Pretransplant Antibodies Research Articles

Imlifidase: Is it the Magic Wand in Renal Transplantation?

Potential kidney transplant patients with HLA-specific antibodies have reduced access to transplantation. Their harmful effects are mediated by the Fc portion of IgG, including activation of the complement system and Fc receptor-initiated cytotoxic processes by circulating leucocytes. Avoiding antibody incompatibility is the conventional approach, but for some patients this can mean extended waiting times, or even no chance of a transplant if there are no alternative, compatible donors. For these cases, pretransplant antibody removal may provide access to transplantation. Plasmapheresis is currently used to achieve this, with acceptable outcome results, but the process can take days to reduce the antibody levels to a safe level, so has limited use for deceased donors. There is now an alternative, in the form of an IgG-digesting enzyme, Imlifidase, which can be administered for in vivo IgG inactivation. Imlifidase cleaves human IgG, separating the antigen-binding part, F(ab')2 from Fc. Typically, within six hours of dosing, most, if not all, of the circulating IgG has been inactivated, allowing safe transplantation from a previously incompatible donor. For deceased donor transplantation, where minimizing cold ischaemia is critical, this six-hour delay before implantation should be manageable, with the compatibility testing processes adjusted to accommodate the treatment. This agent has been used successfully in phase 2 clinical trials, with good short to medium term outcomes. While a donation rate that matches demand may be one essential answer to providing universal access to kidney transplantation, this is currently unrealistic. IgG inactivation, using Imlifidase, is, however, a realistic and proven alternative.

Vaccination Recommendations and Clinical Characteristics of Children after Allogeneic Hematopoietic Stem Cell Transplantation

To investigate the clinical characteristics, the risk factors related to antibody-negative conversion, and the effectiveness and safety of revaccination in children who underwent allogeneic hematopoietic stem cell transplantation (Allo-HSCT). The clinical characteristics of 516 children after Allo-HSCT who were eligible for revaccination in the Vaccination Evaluation Clinic of Shanghai Children's Medical Center from March 2017 to March 2023 were analyzed. Of the 516 patients enrolled, 464 (89.9%) had started revaccination, with a median time of 2.1 (IQR, 1.8-2.6) years after transplantation and 1.1 (IQR, 0.7-1.5) years after cessation of immunosuppressive therapy. There were 418 cases of hepatitis B surface antibody (HBsAb) seropositive before transplantation, and 339 cases (81.1%) became negative at the time of evaluation after transplantation. The visit time for children with persistently HBsAb seropositive was 1.9 (IQR, 1.3-2.3) years after transplantation, which was shorter than the time for children with HBsAb seronegative (2.2 [IQR, 1.9-2.8] years, P<0.001). HBsAb negative conversion was related to the HBsAb titers pre-transplantation, with a lower proportion of high titers in the negative conversion group (4.7% vs. 17.7%, P<0.001). Both univariate and multivariate analyses suggested that HBsAb seroconversion was statistically related to uncompleted three doses of the hepatitis B vaccine before transplantation, low pre-transplantation antibody titers, and ≥2 years after transplantation. Among 40 patients with HBsAb seronegative who received hepatitis B vaccination, 39 (97.5%) had HBsAb titers converted to seropositive. The immune response rates of measles, mumps, and rubella (MMR) were 96.6% (28/29), 69.0% (20/29,) and 88.5% (23/26), respectively. There were no serious adverse side effects after revaccination.After Allo-HSCT, standard evaluation procedures for revaccination are highly recommended. The immune response rates after hepatitis B and MMR revaccination were highly recommended. No severe adverse side effects were observed.

HLA Typing and Donor-Specific Antibody Screening in Kidney Transplantation: Bridging the Past to the Future

