aim to optimally meet the specific requirements of quantitative chimerism analysis. Based on highly stringent selection criteria, the EUC panel provides multiple informative markers in any transplant setting. The standardized STR-PCR tests permit detection of donor- or recipient-derived cells at a sensitivity ranging between 0.8 and 1.6%. Moreover, the EUC assay facilitates accurate and reproducible quantification of donor and recipient hematopoietic cells. Wide use of the European-harmonized protocol for chimerism analysis presented will provide a basis for optimal diagnostic support and timely treatment decisions (read more)

Donor-Specific Antibodies after Ceasing Immunosuppressive Therapy, with or without an Allograft Nephrectomy

Within the last few years, anti–human leukocyte antigen detection assays have significantly improved. This study asked, using the Luminex single-antigen assay, whether an allograft nephrectomy allowed donor-specific alloantibodies to appear that were not previously detected in the serum when the failed kidney was still in place.
Design, setting, participants, & measurements : After losing the kidney allograft and stopping immunosuppressive therapy, the proportions of donor-specific alloantibodies and nondonor-specific alloantibodies were compared in patients who had (n=48; group I) and had not (n=21; group II) undergone an allograft nephrectomy. Allograft nephrectomies were performed at 150 days after kidney allograft loss, and the time between allograft nephrectomy and last follow-up was 538±347 days.
Results : At kidney allograft loss, donor-specific alloantibodies were detected in three group II patients (14.2%) and six group I patients (12.5%). At last follow-up, donor-specific alloantibodies were detected in 11 patients (52.4%) without and 39 patients (81%) with an allograft nephrectomy (P=0.02). Anti–human leukocyte antigen class I donor-specific alloantibodies were positive in 23.8% of group II and 77% of group I patients (P<0.001); anti–human leukocyte antigen class II donor-specific alloantibodies were positive in 42.8% of group II and 62.5% of group I patients. Independent predictive factors for developing donor-specific alloantibodies after losing kidney allograft and stopping immunosuppressants were number of anti–human leukocyte antigen A/B mismatches at transplantation (zero versus one or more) and allograft nephrectomy.
Conclusions : The development of donor-specific alloantibodies was significantly greater in patients with a failed kidney who had undergone an allograft nephrectomy compared with those patients who had not undergone allograft nephrectomy (read more and editorial)

Tuesday, August 7, 2012

Pretransplant Anti-HLA-Cw and Anti-HLA-DP Antibodies in Sensitized Patients.

We investigated the prevalence and the strength of anti-HLA-Cw and DP antibodies and clinical outcomes in kidney transplant recipients with isolated donor-specific anti-HLA-Cw antibodies. Patients on the waiting list were screened by Luminex Single Antigen Beads (One Lambda). The strength of antibodies was determined by mean fluorescence intensity (MFI) values of the beads. Of the 1069 patients on the waiting list, 251 (24%) were sensitized with calculated panel reactive antibody > 0%. The frequency and the median MFI values of anti-HLA antibodies to Cw (56%, 4,955) and DP (35%, 2,945) were lower than anti-HLA antibodies to Cw (56%, 4,955) and DP (35%, 2,945) were lower than anti-HLA-A (79%, 10,194), B (86%, 11,235), DR (66%, 7,866) and DQ (69%, 8,283) (p < 0.01). Among three major sensitizing events, only previous transplant was associated with development of all anti-HLA antibodies and history of pregnancy was associated only with development of anti-HLA-A antibodies. Eight patients with donor-specific anti-HLA-Cw antibodies received transplantation. During a median 6 months of follow-up (range 3-24 months), patient and graft survival was 100% without any acute rejection. In summary, the prevalence and the strength of anti-HLA-Cw and HLA-DP were lower compared to anti-HLA-A, B, DR, and DQ antibodies and previous organ transplantation was the main sensitizing event in our cohort of patients (read more)

Rapid T cell repopulation after rabbit anti-thymocyte globulin (rATG) treatment is driven mainly by cytomegalovirus.

