Desensitization protocols and their outcome

A personalised delisting strategy enables successful kidney transplantation in highly sensitised patients with preformed donor-specific anti HLA antibodies

This study investigates kidney transplant outcomes in highly sensitised patients after implementing a delisting strategy aimed at enabling transplantation despite preformed donor-specific antibodies (preDSA), with the goal of reducing acute antibody-mediated rejection (aAMR) risk. Fifty-three sensitised recipients underwent kidney transplant after delisting prohibited HLA antigens, focusing initially in low MFI antibodies (<5000), except for anti-HLA-DQ. If insufficient, higher MFI antibodies were permitted, especially for those without an immunogenic eplet pattern assigned. Delisting of Complement-fixing antibodies (C1q+) was consistently avoided. Comparison cohorts included 53 sensitised recipients without DSA (SwoDSA) and 53 non-sensitised (NS). The average waiting time prior to delisting was 4.4 ± 1.8 years, with a reduction in cPRA from 99.7 ± 0.5 to 98.1 ± 0.7, followed by transplantation within 7.2 ± 8.0 months (analysed in 34 patients). Rejection rates were similar among preDSA, SwoDSA, and NS groups (16%, 8%, and 11%, respectively; p = 0.46). However, aAMR was higher in the preDSA group (12%, 4%, and 2%, respectively; p = 0.073), only presented in recipients with DSA of MFI >5000. The highest MFI DSA were against HLA-DP (Median: 10796 MFI), with 50% of preDSA aAMR cases due to anti-DP antibodies (n = 3). Graft survival rates at 1 and 5 years in preDSA group were 94%, and 67%, comparable to SwoDSA (94%, and 70%; p = 0.69), being significantly higher in the NS group (p = 0.002). The five-year recipient survival rate was 89%, comparable to SwoDSA and NS groups (p = 0.79). A delisting strategy enables safe kidney transplant in highly sensitised patients with preDSA, with a slight increase in aAMR and comparable graft and patient survivals to non-DSA cohorts.

Pretransplant, Th17 dominant alloreactivity in highly sensitized kidney transplant candidates

Introduction

Sensitization to donor human leukocyte antigen (HLA) molecules prior to transplantation is a significant risk factor for delayed access to transplantation and to long-term outcomes. Memory T cells and their cytokines play a pivotal role in shaping immune responses, thereby increasing the risk of allograft rejection among highly sensitized patients. This study aims to elucidate the precise contribution of different CD4+ memory T cell subsets to alloreactivity in highly sensitized (HS) kidney transplant recipients.

Methods and results

Stimulation of peripheral blood mononuclear cells (PBMC) with various polyclonal stimulating agents to assess non-specific immune responses revealed that HS patients exhibit elevated immune reactivity even before kidney transplantation, compared to non-sensitized (NS) patients. HS patients' PBMC displayed higher frequencies of CD4+ T cells expressing IFNγ, IL4, IL6, IL17A, and TNFα and secreted relatively higher levels of IL17A and IL21 upon stimulation with PMA/ionomycin. Additionally, PBMC from HS patients stimulated with T cell stimulating agent phytohemagglutinin (PHA) exhibited elevated expression levels of IFNγ, IL4 and, IL21. On the other hand, stimulation with a combination of resiquimod (R848) and IL2 for the activation of memory B cells demonstrated higher expression of IL17A, TNFα and IL21, as determined by quantitative real-time PCR. A mixed leukocyte reaction (MLR) assay, employing third-party donor antigen presenting cells (APCs), was implemented to evaluate the direct alloreactive response. HS patients demonstrated notably higher frequencies of CD4+ T cells expressing IL4, IL6 and IL17A. Interestingly, APCs expressing recall HLA antigens triggered a stronger Th17 response compared to APCs lacking recall HLA antigens in sensitized patients. Furthermore, donor APCs induced higher activation of effector memory T cells in HS patients as compared to NS patients.

Conclusion

These results provide an assessment of pretransplant alloreactive T cell subsets in highly sensitized patients and emphasize the significance of Th17 cells in alloimmune responses. These findings hold promise for the development of treatment strategies tailored to sensitized kidney transplant recipients, with potential clinical implications.

Role of therapeutic plasma exchange as a desensitization therapy in human leukocyte antigen incompatible renal transplant patients: A single-center experience

OBJECTIVE

Despite an increase in the rate of successful live donor renal transplantation done annually, the number of potential recipients with acceptable donors is relegated to the ever-expanding cadaver-donor waiting list due to sensitization to human leukocyte antigen (HLA) antibodies. If not sufficiently suppressed, these preformed HLA antibodies can trigger antimicrobial resistance (AMR) and early graft loss. To ameliorate this situation, various desensitization treatments are administered to provide a survival benefit to highly sensitized patients.

METHOD

One hundred and six patients in the time frame of January 2017 to March 2019 were included in the study group. The desensitization protocol included therapeutic plasma exchange and administration of low-dose intravenous immunoglobulin (100 mg/kg per therapeutic plasma exchange (TPE) session) to highly sensitized patients (treatment group) who subsequently underwent renal transplantation after negative pre-transplant Centers for Disease Control and Prevention Luminex crossmatch (CDC/LumXM). We compared graft survival rates between the group undergoing desensitization (treatment group) and matched control group of patients that underwent HLA-compatible transplantation.

RESULTS

In the treatment group, Kaplan-Meier analysis estimates an average rate of patient graft survival of 95.2% at 3 years post-transplant, as compared with the rate of 86.9% in the same time frame for the control-matched group (p < 0.05 for both comparisons).

CONCLUSION

Desensitization treatment with TPE before live donor renal transplantation in the case of patients with HLA sensitization provides better survival benefits along with monitoring for donor-specific antibodies (DSAs) and other infections, rather than waiting for a compatible organ donor. The data lays out evidence that desensitization treatments can assist overcome HLA incompatibility barriers in live donor renal transplantation.

The impact of IdeS (imlifidase) on allo-specific, xeno-reactive, and protective antibodies in a sensitized rhesus macaque model

BACKGROUND

Highly sensitized patients face many barriers to kidney transplantation, including higher rates of antibody-mediated rejection after HLA-incompatible transplant. IdeS, an endopeptidase that cleaves IgG nonspecifically, has been trialed as desensitization prior to kidney transplant, and successfully cleaves donor-specific antibody (DSA), albeit with rebound.

METHODS

IdeS was generated and tested (2 mg/kg, IV) in two naïve and four allosensitized nonhuman primates (NHP). Peripheral blood samples were collected at regular intervals following IdeS administration. Total IgG, total IgM, and anti-CMV antibodies were quantified with ELISA, and donor-specific antibody (DSA) and anti-pig antibodies were evaluated using flow cytometric crossmatch. B cell populations were assessed using flow cytometry.

RESULTS

IdeS successfully cleaved rhesus IgG in vitro. In allosensitized NHP, robust reduction of total, DSA, anti-pig, and anti-CMV IgG was observed within one day following IdeS administration. Rapid rebound of all IgG antibody populations was observed, with antibody levels returning to baseline around day 14 post-infusion. Total IgM level was not affected by IdeS. Interestingly, a comparable reduction in antibody populations was observed after the second dose of IdeS. However, we have not observed any significant modulation of B cell subpopulations after IdeS.

CONCLUSIONS

This study evaluated efficacy of IdeS in the allosensitized NHP in IgG with various specificities, mirroring antibody kinetics in human patients. The efficacy of IdeS on preexisting anti-pig antibodies may be useful in clinical xenotransplantation. However, given the limitation of IdeS on its durability as a monotherapy, optimization of IdeS with other agents targeting the humoral response is further needed.

Antibody-mediated rejection in xenotransplantation: Can it be prevented or reversed?

Antibody-mediated rejection (AMR) is the commonest cause of failure of a pig graft after transplantation into an immunosuppressed nonhuman primate (NHP). The incidence of AMR compared to acute cellular rejection is much higher in xenotransplantation (46% vs. 7%) than in allotransplantation (3% vs. 63%) in NHPs. Although AMR in an allograft can often be reversed, to our knowledge there is no report of its successful reversal in a pig xenograft. As there is less experience in preventing or reversing AMR in models of xenotransplantation, the results of studies in patients with allografts provide more information. These include (i) depletion or neutralization of serum anti-donor antibodies, (ii) inhibition of complement activation, (iii) therapies targeting B or plasma cells, and (iv) anti-inflammatory therapy. Depletion or neutralization of anti-pig antibody, for example, by plasmapheresis, is effective in depleting antibodies, but they recover within days. IgG-degrading enzymes do not deplete IgM. Despite the expression of human complement-regulatory proteins on the pig graft, inhibition of systemic complement activation may be necessary, particularly if AMR is to be reversed. Potential therapies include (i) inhibition of complement activation (e.g., by IVIg, C1 INH, or an anti-C5 antibody), but some complement inhibitors are not effective in NHPs, for example, eculizumab. Possible B cell-targeted therapies include (i) B cell depletion, (ii) plasma cell depletion, (iii) modulation of B cell activation, and (iv) enhancing the generation of regulatory B and/or T cells. Among anti-inflammatory agents, anti-IL6R mAb and TNF blockers are increasingly being tested in xenotransplantation models, but with no definitive evidence that they reverse AMR. Increasing attention should be directed toward testing combinations of the above therapies. We suggest that treatment with a systemic complement inhibitor is likely to be most effective, possibly combined with anti-inflammatory agents (if these are not already being administered). Ultimately, it may require further genetic engineering of the organ-source pig to resolve the problem entirely, for example, knockout or knockdown of SLA, and/or expression of PD-L1, HLA E, and/or HLA-G.

