Development Of Donor-specific Antibodies Research Articles

Chronic Allograft Dysfunction

Premature renal allograft failure is a major problem in kidney transplantation as it is associated with high morbidity, mortality, and health care costs as patients return to dialysis. The most common cause of graft loss the first year after transplantation is death with a functioning graft, closely followed by what is now termed chronic allograft dysfunction (CAD). Development of donor-specific antibodies and chronic antibody rejection are emerging as the major pathophysiologic mechanisms responsible for this entity. There are currently no validated therapies for CAD, but improving adherence and reducing risk factors for CAD may improve outcomes. This review summarizes current understanding of the epidemiology, diagnosis, and pathophysiology of CAD, as well as potential treatment strategies. This review contains 3 figures and 133 references

Interest of epitope load for evaluating the HLA compatibility in pediatric renal transplantation

Introduction Donor–recipient HLA mismatch is widely assessed with the number of HLA antigenic mismatches between donor and recipient. However, the epitope load, i.e. the number of epitope mismatches, seems to be more informative. We ought to evaluate the capacity of epitope load to predict development of Donor Specific Anti-HLA antibodies (DSA) and occurrence of antibody-mediated rejection (AMR) in a paediatric renal transplant population. Methods In this retrospective monocentric study, we included the 76 consecutive children who had undergone renal transplantation at Necker Children's Hospital between 2010 and 2015, without any pre-transplant DSA. The number of HLA antigenic mismatch, the epitope load (determined with the HLA-Matchmaker software), the occurrence of de novo DSA (MFI > 500) and AMR were analysed. Non-adherence and immunising events were also assessed as potential confounding factors. Results We observed a relationship between epitope load and development of de novo DSA. Epitope load was significantly greater in patients who developed DSA: 45 mean ± 16.9 vs. 34 ± 18.7, P = 0.038). A threshold > 20 class I epitope mismatches was associated to a relative risk of developing class I DSA of 3.79 [(1.23–11.73)]. Similarly, a global epitope load > 45 conferred a relative risk of 2.18 [95% CI (1.05–3.69)] of developing class I or II DSA. The model was not predictive for class II only DSA occurrence, maybe due to difficulties in determining the de novo character of some class II DSA. We did not show any direct relationship between epitope load and antibody-mediated rejection, whereas there was a strong link between de novo DSA and humoral rejection as expected (P Conclusion Our study shows in a paediatric population, a relationship between epitope load and de novo DSA known to impair renal allograft survival. We have also found significant epitope load thresholds allowing identification of patients at the highest risk of DSA development, for example after immunosuppression minimization. Envisioned as a graft allocation tool, HLA epitope load, by avoiding highly immunogenic epitope-mismatches, could be a potent strategy to minimize post-transplantation immunisation, deleterious in paediatric patients.

Racial differences in the development of de-novo donor-specific antibodies and treated antibody-mediated rejection after heart transplantation

Despite improvements in outcomes after heart transplantation, black recipients have worse survival compared with non-black recipients. The source of such disparate outcomes remains largely unknown. We hypothesize that a propensity to generate de-novo donor-specific antibodies (dnDSA) and subsequent antibody-mediated rejection (AMR) may account for racial differences in sub-optimal outcomes after heart transplant. In this study we aimed to determine the role of dnDSA and AMR in racial disparities in post-transplant outcomes. This study was a single-center, retrospective analysis of 137 heart transplant recipients (81% male, 48% black) discharged from Emory University Hospital. Patients were classified as black vs non-black for the purpose of our analysis. Kaplan-Meier and Cox regression analyses were used to evaluate the association between race and selected outcomes. The primary outcome was the development of dnDSA. Secondary outcomes included treated AMR and a composite of all-cause graft dysfunction or death. After 3.7 years of follow-up, 39 (28.5%) patients developed dnDSA and 19 (13.8%) were treated for AMR. In multivariable models, black race was associated with a higher risk of developing dnDSA (hazard ratio [HR] 3.65, 95% confidence interval [CI] 1.54 to 8.65, p = 0.003) and a higher risk of treated AMR (HR 4.86, 95% CI 1.26 to 18.72, p = 0.021) compared with non-black race. Black race was also associated with a higher risk of all-cause graft dysfunction or death in univariate analyses (HR 2.10, 95% CI 1.02 to 4.30, p = 0.044). However, in a multivariable model incorporating dnDSA, black race was no longer a significant risk factor. Only dnDSA development was significantly associated with all-cause graft dysfunction or death (HR 4.85, 95% CI 1.89 to 12.44, p = 0.001). Black transplant recipients are at higher risk for the development of dnDSA and treated AMR, which may account for racial disparities in outcomes after heart transplantation.