Rabbit anti-thymocyte globulin (rATG) induces a long-lasting lymphocytopenia. CD4(+) T cells remain depleted for up to 2 years, whereas the CD8(+) T cell compartment is refilled rapidly by highly differentiated CD27(-) CD45RA(+) CD57(+) effector-type cells. Because the presence of these highly differentiated CD8(+) T cells has been associated with cytomegalovirus (CMV) infection, we questioned to what extent restoration of CMV T cell immunity contributes to the re-emergence of T cells following rATG treatment. We compared T cell repopulation in six CMV-seropositive patients with CMV reactivation (reactivating CMV(+) ) to that in three CMV(+) patients without reactivation (non-reactivating CMV(+) ), and to that in three CMV-seronegative recipients receiving a kidney from a CMV-seronegative donor (CMV(-/-) ). All patients received rATG because of acute allograft rejection. Total CD4 and CD8 counts, frequency and phenotype of virus-specific CD8(+) T cells were determined. In reactivating CMV(+) patients, total CD8(+) T cells reappeared rapidly, whereas in non-reactivating CMV(+) patients they lagged behind. In CMV(-/-) patients, CD8(+) T cell counts had not yet reached pretransplant levels after 2 years. CMV reactivation was indeed followed by a progressive accumulation of CMV-specific CD8(+) T cells. During lymphocytopenia following rATG treatment, serum interleukin (IL)-7 levels were elevated. Although this was most prominent in the CMV-seronegative patients, it did not result in an advantage in T cell repopulation in these patients. Repopulated CD8(+) T cells showed increased skewing in their Vβ repertoire in both CMV(-/-) and reactivating CMV-seropositive patients. We conclude that rapid T cell repopulation following rATG treatment is driven mainly by CMV (read more)

Non-HLA-antibodies targeting angiotensin type 1 receptor and antibody mediated rejection.

Antibody-mediated mechanisms directed against non-HLA related targets may exert negative impact on allograft function and survival. Angiotensin type 1 receptor (AT(1)R) emerges as a functional target for non-HLA allo- and autoantibodies (AT(1)R-Abs) comprising of IgG1 and IgG3 subclasses. Proof of concept for pathophysiologic relevance of AT(1)R-Abs in antibody mediated rejection (AMR) in renal transplants was provided by passive transfer studies in animal model and therapeutic rescue of patients. Although AT(1)R-Abs may belong to complement fixing IgG subclasses, C4d positivity in renal transplant biopsies was not frequently detected implicating complement independent mechanisms of injury. AT(1)R-Abs exert direct effects on endothelial and vascular smooth muscle cells by induction of Erk1/2 signaling and increased DNA binding of transcription factors associated with pro-inflammatory and pro-coagulatory responses. Establishment of enzyme-linked immunosorbent assay employing extracts of cells overexpressing AT(1)R in its native conformation was instrumental for recent studies in independent cohorts. Assessing the AT(1)R-Ab-status along with the HLA-antibodies may help to identify patients at particular risk for irreversible acute or chronic allograft injuries and improve overall outcomes. This review summarizes the current state of research in AT(1)R biology, development in diagnostic strategies, discusses recent clinical studies, and provides perspectives on further refinements in understanding AT(1)R-Ab-actions (read more)

Regulation of the CD4(+) T cell allo-immune response by endothelial cells.

Recent studies have revealed the presence of pro-inflammatory and/or regulatory CD4(+) T cells within allografts promoting either graft rejection or tolerance. Histological evidence has identified the microvascular endothelium as the primary site of allograft damage as it is the first site of encounter with the recipient's immune system. The initial view of the human endothelial cell inducing an effector Th1 response leading to graft rejection has been extended by recent results which demonstrate the endothelial cell ability to generate other CD4(+) T cell sub-populations including Th17 and Treg cells. In the transplantation setting, the allo-reactivity of the endothelium with the CD4(+) T cell populations is likely to depend upon multiple factors including the vascular origin of the endothelial cell, the cytokine environment, the presence or absence of pro-inflammatory stimuli including ligands of Toll like receptors and alloantibodies. This review provides an update on the characteristics of the endothelial cell activation of the CD4(+) T cell response and an analysis of the factors, which can modify this activity in favor of either graft rejection or tolerance (read more)

Alloantibody induced platelet responses in transplants: Potent mediators in small packages.