Human leukocyte antigens (HLA) are unique proteins expressed on the surface of human cells, playing a pivotal role in the immune system, particularly in the contexts of infection, cancer, and transplantation. The widespread adoption of HLA typing methods has become an essential component in assessing donor-recipient compatibility, a crucial limiting factor in solid organ transplantation. In general, the greater the disparity between a donor's and recipient's HLA types, the higher the likelihood of provoking an alloimmune response, which frequently results in alloimmune graft rejection. With significant advancements in organ transplantation techniques, immunosuppressive medications, and surgical procedures, attention has increasingly turned toward understanding and managing humoral rejection processes. Pre-transplant antibody screening plays a critical role in identifying individuals with elevated levels of antibodies against potential donor antigens. This screening aids in risk assessment and planning to mitigate the risk of antibody-mediated rejection (AbMR). Several methods are available for assessing circulating antigen-specific antibodies and HLA tissue typing, including cell-based assays like serological assays, complement-dependent cytotoxicity, and flow cytometry. However, non-cell-based approaches, such as molecular methods, HLA imputation techniques and high-throughput HLA-matchmaker assays have gained significant popularity due to their ability to provide higher resolution and robust donor-recipient matching. Despite the advancements in precision and sensitivity observed in HLA cutting-edge technologies, numerous challenges still persist. These challenges involve complexities linked to allelic ambiguities, the differentiation of closely related alleles, and the ongoing effort to establish a standardized HLA testing methodology across diverse laboratories. Additionally, correlating the HLA crossmatch results with the clinical outcomes for transplant donors poses another important aspect that warrants attention and requires expert analysis. In this review, we will enumerate the different methods of HLA typing and DSA screening and discuss the unmet needs and future directions for HLA typing methods.

Donor-Specific Antibody Detection by Single-Antigen Bead Assay for Renal Transplantation: A 2-Year Experience from South India.

Recipient sensitization against donor human leukocyte antigens (HLA) plays a key role in transplant rejection, and this risk is best minimized by efficient pre transplant antibody detection. Determination of antibody specificity with the highest sensitivity and degree of resolution to the allelic antigen level is achieved by using single-antigen bead (SAB) assay. This study evaluated the correlation of Luminex cross match (LXM) with SAB assay for detection of donor-specific antibodies (DSA). A total of 2075 renal transplant patients were screened for the presence of DSA by LXM, complement-dependent cytotoxicity (CDC) cross match, and 125 patients for SAB from January 2018 to December 2019. There was a male preponderance among recipients (P < 0.0001), and the most affected age group was 21-40 years. HLA typing was done in 550/2075 by DNA PCR-reverse sequence-specific oligonucleotide probes (SSOP) method. HLA DSA by LXM was detected in 16.3% of recipients (338/2075). Majority 180/338 (53.2%) of the patients were class II DSA positive, (P < 0.0001). Among the class II DSA positive patients, 20/180 (11.1%) samples gave false-positive results by LXM. SAB for class I and class II HLA IgG antibodies was done in 125/338 renal transplant recipients, which included 20 recipients with false-positive class II Luminex DSA, to check whether the DSA detected were really donor specific or not. The results showed that although 20/125 patients had some antibodies detected in their serum, they were not against the donor HLA antigens, as per the HLA typing reports of the donors. When compared to SAB assay, LXM showed more discrepant results, particularly to class II DSA. In conclusion, LXM, if used in combination with SAB assay and HLA typing of donors if necessary for virtual cross match, will help in avoiding unnecessary exclusion of donors for renal transplant recipients and also for post transplant monitoring of recipients, especially in cadaveric donor transplants.

Outcome of ABO-incompatible kidney transplantation using a modified desensitization protocol without plasmapheresis.

Several controversies regarding desensitization strategies for successful ABO-incompatible (ABOi) kidney transplantation still exist. This study aimed to investigate whether pretransplant anti-A/B antibody removal is mandatory in an ABOi kidney transplant recipient with low baseline isoagglutinin titers. We adopted a modified desensitization protocol with two doses of rituximab (RTX, 100 mg/body) without pretransplant antibody removal for ABOi kidney transplant recipients with a titer of ≤1:64 (group A; n = 35) and investigated the feasibility of this protocol by comparing it with the clinical outcomes of patients undergoing standard pretransplant plasmapheresis (group B; n = 21). There was no significant difference in the rate of antibody-mediated rejection within the first month after transplantation between the two groups (11.4% in group A vs. 2% in group B, p = 0.6019). Moreover, no differences were observed in the short- and long-term graft outcomes between the groups. However, two major critical acute antibody-mediated events occurred in group A; one patient lost the graftdue to hyperacute rejection, and the other patient developed thrombotic microangiopathy after surgery. Risk factors predicting these perioperative complications were not identified. We conclude that not only B-cell depletion using RTX but also pretransplant antibody removal is still recommended even for patients with low isoagglutinin titers. In addition, a new diagnostic tool is needed for accurate risk stratification.