P085 Lung re-transplant with repeated mismatch HLA antigens

Avoidance of previous donor mismatched HLA antigens is often considered for lung re-transplant due to concerns of potential HLA sensitization and memory responses. However, this approach may result in the exclusion of a large number of potential donors from consideration. Recently, we successfully performed a re-transplant with a history of multiple repeated mismatches. A 30+ year old male with a past medical history of cystic fibrosis underwent two previous bilateral lung transplants in August 2004 and in November 2010. Both allografts failed due to CLAD/BOS that developed after respiratory viral infections. The patient also subsequently developed detectable class I and II HLA antibodies with a cPRA > 88% in May 2016. Among these antibodies, strong anti-A1, B7 and DQ2 were first donor HLA specific. The second donor shared an A3-B18-DR4 haplotype with the first donor but not the recipient. No HLA antibodies specific to this A3-B18-DR4 haplotype antigens or to any other mismatched HLA antigens of the second donor were detected. A third lung transplant became urgently necessary in October 2016. Adding his previous donors’ mismatched HLA antigens to the unacceptable HLA list resulted in a cPRA > 96%. Therefore, a personalized listing strategy was developed based on discussions between the HLA lab and the transplant program. A deceased donor became available in November 2016. The virtual crossmatch revealed that the donor had no unacceptable HLA antigens based on HLA antibody detection. However, this donor carried the A3-B18-DR4 haplotype which was a repeated mismatch haplotype of the previous two donors. Based on a risk and benefit assessment, this donor was accepted as the source of lungs for the third transplant. The patient received 5 plasmapheresis sessions post-transplant to prevent antibody mediated rejection. Frequent post-transplant HLA antibody monitoring has not detected development of donor specific antibodies to the third donor and the new allograft functions well. Lung re-transplant can be performed with a cross of a repeated HLA mismatch provided that the recipient has no detectable HLA antibodies specific to the current donor. Our preliminary findings obtained from our study conducted on UNOS lung transplant data supports this conclusion. An assessment of risk and benefit of crossing the repeated mismatch HLA antigens should be done on a case-by-case basis.

P153 Utility of the virtual crossmatch for living donor evaluations

Aim Our institution performs 750–900 flow cytometric crossmatches (FCXM) annually in support of living-donor renal transplantation. The FCXM is costly, time consuming, and has interpretational conundrums (i.e., FCXM + donor specific antibody (DSA) negative or FCXM−/DSA+). By combining high resolution HLA typing with solid-phase antibody (SAB) testing, recipients should be transplantable based solely on a virtual crossmatch (vXM). Given the increased utilization of the vXM, our aim was to assess its utility in living donor evaluations. Methods We reviewed 100 living donor FCXMs and retrospectively performed a vXM for each pair. vXM was performed only on cases with available donor typing and SAB specificity testing. Additionally, ΔMESF values of the FCXM, FlowPRA results, and mean fluorescence intensity (MFI) values of DSA were analyzed. Results Initially, there was a 75% correlation between FCXM and vXM: 60 cases were negative for both FCXM and vXM; 15 cases were positive for both. However, 20 cases were FCXM+ (mostly B-cell) but vXM−, which tended to occur in non-alloimmunized recipients. 3/20 had autoimmune disease and 8/20 were transplanted without development of DSA. Although deemed compatible, the remaining 12 were not transplanted. These 20 cases were considered False Positive FCXMs. 5 cases were FCXM−/vXM+. Of these, 4 had Class I DSAs and 1 had both Class I and II DSAs; however, all 5 had low MFI values. (Table 1). Thus, reclassifying the false positive FCXMs, the final correlation was 95%. Download : Download high-res image (146KB) Download : Download full-size image Conclusions Though the initial FCXM/vXM correlation rate was only 75%, there are key characteristics such as differences in FCXM, ΔMESF, PRA values, and DSA MFI values that can help interpret discrepant result. Notably, there were 4 times more false positive FCXMs then false positive vXMs. Reclassifying the False Positive FCXM cases increased the correlation to 95%. These data support the utility of the vXM as a replacement for a physical FCXM for most living donor evaluations.