Research priorities for therapeutic plasma exchange in critically ill patients

Therapeutic plasma exchange (TPE) is a therapeutic intervention that separates plasma from blood cells to remove pathological factors or to replenish deficient factors. The use of TPE is increasing over the last decades. However, despite a good theoretical rationale and biological plausibility for TPE as a therapy for numerous diseases or syndromes associated with critical illness, TPE in the intensive care unit (ICU) setting has not been studied extensively. A group of eighteen experts around the globe from different clinical backgrounds used a modified Delphi method to phrase key research questions related to "TPE in the critically ill patient". These questions focused on: (1) the pathophysiological role of the removal and replacement process, (2) optimal timing of treatment, (3) dosing and treatment regimes, (4) risk-benefit assumptions and (5) novel indications in need of exploration. For all five topics, the current understanding as well as gaps in knowledge and future directions were assessed. The content should stimulate future research in the field and novel clinical applications.

Correlation of Luminex-Based Single Antigen Based Results With Complement-Dependent Cytotoxicity Crossmatch and Flow Cytometry Crossmatch Results: A Single-Center Experience From Istanbul

BACKGROUND

This study aimed to retrospectively investigate the correlation of mean Class I donor-specific antibody (DSA) intensity values detected in Luminex-based techniques with the results of complement-dependent cytotoxicity crossmatch (CDC-XM) and flow cytometry crossmatch (FC-XM) results.

METHODS

A total of 335 patients with kidney failure and their living donors whose CDC-XM, FC-XM, and single antigen based (SAB) tests were studied between 2018 and 2020 for transplant preparation from living donor candidates were included in the study. Patients were divided into 4 groups according to their mean fluorescence intensity (MFI) values of SAB assay.

RESULTS

Anti-HLA antibodies (class I and/or class II) were detected using SAB in 91.6% patients included in the study (MFI >1000). Class I DSA was positive in 34.8% of patients with anti-HLA antibodies. When CDC-XM and FC-XM results were evaluated in the 4 groups separated according to MFI values, 3 patients with DSA MFI <1000 had negative CDC-XM and T-B-FC-XM results. Of 32 patients with DSA-MFI between 1000 and 3000, 93.75% (n = 30) had T-B-FC-XM or CDC-XM-negative results, and 6.25% (n = 2) had B-FC-XM-positive results. The CDC-XM, T, and B-FC-XM were negative in all 17 patients with DSA-MFI between 3000 and 5000. Our results showed that MFI >5834 DSA values were significantly correlated with positive T-FC-XM (P < .001), and MFI >6016 values were significantly correlated with positive CDC-XM (P = .002). In addition, MFI values >5000 were associated with both CDC-XM and FC-XM in our study.

CONCLUSIONS

The MFI values >5000 correlated with both CDC-XM and FC-XM.

Effects of invivo CXCR4 Blockade and Proteasome Inhibition on Bone Marrow Plasma Cells in HLA-Sensitized Kidney Transplant Candidates

To date, plasma cell (PC)-targeted therapies have been limited by suboptimal PC depletion and antibody rebound. We hypothesized this is partly because of PC residence in protective bone marrow (BM) microenvironments. The purpose of this proof-of-concept study was to examine the effects of the CXCR4 antagonist, plerixafor, on PC BM residence; its safety profile (alone and in combination with a proteasome inhibitor, bortezomib); and the transcriptional effect on BMPCs in HLA-sensitized kidney transplant candidates. Participants were enrolled into 3 groups: group A (n = 4), plerixafor monotherapy; and groups B (n = 4) and C (n = 4), plerixafor and bortezomib combinations. CD34⁺ stem cell and PC levels increased in the blood after plerixafor treatment. PC recovery from BM aspirates varied depending on the dose of plerixafor and bortezomib. Single-cell RNA sequencing on BMPCs from 3 group C participants pretreatment and posttreatment revealed multiple populations of PCs, with a posttreatment enrichment of oxidative phosphorylation, proteasome assembly, cytoplasmic translation, and autophagy-related genes. Murine studies demonstrated dually inhibiting the proteasome and autophagy resulted in greater BMPC death than did monotherapies. In conclusion, this pilot study revealed anticipated effects of combined plerixafor and bortezomib on BMPCs, an acceptable safety profile, and suggests the potential for autophagy inhibitors in desensitization regimens.

Desensitizing With Temporary Donor Splenic Transplant: Hope for the Sensitized Patients on Pancreas and Kidney -Pancreas Transplant Waitlist

BACKGROUND

Sensitized patients on a waitlist with donor specific antibodies (DSA) or positive flow cytometry cross match (FXM) to deceased donor organ have few pretransplant desensitization options due to increasing graft cold ischemia time. Herein, sensitized simultaneous kidney/pancreas recipients received temporary splenic transplant from the same donor under the hypothesis that spleen would function as a DSA graveyard and provide a safe immunologic window for transplant.

METHODS

We analyzed presplenic and postsplenic transplant FXM and DSA results of 8 sensitized patients who underwent simultaneous kidney and pancreas transplantation with temporary deceased donor spleen between November 2020 and January 2022.

RESULTS

Pre-splenic transplant, 4 sensitized patients were both T-cell and B-cell FXM positive; one was only B-cell FXM positive and 3 were DSA positive/FXM negative. Post-splenic transplant, all were FXM negative. Pre-splenic transplant class I and class II DSA were detected in 3 patients, only class I DSA in 4 patients, and only class II DSA in 1 patient. Postsplenic transplant, class I DSA was eliminated in all patients. Class II DSA persisted in 3 patients; all showed a marked decrease in DSA mean fluorescence index. Class II DSA was eliminated in one patient.

CONCLUSION

Donor spleen functions as a DSA graveyard and provides an immunologically safe window for kidney-pancreas transplantation.

Recommendations for living donor kidney transplantation

This Guide for Living Donor Kidney Transplantation (LDKT) has been prepared with the sponsorship of the Spanish Society of Nephrology (SEN), the Spanish Transplant Society (SET), and the Spanish National Transplant Organization (ONT). It updates evidence to offer the best chronic renal failure treatment when a potential living donor is available. The core aim of this Guide is to supply clinicians who evaluate living donors and transplant recipients with the best decision-making tools, to optimise their outcomes. Moreover, the role of living donors in the current KT context should recover the level of importance it had until recently. To this end the new forms of incompatible HLA and/or ABO donation, as well as the paired donation which is possible in several hospitals with experience in LDKT, offer additional ways to treat renal patients with an incompatible donor. Good results in terms of patient and graft survival have expanded the range of circumstances under which living renal donors are accepted. Older donors are now accepted, as are others with factors that affect the decision, such as a borderline clinical history or alterations, which when evaluated may lead to an additional number of transplantations. This Guide does not forget that LDKT may lead to risk for the donor. Pre-donation evaluation has to centre on the problems which may arise over the short or long-term, and these have to be described to the potential donor so that they are able take them into account. Experience over recent years has led to progress in risk analysis, to protect donors' health. This aspect always has to be taken into account by LDKT programmes when evaluating potential donors. Finally, this Guide has been designed to aid decision-making, with recommendations and suggestions when uncertainties arise in pre-donation studies. Its overarching aim is to ensure that informed consent is based on high quality studies and information supplied to donors and recipients, offering the strongest possible guarantees.