Misidentification of preformed anti-HLA-DP antibodies leads to antibody-mediated kidney transplant rejection: a case report

BackgroundPatients who are HLA-sensitized are at high risk for early antibody-mediated rejection (AMR) and worse outcomes. Therefore, it is crucial to detect the presence of donor-specific antibodies (DSAs) using pretransplant antibody identification and crossmatch assays. An error in antibody identification can lead to disastrous clinical outcomes. We present a case of acute AMR associated with preformed HLA-DPα and HLA-DPβ DSAs that were not identified before transplantation.Case presentationA 27-year-old woman received a second kidney transplant from a deceased donor. Her pretransplant panel-reactive antibody level was 94%. The complement-dependent cytotoxicity crossmatch was negative for T and B cells at the time of transplantation. She experienced early acute AMR proven by a kidney biopsy. Single antigen bead testing of the patient’s serum at the time of rejection as well as the pre-second transplant serum revealed strong antibodies against the DPA1*01:03 and DPB1*02:01 alleles in the second donor. These antibodies were not identified by phenotypic bead assay during the patient’s time on the waiting list. The patient was treated with plasmapheresis and anti-thymocyte globulin. However, she experienced abdominal pain on day 37 post-transplantation. Surgical exploration revealed a laceration on the transplanted kidney, which was then repaired. Subsequently, infected hematoma was suspected and the transplanted kidney was removed.ConclusionThe present case highlights the clinical significance of preformed HLA-DPα and HLA-DPβ DSAs. Accuracy in determination of HLA antibodies before transplantattion is critical for transplant outcome. HLA-DP typing and single antigen bead testing are recommended for a precise antibody interpretation, especially in highly sensitized patients. Careful interpretation of antibody testing results is essential for the success of organ transplantation.

Hypogammaglobinemia in Patients Palliated with the Fontan Circulation: Implications for Cardiac Transplantation

<h3>Purpose</h3> Protein-losing enteropathy (PLE) is a complication after the Fontan operation believed to result from lymphatic dysfunction. As a consequence of protein loss, patients can develop hypogammaglobinemia (HGG). PLE typically resolves following heart transplant, but changes in immunoglobulin levels are not well-described. HGG can increase peri-transplant infection risk and may impair the accurate assessment of pre-transplant antibodies against potential donors. In our case series, we present the changes in immunoglobulin levels among patients palliated with the Fontan procedure that later underwent heart transplant. <h3>Methods</h3> Patients who underwent Fontan with subsequent heart or heart-liver transplant were included (n=10). Variables included are listed in Table 1. Post-transplant IgG levels were collected at a minimum of 3 months post-transplant to avoid interference from high-dose steroids and higher doses of immunomodulation used in the immediate post-transplant period. HGG was defined as IgG < 700 mg/dL pre-transplant. <h3>Results</h3> The mean age at transplant was 22.3 years; 90% of patients were male. Three (30%) patients had HGG. Two had complete resolution of HGG. The third was treated with subcutaneous immunoglobulin before transplant. PLE resolved post-transplant. One of the patients with HGG had a persistent de novo donor-specific antibody in the setting of immunosuppression non-adherence. <h3>Conclusion</h3> In this case series, we present HGG as a consideration in patients palliated with Fontan. Due to the risk of infection, HGG may lead clinicians to reduce immunosuppression in the peri-transplant period. HGG may also impact the ability to detect the degree of sensitization as the panel of reactive antibodies relies on sufficient immunoglobulin titers against human-leukocyte antigen to identify unacceptable donors. Lastly, if HGG resolves predictably post heart-transplant, that may have further implications on early risk for rejection in this patient population.

Human leukocyte antigen antibody sensitization, lung transplantation, and health equity

Women with advanced lung disease, particularly Black and Hispanic women, are more likely than other patients to have anti-human leukocyte (HLA) antibodies against potential donors. Sensitized patients, especially those who are highly sensitized, are less likely to be listed for lung transplant or to be considered candidates for mechanical circulatory support. They are also at higher risk for waitlist death. Institutional variability in approach to HLA antibody screening and pre-transplant management creates barriers to transplant that disproportionately impact Black and Hispanic women. At the same time, our understanding of the clinical significance of pre-transplant antibodies lags behind the sophistication of our screening assays. The lack of national data on pre- and post-transplant HLA antibody characteristics hinders research into strategies to mitigate concerns about these antibodies and to improve access to lung transplant among sensitized patients. Ongoing work should be done to identify clinically higher risk antibodies, to develop better strategies for safely crossing antibodies at the time of transplant, and to model changes in lung allocation to give priority to sensitized patients for a HLA antibody-antigen compatible donors. These priorities mandate a commitment to collaborative, multicenter research and to real time translation of results to clinical practice and allocation policy.