The early histological studies of organ allografts noted platelets attached to vascular endothelium. Platelets adhere to vessels before any morphological evidence of endothelial injury. Subsequently, in vitro and in vivo experiments have demonstrated that alloantibodies can induce exocytosis of von Willebrand factor and P-selectin from endothelial cells and attachment of platelets within minutes. Platelets also adhere to and stimulate leukocytes. These interactions are increased by complement activation. After attachment platelets degranulate, releasing preformed mediators. Some chemokines stored together in platelet granules can form heteromers with synergistic functions. Heteromers containing platelet factor 4 (PF4; CXCL4) are specific to platelets and provide insights to unique platelet functions and opportunities for therapeutic intervention (read more)

Anti-HLA antibodies in regenerative medicine stem cell therapy.

Research on stem cell therapies for regenerative medicine is progressing rapidly. Although the use of autologous stem cells is a tempting choice, there are several instances in which they are either defective or not available in due time. Allogenic stem cells derived from healthy donors presents a promising alternative. Whether autologous or allogenic, recent advances have proven that stem cells are not as immune privileged as they were thought. Therefore understanding the interactions of these cells with the recipient immune system is paramount to their clinical application. Transplantation of stem cells induces humoral as well as cellular immune response. This review focuses on the humoral response elicited by stem cells upon their administration and consequences on the survival and maintenance of the graft. Current transplantation identifies pre- and post-transplantation anti-HLA antibodies as immune rejection and cell signaling effectors. These two mechanisms are likely to operate similarly in the context of SC therapeutics. Ultimately this knowledge will help to propose novel strategies to mitigate the allogenic barriers. Immunogenetics selection of the donor cell and immunomonitoring are key factors to allow the implementation of regenerative stem cell in the clinics (read more)

Mechanisms of human smooth muscle cell proliferation and transplant vasculopathy induced by HLA class I antibodies: In vitro and in vivo studies.

Vascular smooth muscle cells (SMC) play an important role in the pathophysiology of transplant vasculopathy (TV), a major cause of late death in patients receiving an organ transplant. In this review we describe the proliferative effect in vitro and in vivo of HLA class I antibodies on human SMC. We have developed an experimental model using segments of human mesenteric arteries transplanted in the position of the infrarenal aorta in immunodeficient mice (SCID/beige). Weekly injections of transplanted mice with a monoclonal antibody towards HLA class I provoked typical lesions of TV after 6weeks in the human graft while transplanted mice receiving an irrelevant antibody did not develop any significant lesion. In vitro, the anti-HLA antibodies were mitogenic to SMC and we showed that they activate a stress-induced signaling pathway implicating matrix metalloproteinases (MMP) and neutral sphingomyelinase 2 (nSMase-2). The proliferative effect of anti-HLA antibodies could be blocked by pharmacological inhibitors or by siRNA. Administration of pharmacological inhibitors diminished the development of TV in grafted mice injected with anti-HLA antibodies demonstrating an important role of the MMP/nSMase-2 pathway in antibody-induced TV. This observation opens new perspectives for the management of TV in clinical settings (read more)

HLA Class I: An unexpected role in integrin β4 signaling in endothelial cells.

The production of anti-donor antibodies to HLA class I and class II antigens following transplantation is associated with development of transplant vasculopathy and graft loss. Antibodies against HLA class I (HLA-I) molecules are thought to contribute to transplant vasculopathy by triggering signals that elicit the activation and proliferation of endothelial cells. The proximal molecular events that regulate HLA-I dependent signal transduction are not well understood. We demonstrated a mutual dependency between HLA-I and integrin β4 to stimulate signal transduction and cell proliferation. Similarly, we found that integrin β4-mediated cell migration was dependent upon its interactions with HLA-I molecules. Since integrin β4 has been implicated in angiogenesis and tumor formation, associations between integrin β4 and HLA-I may play an important role in cancer. Further characterization of interactions between HLA-I and integrin β4 may lead to the development of therapeutic strategies for the treatment and prevention of chronic allograft rejection and cancer (read more)

Role of antibodies to self-antigens in chronic allograft rejection: Potential mechanism and therapeutic implications.

