Probability of deceased donor kidney transplantation based on % PRA

Impact of sensitization and ABO blood types on the opportunity of deceased-donor kidney transplantation with prolonged waiting time

The waiting time to deceased-donor kidney transplantation (DDKT) is long in Asian countries. We investigated the impact of sensitization and ABO blood type (ABO) on DDKT opportunity using two Korean cohorts: a hospital cohort from two centers and a national database. The impact of panel reactive antibody (PRA) based on the maximal PRA% and ABO on DDKT accessibility was analyzed using a competing risks regression model. In the hospital cohort (n = 4722), 88.2%, 8.7%, and 3.1% of patients belonged to < 80%, 80-99%, and ≥ 99% PRA groups, respectively, and 61.1%, 11.6%, and 27.3% belonged to A or B, AB, and O blood types, respectively. When PRA and ABO were combined, PRA < 80%/A or B and 80 ≤ PRA < 99%/AB had fewer DDKT opportunities (median, 12 years; subdistribution hazard ratio [sHR], 0.71) compared with PRA < 80%/AB (median, 11 years). Also, PRA < 80%/O, 80 ≤ PRA < 99%/A or B, and PRA ≥ 99%/AB had a much lower DDKT opportunity (median, 13 years; sHR, 0.49). Furthermore, 80 ≤ PRA < 99%/O and PRA ≥ 99%/non-AB had the lowest DDKT opportunity (sHR, 0.28). We found similar results in the national cohort (n = 18,974). In conclusion, an integrated priority system for PRA and ABO is needed to reduce the inequity in DDKT opportunities, particularly in areas with prolonged waiting times.

Impact of Calcineurin Inhibitor-Based Immunosuppression Maintenance During the Dialysis Period After Kidney Transplant Failure on the Next Kidney Graft Outcome: A Retrospective Multicenter Study With Propensity Score Analysis

The impact of immunosuppressive therapy (IS) strategies after kidney transplant failure (KTF) on potential future new grafts is poorly established. We assessed the potential benefit of calcineurin inhibitor (CNI)-based IS maintenance throughout the dialysis period on the outcome of the second kidney transplant (KT). We identified 407 patients who underwent a second KT between January 2008 and December 2018 at four French KT centers. Inverse probability of treatment weighting was used to control for potential confounding. We included 205 patients with similar baseline characteristics at KTF: a total of 53 received at least CNIs on the retransplant day (G-CNI), and 152 did not receive any IS (G-STOP). On the retransplant date, G-STOP patients experienced a longer pretransplant dialysis time, were more often hyperimmunized, and underwent more expanded-criteria donor KTs than G-CNI patients. During the second KT follow-up period, rejection episodes were similar in both groups. The 10-year survival rates without death and dialysis were 98.7% and 59.5% in G-CNI and G-STOP patients, respectively. In the multivariable analysis, CNI-based IS maintenance was associated with better survival (hazard ratio: 0.08; 95% confidence interval: 0.01-0.58, p = 0.01). CNI-based IS maintenance throughout the dialysis period after KTF may improve retransplantation outcomes.

Continuation of immunosuppression vs. immunosuppression weaning in potential repeat kidney transplant candidates: a care management perspective

Management of immunosuppression in patients with a failing or failed kidney transplant requires a complete assessment of their clinical condition. One of the major considerations in determining immunosuppression is whether or not such an individual is considered a candidate for re-transplantation. Withdrawal of immunosuppression in a re-transplant candidate can result in allosensitization and markedly reduce the chances of a repeat transplant. In this review, we summarize the effects of immunosuppression reduction on HLA sensitization, discuss the impacts of allosensitization in these patients, and explore reduction protocols and future directions. Risks of chronic immunosuppression, medical management of the failing allograft, and the effect of nephrectomy are covered elsewhere in this issue.