Impact of ABO Compatibility/Incompatibility on the Perioperative Anti-SARS-CoV-2 Immunoglobulin G Levels in 2 Preoperatively Vaccinated Patients Undergoing Kidney Transplant: A Case Report

Herein, we monitored the perioperative anti-SARS-CoV-2 spike immunoglobulin G titers in patients who were preoperatively vaccinated with 2 doses of a COVID-19 messenger RNA vaccine. Additionally, we compared the clinical settings between ABO-incompatible and ABO-compatible pre-emptive kidney transplant (KTx). Case 1 was of a 45-year-old man who was an ABO-incompatible KTx recipient. Before transplant, his serum antibody titers decreased from 278 U/mL at baseline to 41.9 U/mL after desensitization therapy (84.9% lower) and 54.7 U/mL (80.3% lower) at day 8; it is now maintained at 4.1 U/mL at 6 months posttransplant (98.5% lower). Case 2 was of a 50-year-old man who was an ABO-compatible KTx recipient. His serum antibody titer level decreased from 786 U/mL at baseline to 386 U/mL on day 8 (50.8% lower) and is now maintained at 156 U/mL at 6 months posttransplant (80.1% lower). We suggest that anti-SARS-CoV-2 spike immunoglobulin G titers should be monitored during the perioperative period to determine the optimal timing of COVID-19 vaccine booster doses for the maintenance of protective immunity, particularly in ABO-incompatible KTx recipients who require desensitization therapy.

Low Incidence of Acute Antibody-Mediated Rejection after HLA Desensitization in Living Donor Kidney Transplant Recipients

Desensitization allows the performance of human leukocyte antigen (HLA)-incompatible transplants. However, the incidence of acute rejection (AR) is high. This study aims to analyze the incidence of AR after transplantation with HLA-incompatible living donors in patients who underwent desensitization. Patients were immunosuppressed with tacrolimus, mycophenolic acid derivatives, and steroids after being desensitized with rituximab, plasma exchange, and/or immunoadsorption with specific cytomegalovirus immunoglobulins. A negative complement-dependent cytotoxicity or flow cytometry crossmatch and a donor-specific antibody titer < 1000 mean fluorescence intensity (MFI) were used to determine desensitization efficacy. A total of 36 patients underwent desensitization, and 27 (75%) were transplanted. After a follow-up of 58 ± 58 months (Min−Max: 0.13−169.5), five episodes of AR occurred: two antibody-mediated and three T-cell-mediated. No differences were found in baseline calculated panel-reactive antibodies (cPRA), class I or II MFI, number of antibodies, or Relative Intensity Scale (RIS) between AR and non-AR patients. Patients with antibody-mediated AR had higher cPRA (NS), MFI class I (p = 0.07) and class II (p = 0.006), and RIS (p = 0.01). The two patients with antibody-mediated AR and one patient with T-cell-mediated AR lost their grafts. In conclusion, the incidence of acute antibody-mediated rejection after desensitization was 7.4%, which occurred early post-transplantation in patients with high MFI and was associated with early graft loss.

New approach to desensitization in solid organ transplantation-imlifidase

The IgG-degrading enzyme derived from Streptococcus pyogenes is a recombinant cysteine protease of S. pyogenes produced in Escherichia coli that cleaves all four human subclasses of IgG with strict specificity. The proteolytic activity on IgG molecules prevents the occurrence of IgG-mediated antibody-dependent, cellular cytotoxicity and complement-mediated cytotoxicity, two processes that are critical for antibody rejection. The results from phase II studies demonstrated that desensitization with imlifidase represents a therapeutic strategy that can operationalize desensitization, allowing life-saving transplants from deceased donors (DD) and living donors (LD) to proceed in highly sensitized kidney transplant candidates with low risk of hyperacute rejection. Its action onset is rapid, allowing kidney transplantation from a deceased donor. Disadvantages of imlifidase include a quick reappearance of DSAs, which poses a risk of antibody-mediated rejection, the quick development of anti-Ides antibodies, which rules out repeated use of imlifidase and its IgG-degrading potential, limiting the use of therapeutic antibodies. Imlifdase received conditional approval on 26 August 2020 in the EU for desensitization treatment of highly sensitized adult kidney transplant patients with positive crossmatch against an available deceased donor.

Effect of pretransplant dialysis vintage on clinical outcomes in deceased donor kidney transplant

The waiting time for deceased donor kidney transplants (DDKT) is increasing. We evaluated DDKT prognosis according to the pretransplant dialysis vintage. A total of 4117 first-time kidney transplant recipients were enrolled from a prospective nationwide cohort in Korea. DDKT recipients were divided into tertiles according to pretransplant dialysis duration. Graft failure, mortality, and composite were compared between DDKT and living donor kidney transplant (LDKT) recipients. Pretransplant dialysis vintage was longer annually in DDKT recipients. In the subdistribution of the hazard model for the competing risk, the first tertile did not show an increased risk of graft failure compared with LDKT recipients; however, the second and third tertile groups had an increased risk of graft failure compared to LDKT recipients (adjusted hazard ratio [aHR] 3.59; 95% confidence interval [CI] 1.69-7.63; P < 0.001; aHR 2.37; 95% CI 1.06-5.33; P = 0.037). All DDKT groups showed a significantly higher risk of patient death than LDKT, with the highest risk in the third tertile group (aHR 11.12; 95% CI 4.94-25.00; P < 0.001). A longer pretransplant dialysis period was associated with a higher risk of the composite of patient death and graft failure in DDKT recipients. DDKT after a short period of dialysis had non-inferior results on graft survival compared with LDKT.

Strategies to Overcome HLA Sensitization and Improve Access to Retransplantation after Kidney Graft Loss

An increasing number of patients waitlisted for kidney transplantation have a previously failed graft. Retransplantation provides a significant improvement in morbidity, mortality, and quality of life when compared to dialysis. However, HLA sensitization is a major barrier to kidney retransplantation and the majority of the highly sensitized patients are waiting for a subsequent kidney transplant. A multidisciplinary team that includes immunogeneticists, transplant nephrologists and surgeons, and adequate allocation policies is fundamental to increase access to a kidney retransplant. A review of Pubmed, ScienceDirect, and the Cochrane Library was performed on the challenges of kidney retransplantation after graft loss, focusing on the HLA barrier and new strategies to overcome sensitization. Conclusion: Technical advances in immunogenetics, new desensitization protocols, and complex allocation programs have emerged in recent years to provide a new hope to kidney recipients with a previously failed graft.

Efficient use of immunosuppressants for kidney transplants

A recent development of immunosuppressive protocols (or simply, suppressants) offers a new option to patients suffering from end-stage renal disease: transplants from biologically incompatible donors. Suppressants are currently being used for direct transplants within patient-donor pairs, but they can be utilized more efficiently when combined with kidney exchanges. To assess the welfare gains from doing so, we introduce the "minimum chains algorithms" for different sizes of feasible exchanges. Using these algorithms, we calculate the minimal number of suppressants needed for transplants for a group of patient-donor pairs. Our simulation results show that (i) a significant reduction of suppressants can be achieved by implementing this proposal, (ii) it suffices to arrange 2-way exchanges for the best use of suppressants, and (iii) the welfare gain varies with the ABO blood-type distribution, and the gain in Korea appears to be larger than that in the United States. Finally, we assess the value (or cost) of each patient-donor pair by comparing the outcomes of the pools with and without the pair.

The impact of Rituximab administered before transplantation in patients undergoing allogeneic hematopoietic stem cell transplantation: A real-world study

Rituximab is used to eliminate B cells as a chimeric monoclonal antibody directed against CD20, a B-cell antigen expressed on B cells. To explore the impact of rituximab administered before transplantation, we implemented a retrospective, monocentric study and utilized real-world data collected at our center between January 2018 and December 2020, and then followed until December 2021. Based on whether a dose of 375mg/m2 rituximab was used at least once within two weeks before transplantation, patients undergoing allo-HSCT were classified into two groups: rituximab (N=176) and non-rituximab (N=344) group. Amongst all the patients, the application of rituximab decreased EBV reactivation (P&lt;0.01) and rituximab was an independent factor in the prevention of EBV reactivation by both univariate and multivariate analyses (HR 0.56, 95%CI 0.33-0.97, P=0.04). In AML patients, there were significant differences in the cumulative incidence of aGVHD between the two groups (P=0.04). Our data showed that rituximab was association with a decreased incidence of aGVHD in AML patients according to both univariate and multivariate analyses. There was no difference between the two groups in other sets of populations. Thus, our study indicated that rituximab administered before transplantation may help prevent EBV reactivation in all allo-HSCT patients, as well as prevent aGVHD in AML patients after allo-HSCT.