Association Between Antibodies Against Lung Self-Antigens and Gastroesophageal Reflux in Lung Transplant Candidates

Gastroesophageal reflux (GER) and pretransplant antibodies against lung self-antigens (SAbs) collagen-V and/or k-alpha 1 tubulin are both independently associated with allograft dysfunction after lung transplantation (LTx). The role of GER in inducing lung injury and SAbs is unknown. We aimed to study the association between pre-LTx GER and SAbs. After IRB approval, we retrieved SAb assays conducted between 2015 and 2019 and collected 24 hour GER data for these patients. Patients were divided into 2 groups: no reflux (GER-) and pathologic reflux (GER+) to compare the prevalence of SAbs. Multivariate analysis was used to study the association between GER and SAbs in the whole cohort and in restrictive lung disease (RLD) and obstructive lung disease (OLD) subsets. Proximal esophageal reflux (PER) events ≥5 was considered abnormal. Patients (n=134; 73 men) were divided into groups: GER- (54.5%, n=73) and GER+ (45.5%, n=61). The prevalence of GER was higher in the RLD than in the OLD subset (p < 0.001). The overall prevalence of SAbs was 53.7% (n=72), higher in the GER+ than the GER- group (65.6% vs 43.8%, p=0.012), but comparable between RLD and OLD subsets. Overall, SAbs were associated with GER (p=0.012) and abnormal PER (p=0.017). GER and abnormal PER increased the odds of SAbs in the RLD subset (OR [95% CI]: 2.825 [1.033-7.725], p=0.040 and OR [95% CI]: 3.551 [1.271-9.925], p=0.014, respectively) but not in the OLD subset. LTx candidates have a high prevalence of SAbs, which are significantly associated with GER and abnormal PER in patients with RLD.

Pre-transplant AT1R antibodies and long-term outcomes in kidney transplant recipients with a functioning graft for more than 5 years.

There is conflicting data regarding the association of pre-transplant AT1R antibody levels and long-term outcomes following kidney transplantation. We examined the association between pre-transplant antibodies and long-term graft outcome by assaying pre-transplant sera from 125 kidney transplant recipients from 1999 to 2009. The mean age at transplant was 55.7±13 years; 67.2% were male, 87.2% were Caucasian, and 67.2% received a deceased donor transplant. Induction therapy included 44.8% thymoglobulin. Human leukocyte antigen (HLA) donor-specific antibodies (DSA) were present in 22 (17.6%) patients, while AT1R antibodies >17U/mL were present in 24 (19.2%). The mean AT1R antibodies level was 13±7.2 U/mL. Patients were followed-up for 7.1±1.9 years after transplant. Pre-transplant AT1R antibodies were associated with rejection (p<0.0001), antibody-mediated rejection (ABMR) (p<0.0001), and death-censored graft failure (DCGF) (p=0.01). This was confirmed by univariate Cox regression analyses for AT1R antibodies >10U/mL (HR 2.64, 95% Cl 1.35 - 5.17, p=0.04) and AT1R antibodies >17U/mL (HR=1.74, 95% Cl 1.061-2.98, p=0.04). Multivariable analyses did not retain AT1R antibodies as independent predictors of DCGF; however, pre-transplant HLA, DSA, and acute rejection during the first year were associated with DCGF (HR 2.07, 95% Cl 1.13 - 3.78, p=0.02 and HR 3.03, 95% Cl 1.13 - 3.78, p=0.0002, respectively). Our study indicates that in patients with a functioning kidney allograft >5years, pre-transplant AT1R antibodies may be associated with a greater risk of rejection and late graft failure.