Significant progress has been made in preventing acute allograft rejection following solid organ transplantation resulting in improved allograft survival. However, long term function still remains disappointing primarily due to chronic allograft rejection. Alloimmune responses primarily defined by the development of antibodies (Abs) to donor mismatched major histocompatibility antigens during the post-transplantation period have been strongly correlated to the development of chronic rejection. In addition, recent studies have demonstrated an important role for autoimmunity including the development of Abs to organ specific self-antigens in the pathogenesis of chronic allograft rejection. Based on this, a new paradigm has evolved indicating a possible cross-talk between the alloimmune responses and autoimmunity leading to chronic rejection. In this review, we will discuss the emerging concept for the role of cellular and humoral immune responses to self-antigens in the immunopathogenesis of chronic allograft rejection which has the potential to develop new strategies for the prevention and/or treatment of chronic rejection (read more)

Induction of Allograft Tolerance by Monoclonal CD3 Antibodies: A Matter of Timing

Despite remarkable progress in organ transplantation through the development of a wealth of immunosuppressive drugs highly effective at controlling acute rejection, two major problems still remain, the loss of transplants due to chronic rejection and the growing number of sensitized recipients due to previous transplants, transfusions or pregnancies. Induction of immune tolerance appears to be the only way to curb this complex situation. Here we describe that a therapy, already successfully used to restore immune tolerance to self-antigens in overt autoimmunity, is effective at promoting transplant tolerance. We demonstrate that a short low-dose course with CD3 antibodies started after transplantation, at the time of effector T cell priming to alloantigens, induces permanent acceptance of fully mismatched islet allografts. Mechanistic studies revealed that antigen-specific regulatory and effector T cells are differentially affected by the treatment. CD3 antibody treatment preferentially induces apoptosis of activated alloreactive T cells which is mandatory for tolerance induction. In contrast, regulatory T cells are relatively spared from CD3 antibody-induced depletion and can transfer antigen-specific tolerance thus arguing for their prominent role in sustaining long-term graft survival (read more).

Fetuin-A acts as an endogenous ligand of TLR4 to promote lipid-induced insulin resistance

Toll-like receptor 4 (TLR4) has a key role in innate immunity by activating an inflammatory signaling pathway. Free fatty acids (FFAs) stimulate adipose tissue inflammation through the TLR4 pathway, resulting in insulin resistance. However, current evidence suggests that FFAs do not directly bind to TLR4, but an endogenous ligand for TLR4 remains to be identified. Here we show that fetuin-A (FetA) could be this endogenous ligand and that it has a crucial role in regulating insulin sensitivity via Tlr4 signaling in mice. FetA (officially known as Ahsg) knockdown in mice with insulin resistance caused by a high-fat diet (HFD) resulted in downregulation of Tlr4-mediated inflammatory signaling in adipose tissue, whereas selective administration of FetA induced inflammatory signaling and insulin resistance. FFA-induced proinflammatory cytokine expression in adipocytes occurred only in the presence of both FetA and Tlr4; removing either of them prevented FFA-induced insulin resistance. We further found that FetA, through its terminal galactoside moiety, directly binds the residues of Leu100–Gly123 and Thr493–Thr516 in Tlr4. FFAs did not produce insulin resistance in adipocytes with mutated Tlr4 or galactoside-cleaved FetA. Taken together, our results suggest that FetA fulfills the requirement of an endogenous ligand for TLR4 through which lipids induce insulin resistance. This may position FetA as a new therapeutic target for managing insulin resistance and type 2 diabetes (read more).

Cutoff values and data handling for solid-phase testing for antibodies to HLA: effects on listing unacceptable antigens for thoracic organ transplantation.