Proteomics for Biomarker Discovery for Diagnosis and Prognosis of Kidney Transplantation Rejection

Renal transplantation is currently the treatment of choice for end-stage kidney disease, enabling a quality of life superior to dialysis. Despite this, all transplanted patients are at risk of allograft rejection processes. The gold-standard diagnosis of graft rejection, based on histological analysis of kidney biopsy, is prone to sampling errors and carries high costs and risks associated with such invasive procedures. Furthermore, the routine clinical monitoring, based on urine volume, proteinuria, and serum creatinine, usually only detects alterations after graft histologic damage and does not differentiate between the diverse etiologies. Therefore, there is an urgent need for new biomarkers enabling to predict, with high sensitivity and specificity, the rejection processes and the underlying mechanisms obtained from minimally invasive procedures to be implemented in routine clinical surveillance. These new biomarkers should also detect the rejection processes as early as possible, ideally before the 78 clinical outputs, while enabling balanced immunotherapy in order to minimize rejections and reducing the high toxicities associated with these drugs. Proteomics of biofluids, collected through non-invasive or minimally invasive analysis, e.g., blood or urine, present inherent characteristics that may provide biomarker candidates. The current manuscript reviews biofluids proteomics toward biomarkers discovery that specifically identify subclinical, acute, and chronic immune rejection processes while allowing for the discrimination between cell-mediated or antibody-mediated processes. In time, these biomarkers will lead to patient risk stratification, monitoring, and personalized and more efficient immunotherapies toward higher graft survival and patient quality of life.

[Perspectives for future development of the kidney paired donation programme in France]

Almost one third of kidney donation candidates are incompatible (HLA and/or ABO) with their directed recipient. Kidney paired donation allows potential donors to be exchanged and gives access to a compatible kidney transplant. The Bioethics Law of 2011 authorised kidney paired donation in France with reciprocity between 2 incompatible "donor-recipient" pairs. A limited number of transplants have been performed due to a too restricted authorization compared to other European practices. This study presents the perspectives of the new Bioethics Law, enacted in 2021, which increases the authorised practices for kidney paired donation in France. The two simulated evolutions are the increase of the number of pairs involved in a kidney paired donation to 6 (against 2 currently) and the use of a deceased donor as a substitution to one of living donor. Different scenarios are simulated using data from the Agence de la Biomedecine; incompatible pairs registered in the kidney paired donation programme in France between December 2013 and February 2018 (78 incompatible pairs), incompatible transplants performed during the same period (476 incompatible pairs) and characteristics of deceased donors as well as proposals made over this period. Increasing the number of pairs has a limited effect on the number of transplants, which increases from 18 (23% of recipients) in the current system to 25 (32% of recipients) when 6 pairs can be involved. The use of a deceased donor significantly increases the number of transplants to 41 (52% of recipients). This study makes it possible to evaluate the increase in possibilities of kidney transplants by kidney paired donation following the new bioethics law. A working group and an information campaign for professionals and patients will be necessary for its implementation.

Tolerance protocol of living kidney transplant for developing countries through basic strategy of lymphocyte depletion

End-stage kidney failure (ESKD) is a global issue where kidney replacement therapy imposes enormous economic burden to people of developing countries, in addition to the severe limitations to the availability of hemodialysis and peritoneal dialysis technique. The best option of kidney transplantation also requires lifelong combination immunosuppressive medicines, the cost of which is equally comparable to lifelong dialysis. A strategy of achieving transplant tolerance that requires minimum immunosuppressive medicines, although in experimental stage, also requires state-of-art technology with costly medicines and interventions. This is evidently beyond the reach of ESKD patients of developing countries. Hence, globally in developing countries, a need for an innovative but cost-effective tolerance protocol is a burning need for a successful transplant program. In brief, transplant tolerance is defined as a state of donor-specific unresponsiveness to the allograft antigens without the need for ongoing pharmacologic immunosuppression or with a minimal need. Current state-of-art techniques involves: (1) A state of hematological chimera, for complete tolerance; (2) Prope or partial tolerance where immune-reactive T-lymphocytes are inhibited using monoclonal antibodies; and (3) Chimeric antigen receptor for T-regulatory (T-reg) cell therapy using genetically engineered T-reg cells targeting specific T-lymphocyte receptors for inducing anergy. From our real-world experience in transplant management in post-transplant lympho-proliferative disorders (PTLD), we noticed frequently a drastic reduction in the need of immunosuppressive medicines following lympho-ablative therapy for PTLD. We recently published a case study on a real-world experience transplant case where we explained a partial or prope tolerance that developed after lymphocyte ablation therapy, following which the allograft was maintained with low dose dual standard immunosuppressive medicines. Based on this publication, we propose here an innovative tolerance protocol for living related low risk kidney transplantation for developing countries, in this opinion review.

The Impact of Panel Reactive Antibodies and Different Desensitization Methods on Pediatric Allogeneic Hematopoietic Stem Cell Transplantation Outcomes

INTRODUCTION

In highly sensitized patients who have panel reactive antibodies (PRAs) before hematopoietic stem cell transplantation, primary graft failure risk may increase. In this study, we aimed to determine the association of PRA with engraftment, and graft versus host disease (GVHD) in pediatric patients.

MATERIALS AND METHODS

Forty-three PRA-positive and 42 PRA-negative patients were taken into study. Both groups were compared in terms of graft failure, acute GVHD, viral infection and survival rates. PRA-positive group was also divided into 2 according to treatment modality (steroid-only group/combination therapy) and compared for the same parameters.

RESULTS

There was no difference in PRA-positive and negative patients in terms of graft failure, acute GVHD and viral infections. Analysis of the PRA-positive group in itself showed that there was also no difference in terms of graft failure and viral infection frequency. The only difference is that acute grade 3 to 4 GVHD was higher in the steroid-only group. The 100-day overall survival was 90.2% and 90.4% for the PRA-positive and negative groups, respectively.

CONCLUSIONS

Different treatment strategies like plasmapheresis, steroid, rituximab, or combination therapies can be used for the desensitization of PRA-positive patients before hematopoietic stem cell transplantation. Patient-specific treatment modality for sensitized patients before transplant can increase the success rate.

Long-term Persistence of Allosensitization After Islet Allograft Failure

BACKGROUND

Allosensitization has been reported after discontinuation of immunosuppression following graft failure in islet transplantation (ITx) recipients, though duration of its persistence is unknown.

METHODS

We evaluated 35 patients with type 1 diabetes who received ITx, including 17 who developed graft failure (ITx alone, n = 13; ITx plus bone marrow-derived hematopoietic stem cells, n = 4) and 18 with persistent graft function. Panel-reactive antibody (PRA) was measured yearly for the duration of graft function within 1 y after graft failure at enrollment and yearly thereafter.

RESULTS

In ITx alone graft failure patients, 61% (8/13) were PRA-positive at 6 y postgraft failure, and 46% (6/13) developed donor-specific anti-HLA antibodies (DSA to 2 ± 1 donors) during follow-up. The degree of sensitization was variable (cPRA ranging between 22% and 100% after graft failure). Allosensitization persisted for 7-15 y. Three subjects (3/13) were not allosensitized. In ITx plus bone marrow-derived hematopoietic stem cell recipients, cPRA-positivity (88%-98%) and DSA positivity persisted for 15 y in 75% (3/4) of subjects.

CONCLUSIONS

Allosensitization was minimal while subjects remained on immunosuppression, but after discontinuation of immunosuppressive therapy, the majority of subjects (77%) became allosensitized with persistence of PRA positivity for up to 15 y. Persistence of allosensitization in this patient population is of clinical importance as it may result in longer transplant waiting list times for identification of a suitable donor in the case of requiring a subsequent transplant.

Chronic intermittent intravenous immunoglobulin in heart transplant recipients with elevated donor-specific antibody levels

Donor-specific antibodies (DSA) are associated with antibody-mediated rejection (AMR) and poor patient survival. In heart transplant, the efficacy of intermittent intravenous immunoglobulin (IVIg) in reducing de novo DSA levels and treating AMR has not been characterized. We retrospectively studied a cohort of 19 patients receiving intermittent IVIg for elevated DSA and examined changes in DSA levels and graft function. Intermittent IVIg infusions were generally safe and well tolerated. Overall, 23 of 62 total DSA (37%) were undetectable after treatment, 21 DSA (34%) had MFI decrease by more than 25%, and 18 (29%) had MFI decrease by less than 25% or increase. The average change in MFI was -51% ± 71% (P < .001). Despite reductions in DSA, among the six patients (32%) with biopsy-confirmed AMR, left ventricular ejection fraction (LVEF) decreased in five (83%) and cardiac index (CI) decreased in three (50%). Conversely, LVEF increased in 91% and CI increased in 70% of biopsy-negative patients. All six AMR patients were readmitted during treatment, four for confirmed or suspected rejection. IVIg infusions may stabilize the allograft in patients with elevated DSA and negative biopsies, but once AMR has developed does not appear to improve allograft function despite decreasing DSA levels.