Association between Pretransplant Antibody against Angiotensin II Type 1 Receptor and Posttransplant Allograft Injury

In heart transplantation (HT), antibodies directed against Angiotensin II type 1 receptor (AT1RAb) have been associated with antibody-mediated rejection (AMR), acute cellular rejection (ACR), and microvasculopathy. The effect of AT1RAb detected pre-HT on immediate post-HT allograft injury remains poorly defined. In this study, we leverage a validated and sensitive blood based biomarker for allograft injury, donor-derived cell-free DNA (ddcfDNA), to examine the association of pre-HT AT1RAb to post-HT allograft injury. AT1RAb testing was performed on pretransplant plasma from HT recipients in the Genomic Research Alliance for Transplantation (GRAfT) multicenter, prospective cohort study, using a quantitative ELISA (One Lambda, ThermoFisher). After HT, serial plasma samples were collected and used to quantitate %ddcfDNA by shotgun sequencing. AT1RAb concentration (units/ml) was used to categorize patients as AT1RAb<30 (n=32) or AT1RA>30 (n=17). A mixed linear model was used to examine post-HT %ddcfDNA trajectories across AT1RAb groups. Histopathology slides were read by a consensus of pathologists to define AMR using ISHLT criteria. Age, gender and clinical features were similar between AT1RAb<30 and AT1RA>30 groups. AT1RAb>30 had a greater proportion of White recipients compared to AT1RAb<30 (59% versus 38%; p = 0.003). While %ddcfDNA on posttransplant Day 1 were similar between AT1RAb<30 vs AT1RAb>30 (p=0.6), in the first year post-HT, ddcfDNA declined by 87% (95% CI 79%-92%) among patients with AT1RAb<30 vs 67% (CI=34%-84%) among patients with AT1RAb>30 (p = 0.04) (Figure). AMR in the first year post-HT was more common among AT1RAb>30 than AT1RAb<30 patients (18% vs 3%, p=0.07); CMR was comparable in each group (41% vs 24%, p=0.2). Preliminary analysis of this heart transplant cohort suggest that high pre-HT AT1RAb is associated with increased early post-HT allograft injury.

Individualized Preconditioning for ABO-Incompatible Living-Donor Kidney Transplantation: An Initial Report of 48 Cases from China.

BackgroundABO-incompatible (ABOi) living-donor kidney transplantation (KTx) is well established in developed countries, but not yet in China.Material/MethodsWe developed individualized preconditioning protocols for ABOi KTx based on initial ABO antibody titers. After propensity score matching of ABOi with ABO-compatible (ABOc) KTx, post-transplant outcomes were compared.ResultsBetween September 2014 and June 2018, 48 ABOi living-donor KTx candidates received individualized preconditioning, and all underwent subsequent KTx (median initial ABO titers: 16 for IgM and 16 for IgG). Thirty-one recipients (64.6%) were preconditioned with rituximab (median dose: 200 mg, range: 100–500 mg). Among 37 patients (77.1%) who received pre-transplant antibody removal, the median number of sessions of antibody removal required to achieve ABOi KTx was 2 (range: 1–5), which was conducted between days −10 and −1. Eleven ABOi recipients (22.9%) were preconditioned with oral immunosuppressants alone. Hyperacute rejection led to the loss of 2 grafts in the ABOi group. After a median follow-up of 27.6 months (ABOi group) and 29.8 months (ABOc group), there were no significant differences in graft/recipient survival, rejection, and infection. There were marginally higher rates of severe thrombocytopenia (<50×109/L) (P=0.073) and delayed wound healing (P=0.096) in ABOi recipients.ConclusionsOur individualized preconditioning protocol evolved as our experience grew, and the short-term clinical outcomes of ABOi KTx did not differ from those of matched ABOc patients. ABOi KTx may be a major step forward in expanding the kidney living-donor pool in China.

Renal transplant patients with preformed anti-HLA antibodies: early biopsy findings and clinical outcomes.

Introduction:Renal fibrosis is the end point of a process that begins at transplant, with ischemia reperfusion and early inflammation, and progresses over time with immunological and non-immunological phenomena. Early identification of morphological markers and intervention could improve graft function and survival.Objective:to evaluate the correlation between intensity and specificity of pre-transplant anti-HLA antibodies and kidney allograft pathology in order to identify early risk factors or markers of allograft dysfunction.Methods:A retrospective cohort of kidney transplant recipients with pre-transplant anti-HLA antibodies who underwent graft biopsy within the first two years post-transplant was divided into two groups according to the specificity of anti-HLA antibodies: nonspecific (non-DSA, n = 29) and specific (DSA+, n = 16). Kidney graft pathology, renal function, and proteinuria were analyzed.Results:general characteristics were similar in both groups, except for the higher dose of thymoglobulin in DSA+ group (p < 0.05). The non-DSA group had higher scores for glomerulosclerosis, interstitial inflammation (i) and interstitial fibrosis (ci) (p < 0.05) and higher incidence of cell-mediated acute rejection. No statistical difference in incidence of antibody-mediated rejection, renal function, and proteinuria was observed during follow up.Discussion and conclusions:the difference in inflammation scores and interstitial fibrosis may be associated to the higher incidence of acute cell-mediated rejection and polyomavirus nephropathy in the Non-DSA group. We also should take into account the protective effect of higher doses of thymoglobulin, reducing ischemia reperfusion injury in the DSA+ group. The short follow-up might have been insufficient to detect long-term changes in allograft tissue, renal function, and proteinuria.