Application of single-antigen solid-phase immunoassay (SPI) in virtual crossmatch-based organ allocation has been hindered by continued debate over the biologic relevance of detected antibodies and the relationship between cutoff mean fluorescence intensity (MFI) values with crossmatch testing results. To define SPI parameters accurately predicting crossmatch testing, we analyzed a series of anti-HLA antibodies from highly-sensitized patients awaiting lung or heart transplantation. Serial dilution of serum for SPI and cytotoxic crossmatch (CXM) enabled comparison over a wide spectrum of antibody "strengths". Receiver operating characteristic (ROC) analysis identified predictive cutoff values for HLA Class I and DR-specific antibodies. However, antibodies to HLA-DQ antigens demonstrated a significantly different characteristic, highlighting difficulties in interpretation of clinical significance. We also quantitatively characterized two data handling methods, MFI ratio (MR) and relative ratio (RR), to examine their potential impact on identifying unacceptable antigens. In combination with user defined cutoff values, MFI, MR and RR lead to discordant identification of antibodies. Establishment of cutoff values for MR and RR that are comparable to MFI demonstrated increased consistency in antibody identification. This single laboratory experience is an example of establishing statistically robust cutoff values and validation across different data handling methods for use of SPI in virtual crossmatch. (read more)

Monday, August 6, 2012

Predicting renal graft failure by sCD30 levels and de novo HLA antibodies at 1year post-transplantation.

HLA antibodies and sCD30 levels were detected in the serum sampled from 620 renal graft recipients at 1 year post-transplantation, which were followed up for 5 years. Six-year graft and patient survivals were 81.6% and 91.0%. HLA antibodies were detected in 45 recipients (7.3%), of whom there were 14 cases with class I antibodies, 26 cases with class II, and 5 cases with both class I and II. Much more graft loss was record in recipients with HLA antibodies than those without antibodies (60% vs. 15.1%, p<0.001). Significantly higher sCD30 levels were recorded in recipients suffering graft loss than the others (73.9±48.8 U/mL vs. 37.3±14.6 U/mL, p<0.001). Compared with those with high sCD30 levels, recipients with low sCD30 levels (<50 U/mL) had much better 6-year graft survival (92.4% vs. 46.6%, p<0.001). Further statistical analysis showed that detrimental effect of de novo HLA antibodies and high sCD30 on graft survival was not only independent but also additive. Therefore, post-transplantation monitoring of HLA antibodies and sCD30 levels is necessary and recipients with elevated sCD30 level and/or de novo HLA antibody should be paid more attention in order to achieve better graft survival (read more)

Proteasome inhibition by bortezomib: effect on HLA-antibody levels and specificity in sensitized patients awaiting renal allograft transplantation.

BACKGROUND: Sensitization to human leukocyte antigen (HLA) prolongs waiting list time and reduces allograft survival in solid organ transplantation. Current strategies for pretransplant desensitization are based on B-cell depletion and extracorporeal treatment. The proteasome inhibitor bortezomib allows direct targeting of the antibody-producing plasma cell and has been used in antibody-mediated rejection (AMR) and recipient desensitization with varying results. Here, we report the effect of bortezomib preconditioning on HLA antibody titers and specificity in highly sensitized patients awaiting renal allograft transplantation.
PATIENTS AND METHODS: Two highly sensitized patients awaiting third kidney transplantation were given one cycle of bortezomib (1.3 mg/m², days 1, 4, 8, 11), as part of recipient desensitization. Time-course and levels of anti-HLA antibodies, as well as specificity to previous transplant antigens were monitored by luminex technology. In addition, measles and tetanus toxoid immunoglobulin G (IgG) was measured.
RESULTS: Following bortezomib, overall changes in IgG levels were small and no sustained reduction in anti-HLA class I or II antibody levels was observed over more than 100 days of follow-up to both, donor specific and non-donor specific antigens. Moreover, anti-measles and -tetanus toxoid IgG levels remained unchanged.
CONCLUSIONS: Bortezomib preconditioning alone does not result in sustained reduction of HLA antibody levels or alter protective immunity in sensitized patients. This supports the notion, that bortezomib requires activation of plasma cells, as in AMR, to effectively reduce HLA antibody production. Hence, in a pretransplant setting, combination strategies may be required to derive benefit from proteasome inhibition (read more).