Immortal Time-Bias-Corrected Survival of Highly Sensitized Patients and HLA-desensitized Kidney Transplant Recipients

Introduction

In the setting of kidney transplantation (KT), we assessed the efficacy of desensitization and compared the survival of desensitized patients (HLA-incompatible KT) with similarly sensitized patients receiving HLA-compatible KT or sensitized patients still on a waiting list after adjusting for the usually unaccounted immortal time bias.

Methods

All patients in a French KT center on the waiting list between August 1994 and December 2019 with a high level of sensitization (panel-reactive antibodies [PRAs] ≥80%) were included. The primary outcome was all-cause mortality. A time-varying covariate Cox survival model was used to account for the immortal time bias. A landmark analysis was used as a sensitivity analysis.

Results

During the study period, 326 patients with high PRAs were followed, among which 147 (45%) remained on the waiting list at the time of last follow-up and 179 benefited from a KT. Thirty-six patients were desensitized, of which 30 received a kidney transplant, including eight deceased kidney donors. There were no differences in mortality rates between desensitized KT patients, nondesensitized KT patients, and waitlisted patients after adjusting for immortal time bias (hazard ratio [HR] = 0.48, P = 0.22). Death-censored graft survival was similar between desensitized and nondesensitized KT patients (HR = 0.92, P = 0.88 adjusting for donor age >65 years, donor status, and time on the waiting list). Mean estimated glomerular filtration rate at 1 year post-KT was similar for desensitized KT patients (53.3 ± 21 vs. 53.6 ± 21 ml/min per 1.73 m² for nondesensitized patients; P = 0.95).

Conclusions

HLA-desensitization was effective for highly sensitized patients and gave access to KT without detrimental effects on patient or graft survival rates.

Impact of delayed graft function on clinical outcomes in highly sensitized patients after deceased-donor kidney transplantation

Background

We investigated whether the development of delayed graft function (DGF) in pre-sensitized patients affects the clinical outcomes after deceased-donor kidney transplantation (DDKT).

Methods

The study included 709 kidney transplant recipients (KTRs) from three transplant centers. We divided KTRs into four subgroups (highly sensitized DGF, highly sensitized non-DGF, low-sensitized DGF, and low-sensitized non-DGF) according to panel reactive antibody level of 50%, or DGF development. We compared post-transplant clinical outcomes among the four subgroups.

Results

Incidence of biopsy-proven acute rejection (BPAR) was higher in two highly sensitized subgroups than in low-sensitized subgroups. It tended to be higher in highly sensitized DGF subgroups than in the highly sensitized non-DGF subgroups. In addition, the highly sensitized DGF subgroup showed the highest risk for BPAR (hazard ratio, 3.051; P=0.005) and independently predicted BPAR. Allograft function was lower in the two DGF subgroups than in the non-DGF subgroup until one month after transplantation, but thereafter it was similar. Death-censored graft loss rates and patient mortality tended to be low when DGF developed, but it did not reach statistical significance.

Conclusions

DGF development in highly sensitized patients increases the risk for BPAR in DDKT compared with patients without DGF, suggesting the need for strict monitoring and management of such cases.

Impact of low-level pretransplant donor-specific antibodies on outcomes after kidney transplantation

Background

The effect of low‐level pretransplant donor‐specific antibody (DSA) on kidney transplant outcomes is not well described. The goal of this study was to compare outcomes among patients of varying immunologic risk, based on the level of pretransplant DSA.

Methods

We retrospectively reviewed all adult kidney transplant recipients who had undergone a transplant at our center between January 2013 and May 2017. Patients were grouped as negative DSA (mean fluorescence intensity, [MFI_SUM < 100]), low‐level DSA (MFI_SUM 100–1000), and positive DSA (MFI_SUM > 1000). Rejection, infection, graft, and patient survival were outcomes measured.

Results

Of 952 patients, 82.1% had negative DSA, 10.7% had low‐level DSA, and 7.1% had positive DSA. The positive DSA group had the highest rate of antibody‐mediated rejection (10.3%), followed by low‐level DSA (7.8%) and the negative DSA group (4.5%) (p = .034). The rate of BK viremia was highest in the positive DSA group (39.7%), followed by the low‐level group (30.4%) and the negative DSA group (25.6%), (p = .025). None of the other outcomes, including graft or patient survival, were different between the groups.

Conclusion

While low‐level DSA should not prevent proceeding with kidney transplantation, it should not be ignored. Future studies are needed to investigate the long‐term effects of varying levels of pre‐transplant DSA on outcomes.

Synergistic impact of pre-sensitization and delayed graft function on allograft rejection in deceased donor kidney transplantation

The aim of this study is to investigate whether or not delayed graft function (DGF) and pre-transplant sensitization have synergistic adverse effects on allograft outcome after deceased donor kidney transplantation (DDKT) using the Korean Organ Transplantation Registry (KOTRY) database, the nationwide prospective cohort. The study included 1359 cases between May 2014 and June 2019. The cases were divided into 4 subgroups according to pre-sensitization and the development of DGF post-transplant [non-pre-sensitized-DGF(−) (n = 1097), non-pre-sensitized-DGF(+) (n = 127), pre-sensitized-DGF(−) (n = 116), and pre-sensitized-DGF(+) (n = 19)]. We compared the incidence of biopsy-proven allograft rejection (BPAR), time-related change in allograft function, allograft or patient survival, and post-transplant complications across 4 subgroups. The incidence of acute antibody-mediated rejection (ABMR) was significantly higher in the pre-sensitized-DGF(+) subgroup than in other 3 subgroups. In addition, multivariable cox regression analysis demonstrated that pre-sensitization combined with DGF is an independent risk factor for the development of acute ABMR (hazard ratio 4.855, 95% confidence interval 1.499–15.727). Moreover, DGF and pre-sensitization showed significant interaction (p-value for interaction = 0.008). Pre-sensitization combined with DGF did not show significant impact on allograft function, and allograft or patient survival. In conclusion, the combination of pre-sensitization and DGF showed significant synergistic interaction on the development of allograft rejection after DDKT.

Disparity in the access to kidney transplantation for sensitized patients in the state of Sao Paulo-Brazil

Highly sensitized (HS) patients accumulate on deceased donor kidney transplantation (DDKT) waitlists worldwide due to matching difficulty and inequity of allocation policies. Current situation of HS patients on KT waitlist in Brazil has not been published. All patients enrolled on the KT waitlist of the State of São Paulo from 2002 to 2017 were retrospectively assessed. Patients were divided into eight groups according to their degree of sensitization, PRA of 0%, >0-40%, >40-80%, >80-85%, >85-90%, >90-95%, >95-98% and > 98%. Cumulative incidence curves for transplantation or mortality/removal from waitlist were estimated by competing risk. Among 50,249 waitlisted candidates, 1247 prioritized, 2467 with age < 18 or > 75 years and 4152 submitted to living-donor KT were excluded from the analysis, remaining 42,383 patients. There were 29,664(70%) PRA 0%, 5611(13.2%) PRA > 0-40%, 3442(8.2%) PRA > 40-80%, 507(1.2%) PRA > 80-85%, 564(1.3%) PRA > 85-90%, 825(1.9%) PRA >90-95%, 859(2%) PRA > 95-98% and 911(2.2%) PRA > 98%. There was a progressive increase in the need of prioritization, waiting time for KT or on waitlist and time on dialysis as PRA increased (p < 0.001). Probability of DDKT clearly increased as PRA decreased so that PRA 0% candidates were much more likely to be transplanted compared to PRA > 98% patients(HR:13.02, p < 0.001). Waiting list mortality/removal was higher among PRA > 0-40%(HR1.05,p = 0.03), PRA > 90-95%(HR:1.10,p = 0.05), PRA > 95-98%(HR:1.26,p < 0.001) and PRA > 98%(HR:1.09,p = 0.05) patients compared to PRA zero candidates. HS patients in Sao Paulo-Brazil required greater prioritization due to lack of venous access, longer dialysis and waitlist times, lower probability of DDKT and higher rates of waitlist mortality/removal. We confirmed the disparity of access to KT among HS patients in Sao Paulo-Brazil, indicating the need of new strategies that optimize transplantation for this subcategory of patients.

Imlifidase Desensitization in Crossmatch-positive, Highly Sensitized Kidney Transplant Recipients: Results of an International Phase 2 Trial (Highdes)

BACKGROUND

Highly HLA sensitized patients have limited access to life-saving kidney transplantation because of a paucity of immunologically suitable donors. Imlifidase is a cysteine protease that cleaves IgG leading to a rapid decrease in antibody level and inhibition of IgG-mediated injury. This study investigates the efficacy and safety of imlifidase in converting a positive crossmatch test to negative, allowing highly sensitized patients to be transplanted with a living or deceased donor kidney.

