Development Of HLA Antibodies Research Articles

Optimization of Hypercholesterolemia Treatment after Heart Transplant: The Role of PCSK9 Inhibitors.

Previous studies have reported the benefit of statins after Heart Transplant (HT). However, the use of high-dose statins might be limited in some HT patients due to intolerance and interactions with immunosuppression or might not be enough to achieve Low-Density Lipoprotein (LDL) cholesterol goals. Hyperlipidemia has been associated with coronary allograft vasculopathy. Proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors might be a safe and effective option in HT patients with suboptimal lipid control. In a retrospective study, we identified HT patients in our center with LDL cholesterol >100 mg/dL, after diet modifications and up-titration of statins to maximum tolerated dose, treated with PCSK9i. The primary endpoint was LDL reduction one month after, and secondary endpoints were the development of donorspecific HLA antibodies (DSA) and the presence of coronary allograft vasculopathy or rejection. From January, 2018, to January, 2024, we identified five HT patients treated with PCSK9 inhibitors. In all cases, evolocumab was used. A significant reduction in LDL cholesterol was observed (151.6 ± 13.5 mg/dl to 72.4 ± 14.6 mg/dl; p = 0.04, mean reduction 75.7 ± 14.1 mg/dl), as well as in total cholesterol (231 ± 34.6 mg/dl to 152.2 ± 38.9 mg/dl; p < 0.01, mean reduction 78.8 ± 22.2 mg/dl). A significant increase in HDL cholesterol was not observed (45.4 ± 10.9 mg/dl to 46.2 ± 11.1 mg/dl; p = 0.60). One patient developed DSA five years after treatment onset. Rejection and coronary allograft vasculopathy were not observed. PCSK9 inhibitors are safe and effective in reducing LDL in HT patients. However, larger studies are needed to clarify if they can reduce the development of coronary allograft vasculopathy.

Human leukocyte antigen immunization in transfusion-dependent Moroccan patients with beta-thalassemia major: prevalence and risk factors

IntroductionBeta-thalassemia major patients need a regular blood transfusion to have an initial normal growth. However, these patients have an increased risk of developing alloantibodies. Our main goal was to study HLA alloimmunization in Moroccan Beta-thalassemia patients by confronting it with transfusion and demographic criteria, exploring the involvement of HLA typing profile in the development of HLA antibodies and in turn determining risk factors for their development. MethodsThe study consisted of 53 Moroccan pediatric patients with Beta-thalassemia major. Screening for HLA alloantibodies was performed using Luminex technology Whereas HLA genotyping was done with sequence-specific primers (PCR-SSP). Results: In this study, 50.9% of patients have been identified as positive for HLA antibodies, with 59.3% having both HLA Class I and Class II antibodies. A significant increase frequency of DRB1*11 allele was revealed in non-immunized patients (34.6% vs. 0%, p = 0.001). Our results also revealed that the majority of our HLA immunized patients were women (72.4% vs. 27.6%, p = 0.001), and transfused with more than 300 units of RBC units (66.7% vs. 33.3%, p = 0.02). There were statistically significant differences when comparing these frequencies. ConclusionsThis paper revealed that the transfusion dependent Beta-thalassemia major patients are exposed to risk of developing HLA antibodies following transfusions with leukoreduced RBC units. The HLA DRB1*11 was a protective factor against HLA alloimmunization in our beta-thalassemia major patients.

Effect of Temporary versus Durable Support Devices as Bridge to Transplant on HLA Antibody Production in Heart Transplant Recipients