Belatacept-Based Maintenance Immunosuppression Controls the Post-Transplant Humoral Immune Response in Highly Sensitized Nonhuman Primates

Preexisting donor-specific antibodies (DSA) to MHC antigens increase the risk of antibody-mediated rejection (AMR) in sensitized transplant recipients and reduces graft survival. Pretransplant desensitization with costimulation blockade and proteasome inhibition has facilitated transplantation in our preclinical nonhuman primate (NHP) model. However, long-term graft survival is limited by rebound of DSA after transplantation. In this study, we performed kidney transplants between highly sensitized, maximally MHC-mismatched NHPs (n=14). At kidney transplantation, primates received T cell depletion with rhesus-specific anti-thymocyte globulin (rhATG; n=10) or monoclonal anti-CD4 and anti-CD8 antibodies (n=4). Maintenance immunosuppression consisted of belatacept and tacrolimus (n=5) or belatacept and rapamycin (n=9) with steroids. Rebound of DSA post-kidney transplantation was significantly reduced compared with maintenance immunosuppression with tacrolimus, mycophenolate, and steroids. Protocol lymph node biopsy specimens showed a decrease in germinal center activity, with low frequencies of T follicular helper cells and class-switched B cells after kidney transplantation. Combined belatacept and rapamycin was superior in controlling viral reactivation, enabling weaning of ganciclovir prophylaxis. Tacrolimus was associated with increased morbidity that included cytomegalovirus and parvovirus viremia and post-transplant lymphoproliferative disorder. All primates in the tacrolimus/belatacept group failed discontinuation of antiviral therapy. Overall, belatacept-based immunosuppression increased AMR-free graft survival by controlling post-transplant humoral responses in highly sensitized NHP recipients and should be further investigated in a human clinical trial.

Presence of Panel-reactive Antibodies after Penetrating Keratoplasty

PURPOSE

To evaluate the relationship between penetrating keratoplasty (PK) and postoperative PRA level and number of unacceptable antigens.

METHODS

A cross-sectionalstudy was performed on patients with history of PK. Patients with prior solid organ transplantation, pregnancy, or blood transfusion were excluded. These findings were combined with a retrospective review. Patients were grouped by single or multiple PKs. The primary outcome was postoperative PRA level.

RESULTS

Incidence of postoperative PRA elevation and mean peak PRA was higher in the multiple PK group (p = .08 and p = .010, respectively). Mean number of unacceptable antigens was elevated in the multiple PK group (p = .024). There was a moderately positive correlation between number of PK grafts and PRA level (r = 0.629, p = .0002).

CONCLUSIONS

PRA level may be influenced by PKs, with higher PRA associated with increased prior PKs. Further studies are necessary to determine the potential prognostic value.Abbreviations: PK: penetrating keratoplasty; PRA: panel reactive antibodies; OSST: ocular surface stem cell transplantation; LSCD: limbal stem cell deficiency.

Impact of the Type of Dialysis on Time to Transplantation: Is It Just a Matter of Immunity?

Background: Renal transplantation represents the therapeutic gold standard in patients with end stage renal disease (ESRD). Still the role of pre-transplant dialysis in affecting time to transplantation has yet to be determined. We wanted to verify whether the type of renal replacement therapy (hemodialysis vs. peritoneal dialysis) affects time to transplantation and to identify clinical features related to the longer time to transplantation. Methods: We performed a retrospective single-center observational study on patients who had received a transplant in the Bologna Transplant Unit from 1991 to 2019, described through the analysis of digital transplant list documents for sex, age, body mass index (BMI), blood group, comorbidities, underlying disease, serology, type of dialysis, time to transplantation, Panel Reactive Antibodies (PRA) max, number of preformed anti Human Leukocyte Antigens (HLA) antibodies. A p-value < 0.05 was considered statistically significant. Results: In the 1619 patients analyzed, we observed a significant difference in time to transplant, PRA max and Preformed Antibodies Number between patients who received Hemodialysis (HD) and Peritoneal dialysis (PD). Then we performed a multiple regression analysis with all the considered factors in order to identify features that support these differences. The clinical variables that independently and directly correlate with longer time to transplantation are PRA max (p < 0.0001), Antibodies number (p < 0.0001) and HD (p < 0.0001); though AB blood group (p < 0.0001), age (p < 0.003) and PD (p < 0.0001) inversely correlate with time to transplantation. Conclusions: In our work, PD population received renal transplants in a shorter period of time compared to HD and turned out to be less immunized. Considering immunization, the type of dialysis impacts both on PRA max and on anti HLA antibodies.

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.