The Presence of Pretransplant HLA Antibodies Does Not Impact the Development of Chronic Lung Allograft Dysfunction or CLAD-Related Death

Development of donor-specific antibodies (DSA) after lung transplantation is associated with antibody mediated rejection, acute cellular rejection, and bronchiolitis obliterans syndrome; however, the significance of circulating antibodies before transplant remains unclear. We performed a retrospective cohort study including recipients of primary lung transplants between 2008 and 2012. We assessed the impact of circulating HLA and noncytotoxic DSA detected before transplant on development of Chronic Lung Allograft Dysfunction (CLAD) or CLAD-related death. 30% of subjects had circulating class I antibodies alone, 4% Class II, and 14.4% class I and class II at mean fluorescent intensity greater than 1000. Nine percent of the subjects had DSA class I, 9% class II, and 2.4% both DSA classes 1 and 2. Neither the presence of circulating antibodies (adjusted hazard ratio, 0.87; 95% confidence interval, 0.50-1.54) nor the presence of DSA (adjusted hazard ratio, 1.56; 95% confidence interval, 0.77-3.18) before transplant at mean fluorescent intensity greater than 1000 was associated with the development of CLAD or CLAD-related death. Although in previous studies we have shown an increased incidence of antibody-mediated rejection in patients with pretransplant DSA, neither the presence of HLA antibodies nor DSA translated to an increased risk of allograft dysfunction or death if prospective crossmatch testing was negative. Prospective studies are needed to define the impact of pretransplant sensitization on lung transplant recipients.

P101 Development of C1Q binding donor specific anti-HLA antibodies in pediatric kidney transplant recipients

Aim De novo donor specific anti-HLA antibodies (DSA) have been associated with poor allograft outcomes in kidney transplantation. However, the value of post-transplant DSA monitoring in pediatric kidney transplant recipients is still debated. In this study, we investigated the incidence of de novo DSA, their ability to bind complement and their relationship with clinical outcomes in a population of pediatric kidney transplant recipients. Methods Serial samples of serum from 34 pediatric kidney transplant recipients without pre-transplant DSA were tested using the conventional and C1q single antigen bead assays (One Lambda/ThermoFisher). Patients were transplanted at our center from July 2009 to September 2015. All patients had negative flow crossmatches at the time of transplant. The MFI cutoff values used in the conventional and C1q assays were 1000 and 500, respectively. Typing of HLA-A, B, C, DR and DQB genes was performed by SSO. Results During the follow up interval (median 4 years), 9 (26%) out of 34 recipients developed DSA. Median time from transplant to DSA development was 12 months. At the time of detection, DSA were C1q positive in 8 of 9 patients. The mean number of C1q + DSA per patient was 2.7. Seven out of 8 patients had C1q + DSA directed to the donor HLA-DQB antigen(s). C1q + DSA persisted over time and were associated with worse graft function at 1 year ( p = 0.004), increased incidence of antibody mediated rejection (AMR; p p = 0.08). Despite treatment for AMR, 5 (63%) of 8 patients with C1q + DSA lost their grafts during the follow up interval. In contrast, only 2 (8%) out of 26 patients without DSA lost their graft during the same interval ( p Conclusions The incidence of de novo C1q binding DSA in our pediatric patient population is high, likely due to increased non-compliance. C1q + DSA identified patients at high risk for graft loss. These findings support the role of frequent monitoring of DSA, particularly during the first year post-transplantation, and highlight the need for prompt therapeutic intervention in patients with C1q + DSA.

A Model of Acute Antibody-Mediated Renal Allograft Rejection in the Sensitized Rata.