Purpose Development of HLA antibodies with the use of durable left ventricular assist devices (LVAD) as a bridge to transplant (BTT) is well established. However, the effect of temporary support devices (TSD) (such as intra-aortic balloon pump (IABP) and Impella 5.5®) on HLA antibodies has not yet been reported. The aim of this study was to assess the effect of TSD as BTT on development and magnitude of HLA Class I and II antibodies compared to durable LVAD pre-transplant. Methods The prevalence and magnitude of HLA Class I and II HLA antibodies was assessed retrospectively from 32 cardiac transplant patients with TSD or durable LVAD as BTT (13 with Impella 5.5® (41%), 8 with IABP (25%), and 11 with durable LVAD (Heart Mate II, Heart Mate III, or HeartWare (34%). One Lambda LABScreen kit was used to detect anti-HLA antibodies in serum samples pre- and post-support device up to the day of heart transplantation. Results The total number of HLA antibodies detected was 22, 22, and 146 in patients with Impella 5.5®, IABP, and durable LVAD respectively (Table 1). There was no significant increase in the number and magnitude of HLA class I and II antibodies after TSD placement (Impella 5.5® and IABP). In contrast, there was a significant increase in the number and magnitude of HLA antibodies in durable LVAD recipients. Mean duration of TSD was between 7-30 days compared to 9 months-10 years for durable LVAD as BTT. Conclusion The short-term use of TSD with either (Impella 5.5® or IABP) as BTT appears to offer a reduced risk profile for developing significant HLA sensitization prior to heart transplantation compared to durable LVAD. Further long-term outcome studies should be considered to establish this potential benefit. Development of HLA antibodies with the use of durable left ventricular assist devices (LVAD) as a bridge to transplant (BTT) is well established. However, the effect of temporary support devices (TSD) (such as intra-aortic balloon pump (IABP) and Impella 5.5®) on HLA antibodies has not yet been reported. The aim of this study was to assess the effect of TSD as BTT on development and magnitude of HLA Class I and II antibodies compared to durable LVAD pre-transplant. The prevalence and magnitude of HLA Class I and II HLA antibodies was assessed retrospectively from 32 cardiac transplant patients with TSD or durable LVAD as BTT (13 with Impella 5.5® (41%), 8 with IABP (25%), and 11 with durable LVAD (Heart Mate II, Heart Mate III, or HeartWare (34%). One Lambda LABScreen kit was used to detect anti-HLA antibodies in serum samples pre- and post-support device up to the day of heart transplantation. The total number of HLA antibodies detected was 22, 22, and 146 in patients with Impella 5.5®, IABP, and durable LVAD respectively (Table 1). There was no significant increase in the number and magnitude of HLA class I and II antibodies after TSD placement (Impella 5.5® and IABP). In contrast, there was a significant increase in the number and magnitude of HLA antibodies in durable LVAD recipients. Mean duration of TSD was between 7-30 days compared to 9 months-10 years for durable LVAD as BTT. The short-term use of TSD with either (Impella 5.5® or IABP) as BTT appears to offer a reduced risk profile for developing significant HLA sensitization prior to heart transplantation compared to durable LVAD. Further long-term outcome studies should be considered to establish this potential benefit.

Appearance of new CDC-reactive antibodies in patients waiting for kidney transplantation

BackgroundPatients awaiting kidney transplantation are regularly screened for HLA-antibodies, but there is scarce data about the optimal interval. MethodsResults from Complement-dependent cytotoxicity testing (CDC) for waitlisted patients were reviewed for increases in panel reactive antibodies (PRA) by at least 10%-points. Clinical records were screened for historic immunizing events and possible trigger factors preceding the PRA-increase. Additionally, non-pretransplanted men tested negative for HLA antibodies by solid-phase assays (SPA) out of their first two samples on the waiting list (“non-immunized men”) were evaluated for detection of HLA antibodies by SPA during their further stay on the waiting list. Results15,360 samples from 1928 patients tested by CDC were analyzed for changes in PRA. PRA-increases occurred most frequently in patients waitlisted recently for retransplantation (annual incidence 6%). Removal of previous transplants, severe infections and/or reduced immunosuppression triggered 65% of PRA-increases during the first year after waitlisting. Transfusions accounted for 55% of PRA-increases in later years. Leucocyte-reduced red blood cell units not only boosted historic antibodies, but even induced primary immunization. In the second part of the study, 6780 samples tested by SPA from 703 non-immunized men were evaluated for development of HLA-antibodies. Only 9 men (1.3%) turned HLA antibody-positive (annual incidence 0.4%). ConclusionA uniform screening interval does not fit all: Frequencies should be highest in patients newly waitlisted for re-transplant and lowest in non-immunized men. Transfused patients should be monitored closely for development of HLA-antibodies even if leukoreduced products are used.

Prevalence and impact of HLA and MICA allele mismatching on donor-specific antibodies induction in kidney transplant rejection.