KDIGO Clinical Practice Guideline on the evaluation and management of candidates for kidney transplantation. Transplantation. 2020;104:S11-S103. [PMID: 32301874 DOI: 10.1097/tp.0000000000003136]

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.

Use of Panel-Reactive Antibody Testing in the Planning and Management of Ocular Surface Stem Cell Transplantation

PURPOSE

Panel-reactive antibody (PRA) testing has been widely adopted in solid organ transplantation for risk assessment in potential allograft recipients but has not been studied in the context of ophthalmic transplantation. The purpose of this study is to evaluate outcomes in patients undergoing ocular surface stem cell transplantation (OSST) for limbal stem cell deficiency (LSCD) relative to preoperative PRA level.

METHODS

This is retrospective chart review of all eyes with documented PRA level that underwent OSST for LSCD between May 2000 and March 2019 at a single institution. Eyes with stable ocular surface but <1 year of follow-up and eyes without updated PRA before repeat OSST were excluded. Eyes were grouped by PRA <80% and ≥80%. The primary outcome was ocular surface failure, whereas the secondary outcome was clinical allograft rejection.

RESULTS

Sixty-nine surgeries met inclusion criteria, consisting of 54 living-related conjunctival limbal allografts, 5 keratolimbal allografts, and 10 combined living-related conjunctival limbal allografts/keratolimbal allografts (Cincinnati procedure). The most common etiologies for LSCD were aniridia (33%), chemical/thermal injury (28%), and contact lens associated (14%). Surface failure occurred in 5 of 12 eyes (58%) with PRA ≥80% versus 12 of 57 eyes (21%) with PRA <80% (P = 0.01). The relative risk for surface failure with PRA ≥80% was 2.8 [confidence interval (CI), 1.38-5.55]. There was no significant difference in acute rejection (P = 1).

CONCLUSIONS

Pretransplant PRA level is an important prognostic factor for ocular surface stability in eyes undergoing OSST for LSCD, with implications for donor selection, perioperative management, and systemic immunosuppression.

How do highly sensitized patients get kidney transplants in the United States? Trends over the last decade

Prioritization of highly sensitized (HS) candidates under the kidney allocation system (KAS) and growth of large, multicenter kidney-paired donation (KPD) clearinghouses have broadened the transplant modalities available to HS candidates. To quantify temporal trends in utilization of these modalities, we used SRTR data from 2009 to 2017 to study 39 907 adult HS (cPRA ≥ 80%) waitlisted candidates and 19 003 recipients. We used competing risks regression to quantify temporal trends in likelihood of DDKT, KPD, and non-KPD LDKT for HS candidates (Era 1: January 1, 2009-December 31, 2011; Era 2: January 1, 2012-December 3, 2014; Era 3: December 4, 2014-December 31, 2017). Although the likelihood of DDKT and KPD increased over time for all HS candidates (adjusted subhazard ratio [aSHR] Era 3 vs 1 for DDKT: 1.74 1.851.97 , P < .001 and for KPD: 1.70 2.202.84 , P < .001), the likelihood of non-KPD LDKT decreased (aSHR: 0.69 0.820.97 , P = .02). However, these changes affected HS recipients differently based on cPRA. Among recipients, more cPRA 98%-99.9% and 99.9%+ recipients underwent DDKT (96.2% in Era 3% vs 59.1% in Era 1 for cPRA 99.9%+), whereas fewer underwent non-KPD LDKT (1.9% vs 30.9%) or KPD (2.0% vs 10.0%). Although KAS increased DDKT likelihood for the most HS candidates, it also decreased the use of non-KPD LDKT to transplant cPRA 98%+ candidates.