Antibody-mediated rejection in transplant recipients with preexisting donor-specific antibodies is a challenging clinical situation. However, we lack suitable animal models to study this scenario. The aim of this study was to develop an animal model of acute antibody-mediated rejection of renal allografts in sensitized recipients. We used major histocompatibility complex class I and II incompatible rat strains (Dark Agouti RT1av1 and Lewis RT1l), which develop aggressive rejection. Recipient Lewis rats were immunized with donor strain spleen cells 5 days before surgery to induce donor-specific antibodies. Rats underwent bilateral nephrectomy and orthotopic transplant of the donor kidney. To minimize T-cell-mediated rejection while allowing the development of donor-specific antibodies, recipient animals were given tacrolimus starting the day before surgery. Hyperacute rejection was not seen, but acute graft dysfunction was evident on day 1 with a rapid deterioration of graft function by day 3. Histologic damage featured glomerulopathy, capillaritis, capillary thrombosis, and acute tubular injury. Recipients exhibited high serum levels of donor-specific antibodies and deposition of immunoglobulin G and C4d on graft endothelium. Immunostaining showed substantial endothelial damage, fibrin deposition in glomerular and peritubular capillaries, and infiltrates of macrophages, neutrophils, and natural killer cells. T-cell activation was efficiently suppressed by tacrolimus. We have developed a clinically relevant model of acute antibody-mediated rejection in recipients with preexisting donor-specific antibodies, which is suitable for testing novel therapies.

Class II Eplet Mismatch Modulates Tacrolimus Trough Levels Required to Prevent Donor-Specific Antibody Development.

Despite more than two decades of use, the optimal maintenance dose of tacrolimus for kidney transplant recipients is unknown. We hypothesized that HLA class II de novo donor-specific antibody (dnDSA) development correlates with tacrolimus trough levels and the recipient's individualized alloimmune risk determined by HLA-DR/DQ epitope mismatch. A cohort of 596 renal transplant recipients with 50,011 serial tacrolimus trough levels had HLA-DR/DQ eplet mismatch determined using HLAMatchmaker software. We analyzed the frequency of tacrolimus trough levels below a series of thresholds <6 ng/ml and the mean tacrolimus levels before dnDSA development in the context of HLA-DR/DQ eplet mismatch. HLA-DR/DQ eplet mismatch was a significant multivariate predictor of dnDSA development. Recipients treated with a cyclosporin regimen had a 2.7-fold higher incidence of dnDSA development than recipients on a tacrolimus regimen. Recipients treated with tacrolimus who developed HLA-DR/DQ dnDSA had a higher proportion of tacrolimus trough levels <5 ng/ml, which continued to be significant after adjustment for HLA-DR/DQ eplet mismatch. Mean tacrolimus trough levels in the 6 months before dnDSA development were significantly lower than the levels >6 months before dnDSA development in the same patients. Recipients with a high-risk HLA eplet mismatch score were less likely to tolerate low tacrolimus levels without developing dnDSA. We conclude that HLA-DR/DQ eplet mismatch and tacrolimus trough levels are independent predictors of dnDSA development. Recipients with high HLA alloimmune risk should not target tacrolimus levels <5 ng/ml unless essential, and monitoring for dnDSA may be advisable in this setting.

Immunogenicity of Class I HLA but not preformed low MFI donor specific antibodies correlates with outcomes after first renal transplantation

BackgroundThe role of low levels of circulating donor specific antibodies (DSA) producing negative flow cytometry cross match is not completely defined. The purpose of this study was to examine the clinical significance of preexisting low levels of class I DSAs in flow cytometry cross match (FC CM) negative first kidney transplant recipients (KTRs). MethodsAll of the KTRs (n=41) had low levels of anti-class I antibodies only. The kidney transplant outcome was evaluated by the development of a deleterious effect (DE) in recipients in the study cohort (Group 1: DE+, Group 2: DE-). Positivity for DE was determined based on the following criteria: biopsy proven transplant glomerulopathy (TG), de novo development of DSAs, increasing MFI values for preexisting DSAs, and the development of biopsy proven AMR. Anti-HLA antibodies were tested using single antigen Luminex technology. The HLAMatchmaker computer algorithm was used for the immunogenicity analysis of antibody verified (AbVer) mismatched eplets (MME) at the HLA-A and B loci. ResultsThe results of this study showed that the number of AbVer MME is larger (P=0.03) in the group of KTR who developed DE. We also demonstrated that the number of AbVer MME is a strong predictor of post-transplant DE. These results indicate that persistent weakly reactive DSA is not a significant risk factor for the development of post-transplant DE and that recipients with such antibodies can be successfully transplanted. ConclusionsImmunogenicity of AbVer MME at HLA-A and B loci is strong predictor of post-transplant increases of the MFI values of preexisting or de novo developed DSA in the FC CM negative first KTR. Avoiding of transplants with more than eleven Class I AbVer MMEs may be the optimal approach to reduce the risk of kidney graft failure.