Donor-recipient antigen mismatching for anti-human leucocyte antigen (HLA) and MICA is one of the risk factors for antibody induction leading to graft rejection. Our aim was to analyze the incidence and specificity of the different DSAs developing and to investigate the impact of HLA and MICA allele mismatches on antibody production in kidney transplant patients experiencing antibody-mediated rejection (AMR). We retrospectively reviewed 253 consecutive recipients of kidney transplant who were diagnosed as experiencing AMR. Our results showed that around 27% of our patients were positive for DSAs over a median follow-up period of 24 months. Antibody to HLA-DQ7 was the most prevalent DSA detected. The allele mismatch number was significantly lower for DQ loci than -A and -B loci (DQ vs. A, p < .001; DQ vs. B, p=.002). Considering each HLA antigen, the incidence rate of DQ-DSA [41.9 (32.92-51.46; 95%CI)] was much higher than the rate observed for DSA directed to -A, -DR and -B loci. Half of the recipients in the DQ-DSA-only group, and the DQ-DSA together with non-DQ group, had MFI > 5000. Only one case developed de novo MICA-DSA (MICA002). Our study indicates that mismatching for HLA and MICA alleles leads to the development of HLA and MICA antibodies in some kidney transplant recipients. We have also demonstrated that DSA to the DQ locus is the most prevalent in kidney transplant patients with AMR. Thus, matching the DQ locus in kidney allocation algorithms may reduce post-transplant development of DSA.

Development of De Novo Donor-specific HLA Antibodies and AMR in Renal Transplant Patients Depends on CYP3A5 Genotype.

Background.The single-nucleotide polymorphism CYP3A5 rs776746 is related to a reduction in the metabolizing activity of the CYP3A5 enzyme. People carrying at least one copy of the wild-type allele, defined as CYP3A5 expressers, exhibit higher clearance and lower trough concentrations of tacrolimus than homozygous nonexpressers, and this difference may affect alloimmunization and allograft function.Methods.We retrospectively studied 400 kidney transplant recipients treated with a tacrolimus-based immunosuppression regimen to detect CYP3A5 genotype, de novo formation of HLA antibodies and donor-specific antibodies (DSAs), and clinical outcome up to 5 y after transplant.Results.We found that 69 (17%) of the 400 patients were CYP3A5 expressers. During the first 3 y after transplant, CYP3A5 expressers tended to have lower tacrolimus trough levels than nonexpressers, although their tacrolimus dosage was as much as 80% higher. De novo DSAs were found more frequently in CYP3A5 expressers than in nonexpressers (13/69 [19%] versus 33/331 [10%], P = 0.02). De novo DSA-free survival rates (P = 0.02) were significantly lower for expressers than for nonexpressers. CYP3A5 genotype had no effect on allograft failure, but CYP3A5 expressers exhibited a significantly higher frequency of antibody-mediated rejection. CYP3A5 expresser status was an independent risk factor for the development of de novo DSAs (relative risk, 2.34, P = 0.01).Conclusions.Early detection of CYP3A5 expressers, enabling genotype-based dose adjustment of tacrolimus immediately after renal transplant, may be a useful strategy for reducing the risk of de novo DSA production and antibody-mediated rejection.

Continuous Platelet Transfusion As a Potential Desensitization Regimen in HLA Class I Alloimmune-Mediated Platelet Refractoriness