Immunosuppression with Calcineurin Inhibitor after Renal Transplant Failure Inhibits Allosensitization

Immunosuppression withdrawal after graft failure seems to favor sensitization. A high percentage of calculated panel-reactive antibody (cPRA) and the development of de novo donor specific antibodies (dnDSA) indicate human leukocyte antigen (HLA) sensitization and may hinder the option of retransplantation. There are no established protocols on the immunosuppressive treatment that should be maintained after transplant failure. A retrospective analysis including 77 patients who lost their first renal graft between 1 January 2006–31 December 2015 was performed. Two sera were selected per patient, one immediately prior to graft loss and another one after graft failure. cPRA was calculated by Single Antigen in all patients. It was possible to analyze the development of dnDSA in 73 patients. By multivariate logistic regression analysis, the absence of calcineurin inhibitor (CNI) at 6 months after graft failure was related to cPRA > 75% (OR 4.8, CI 95% 1.5–15.0, p = 0.006). The absence of calcineurin inhibitor (CNI) at 6 months after graft loss was significantly associated with dnDSA development (OR 23.2, CI 95% 5.3–100.6, p < 0.001). Our results suggest that the absence of CNI at the sixth month after graft loss is a risk factor for sensitization. Therefore, maintenance of an immunosuppressive regimen based on CNI after transplant failure should be considered when a new transplant is planned, since it seems to prevent HLA allosensitization.

Annual Analysis (2018) of the Kidney Transplant Waiting List of a Social Security Hospital in Veracruz, Mexico

BACKGROUND

In Mexico during 2018, 15,072 patients were waiting for a deceased donor kidney transplant, and 969 deceased donor kidney transplants were performed. There is no annual data report of the waiting list activity in Mexico. Herein, we analyzed our kidney transplant waiting list activity in 2018.

METHODS

We performed a waiting list analysis in our unit during 2018. Patient and status characteristics (active, deceased, inactive, or transplant) were registered. Differences between status were determined. A P < .05 was considered statistically significant.

RESULTS

In total, 467 patients were waiting, and 74 patients were included on the list (57.7% male, mean age 38.5 ± 11.3 years and mean BMI 24.9 ± 4.7 kg/m²); 92.8% were state residents. The most common end-stage renal disease diagnosis was unknown (40.9%). In total, 94.9% were on dialysis (mean time 5.1 ± 3.14 years), and for 90.9%, this was the first transplant. PRA class I and class II were 19.9% ± 30.6% and 12.9% ± 27.1%, respectively. Mean EPTS was 19.8% ± 9.4%. Mean waiting time was 2.88 ± 2.3 years. In total, 21 deceased donor patients (3.9%) were transplanted; 57 (10.5%) patients had an inactive status, and 3 (0.6%) received a living donor kidney transplant with a proven mortality of 1.8% (n = 10). Patients who underwent deceased donor transplant were younger and had more time on dialysis, lower PRA class I, and more time on the waiting list (P < .05 by analysis of variance).

CONCLUSION

There are more patients included on the list than patients off the list. There are significant differences between patients who received a transplant and inactive and active patients that needs to be shortened.

A prospective, iterative, adaptive trial of carfilzomib-based desensitization

Proteasome inhibitor-based strategies hold promise in transplant but have yielded varying results. Carfilzomib, a second-generation proteasome inhibitor, may possess advantages over bortezomib, the first-generation proteasome inhibitors. The purpose of this study was to evaluate the safety, toxicity, and preliminary efficacy of carfilzomib in highly HLA-sensitized kidney transplant candidates. Renal transplant candidates received escalating doses of carfilzomib followed by plasmapheresis (group A) or an identical regimen with additional plasmapheresis once weekly before carfilzomib dosing. Thirteen participants received carfilzomib, which was well tolerated with most adverse events classified as low grade. The safety profile was similar to bortezomib desensitization; however, neurotoxicity was not observed with carfilzomib. Toxicity resulted in permanent dose reduction in 1 participant but caused no withdrawals or deaths. HLA antibodies were substantially reduced with carfilzomib alone, and median maximal immunodominant antibody reduction was 72.8% (69.8% for group A, P = .031, 80.1% for group B, P = .938). After depletion, rebound occurred rapidly and antibody levels returned to baseline between days 81 and 141. Bone marrow studies revealed that approximately 69.2% of plasma cells were depleted after carfilzomib monotherapy. Carfilzomib monotherapy-based desensitization provides an acceptable safety and toxicity profile while leading to significant bone marrow plasma cell depletion and anti-HLA antibody reduction.