The risk of cancer is not increased in patients with multiple kidney transplantations.

BACKGROUND: The aim of this study was to investigate whether the number of transplantations, as a marker of the graft rejection status of the patient, is associated with an increased risk of malignancies.
METHODS: In a cohort study, 1213 patients, receiving a kidney transplantation between 1966 and 1995 at the Leiden University Medical Center, were analyzed. All cutaneous squamous cell carcinoma and internal malignancies, which had developed between 1966 and 2007, were recorded. The influence of number of transplantations, age, sex and time on immunosuppression on the risk of squamous cell carcinoma and internal malignancies was investigated by time-dependent multivariate Cox's proportional hazard models.
RESULTS: Of the 1213 kidney transplant recipients, 319 received a second kidney, 78 a third; 13 of them a fourth and 4 of them a fifth transplantation. After adjustment for potentially confounding factors, including age, sex and years on immunosuppressive therapy we did not detect an increased risk of cancer in patients with multiple transplantations. On the contrary, patients with three or more transplantations had a 1.6-fold decreased risk of squamous cell carcinomas and a 3.6-fold decreased risk of internal malignancies.
CONCLUSION: We conclude that kidney transplant recipients with three or more transplantations do not have an increased risk of cutaneous squamous cell carcinoma and internal malignancies (read more)

Lymphocyte activation induces cell surface expression of an immunogenic vimentin isoform.

High titers of anti-vimentin antibodies after transplantation are known to be associated with poor long-term graft survival. Vimentin is an intracellular protein which is present in different isoforms in the cell. In a previous study with sera from hemodialysis patients on the kidney transplantation waiting list we could show that only a 49kDa and a 60kDa isoform are recognized by patients' anti-vimentin antibodies while the other isoforms remain undetected. However, it is still unclear whether antibodies against this intracellular protein can bind to intact cells. Here we show that vimentin can be present on the cell surface under certain conditions. Lymphocytes from healthy volunteers were used as a model for allogeneic cells. We could show by immunofluorescence microscopy, flow cytometry and Western blot experiments that concanavalin A (Con A) activated lymphocytes express a 49kDa vimentin isoform on their cell surface while the 60kDa isoform remains inaccessible from the outside. This expression is associated with an increased binding of sera from hemodialysis patients which were positive for anti-vimentin antibodies. These results suggest that cell activation enhances binding of anti-vimentin antibodies to intact cells which might contribute to chronic allograft nephropathy (read more)

EpHLA software: a timesaving and accurate tool for improving identification of acceptable mismatches for clinical purposes.

The HLAMatchmaker algorithm, which allows the identification of “safe” acceptable mismatches (AMMs) for recipients of solid organ and cell allografts, is rarely used in part due to the difficulty in using it in the current Excel format. The automation of this algorithm may universalize its use to benefit the allocation of allografts. Recently, we have developed a new software called EpHLA, which is the first computer program automating the use of the HLAMatchmaker algorithm. Herein, we present the experimental validation of the EpHLA program by showing the time efficiency and the quality of operation. The same results, obtained by a single antigen bead assay with sera from 10 sensitized patients waiting for kidney transplants, were analyzed either by conventional HLAMatchmaker or by automated EpHLA method. Users testing these two methods were asked to record: (i) time required for completion of the analysis (in minutes); (ii) number of eplets obtained for class I and class II HLA molecules; (iii) categorization of eplets as reactive or non-reactive based on the MFI cutoff value; and (iv) determination of AMMs based on eplets' reactivities. We showed that although both methods had similar accuracy, the automated EpHLA method was over 8 times faster in comparison to the conventional HLAMatchmaker method. In particular the EpHLA software was faster and more reliable but equally accurate as the conventional method to define AMMs for allografts. CONCLUSION: The EpHLA software is an accurate and quick method for the identification of AMMs and thus it may be a very useful tool in the decision-making process of organ allocation for highly sensitized patients as well as in many other applications (read more)

Friday, August 3, 2012

Neutropenic enterocolitis after high-dose chemotherapy and autologous stem cell transplantation: incidence, risk factors, and outcome