Background: The development of HLA antibodies is responsible for 4-8% of platelet transfusion refractoriness (PTR). The presence of HLA antibodies is a clinical complication that is generally managed by the selection of products that are negative for the antigens cognate to the patient's antibodies. Often, this selection is facilitated by targeted recruitment of donors with known HLA types. However, for very broadly HLA-alloimmunized patients, compatible products may be exceedingly scarce or completely unavailable, precluding the ability to consistently provide products the patient will likely increment to and benefit from. Here we describe a case of a patient with severe aplastic anemia (platelet count chronically <1 K/uL) and platelet transfusion refractoriness secondary to broad HLA-alloimmunization (98% PRA). HLA compatible products were unavailable due to the patient's rare HLA type and breadth of antibodies, and attempts at procuring compatible products via multiple national agency searches were unsuccessful. Thus, the patient could only be supplied with HLA incompatible products, which yielded insufficient post-transfusion platelet corrected-count increments (CCI). Her course was eventually complicated by multifocal intracranial hemorrhages, necessitating ICU admission with aggressive platelet transfusion support, immune-targeting therapy consisting of IVIg, and aminocaproic acid and recombinant activated factor VIIa.Methods: A continuous platelet infusion, or “platelet drip,” was employed in order to provide platelet transfusion support in the face of her severe thrombocytopenia with profound refractoriness. This consisted of consecutive transfusions of 4-6 equivalent unit apheresis platelet products (“doses”) transfused over 4 hours with a 15 minute post-transfusion CBC obtained from Q8 to Q12 hours to assess platelet increments. This ultimately resulted in 24-30 equivalent unit platelet product infusions/day.Results: Two days into the continuous platelet infusion, the patient began incrementing appropriately to occasional platelet products (CCI>>5) and, consequently, the infusions were able to sustain a platelet count >10K/uL, with a range of 20-70 K/uL, over the subsequent week. The improved counts, along with the patient's improved clinical condition and stable imaging findings showing resolving intracranial hemorrhages, allowed the transfusion support to be goal-directed targeting a prophylactic platelet threshhold of 10K/uL. Continued monitoring of the patient's CCIs enabled the identification of permissive antigens (i.e., allogeneic platelets with HLA antigens predicted to be incompatible with the patient's serum by solid-phase testing but were found to result in satisfactory increments); this knowledge allowed progressive widening of her permissive donor pool and enabled continued prophylactic support as needed. After three weeks the patient was able to be discharged from the ICU.Subsequent HLA class I antibody screens using flow-cytometry based single antigen bead (SAB) technology revealed progressive decrease in the patient's mean fluorescence intensity for most of her antibody specificities, with the majority of her class I A antibodies falling to undetectable or near-undetectable levels (while previously >5000 MFI). Simple regression analysis (RStudio 1.0.153, R version 3.4.1) was used to test to how level of exposure to individual HLA platelet antigens (as measured by the number of doses with a given antigen) affected subsequent MFI levels. The results of the regression indicate that pre MFI and exposure explain 70.6% of the variance (R2=0.706, F(2,78)=93.7, p=<2.2e-16). It was found that exposure is a significant predictor of decreased MFI (b=-107.20, p=0.01422). High initial MFI was strongly associated with high subsequent MFI (b=0.75, p= <2.2e-16).Conclusions: This data raises the possibility that large bolus platelet infusions could not only be of immediate therapeutic benefit in patients with HLA-alloimmune-mediated platelet refractoriness, but may also accelerate the evanescence of the responsible antibodies. Further research is warranted to explore this possibility, and to ascertain the potential magnitude of this effect in comparison to competing factors such as natural evanescence and/or B-cell immunosuppressive or immunomodulatory therapies. DisclosuresNo relevant conflicts of interest to declare.

The relevance of a bank with genotyped platelets donors

ObjectiveDescribe the clinical and laboratory characteristics and the transfusion strategy of patients at Hospital Israelita Albert Einstein with platelet refractoriness and identify their etiological characteristics. Standardize the platelet immunofluorescence technique by flow cytometry as a test for platelet compatibility in immune platelet refractoriness in transfusion support. MethodsReview of medical records of refractory platelet patients followed at HIAE from January 2011 to May 2017. Clinical-demographic data, laboratory data and identification of the use of compatible genotyped platelets for patients in need of transfusion therapy were collected. The analyzed patients were classified according to the etiology of their platelet refractoriness. To standardize the FC-PIFT technique, blood group O platelets were incubated with serum from blood group AB donors and anti-IgG monoclonal antibody to determine the negative control. In order to verify the influence of the ABO system, monoclonal anti-IgG antibodies were incubated with blood group A or B platelets and with blood group O donor serum with isohemagglutinins below and above 1/64. ResultsA total of 47 patients were evaluated, a 51% (24/47) preponderance of associated immune and non-immune factors (NIPR + IPR). The most common causes of NIPR + IPR were splenomegaly (54%) and the development of HLA antibodies (88%), consistent with the literature. For patients who required therapeutic transfusion, only a small portion received compatible genotyped platelets. ConclusionAlthough 60% of patients could benefit from the therapeutic transfusion of genotyped platelets, only 10% were actually transfused with this type of blood component. This reaffirms the need for investments in a bank of genotyped platelet donors.