Characterization of the C1q-Binding Ability and the IgG1-4 Subclass Profile of Preformed Anti-HLA Antibodies by Solid-Phase Assays

Humoral alloimmunity, particularly that triggered by preformed antibodies against human leukocyte antigens (HLA), is associated with an increased prevalence of rejection and reduced transplant survival. The high sensitivity of solid phase assays, based on microbeads coated with single antigens (SAB), consolidated them as the gold-standard method to characterize anti-HLA antibodies, ensuring a successful allograft allocation. Mean fluorescence intensity (MFI) provided by SAB is regularly used to stratify the immunological risk, assuming it as a reliable estimation of the antibody-level, but it is often limited by artifacts. Beyond MFI, other properties, such as the complement-binding ability or the IgG1-4 subclass profile have been examined to more accurately define the clinical relevance of antibodies and clarify their functional properties. However, there are still unresolved issues. Neat serum-samples from 20 highly-sensitized patients were analyzed by SAB-panIgG, SAB-IgG1-4 subclass and SAB-C1q assays. All 1:16 diluted serum-samples were additionally analyzed by SAB-panIgG and SAB-IgG1-4 subclass assays. A total of 1,285 anti-HLA antibodies were identified as positive, 473 (36.8%) of which were C1q-binding. As expected, serum-dilution enhanced the correlation between the C1q-binding ability and the antibody-strength, measured as the MFI (r_neat = 0.248 vs. r_diluted = 0.817). SAB-subclass assay revealed at least one IgG1-4 subclass in 1,012 (78.8%) positive antibody-specificities. Among them, strong complement-binding subclasses, mainly IgG1, were particularly frequent (98.9%) and no differences were found between C1q- and non-C1q-binding antibodies regarding their presence (99.4 vs. 98.5%; p = 0.193). In contrast, weak or non-C1q-binding subclasses (IgG2/IgG4) were more commonly detected in C1q-binding antibodies (78.9 vs. 38.6%; p < 0.001). Interestingly, a strong association was found between the C1q-binding ability and the IgG1 strength (r_IgG1dil = 0.796). Though lower, the correlation between the IgG2 strength and the C1q-binding ability was also strong (r_IgG2dil = 0.758), being both subclasses closely related (r_IgG1−IgG2 = 0.817). We did not find any correlation with the C1q-binding ability considering the remaining subclasses. In conclusion, we demonstrate that a particular profile of IgG subclasses (IgG1/IgG3) itself does not determine at all the ability to bind complement of anti-HLA antibodies assessed by SAB-C1q assay. It is the IgG subclass strength, mainly of IgG1, which usually appears in combination with IgG2, that best correlates with it.

Effect of Calculated Panel Reactive Antibody Value on Waitlist Outcomes for Lung Transplant Candidates

Background

We conducted a retrospective cohort study using United Network of Organ Sharing (UNOS) data to determine the effect of the calculated panel reactive antibody (cPRA) value on waitlist outcomes for lung transplant candidates.

Material/Methods

We divided lung transplant candidates into groups based on their cPRA value at the time of waitlist activation (0–25%, 25.1–50%, 50.1–75%, and 75.1–100%) and compared each group’s waitlist outcomes to the lowest quartile (“minimally sensitized”) group. The primary outcome was lung transplantation and the secondary outcome was waitlist mortality (a composite of death on the waitlist/delisting for clinical deterioration).

Results

Compared to the minimally sensitized group, candidates with a cPRA value of 25.1–50% did not have a significantly different likelihood of undergoing lung transplant or waitlist mortality, candidates with a cPRA value of 50.1–75% were 25% less likely to undergo lung transplant and 44% more likely to die on the waitlist, and candidates with a cPRA value of 75.1–100% were 52% less likely to undergo lung transplant and 92% more likely to die on the waitlist.

Conclusions

CPRA values of greater than 50% are associated with significantly lower rates of transplantation and higher waitlist mortality.