METHODS

This open-label, single-arm, phase 2 trial conducted at 5 transplant centers, evaluated the ability of imlifidase to create a negative crossmatch test within 24 h. Secondary endpoints included postimlifidase donor-specific antibody levels compared with predose levels, renal function, and pharmacokinetic/pharmacodynamic profiles. Safety endpoints included adverse events and immunogenicity profile.

RESULTS

Of the transplanted patients, 89.5% demonstrated conversion of baseline positive crossmatch to negative within 24 h after imlifidase treatment. Donor-specific antibodies most often rebounded 3-14 d postimlifidase dose, with substantial interpatient variability. Patient survival was 100% with graft survival of 88.9% at 6 mo. With this, 38.9% had early biopsy proven antibody-mediated rejection with onset 2-19 d posttransplantation. Serum IgG levels began to normalize after ~3-7 d posttransplantation. Antidrug antibody levels were consistent with previous studies. Seven adverse events in 6 patients were classified as possibly or probably related to treatment and were mild-moderate in severity.

CONCLUSIONS

Imlifidase was well tolerated, converted positive crossmatches to negative, and enabled patients with a median calculated panel-reactive antibody of 99.83% to undergo kidney transplantation resulting in good kidney function and graft survival at 6 mo.

HLA Antibody Incompatible Renal Transplantation: Long-term Outcomes Similar to Deceased Donor Transplantation

Background.

HLA incompatible renal transplantation still remains one of best therapeutic options for a subgroup of patients who are highly sensitized and difficult to match but not much is known about its long-term graft and patient survival.

Methods.

One hundred thirty-four HLA incompatible renal transplantation patients from 2003 to 2018 with a median follow of 6.93 y were analyzed retrospectively to estimate patient and graft survivals. Outcomes were compared with groups defined by baseline crossmatch status and the type and timings of rejection episodes.

Results.

The overall patient survival was 95%, 90%, and 81%; and graft survival was 95%, 85%, and 70% at 1, 5, and 10 y, respectively. This was similar to the first-time deceased donor transplant cohort. The graft survival for pretreatment cytotoxic-dependent crossmatch (CDC) positive crossmatch group was significantly low at 83%, 64%, and 40% at 1, 5, and 10 y, respectively, compared with other groups (Bead/CDC, P = 0.007; CDC/Flow, P = 0.001; and microbead assay/flow cytometry crossmatch, P = 0.837), although those with a low CDC titer (<1 in 2) have comparable outcomes to the CDC negative group. Female patients in general fared worse in both patient and graft survival outcomes in each of the 3 groups based on pretreatment crossmatch, although this did not reach statistical significance. Antibody-mediated rejection was the most frequent type of rejection with significant decline in graft survival by 10 y when compared with no rejection (P < 0.001). Rejection that occurred or continued to occur after the first 2 wk of transplantation caused a significant reduction in graft survivals (P < 0.001), whereas good outcomes were seen in those with a single early rejection episode.

Conclusions.

One-, 5-, and 10-y HLA incompatible graft and patient survival is comparable to deceased donor transplantation and can be further improved by excluding high-CDC titer cases. Antibody-positive female patients show worse long-term survival. Resolution of early rejection is associated with good long-term graft survival.

Long-Term Follow-Up of Renal Transplant Recipients Treated With IVIG for De Novo Donor-Specific Antibodies

BACKGROUND

Renal allograft survival is negatively affected by the development of de novo posttransplant donor-specific antibodies (dnDSA). We sought to determine whether treatment with intravenous immunoglobulin (IVIG) could remove or reduce the intensity of dnDSA.

METHODS

A single-center study of 12 recipients with dnDSA and stable function who received IVIG 1 g/kg monthly for 6 months were compared with a contemporaneous cohort of 24 recipients with dnDSA who did not receive IVIG.

RESULTS

The median time to first dnDSA was 6 months (interquartile range [IQR], 1-12), and follow-up was 83 months (IQR, 58-94) posttransplant. Resolution of dnDSA occurred in 27% of IVIG vs 46% of control recipients (P = .48). Fifty-eight percent of recipients in both cohorts demonstrated a reduction in the intensity of the dominant DSA at last follow-up (P =1.0). A reduction in the number of dnDSAs occurred in 58% vs 62% of the IVIG and control cohorts, respectively (P = .81). Post-dnDSA, acute rejection occurred in 8% of the IVIG vs 42% in the control group (P = .06). Forty-two percent of IVIG-treated vs 49% of control recipients had a deterioration in function from first dnDSA until most recent follow-up (P = .81). Actuarial graft survivals were equivalent between groups.

CONCLUSIONS

IVIG treatment of dnDSA in recipients with stable graft function had no impact on DSA clearance or MFI reduction, but this outcome may also be owing to sample size. Larger studies or alternate dosing regimens may be required to determine if there is any role for the use of IVIG as a treatment for dnDSA.

Peptide Allergen Immunotherapy: A New Perspective in Olive-Pollen Allergy

Allergic diseases are highly prevalent disorders, mainly in industrialized countries where they constitute a high global health problem. Allergy is defined as an immune response “shifted toward a type 2 inflammation” induced by the interaction between the antigen (allergen) and IgE antibodies bound to mast cells and basophils that induce the release of inflammatory mediators that cause the clinical symptoms. Currently, allergen-specific immunotherapy (AIT) is the only treatment able to change the course of these diseases, modifying the type 2 inflammatory response by an allergenic tolerance, where the implication of T regulatory (Treg) cells is considered essential. The pollen of the olive tree is one of the most prevalent causes of respiratory allergic diseases in Mediterranean countries, inducing mainly nasal and conjunctival symptoms, although, in areas with a high antigenic load, olive-tree pollen may cause asthma exacerbation. Classically, olive-pollen allergy treatment has been based on specific immunotherapy using whole-olive pollen extracts. Despite extracts standardization, the effectiveness of this strategy varies widely, therefore there is a need for more effective AIT approaches. One of the most attractive is the use of synthetic peptides representing the B- or T-cell epitopes of the main allergens. This review summarizes experimental evidence of several T-cell epitopes derived from the Ole e 1 sequence to modulate the response to olive pollen in vitro, associated with several possible mechanisms that these peptides could be inducing, showing their usefulness as a safe preventive tool for these complex diseases.

Highly Sensitized Patients Are Well Served by Receiving a Compatible Organ Offer Based on Acceptable Mismatches

Highly sensitized kidney patients accrue on the transplant waiting list due to their broad immunization against non-self Human Leucocyte Antigens (HLA). Although challenging, the best option for highly sensitized patients is transplantation with a crossmatch negative donor without any additional therapeutic intervention. The Eurotransplant Acceptable Mismatch (AM) program was initiated more than 30 years ago with the intention to increase the chance for highly sensitized patients to be transplanted with such a compatible donor. The AM program allows for enhanced transplantation to this difficult to transplant patient group by allocating deceased donor kidneys on the basis of a match with the recipient’s own HLA antigens in combination with predefined acceptable antigens. Acceptable antigens are those HLA antigens towards which the patients has never formed antibodies, as determined by extensive laboratory testing. By using this extended HLA phenotype for allocation and giving priority whenever a compatible donor organ becomes available, organ offers are made for roughly 80% of patients in this program. Up till now, more than 1700 highly sensitized patients have been transplanted through the AM program. Recent studies have shown that the concept of acceptable mismatches being truly immunologically acceptable holds true for both rejection rates and long-term graft survival. Patients that were transplanted through the AM program had a similar rejection incidence and long-term graft survival rates identical to non-sensitized patients transplanted through regular allocation. However, a subset of patients included in the AM program does not receive an organ offer within a reasonable time frame. As these are often patients with a rare HLA phenotype in comparison to the Eurotransplant donor population, extension of the donor pool for these specific patients through further European collaboration would significantly increase their chances of being transplanted. For those patients that will not benefit from such strategy, desensitization is the ultimate solution.

Rapid re-transplantation safety following early kidney graft loss

INTRODUCTION

Early graft loss is a devastating kidney transplant complication associated with high mortality and an increased risk of sensitization to antigens from the failed graft. Moreover, if rapid re-transplantation were to occur, given that the human leukocyte antigen antibodies identification may not be reliable until several weeks after transplantation, the recipient's immunological status would be uncertain. Hence, there could be an increased immunological risk. To date, there is no information on whether a rapid re-transplantation after early graft loss, without a new reliable anti-HLA determination, is safe.

METHODS

We retrospectively analysed the number of rejections and the graft survival of re-transplanted patients with early graft loss (defined as graft failure before 30 days from transplant) from our centre between June 2003 and November 2019. The studied population was divided into rapid re-transplantation (performed within 30 days of early graft loss) and late re-transplantation (performed beyond those 30 days).