Association of genetic polymorphisms of macrophage inhibitory factor (MIF) and B-cell activating factor (BAFF) with the detection of donor specific antibodies in kidney allograft recipients

The posttransplant development of donor specific antibodies (DSA) initiates the antibody mediated rejection (AMR), which is associated with the increased rate of graft loss. One of the characteristics of AMR is the infiltration of innate immune system including macrophages, monocytes, neutrophils or NK cells. Macrophage inhibitory factor (MIF) and B-cell activating factor (BAFF) are well known cytokines that are associated with the activation of the innate immune system which can damage kidney allograft. In this article, the association of the genetic polymorphisms of MIF and BAFF with the development of DSA including Class I and II in kidney transplant patients is investigated. A total of 231 renal transplant patients between 2008 and 2012 at St. Vincent Medical Center, CA were studied in a retrospective study design. DSA were determined by Luminex technology, and single nucleotide polymorphisms (SNP) of MIF and BAFF were determined by the real time PCR based on 5′ nuclease allelic discrimination assay. The genetic polymorphisms of MIF rs1007888 (C/T) was associated with increased risk of positive DSA detection (p=0.04) after transplantation, and consistently significant after 1year (p=0.016). Furthermore, the presence of C allele were associated with the increased risk of Class I DSA detection (OR 1.816, CI 1.141–2.889, p=0.011). Also, genetic polymorphisms of BAFF rs12583006 were associated with the increased risk of Class II DSA detection (p=0.033). In conclusion, the genetic polymorphisms of MIF and BAFF may increase the risk of posttransplant development of DSA. This result suggests the association between the development of posttransplant DSA and the activation of innate immune system.

Immunosuppression with mTOR inhibitors prevents the development of donor-specific antibodies after liver transplant.

Donor-specific antibodies (DSAs) are an important cause of complications after solid organ transplant. Risk factors and, thus, strategies for preventing DSA development are not well defined. The DSA status of 400 patients who underwent liver transplant (LT) at the outpatient clinic of the University Hospital Essen was determined. Human leukocyte antigen (HLA) antibodies were detected by single-antigen bead technology. The strength of DSAs was reported as mean fluorescence intensity. Detectable DSAs were found in 74 (18.5%) patients and significantly more often in patients who underwent LT for autoimmune liver disease than for all other indications (29.3%; P=.022), but significantly less often found in patients who underwent LT for hepatocellular carcinoma (7.6%, P=.005). The incidence of DSAs increased with time after LT, and the risk was generally higher for female patients. The frequency of DSA detection was significantly lower (10.6%) for patients receiving immunosuppressive treatment with mammalian target of rapamycin (mTOR) inhibitors than for those receiving other regimens (20.5%; P=.025). Autoimmune liver diseases, female sex, and time of more than 8 years since LT predispose patients to the development of DSAs. Immunosuppression with the mTOR inhibitor everolimus protects against DSA development after liver transplant.

Defining the immunogenicity and antigenicity of HLA epitopes is crucial for optimal epitope matching in clinical renal transplantation.

Transplantation of an human leukocyte antigen (HLA) mismatched graft can lead to the development of donor-specific antibodies (DSA), which can result in antibody mediated rejection and graft loss as well as complicate repeat transplantation. These DSA are induced by foreign epitopes present on the mismatched HLA antigens of the donor. However, not all epitopes appear to be equally effective in their ability to induce DSA. Understanding the characteristics of HLA epitopes is crucial for optimal epitope matching in clinical transplantation. In this review, the latest insights on HLA epitopes are described with a special focus on the definition of immunogenicity and antigenicity of HLA epitopes. Furthermore, the use of this knowledge to prevent HLA antibody formation and to select the optimal donor for sensitised transplant candidates will be discussed.

Assessment of Tocilizumab (Anti-Interleukin-6 Receptor Monoclonal) as a Potential Treatment for Chronic Antibody-Mediated Rejection and Transplant Glomerulopathy in HLA-Sensitized Renal Allograft Recipients.