Preformed Donor-Specific HLA Antibodies in Living and Deceased Donor Transplantation: A Multicenter Study.

The prognostic value of preformed donor-specific HLA antibodies (DSA), which are only detectable by sensitive methods, remains controversial for kidney transplantation. The outcome of 4233 consecutive kidney transplants performed between 2012 and 2015 in 18 German transplant centers was evaluated. Most centers used a stepwise pretransplant antibody screening with bead array tests and differentiation of positive samples by single antigen assays. Using these screening results, DSA against HLA-A, -B, -C, -DRB1 and -DQB1 were determined. Data on clinical outcome and possible covariates were collected retrospectively. Pretransplant DSA were associated with lower overall graft survival, with a hazard ratio of 2.53 for living donation (95% confidence interval [95% CI], 1.49 to 4.29; P<0.001) and 1.59 for deceased donation (95% CI, 1.21 to 2.11; P=0.001). ABO-incompatible transplantation was associated with worse graft survival (hazard ratio, 2.09; 95% CI, 1.33 to 3.27; P=0.001) independent from DSA. There was no difference between DSA against class 1, class 2, or both. Stratification into DSA <3000 medium fluorescence intensity (MFI) and DSA ≥3000 MFI resulted in overlapping survival curves. Therefore, separate analyses were performed for 3-month and long-term graft survival. Although DSA <3000 MFI tended to be associated with both lower 3-month and long-term transplant survival in deceased donation, DSA ≥3000 MFI were only associated with worse long-term transplant survival in deceased donation. In living donation, only strong DSA were associated with reduced graft survival in the first 3 months, but both weak and strong DSA were associated with reduced long-term graft survival. A higher incidence of antibody-mediated rejection within 6 months was only associated with DSA ≥3000 MFI. Preformed DSA were associated with an increased risk for graft loss in kidney transplantation, which was greater in living than in deceased donation. Even weak DSA <3000 MFI were associated with worse graft survival. This association was stronger in living than deceased donation.

Impact of pretransplant antibodies on outcomes after heart transplantation.

Purpose of reviewSince the discovery of human leukocyte antigen (HLA) in the 1950s, there has been great interest in the role of antibodies in posttransplant rejection. The development of the lymphocyte toxicity test by Terasaki et al. in the 1960s was the first step toward understanding the role of antibodies in posttransplant rejection.Recent findingsSubsequently, various organs have been transplanted and improving posttransplant outcomes have become a focus of research. In particular, methods to measure antibodies that affect posttransplant outcomes, including anti-HLA antibodies, and methods to desensitize patients from specific antibodies have been explored. One recent method for measuring antibodies is called the solid-phase assay, which uses purified HLA fixed to microbeads. This assay does not use donor lymphocytes and allows clinicians to test the reactivity of patient serum against a panel of antibodies. It has also enabled the identification of specific anti-HLA antibodies using a single HLA.SummaryIn addition to advances in methods to measure and analyze anti-HLA antibodies, the clinical impact of non-HLA antibodies has also received much attention recently.

Profiling Pre-Existing Autoantibodies for Prediction of Primary Graft Dysfunction

Purpose Primary Graft Dysfunction (PGD) results in increased mortality and morbidity after lung transplantation (LT). While the role of pre transplant antibodies to self -antigens (AutoAbs) is described, no validated laboratory biomarker panel exists to predict PGD. Our objective was to evaluate effects of pre transplant antibodies to self-antigens (AutoAbs) and examine specific patterns that correlate with PGD. Methods Serum samples collected on the day of transplant prior to surgery and stored in HLA lab were obtained after IRB approval. Pre-transplant AutoAbs were measured using a multiplexed protein array bearing 375 auto antigens developed by Microarray core lab. The score of each AutoAb was calculated based on the signal intensity and signal to noise ratio (SNR) and compared between patients with and without PGD. Kaplan-Meier or Cox proportional hazards model was used to evaluate effects of differential AutoAbs on survival. GLMNET in R package was used for selection and developing a panel for prediction. Results Patients with PGD had lower survival rate, but did not meet statistical significance (p=0.27, figure 1A). 4 AutoAbs, (anti-AchR3, anti-AGTR1, anti-CRP, anti-factor 1) showed significant higher expression in PGD group (fold change > 1.5, p Conclusion Our study reveals a panel of 25 AutoAbs that predict subsequent PGD in LT recipients. While several donor and recipient factors play a role in PGD, prediction model developed with a panel of AutoAbs with high accuracy can make a significant impact in the management of PGD.