RESULTS

Forty-seven patients were re-transplanted after early graft loss. There were nine rapid re-transplantation cases with an 89% five-year graft survival and one antibody-mediated rejection episode. Furthermore, we identified 38 cases of late re-transplantation with a 69% five-year graft survival, 4 T cell-mediated, and 11 antibody-mediated rejections.

CONCLUSIONS

Rapid re-transplantation appears to be safe and does not entail increased rejection risk, nor does it impact long-term graft survival when compared to late re-transplantation.

A Retrospective Study on Human Leukocyte Antigen Types and Haplotypes in a South African Population

CONTEXT.—

Human leukocyte antigen (HLA) is a polymorphic protein of the immune system with a central role in organ transplantation. Organ recipients can be sensitized against HLA from previous exposure, which increases the likelihood of antidonor immune responses and subsequently organ rejection. HLA matching represents an attractive option to improve graft function, reduce sensitization of recipients in first transplantations, and improve organ allocation.

OBJECTIVE.—

To examine the feasibility of the reintroduction of HLA matching into the criteria in the Johannesburg program, we retrospectively assessed HLA types in our donor population.

DESIGN.—

HLA types of 782 deceased and related living donors from 2015 until 2019 were recorded and analyzed to identify the most common HLA types and haplotypes. A virtual crossmatch was also done to examine the anti-HLA antibodies in the recipient population compared with the common HLA types identified in this study.

RESULTS.—

Of the most common HLA types identified, at least 1 was present in 732 (93.6%) of the renal donors assessed. The virtual crossmatch confirmed that most recipients are sensitized against most donors, and this greatly impacts the number of recipients who can receive organ transplants.

CONCLUSIONS.—

This study determined the most common HLA types and haplotypes in a South African organ donor population. This information, combined with the evidence suggesting the immunogenic potential of these common types, the high number of recipients with antibodies against common HLA types, and the ethnic distribution of the donor and recipient populations, informs the recommendation that the pretransplantation workup should not reinclude HLA matching.

KDIGO Clinical Practice Guideline on the Evaluation and Management of Candidates for Kidney Transplantation

The 2020 Kidney Disease: Improving Global Outcomes (KDIGO) Clinical Practice Guideline on the Evaluation and Management of Candidates for Kidney Transplantation is intended to assist health care professionals worldwide who evaluate and manage potential candidates for deceased or living donor kidney transplantation. This guideline addresses general candidacy issues such as access to transplantation, patient demographic and health status factors, and immunological and psychosocial assessment. The roles of various risk factors and comorbid conditions governing an individual's suitability for transplantation such as adherence, tobacco use, diabetes, obesity, perioperative issues, causes of kidney failure, infections, malignancy, pulmonary disease, cardiac and peripheral arterial disease, neurologic disease, gastrointestinal and liver disease, hematologic disease, and bone and mineral disorder are also addressed. This guideline provides recommendations for evaluation of individual aspects of a candidate's profile such that each risk factor and comorbidity are considered separately. The goal is to assist the clinical team to assimilate all data relevant to an individual, consider this within their local health context, and make an overall judgment on candidacy for transplantation. The guideline development process followed the Grades of Recommendation Assessment, Development, and Evaluation (GRADE) approach. Guideline recommendations are primarily based on systematic reviews of relevant studies and our assessment of the quality of that evidence, and the strengths of recommendations are provided. Limitations of the evidence are discussed with differences from previous guidelines noted and suggestions for future research are also provided.

BAFF Inhibition Effectively Suppresses the Development of Anti-HLA.A2 Antibody in the Highly Sensitized Mouse Model

B cell activating factor (BAFF) is a cytokine that plays a role in the survival, proliferation and differentiation of B cells. We proposed to observe the effects of BAFF inhibition on the humoral immune responses of an allosensitized mouse model using HLA.A2 transgenic mice. Wild-type C57BL/6 mice were sensitized with skin allografts from C57BL/6-Tg (HLA-A2.1)1Enge/J mice and were treated with anti-BAFF monoclonal antibody (mAb) (named Sandy-2) or control IgG1 antibody. HLA.A2-specific IgG was reduced in BAFF-inhibited mice compared to the control group (Δ-13.62 vs. Δ27.07, p < 0.05). BAFF inhibition also resulted in increased pre-pro and immature B cell proportions and decreased mature B cells in the bone marrow (p < 0.05 vs. control). In the spleen, an increase in transitional B cells was observed with a significant decrease in marginal and follicular B cells (p < 0.05 vs. control). There was no significant difference in the proportions of long-lived plasma and memory B cells. Microarray analysis showed that 19 gene probes were significantly up- (>2-fold, p < 0.05) or down-regulated (≤2-fold, p < 0.05) in the BAFF-inhibited group. BAFF inhibition successfully reduced alloimmune responses through the reduction in alloantibody production and suppression of B cell differentiation and maturation. Our data suggest that BAFF suppression may serve as a useful target in desensitization therapy.

A Europe wide acceptable mismatch program will enable transplantation of long waiting highly sensitised patients with a compatible donor

Immunisation against Human Leucocyte Antigens (HLA) can be caused by pregnancy, blood transfusion, or organ transplants. The HLA antibody status of a given patient significantly influences their access and waiting time to transplant. For some highly sensitised patients (HSP) there is hardly any suitable donor available in the deceased donor pool of their allocation organisation and therefore they wait a very long time before being offered a kidney for transplant. Especially patients with rare HLA phenotypes in relation to the actual donor pool are waiting extremely long. As HLA phenotypes are different in the various European populations, we hypothesized that extension of the donor pool outside the respective allocation system will increase the chance of receiving a compatible transplant for this subgroup of highly sensitised patients. One of the objectives of the EUROSTAM project, (a Europe-wide Strategy to enhance Transplantation of highly sensitised patients on the basis of Acceptable HLA Mismatches) was to develop a tool to compare the chance of transplanting HSP in different European populations with donor organs from within and outside their own donor pool. Information on the HLA type and ABO blood group of the actual donor population, as well as the acceptable mismatches of long waiting HSP were obtained from the EUROSTAM partner organizations i.e. Eurotransplant (ET), UK National Health Service Blood and Transplant (NHSBT), Barcelona, Prague and Athens. Results from simulations using the newly developed tool shows that 195 (27%) of the 724 long waiting highly sensitised patients registered at each partner organisation have increased chances of transplant in a different European donor pool. This makes a strong case for sharing kidneys between European countries for selected difficult to transplant patients.

Double-Filtration Plasmapheresis Plus Low-Dose Anti-thymocyte Globulin and Tacrolimus in Asian Living-Donor Kidney Transplantation With Donor-Specific Anti-HLA Antibody

BACKGROUND

Pretransplant desensitization protocols, including plasmapheresis, intravenous immunoglobulin, induction antibody therapy, and intensive maintenance immunosuppression, are generally employed in kidney transplant recipients who have positive status for donor-specific anti-HLA antibody (DSA). To avoid serious infectious complications, the authors designed a novel low-dose protocol in Thai patients undergoing DSA+ living-related kidney transplantation (LRKT).

METHODS

A retrospective cohort study of the patients who underwent DSA+ LRKT was conducted. The novel protocol consisted of 3 to 5 sessions of pretransplant double-filtration plasmapheresis (DFPP) with or without low-dose intravenous immunoglobulin together with low-dose anti-thymocyte globulin (ATG) induction (1-1.5 mg/kg/d for 3-4 days) and low-dose tacrolimus (Tac) (trough level 5-10 ng/mL), mycophenolate, and prednisolone.

RESULTS

The study included 17 patients. The lymphocyte crossmatch via complement-dependent cytotoxicity was negative in 12 patients and positive for B cell immunoglobulin M in 5 patients. The novel desensitization protocol resulted in a decrease of at least 50% of DSA mean fluorescence intensity from baseline (from 4320 ± 549 before DFPP to 1601 ± 350 before transplantation, P < .005) and successful kidney transplantation with good allograft function in all cases. Early DSA rebound was observed in 3 patients after transplantation, and kidney biopsy revealed subclinical antibody-mediated rejection in 1 patient and diffuse C4d staining without cell infiltration in 2 patients. There were good long-term outcomes in patient and graft survival (100% and 94.1%, respectively). Only 1 allograft loss occurred because of nonadherence. The majority of patients have stable allograft function with serum creatinine less than 1.5 mg/dL. However, infections, including CMV and other organisms, were commonly observed.

CONCLUSIONS

Desensitization protocol with DFPP, low-dose ATG, and Tac provides excellent outcomes in living donor kidney transplantation in highly sensitized Asian populations.