Extending the functional integrity of renal allografts is the primary goal of transplant medicine. The development of donor-specific antibodies (DSAs) posttransplantation leads to chronic active antibody-mediated rejection (cAMR) and transplant glomerulopathy (TG), resulting in the majority of graft losses that occur in the United States. This reduces the quality and length of life for patients and increases cost. There are no approved treatments for cAMR. Evidence suggests the proinflammatory cytokine interleukin 6 (IL-6) may play an important role in DSA generation and cAMR. We identified 36 renal transplant patients with cAMR plus DSAs and TG who failed standard of care treatment with IVIg plus rituximab with or without plasma exchange. Patients were offered rescue therapy with the anti-IL-6 receptor monoclonal tocilizumab with monthly infusions and monitored for DSAs and long-term outcomes. Tocilizumab-treated patients demonstrated graft survival and patient survival rates of 80% and 91% at 6 years, respectively. Significant reductions in DSAs and stabilization of renal function were seen at 2 years. No significant adverse events or severe adverse events were seen. Tocilizumab provides good long-term outcomes for patients with cAMR and TG, especially compared with historical published treatments. Inhibition of the IL-6-IL-6 receptor pathway may represent a novel approach to stabilize allograft function and extend patient lives.

Multicenter evaluation of a national organ sharing policy for highly sensitized patients listed for heart transplantation in Canada

Transplantation of sensitized recipients has been associated with increased risk of post-transplant complications. In 2010, the Canadian Cardiac Transplant Network (CCTN) created a unique status listing for highly sensitized heart transplant candidates. Status 4S listing requires calculated panel-reactive antibody (cPRA) level >80% as the sole listing criteria and enables geographic expansion of the donor pool by providing national access. In this study, we describe patient characteristics and outcomes of those transplanted as Status 4S in Canada. Patients' characteristics and clinical outcomes were retrospectively collected from all 11 adult heart transplant centers in Canada. Ninety-six patients were listed Status 4S from January 2010 to September 2015. Fifty-two were transplanted as Status 4S. Of these 52 transplants, mean cPRA level was 93.4%, mean age was 47 years, 46% were male, 44% had dilated cardiomyopathy and 17% were re-transplanted for cardiac allograft vasculopathy (CAV). Blood group O comprised 42% and 53% had a left ventricular assist device as a bridge to transplant. Desensitization therapy occurred in 9 patients (17%). Over a mean follow-up period of 28 months (1 week to 5.3 years), 9 patients died (17%). Kaplan-Meier 1-year year survival is 86%. Two patients were treated for antibody-mediated rejection (AMR) in the first year post-transplant and 33% of patients had at least 1 ISHLT Grade ≥2R cellular rejection in the first year. Twenty-nine percent of patients developed de novo door-specific antibodies and demonstrated no correlation with AMR. Freedom from CAV at 1 year is 88.5% and at 5 years is 81.0%. Fifty-two percent of donor hearts originated from outside the recipients' geographic and organ donation organization. A national strategy of prioritizing highly sensitized heart transplant recipients has demonstrated effective expansion of the donor pool, acceptable short-term survival, freedom from CAV and low rates of clinically relevant AMR. However, we observed significantly higher rates of cellular rejection and de novo donor-specific antibody development in this population. It is currently unknown whether this will translate into poorer long-term outcome.

Application of Operational Tolerance Signatures Are Limited by Variability and Type of Immunosuppression in Renal Transplant Recipients: A Cross-Sectional Study.

Renal transplant recipients (RTR) frequently develop complications relating to chronic immunosuppression. Identifying RTR who could safely reduce immunosuppression is therefore highly desirable. We hypothesized that "signatures" described in RTR who have stopped immunosuppression but maintained stable graft function ("operational tolerance") may enable identification of immunosuppressed RTR who are candidates for immunosuppression minimization. However, the effect of immunosuppression itself on these signatures and circulating B-cell populations is currently unknown. We undertook a cross-sectional study of 117 RTR to assess the effect of immunosuppression upon circulating B cell populations, humoral alloresponse and 2 previously published "signatures" of operational tolerance. Immunosuppression associated with alterations in both published "signatures." Azathioprine associated with a decrease in transitional and naive B-cell numbers and calcineurin inhibition associated with an increase in the number of circulating plasmablasts. However, only azathioprine use associated with the presence of donor-specific anti-HLA IgG antibodies. Calcineurin inhibition associated with an increase in total serum IgM but not IgG. Data were corrected for age, time since last transplant, and other immunosuppression. Current signatures of operational tolerance may be significantly affected by immunosuppressive regimen, which may hinder use in their current form in clinical practice. Calcineurin inhibition may prevent the development of long-lasting humoral alloresponses, whereas azathioprine therapy may be associated with donor specific antibody development.