Predictive Biomarkers for Bronchiolitis Obliterans

Purpose Chronic Allograft Dysfunction (CLAD) with Bronchiolitis obliterans (BOS) phenotype is a major limitation for long term survival after lung transplantation (LT). Predictive biomarkers for BOS are unavailable. Purpose of our study was to establish a tractable system to evaluate the effects of pre-transplant antibodies to self-antigens (AutoAbs) and to examine specific patterns that correlate with BOS. Methods Serum samples collected pre-transplant and stored in HLA lab were retreived after IRB approval. Pre-existing AutoAbs in sera were measured using a multiplexed protein array bearing 375 auto antigens developed by Microarray core lab. Microarray data was analyzed using GLMNET in R package. Machine learning program was used to select panel of AutoAbs with best predictive value for BOS. Survival analysis was done using Kaplan-Meier estimation or cox proportional hazards model . Results 41 recipients who met inclusion criteria were grouped into low BOS (BOS grade 0 and 1, n=20) and high BOS (BOS grade 2, 3; n=21). Survival analysis showed worse survival in patients with higher BOS grade (figure 1A). 75 AutoAbs were significantly higher in high BOS compared to low BOS in pre transplant samples (figure 1B). Top 5 significantly elevated AutoAbs in high BOS were: anti-peptidyl arginine deiminases , anti-endothelial cell extract, anti-MPO, anti beta 2 glycoprotein 1 and anti-ribosomal phosphoprotein1. Using the machine learning program, 15 AutoAbs (figure 1C)were selected for best prediction of BOS with area under curve 0.91, CI (95%) 0.83-0.99. Sensitivity of prediction with the panel is 90% and specificity 85% (figure 1D). Conclusion Our study points to a panel of 15 AutoAb that can predict BOS before LT. Novel findings reported in our study are being confirmed in a replication cohort. Prediction models with a panel of AutoAb can significantly transform management of LT recipients for improved survival.

Non-HLA Antibodies in Highly Sensitized Renal Transplant Candidates.

Introduction Non-HLA allo- and autoantibodies, as are antibodies (abs) against Major-histocompatibility-complex class I–related-chain A (anti-MICA) and angiotensin II type 1 receptor (anti-AT1R), are implicated in rejection and graft failure post renal transplantation. These abs are not detected with the classical crossmatch before transplantation. The aim of this study was to assess the incidence of preformed anti-MICA and anti-AT1R abs in highly sensitized renal transplant candidates (HSP, with %cPRAs>70) as compared to non sensitized patients (%cPRAs<5) awaiting for renal transplantation, in order to define possible additional pre-transplant immunological risk factors. Materials and Methods In total, 169 renal transplant candidates were tested, including 115 HSP (study group) and 54 non-sensitized patients (control group-CG-pts). Anti- HLA sensitization in HSP vs CG-pts was due to previous transplantation(s) (81 vs 0 pts), pregnancies (25 vs 6 pts) and transfusions (82 vs 10 pts). Blood samples were tested (a) for anti-HLA and anti-MICA antibody specificities by Single Antigen Bead Assay (Luminex, One Lambda) and (b) for AT1R-abs by ELISA (EIA-AT1R kit, One Lambda). For anti-HLA and anti-MICA abs an MFI >1000 was considered as positive. Anti-AT1R-ab levels were classified as low <10U/mL, at risk 10-17U/mL and high>17U/mL. The Chi Square test (Yate’s corrected) was used for statistical analysis. Results and Discussion Broad sensitization against HLA alleles was observed in HSP with 93/115 HSP to exhibit abs against both HLA class I & II loci. More precisely, antibodies against HLA-A,-B,-C,-DRB1,-DQA1,-DQB1,-DPB1 was observed in 83%, 85%, 58%, 82%, 32%, 73% and 32% of the HSP respectively. Anti-MICA-abs were detected in 17/115 (14,8%) HSP and in 1/54 (1.8%) CG-pts (p=0.02). Anti-AT1R-abs were detected in 44/115 (38,3%) HSP and 5/54 (9.2%) CG-pts (p=0.0002). The anti-AT1R-abs were detected either in intermediate (n=32, 27,8%) or high levels (n=12, 10,4%) in HSP with mean±SD values of 12.3±1.9 and 25.4±10.5 U/ml respectively. The anti-AT1R-ab levels in 4 positive CG-pts were close to cut-off with mean±SD values 11.2±1.5 U/ml while only one patient presented high levels. The presence of anti-AT1R-abs was associated with pregnancies and/or graft loss. All HSP with only transfusion history had low anti-AT1R levels. The presence of anti-MICA-abs was significantly correlated with anti-AT1R-abs (p=0.01). Conclusion Given the complexity of mechanisms involved in kidney graft rejection, HLA as well as non-HLA pre transplant antibody responses should be taken into account in order to define patients with particular risk for irreversible graft injury. Highly sensitized renal transplant candidates have additional to donor HLA risk factors before renal transplantation. Detection of non-HLA antibodies may be useful in immunological risk assessment pre-transplantation and may help clinicians to establish therapeutic protocols in order to improve graft outcome.