P1776HLA TYPING BY NGS ENHANCES MISMATCH DETECTION IN LIVING KIDNEY TRANSPLANTATION

Abstract Background and Aims Antibody mediated rejection (ABMR) due to the development of donor specific HLA antibodies is the most common cause for graft loss in kidney transplant recipients. Therefore, a low count of HLA mismatches is favorable in the course of transplantation. Hitherto, several techniques for HLA typing have been adapted in parallel, e.g. serological or low-resolution PCR. In this single-center study, we aimed to perform “HLA re-typing” by next generation sequencing (NGS) in a living kidney transplant cohort (n=143), in order to identify HLA mismatches in donor/recipient pairs, that were missed by previous HLA typing methods. Method We isolated DNA of 102 donor/recipient pairs, that received a living kidney transplantation at the University Hospital Leipzig (Germany) between 1998 and 2018, and performed long range PCR of all known HLA loci. Using these NGS results, we compiled a genomic HLA mismatch formula. We evaluated, if genomic HLA typing identifies more HLA mismatches compared to the results of previous HLA typing methods, that were recorded in the Eurotransplant database for our donor/recipient pairs. Results By genomic HLA typing, we were able to identify HLA mismatches in 10.2 % of donor/recipient pairs, that have been missed by previous methods. In our cohort, we recognized most mismatches in the DRB1 locus, that were missed with other HLA typing techniques. Conclusion Our results suggest, that genomic HLA typing can be more precise in detecting HLA mismatches in donor recipient/pairs. Especially in the course of living kidney transplantation, a higher accuracy in HLA typing might enhance donor selection. Furthermore, accurate HLA typing can influence graft management in the course of ABMR, as it may improve the detection of donor specific HLA directed antibodies.

The Impact of Withdrawal of Maintenance Immunosuppression and Graft Nephrectomy on HLA Sensitization and Calculated Chance of Future Transplant.

BackgroundThe development of HLA antibodies towards a failing renal allograft is a barrier to retransplantation. This study aimed to compare the formation of HLA donor-specific antibodies (DSA) in patients undergoing graft nephrectomy and in those with a failed graft left in situ who had maintenance immunosuppression (IS) stopped, and assess the relative impact of IS cessation and graft nephrectomy on future relative chance of transplant (R-CoT).MethodsA single-center retrospective study of patients with failed grafts between 2005 and 2015 was performed. Samples were tested for DSA pre-IS wean, post-IS wean, and post-IS cessation. Nephrectomy patients additionally had samples tested for DSA before and after nephrectomy. Calculated reaction frequency (cRF) was determined at each timepoint and entered into the UK Organ Donation and Transplant R-CoT calculator.ResultsForty-one patients were included in the study: 24 with nephrectomy and 17 with a failed graft in situ. Patient demographics and duration of IS wean were similar between groups. There was a higher rate of blood transfusion (54% vs 24%) in nephrectomy patients. In patients whose graft remained in situ, cRF rose from 13% pre-IS wean to 40% post-IS wean and 62% after IS cessation. This equated to a reduction in mean R-CoT from 54% to 46% at 5 years. In patients undergoing nephrectomy mean cRF rose from 31% pre-IS wean to 69% post-IS wean and 89% post-IS cessation. Mean R-CoT fell from 54% to 42% at 5 years.ConclusionsA stepwise increase in cRF with reduced chance of transplant was observed in both groups as IS was withdrawn, with a similar pattern irrespective of graft nephrectomy. Calculated reaction frequency was higher in the nephrectomy group. The risks and benefits of stopping IS need to be carefully considered on an individual basis to maximize chance of future transplant.

Posttransplant peripheral blood donor–specific interferon-γ enzyme-linked immune spot assay differentiates risk of subclinical rejection and de novo donor-specific alloantibodies in kidney transplant recipients