Rapid and strong de novo donor-specific antibody development in a lung transplant recipient: Short communication/case report

A 66-yo female patient (typed B*39:01, 44:02) underwent first left single lung transplant (typed B*81:01, 15:17) on 02/07/2016 with negative for DSA in current and historical samples. On 02/17/2016 strong de novo DSA (MFI=15,200, C1q+) to B81 were detected. The recipient has two children typed B*07:02, 44:02 B*27:03, 39:01, and had received multiple vaccinations. Twinrix, Zostavax and MMR vaccines contain viruses grown on live human lung fibroblasts (MRC-5, typed B*07:02, 44:02, and WI-38, typed B*08:01, 58:01). Each dose of vaccine used for injection is known to contain protein components of fibroblasts including HLA. Most likely rapid de novo DSA development is due to booster effect produced by five exposures to mismatched B locus alleles which share the following epitopes: 70IAQ, 65QIA, 65QIA+76esn, 69aa+80n, and 163ew+73te. The later three consist of paired non-self and self eplets. Although likelihood of bystander effect produced by multiple vaccinations is low its impact cannot be ruled out.

Antibody-Mediated Rejection in Kidney Transplantation Without Evidence of Anti-HLA Antibodies?

IntroductionThe definition of antibody-mediated rejection (AMR) is based on serologic (presence and/or development of donor-specific anti-HLA antibodies [DSAs]) and histologic (C4d deposition and endothelial damage) criteria. However, several cases of AMR have been described without C4d deposition, and other cases of histologic AMR without DSAs, which could be driven by other non-HLA alloantibodies such as anti-MICA or anti-angiotensin II type I receptor (AT1R). Here we studied clinical and histologic humoral rejection in kidney transplant recipients without evidence of anti-HLA antibodies. Materials and MethodsFifteen kidney transplant recipients with AMR defined as C4d+ and/or histologic g+ptc without anti-HLA antibodies in screening test were studied. Sera at the moment of biopsy and 2 months earlier were studied for anti-HLA antibodies by Luminex, in neat, diluted 1/160, and sera after treatment with dithiothreitol (DTT) and confirmed by single-antigen test. The anti-AT1R was measured by enzyme-linked immunosorbent assay. ResultsA lack of anti-HLA and MICA antibodies was confirmed after anti-HLA screening test in all conditions (neat, diluted, and DTT-treated) and de novo development of AT1R antibodies was ruled out. Nevertheless, after single-antigen test, 3 patients were identified with a weak reaction against class I antigen and another 4 patients against class II antigen. Due to the lack of locus-C typing in the donors, the DSA assignment cannot be confirmed, whereas anti-HLA class II antigens were DSA. ConclusionsA low sensitivity in the screening of anti-HLA antibody testing was observed. Our results suggest performing single-antigen test in seronegative patients with clinical humoral rejection after screening to confirm the presence of DSA.

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.

Donor-specific antibodies and antibody-mediated rejection in vascularized composite allotransplantation.

The presence of donor-specific antibodies (DSA) increases the risk of graft failure. Although DSA characteristics, human leukocyte antigen class specificity, mean fluorescence intensity and immunoglobulin G subclasses, and their impact on the graft are quite well studied in solid organ transplants, very little information is known about their impact on vascularized composite allotransplantation (VCA). The aim of this review is to highlight recent publications regarding occurrence and effects of DSA, their follow-up and treatment in the field of VCA. The latest publications dealing with antibody-mediated rejection in VCA are mainly case presentations and reports embedded in reviews. The most important findings shown were the demonstration of the severe clinical impact of de-novo DSA and the urgent need of finding a therapeutic strategy for patients with acute antibody-mediated rejection. Suggested protocols for desensitization of possible candidates for reconstructive transplantation have been published, as these individuals are often highly sensitized and not appropriate patients for a standard surgical procedure because of their major tissue defects. The functional outcome of reconstructive transplantation has clearly exceeded the results achieved with conventional surgical techniques. The recipients' immune response, particularly development of DSA and the long-term adherence, which is probably associated with the occurrence of chronic rejection, remain a challenge.