Background : Neutropenic enterocolitis (NE) is a life-threatening complication occurring after intensive chemotherapy; however, no data are available on NE development after hematopoietic stem cell transplantation (SCT). The aim of this study was to determine the incidence, risk factors, and outcome of NE after high-dose chemotherapy and autologous SCT (autoSCT).
Methods: A total of 297 adult patients who qualified for autoSCT with non-Hodgkin's lymphoma (NHL), Hodgkin's disease, multiple myeloma, and acute myeloid leukemia were analyzed. Patients were conditioned with carmustine, etoposide, cytarabine, melphalan (BEAM); melphalan alone; or busulfan and cyclophosphamide (BuCy2), and transplanted with peripheral blood or bone marrow CD34+ cells. Diagnosis of NE was established in case of neutropenic fever, abdominal pain or diarrhea, and bowel wall thickening >4 mm on abdominal sonography.
Results : Neutropenic infections occurred in 262 patients (88%). NE was diagnosed in 32 patients (12%), a median +3 (1-5) days after SCT. Bloodstream infections were present in 18 patients, with gram-negative bacteria in 11 patients. All patients were treated conservatively with carbapenems and total parenteral nutrition with bowel rest. The course of disease was complicated by ileus or septic shock in 9 patients, and was fatal for 3 (9.6%) patients. In univariate analysis, the initial diagnosis of NHL (= 0.017) and conditioning with BEAM (= 0.043) had prognostic value. In multivariate analysis, only initial diagnosis of NHL (= 0.017) had prognostic significance.
Conclusions : NE is a rare but severe complication in patients undergoing autoSCT. Gram-negative bacteria remain the main causative pathogen. Abdominal sonography allows early diagnosis and treatment, effective in most of patients without surgery. In our analysis, NE was seen more often in NHL patients treated with a BEAM regimen (read more).

Wednesday, August 1, 2012

Deceased-donor kidney perfusate and urine biomarkers for kidney allograft outcomes: a systematic review

Background:Accurate and reliable assessment of kidney quality before transplantation is needed to predict recipient outcomes and to optimize management and allocation of the allograft. The aim of this study was to systematically review the published literature on biomarkers in two mediums (the perfusate from deceased-donor kidneys receiving machine perfusion and deceased-donor urine) that were evaluated for their possible association with outcomes after kidney transplantation.
Methods: We searched the Ovid Medline and Scopus databases using broad keywords related to deceased-donor biomarkers in kidney transplantation (limited to humans and the English language). Studies were included if they involved deceased-donor kidneys, measured perfusate or urine biomarkers and studied a possible relationship between biomarker concentrations and kidney allograft outcomes. Each included article was assessed for methodological quality.
Results: Of 1430 abstracts screened, 29 studies met the inclusion criteria. Of these, 23 were studies of perfusate (16 biomarkers examined) and 6 were studies of urine (18 biomarkers examined). Only 3 studies (two perfusate) met the criteria of ‘good’ quality and only 12 were published since 2000. Perfusate lactate dehydrogenase, glutathione-S-transferase (GST) and aspartate transaminase were all found to be significantly associated with delayed graft function in a majority of their respective studies (6/9, 4/6 and 2/2 studies, respectively). Urine neutrophil gelatinase-associated lipocalin, GST, Trolox-equivalent antioxidant capacity and kidney injury molecule-1 were found to be significantly associated with allograft outcomes in single studies that examined diverse end points.
Conclusion: Higher quality studies are needed to investigate modern kidney injury biomarkers, to validate novel biomarkers in larger donor populations and to determine the incremental predictive value of biomarkers over traditional clinical variables (read more).