Noninvasive diagnosis of kidney allograft inflammation in transplant recipients with stable graft function (subclinical rejection) could permit more effective therapy and prevent later development of de novo anti-donor HLA antibodies and/or graft dysfunction. Here we tested whether quantifying posttransplant donor-specific alloreactive T-cells by IFN-γ ELISPOT assay noninvasively detects subclinical T-cell mediated rejection and/or predicts development of anti-donor HLA antibodies. Using an initial cross-sectional cohort of 60 kidney transplant patients with six-month surveillance biopsies, we found that negative donor-specific IFN-γ ELISPOT assays accurately ruled out the presence of subclinical T-cell mediated rejection. These results were validated using a distinct prospective cohort of 101 patients where donor-specific IFN-γ ELISPOT results at boththree- and six-months posttransplant significantly differentiated patients with subclinical T-cell mediated rejection at six months, independent of other clinical variables (odds ratio 0.072, 95% confidence interval 0.008-0.653). The posttransplant donor-specific IFN-γ ELISPOT results independently associated with subsequent development of significant anti-donor HLA antibodies (0.085, 0.008-0.862) and with significantly worse two-year function (estimated glomerular filtration rate) compared to patients with a negative test. Thus, posttransplant immune monitoring by donor-specific IFN-γ ELISPOT can assess risk for developing subclinical T-cell mediated rejection and anti-donor HLA antibodies, potentially limiting the need for surveillance biopsies. Our study provides a guide for individualizing immunosuppression to improve posttransplant outcomes.

PT-VWD posing diagnostic and therapeutic challenges – small case series

Despite the increased worldwide awareness, over the last decade, of the platelet-type von Willebrand Disease (PT-VWD), many uncertainties remain around this rare platelet bleeding disorder. This report aims to correctly identify and study the phenotype of new patients and highlights the diagnostic and therapeutic challenges this disease remains to pose. We describe four PT-VWD cases confirmed by genetic analysis in which either the diagnosis and/or the treatment posed challenge. We provide the details of the clinical presentation, laboratory analysis, and the treatment and the responses in each case. We show that in addition to type 2B VWD, PT-VWD can be misdiagnosed as idiopathic thrombocytopenic purpura, neonatal alloimmune thrombocytopenia, and unexplained gestational thrombocytopenia. The disease can be diagnosed as early as 1 year of age and with phenotypically normal parents. Bleeding in some patients can be managed successfully using Humate P and DDAVP combined with tranexamic acid with no significant thrombocytopenia. We provide for the first time an evidence of an efficient response to rFVIIa in PT-VWD. Anaphylactic reaction to VWF preparations may be related to PT-VWD and the development of HLA antibodies is not uncommon. Progressive thrombocytopenia with normal VWF levels can be seen with PT-VWD and the platelet count was normalized at 2.5 weeks postpartum in one case. We conclude that these studies represent a record of clinical observations/interventions that help improve diagnoses/management of PT-VWD, highlight the variations in age and clinical presentations, laboratory diagnostic approaches, the importance of genetic testing for accurate diagnosis and consideration of therapeutic alternatives.

Non-HLA-matched 3rd party vascular allograft in renal transplant may lead to sensitization against donor HLA.

3rd party donor vessels are often used for vascular reconstruction in organ transplantation. While current practice ensures that 3rd party vessels are blood group matched, HLA matching to the non-intended recipient is not performed. This practice potentially sensitizes the recipient and may reduce their future chance of renal transplant from a larger pool of donors. We examined our cohort of renal transplant recipients who received non-HLA-matched 3rd party vessels for the de-novo development of donor-specific HLA antibodies. Our institution's Human Tissue Authority (HTA) blood vessel registers were examined to identify stored donor vessels and their non-intended recipients. Donor vessel HLA status was cross-referenced with the recipient HLA status. Between 2004 and 2014, five patients were identified that received 3rd party non-HLA-matched vessels for vascular reconstruction during renal transplantation. Three patients (60%) subsequently developed donor-specific HLA antibodies. These data provide evidence that use of non-HLA-matched stored 3rd party vascular grafts may lead to sensitization in the recipient. Where time permits, HLA matching should be performed to avoid this allogeneic response. Laboratories monitoring DSA should be aware of any patient receiving a non-HLA-matched 3rd party vascular graft, and recipients may benefit from increased post-transplant immunological vigilance.