Preoperative carfilzomib and lulizumab based desensitization prolongs graft survival in a sensitized non-human primate model

Sensitized patients are difficult to transplant due to pre-formed anti-donor immunity. We have previously reported successful desensitization using carfilzomib and belatacept in a non-human primate (NHP) model. Here we evaluated selective blockade of the co-stimulatory signal (CD28-B7) with Lulizumab, which preserves the co-inhibitory signal (CTLA4-B7). Five maximally MHC-mismatched pairs of NHPs were sensitized to each other with two sequential skin transplants. Individuals from each pair were randomized to either desensitization with once-weekly Carfilzomib (27mg/m² IV) and Lulizumab (12.5mg/kg SC) over four weeks, or no desensitization (Control). NHPs then underwent life-sustaining kidney transplantation from their previous skin donor. Rhesus-specific anti-thymocyte globulin was used as induction therapy and immunosuppression maintained with tacrolimus, mycophenolate, and methylprednisolone. Desensitized subjects demonstrated a significant reduction in donor-specific antibody, follicular helper T cells (CD4⁺PD-1⁺ICOS⁺), and proliferating B cells (CD20⁺Ki67⁺) in the lymph nodes. Interestingly, regulatory T cell (CD4⁺CD25⁺CD127^lo) frequency was maintained after desensitization in addition to increased frequency of naïve CD4 T cells (CCR7⁺CD45RA⁺) and naïve B cells (IgD⁺CD27^-CD20⁺) in circulation. This was associated with significant prolongation in graft survival (MST = 5.8 ± 4.0 vs. 64.8 ± 36.3; p<0.05) and lower antibody-mediated rejection scores compared to control animals. However, all desensitized animals eventually developed AMR and graft failure. Desensitization with CFZ and Lulizumab improves allograft survival in allosensitized NHPs, by transient control of the germinal center and shifting of the immune system to a more naive phenotype. This regimen may translate into clinical practice to improve outcomes of highly sensitized transplant patients.

Epstein-Barr virus-associated smooth muscle tumor in a kidney transplant recipient: A case-report and review of the literature

INTRODUCTION

Epstein-Barr virus (EBV) is a herpesvirus linked to pre-malignant lymphoproliferative diseases and up to nine distinct human tumors. The most frequent EBV-associated malignancies are lymphomas and nasopharyngeal carcinoma. By promoting smooth muscle proliferation, EBV can induce EBV-associated smooth muscle tumors (SMT) which remain a very rare oncological entity. This study reports one case report of SMT and aims to offer the largest review of literature on post-transplantation-SMT (PT-SMT) in kidney transplant recipients, with a focus on therapeutic management and evolution of graft function.

METHODS

Case reports and case series of PT-SMT in kidney transplant recipients were collected from 1996 to 2019.

RESULTS

A total of 59 PT-SMT were evaluated. The median time at diagnosis was 74.6 months after kidney transplantation. The most frequent localizations were liver and lung. EBV seroconversion was notified in all six patients with previously negative status. Preferred therapeutic option was surgery (65.9%), associated with a reduction in immunosuppression (77.2%), which includes switch to mTOR inhibitors (29.5%), and discontinuation of MMF (32%). In our review, 13% of patients experienced rejection, 8.7% lost their graft and went back on hemodialysis; 8.8% of patients died of PT-SMT.

CONCLUSION

PT-SMT is a rare but serious condition in kidney transplant recipients. EBV seroconversion following transplantation appears as a risk factor in developing PT-SMT in solid-organ recipients. In the absence of guidelines, therapeutic management for PT-SMT is challenging and exposes the patient to high risk of graft loss.

Paired kidney exchange transplantation - pushing the boundaries

The scarcity of living organ donors makes it imperative to develop newer innovations to optimize and maximize the utilization of the available pool. ABO and HLA sensitization are important immunological barriers in renal transplant and can potentially lead to rejection of almost one-third of the willing living donors. Paired kidney exchange (PKE) is a rapidly growing method used to overcome these barriers and has grown in popularity over the last three decades since its introduction in 1986. Evolution of the matching strategies and use of complex algorithms has led to increase in the number of possible matches thereby benefiting multiple recipients. The use of altruistic donors and compatible pairs has also helped in increasing the possible exchanges. This review provides an in-depth analysis of the evolution, the present global scenario, and the future of PKE. It also discusses the recent trends of advanced donation, trans-organ paired exchange and global kidney exchange and the associated ethical concerns.

Perioperative blood usage and therapeutic plasma exchange in kidney transplantation during a 16-year period in South Korea

BACKGROUND

The frequency of kidney transplantation (KT) is increasing. Blood transfusion plays an important role in the success of KT. Therapeutic plasma exchange (TPE) is also used for desensitisation in ABO-incompatible KT and treatment of antibody-mediated rejection.

MATERIALS AND METHODS

We analysed red blood cell (RBC), platelet, and fresh frozen plasma (FFP) usage and the number of TPE procedures performed during the hospitalisation of KT patients from 2002 to 2017 using the Korean National Health Insurance Service-National Health Information Database.

RESULTS

A total of 18,331 KT patients were included in this study. The number of transfused RBCs continued to increase from 4,806 units in 2002-2005 to 12,390 units in 2014-2017. However, the average number of RBCs transfused per patient decreased from 2.17 to 1.79 units. Estimated platelet usage increased from 4,259 units in 2002-2005 to 11,519 units in 2014-2017, and the proportion of filtered platelets increased from 72.6% to 83.4% during the same period. There was a huge increase in the total number of FFP units used, from 2,255 units in 2002-2005 to 51,531 units in 2014-2017. The number of TPE procedures performed also increased from 296 to 6,479 during the same period. Patients with acute rejection accounted for 8.8% of all KT patients, and more RBC and FFP were used for these patients and a greater number of TPE procedures were performed compared to those who did not experience rejection.

DISCUSSION

Blood usage and TPE have increased steadily with the increasing numbers of KTs. Therefore, continuous efforts are needed to ensure appropriate perioperative blood preparation and usage for KT patients.

Low-dose alemtuzumab induction in a tailored immunosuppression protocol for sensitized kidney transplant recipients

Background

Induction therapy is crucial in kidney transplantation and constitutes an important cornerstone for long-term allograft survival. Alemtuzumab is a depleting CD52-specific antibody with T- and B-cell activity, leading to prolonged lymphocyte depletion for up to 12 months, with profound immunosuppression and an associated risk of serious infections. Current concepts aim to optimize dosing strategies to reduce side effects. Here we present data from an ongoing centre protocol consisting of low-dose alemtuzumab induction and tailored immunosuppression in sensitized patients undergoing kidney transplantation.

Methods

10-year results of the protocol were analysed. Low-dose alemtuzumab induction consisted of a single dose of 20 mg intraoperatively, followed by tacrolimus and corticosteroids for initial immunosuppression, with mycophenolate mofetil suspended until a total lymphocyte count (TLC) >5% or 200/μl was reached.

Results

Between 01/2007 and 04/2017, 46 patients were treated in accordance with the protocol in 48 kidney transplantations. Median PRA_max was 43 [22-76; IQR] %; all patients had negative CDC-crossmatch prior to transplantation. Low-dose alemtuzumab was well tolerated. Median time to TLC recovery was 77 [62-127; IQR] d. Within a median follow-up of 3.3 [1.5-5.6; IQR] years, 12 (25%) patients developed BPAR, 10 of which were antibody-mediated (3 acute, 7 chronic ABMR). Death-censored 5-year allograft survival was 79.2%, with an excellent allograft function at the end of follow-up. There was no increased rate of infections, in particular viral infections.

Conclusions

Our protocol, comprising low-dose alemtuzumab induction, initial suspension of mycophenolate mofetil and triple maintenance immunosuppression, provides excellent patient and allograft outcome in sensitized renal allograft recipients.

Evaluation and Treatment of Acute Rejection in Kidney Allografts

Advances in immunosuppressive therapy have drastically improved acute rejection rates in kidney transplant recipients over the past five decades. Nevertheless, it should remain high on any differential diagnosis of unexplained graft dysfunction because of the potential negative effect on graft longevity. Understanding the pre- and post-transplant risk factors for acute rejection can help estimate the probability of immunologic graft damage, and accurate identification of the type and severity of acute rejection will guide appropriate treatment. Tissue biopsy remains the gold standard for evaluating immunologic graft damage, and the histologic definition of acute rejection has evolved in recent years. Intravenous steroids and T cell depletion remain the standard therapy for T cell-mediated rejection and are effective in reversing most cases. Plasma exchange and intravenous Ig, with or without rituximab, are most commonly used for the treatment of antibody-mediated rejection and several newer agents have recently been investigated for severe cases. This review aims to provide the general nephrologist caring for transplant recipients with an approach to immunologic risk assessment and a summary of recent advances in the diagnosis and treatment of acute graft rejection.