Clinical Impact of Pre-transplant Antibodies Against Angiotensin II Type I Receptor and Major Histocompatibility Complex Class I-Related Chain A in Kidney Transplant Patients.

BackgroundEvidence of antibody-mediated injury in the absence of donor-specific HLA antibodies (HLA-DSA) has recently emerged, suggesting a role of antibodies in targeting non-HLA antigens expressed on renal allograft tissue. However, the clinical significance of pre-transplant non-HLA antibodies remains unclear. We compared the histological and clinical impact of pre-transplant HLA-DSA and non-HLA antibodies, especially angiotensin II type I receptor (anti-AT1R) and MHC class I-related chain A (anti-MICA), in kidney transplant patients.MethodsPre-transplant HLA-DSA, anti-AT1R, and anti-MICA were retrospectively examined in 359 kidney transplant patients to determine the effect of each antibody on allograft survival and clinical characteristics.ResultsPre-transplant HLA-DSA, anti-AT1R, and anti-MICA were detected in 37 (10.3%), 174 (48.5%), and 50 patients (13.9%), respectively. Post-transplant antibody-mediated rejection was associated with a pre-transplant HLA-DSA (+) status only. The development of microvascular inflammation (MVI) was associated with pre-transplant HLA-DSA (P=0.001) and anti-AT1R (P=0.036). Anti-AT1R (+) patients had significantly lower allograft survival compared with anti-AT1R (−) patients (P=0.042). Only pre-transplant anti-AT1R positivity was an independent risk factor for allograft failure (hazard ratio 4.824, confidence interval 1.017–24.888; P=0.038). MVI was the most common histological feature of allograft failure in patients with pre-transplant anti-AT1R.ConclusionsPre-transplant anti-AT1R is an important risk factor for allograft failure, which may be mediated by MVI induction in the allograft tissue.

Incidence, characterization, and impact of newly detected donor-specific anti-HLA antibody in the first year after pediatric heart transplantation: A report from the CTOTC-04 study.

Data on the clinical importance of newly detected donor-specific anti-HLA antibodies (ndDSAs) after pediatric heart transplantation are lacking despite mounting evidence of the detrimental effect of de novo DSAs in solid organ transplantation. We prospectively tested 237 pediatric heart transplant recipients for ndDSAs in the first year posttransplantation to determine their incidence, pattern, and clinical impact. One-third of patients developed ndDSAs; when present, these were mostly detected within the first 6weeks after transplantation, suggesting that memory responses may predominate over true de novo DSA production in this population. In the absence of preexisting DSAs, patients with ndDSAs had significantly more acute cellular rejection but not antibody-mediated rejection, and there was no impact on graft and patient survival in the first year posttransplantation. Risk factors for ndDSAs included common sensitizing events. Given the early detection of the antibody response, memory responses may be more important in the first year after pediatric heart transplantation and patients with a history of a sensitizing event may be at risk even with a negative pretransplantation antibody screen. The impact on late graft and patient outcomes of first-year ndDSAs is being assessed in an extended cohort of patients.