P072 De novo anti-HLA-class II donor specific antibodies are associated with patient mortality after lung transplant failure

Aim The development of donor-specific HLA antibodies (DSA) after lung transplantation has been implicated in acute and chronic rejection. The diagnosis of lung antibody mediated rejection (AMR) is based upon histology, DSA testing and clinical assessment of graft function. Post-transplant DSA monitoring has become more and more common as a guide toward diagnosis and sometimes institution of AMR treatment. In this study, we aimed to assess DSA with biopsy surveillance and associate with patient mortality after lung transplant failure (MLTF). Methods We retrospectively selected 127 patients, transplanted between Jan, 2004 and July, 2015 whose DSA were tested for clinical indications post-transplantation. Protocol biopsies were performed for these patients at 1, 3, 6, 9, and 12-months after transplant for clinical suspicions. DSA were monitored using LabScreen single antigen bead assays. Biopsy HE however, no association was found for Class I DSA. No significant relationship between DSA and histological changes of AMR in lung transplant biopsies was found in this cohort. Conclusion HLA Class II DSA is associated with graft dysfunction and mortality in pulmonary transplant patients although we did not find the correlation with biopsy findings. Our study suggests that post-transplant protocol DSA surveillance may add value to assess allograft function and to treat graft rejection at the early stage.

The importance of non-HLA antibodies in transplantation.

The development of post-transplantation antibodies against non-HLA autoantigens is associated with rejection and decreased long-term graft survival. Although our knowledge of non-HLA antibodies is incomplete, compelling experimental and clinical findings demonstrate that antibodies directed against autoantigens such as angiotensin type 1 receptor, perlecan and collagen, contribute to the process of antibody-mediated acute and chronic rejection. The mechanisms that underlie the production of autoantibodies in the setting of organ transplantation is an important area of ongoing investigation. Ischaemia-reperfusion injury, surgical trauma and/or alloimmune responses can result in the release of organ-derived autoantigens (such as soluble antigens, extracellular vesicles or apoptotic bodies) that are presented to B cells in the context of the transplant recipient's antigen presenting cells and stimulate autoantibody production. Type 17 T helper cells orchestrate autoantibody production by supporting the proliferation and maturation of autoreactive B cells within ectopic tertiary lymphoid tissue. Conversely, autoantibody-mediated graft damage can trigger alloimmunity and the development of donor-specific HLA antibodies that can act in synergy to promote allograft rejection. Identification of the immunologic phenotypes of transplant recipients at risk of non-HLA antibody-mediated rejection, and the development of targeted therapies to treat such rejection, are sorely needed to improve both graft and patient survival.

(1166) - Fontan Patients Have Similar Rates of Development of HLA Antibodies After Heart Transplant Regardless of PLE Status

(1166) - Fontan Patients Have Similar Rates of Development of HLA Antibodies After Heart Transplant Regardless of PLE Status

The Clinical Spectrum of De Novo Donor-Specific Antibodies in Pediatric Renal Transplant Recipients

The development of donor-specific HLA antibodies (DSA) is associated with worse renal allograft survival in adult patients. This study assessed the natural history of de novo DSA, and its impact on renal function in pediatric renal transplant recipients (RTR). HLA antibodies were measured prospectively using single-antigen-bead assays at 1, 3, 6 and 12 months posttransplant followed by 12-monthly intervals and during episodes of allograft dysfunction. Of 215 patients with HLA antibody monitoring, 75 (35%) developed DSA at median of 0.25 years posttransplant with a high prevalence of Class II (70%) and HLA-DQ (45%) DSA. DSA resolved in 35 (47%) patients and was associated with earlier detection (median, inter-quartile range 0.14, 0.09-0.33 vs. 0.84, 0.15-2.37 years) and lower mean fluorescence intensity (MFI) (2658, 1573-3819 vs. 7820, 5166-11 990). Overall, DSA positive patients had more rapid GFR decline with a 50% reduction in GFR at mean 5.3 (CI: 4.7-5.8) years versus 6.1 (5.7-6.4) years in DSA negative patients (p = 0.02). GFR decreased by a magnitude of 1 mL/min/1.73 m(2) per log10 increase in Class II DSA MFI (p < 0.01). Using Cox regression, independent factors predicting poorer renal allograft outcome were older age at transplant (hazard ratio 1.1, CI: 1.0-1.2 per year), tubulitis (1.5, 1.3-1.8) and microvasculature injury (2.9, 1.4-5.7). In conclusion, pediatric RTR with de novo DSA and microvasculature injury were at risk of allograft failure.

Peri-Transplant Blood Transfusion Is Associated With Significant Formation of HLA Antibodies Despite Immunosuppression.