Cold ischaemia, innate immunity and deterioration of the glomerular filtration barrier in antibody-mediated acute rejection

Background: In renal transplantation, cold ischaemia (CI) determines acute rejection through innate immunity among others. Acute rejection episodes are a risk factor for late allograft dysfunction and proteinuria. This implies some alteration of the glomerular filtration barrier (GFB). Besides its effects on acute rejection, we hypothesized that CI might somehow damage the GFB being directly responsible for late proteinuria.
Methods: On rat kidney allografts suffering from antibody-mediated acute rejection with or without CI and compared with syngeneic grafts, we quantified the gene expression of innate and adaptive immune mediators and assessed the capillary glomerular basement membranes (CapBM) by immunostaining collagen-IV (ColIV). ColIV was also assessed in equivalent groups from a previous chronic study followed up for 24 weeks.
Results: CI up-regulated enzymes critical in the stabilization of collagen chains, increasing ColIV deposition and thickening the CapBM. CI increased the C4d and IgG deposits within grafts, amplified innate immunity (heat shock protein 70, fibronectin, Toll-like-receptor-4 and MyD88) and synergized with alloreactivity in triggering adaptive response through CD40.
Conclusions : Initial CI increased the ColIV deposition in CapBM, damaging the GFB and being responsible for part of the proteinuria associated with late allograft dysfunction. This deterioration of the GFB is related to the early innate immunity activation and subsequent up-regulation of CD40 in acute rejected grafts. In chronic rejected allografts, thickened CapBM may be a consequence of an unresolved immune–inflammatory response worsened by CI (read more).

In vitro reconstitution of human kidney structures for renal cell therapy

Background:Recent advances in cell therapies have provided potential opportunities for the treatment of chronic kidney diseases (CKDs). We investigated whether human kidney structures could be preformed in vitro for subsequent implantation in vivo to maximize tissue-forming efficiency.
Methods: Human renal cells were isolated from unused donor kidneys. Human renal cells were cultured and expanded. Migration was analyzed using growth factors. To form structures, cells were placed in a three-dimensional culture system. Cells were characterized by immunofluorescence, western blots and fluorescence-activated cell sorting using renal cell-specific markers for podocin, proximal and distal tubules and collecting ducts. An albumin uptake assay was used to analyze function. Three-dimensional cultures were implanted into athymic rat kidneys to evaluate survival.
Results : Human renal cells were effectively expanded in culture and retained their phenotype, migration ability and albumin uptake functions. Human renal cell in three-dimensional culture-formed tubules, which stained positively for proximal, distal tubule and collecting duct markers, and this was confirmed by western blot. Polarity of the tubular cells was determined by the presence of E-cadherin, N-cadherin and Na-K ATPase. Colocalization of labeled albumin and proximal tubule markers proved functionality and specificity of the newly formed tubules. An in vivo study showed that cells survived in the kidney for up to 6 weeks.
Conclusions : these findings demonstrate that human renal cell grown in three-dimensional culture are able to generate kidney structures in vitro. This system may ultimately be developed into an efficient cell-based therapy for patients with CKD (read more).

Therapeutic potential of mesenchymal stem cell-derived microvesicles

Several studies have demonstrated that mesenchymal stem cells have the capacity to reverse acute and chronic kidney injury in different experimental models by paracrine mechanisms. This paracrine action may be accounted for, at least in part, by microvesicles (MVs) released from mesenchymal stem cells, resulting in a horizontal transfer of mRNA, microRNA and proteins. MVs, released as exosomes from the endosomal compartment, or as shedding vesicles from the cell surface, are now recognized as being an integral component of the intercellular microenvironment. By acting as vehicles for information transfer, MVs play a pivotal role in cell-to-cell communication. This exchange of information between the injured cells and stem cells has the potential to be bi-directional. Thus, MVs may either transfer transcripts from injured cells to stem cells, resulting in reprogramming of their phenotype to acquire specific features of the tissue, or conversely, transcripts could be transferred from stem cells to injured cells, restraining tissue injury and inducing cell cycle re-entry of resident cells, leading to tissue self-repair. Upon administration with a therapeutic regimen, MVs mimic the effect of mesenchymal stem cells in various experimental models by inhibiting apoptosis and stimulating cell proliferation. In this review, we discuss whether MVs released from mesenchymal stem cells have the potential to be exploited in novel therapeutic approaches in regenerative medicine to repair damaged tissues, as an alternative to stem cell-based therapy (read more).