Blood transfusion is a recognised source of allo-sensitization in transplantation. Despite pre-treatment with immunosuppressive therapy transfusion in the perioperative period may potentially increase the risk of sensitization. We studied the prevalence of transfusion during the transplantation period in our centre and analysed the impact on HLA antibody status. We retrospectively analysed all adult kidney recipients transfused with leuko-depleted red blood cells and platelets during the first 48 hours of transplantation surgery from January 2010-April 2013. HLA antibody screening was performed by single antigen Luminex® bead assay (GenProbe). HLA antibodies and donor specific antibodies (DSA) pre- and post-transplantation (between days 14-31) were analysed. All patients (n=187) received corticosteroid, tacrolimus and mycophenolic acid based immunosuppression. We also examined the occurrence of Delayed Graft Function (DGF) and incidence of acute rejection in the first 2 months post transplant compared with an un-transfused control group. Among 187 patients included in the study, 67 patients (36%) received blood transfusion (median 2 units) and 120 patients (64%) were not transfused. 18 patients (29%) among the transfused group developed HLA antibodies compared to 12 (10.4%) in the non-transfused group. The risk factors for sensitization with transfusion were female recipients, second graft recipients, primary polycystic kidney disease and non-Caucasian populations- all were more likely to develop HLA Antibodies. Transfused kidney transplant recipients developed clinically significant HLA antibodies (MFI>300) [ Odds ratio 3.37] in 26% of cases. A higher rate of DGF was observed in the transfused group compared to the un-transfused group. Conclusion: Despite immunosuppressive drug therapy with tacrolimus, mycophenolic acid, cortico-steroid and IL2Receptor blockade, blood transfusion in the peri-operative period is associated with significant development of HLA antibodies. DISCLOSURES:Coates, P.: Speaker's Bureau, Alexion, Other, Novartis, Advisory Board.

Predictive factors of allosensitization in renal transplant patients switched from calcineurin to mTOR inhibitors

Conversion of kidney-transplant recipients from calcineurin inhibitors to mTOR inhibitors has been suggested to be a risk factor for increased alloimmune response. We have analyzed the development of new HLA-antibodies (HLA-Abs) early after conversion in 184 patients converted in stable phase at our hospital and compared with a control group of nonconverted comparable 63 transplants. Using single-antigen solid-phase immunoassay analysis, a preconversion and a 3-6months postconversion sera were prospectively analyzed in every patient for the appearance of new HLA-Abs. Renal function at 2years postconversion and cumulative graft survival were compared between groups. In 16 patients, new HLA-Abs (3-DSA and 13-NonDSA), not present at the moment of conversion, were detected (8.7% vs. 3.1% in the control group). The type of mTORi used, type of CNI preconversion, the presence of steroids, time of conversion, or indication for conversion did not have influence on this effect but the presence of HLA-Abs before conversion highly correlated with the appearance of new specificities. Patients with de novo HLA-Abs showed a trend to worst graft function and survival. In conclusion, conversion to mTORi can be followed by early appearance of de novo HLA-Abs, especially in patients with HLA-Abs preconversion, and this complication should be screened early after conversion.

Screening for HLA antibodies in plateletpheresis donors with a history of transfusion or pregnancy

Transfusion-related acute lung injury (TRALI) is known as a life-threatening complication of transfusion. HLA and HNA antibodies have been associated with the immune pathway of TRALI. Since donors with a history of transfusion and/or pregnancy are presumed to have an increased risk of carrying such antibodies, we investigated the association of a history of transfusion or pregnancy with the occurrence of HLA alloimmunization in our donor population. A total of 1018 female plateletpheresis donors and male plateletpheresis donors with a history of transfusion were enrolled in the study. Included donors were systematically screened, using Luminex technology, for anti-HLA Class I and II. The association of donor history with HLA alloimmunization status was analyzed. The overall alloimmunization rate was 20.2%. In 0.0% of the nulliparous transfused female donors and in 1.3% of the transfused male donors, anti-HLA were detected. Thirty-one percent of the parous women versus 4.2% of the nulliparous women screened positive for anti-HLA. The rate of HLA alloimmunization increased with parity. Our data indicate that a history of transfusion is a minor risk factor for immunization against HLA antigens. In contrast, former pregnancies constitute a major risk factor for the development of HLA antibodies. Since HLA alloimmunization rate increases with parity, TRALI risk reduction measures should focus on this particular donor population. Repeated testing of female plateletpheresis donors after each pregnancy is implemented in our blood service.