Kidney transplant outcomes associated with the use of increased risk donors in children

Increased risk donors (IRDs) may inadvertently transmit blood-borne viruses to organ recipients through transplant. Rates of IRD kidney transplants in children and the associated outcomes are unknown. We used the Scientific Registry of Transplant Recipients to identify pediatric deceased donor kidney transplants that were performed in the United States between January 1, 2005 and December 31, 2015. We used the Cox regression analysis to compare patient and graft survival between IRD and non-IRD recipients, and a sequential Cox approach to evaluate survival benefit after IRD transplants compared with remaining on the waitlist and never accepting an IRD kidney. We studied 328 recipients with and 4850 without IRD transplants. The annual IRD transplant rates ranged from 3.4% to 13.2%. IRDs were more likely to be male (P = .04), black (P < .001), and die from head trauma (P = .006). IRD recipients had higher mean cPRA (0.085 vs 0.065, P = .02). After multivariate adjustment, patient survival after IRD transplants was significantly higher compared with remaining on the waitlist (adjusted hazard ratio [aHR]: 0.48, 95% CI: 0.26-0.88, P = .018); however, patient (aHR: 0.93, 95% CI: 0.54-1.59, P = .79) and graft survival (aHR: 0.89, 95% CI: 0.70-1.13, P = .32) were similar between IRD and non-IRD recipients. We recommend that IRDs be considered for transplant in children.

Allosensitization after transplant failure: the role of graft nephrectomy and immunosuppression - a retrospective study

There are conflicting data about the role of transplant nephrectomy and immunosuppression withdrawal on the development of allosensitization and the impact on re-transplantation. We divided 109 first graft recipients into two groups according to whether they underwent nephrectomy (NX+, n = 61) or their graft was left in situ (NX-, n = 48). Sera were assessed for HLA-A/B/Cw/DR/DQ antibodies at the time of NX/transplant failure and after 3, 6, 12, 24 months. The NX+ group showed a higher rate of donor specific antibody (DSA) and non-DSA human leukocyte antigen (HLA) antibody production at all the time points. Multivariable analysis showed that nephrectomy was a strong, independent risk factor for the development of DSAs after 12 and 24 months (P = 0.005 and 0.008). In the NX- group, low tacrolimus levels correlated with DSA formation (AUC 0.817, P = 0.002; best cut-off level 2.9 ng/ml). Analysis with a standardized pool of UK donors showed a more difficult grade of HLA matchability following nephrectomy compared with the NX- group. Nephrectomy is followed by the long-term production of DSA and non-DSA HLA antibodies and negatively impacts on the chances of finding a HLA-compatible kidney. Tacrolimus levels ≥3 ng/ml are protective against the development of allosensitization and could facilitate re-transplantation in the NX- group.

The national landscape of deceased donor kidney transplantation for the highly sensitized: Transplant rates, waitlist mortality, and posttransplant survival under KAS

Deceased donor kidney transplantation (DDKT) rates for highly sensitized (HS) candidates increased early after implementation of the Kidney Allocation System (KAS) in 2014. However, this may represent a bolus effect, and a granular investigation of the current state of DDKT for HS candidates remains lacking. We studied 270 722 DDKT candidates from the SRTR from 12/4/2011 to 12/3/2014 ("pre-KAS") and 12/4/2014 to 12/3/2017 ("post-KAS"), analyzing DDKT rates for HS candidates using adjusted negative binomial regression. Post-KAS, candidates with the highest levels of sensitization had an increased DDKT rate compared with pre-KAS (cPRA 98% adjusted incidence rate ratio [aIRR]:1.27 1.772.46 P = .001, cPRA 99% aIRR:3.18 4.365.98 P < .001, cPRA 99.5-99.9% aIRR:16.91 24.2934.89 P < .001, and cPRA 99.9%+ aIRR:8.79 11.5815.26 P < .001). To determine whether these changes produced more equitable access to DDKT, we compared DDKT rates of HS to non-HS candidates (cPRA 0-79%). Post-KAS, cPRA, 98% candidates had an equivalent DDKT rate (aIRR:0.65 0.941.36 , P = .8) to non-HS candidates, whereas 99% candidates had a higher DDKT rate (aIRR:1.19 1.682.38 , P = .02). Although cPRA 99.5-99.9% candidates had an increased DDKT rate (aIRR:2.46 3.504.98 , P < .001) compared to non-HS candidates, cPRA 99.9%+ candidates had a significantly lower DDKT rate (aIRR:0.29 0.400.56 , P < .001). KAS has improved access to DDKT for HS candidates, although substantial imbalance exists between cPRA 99.5-99.9% and 99.9%+ candidates.

Detecting donor-specific antibodies: the importance of sorting the wheat from the chaff

Human leukocyte antigen (HLA) compatibility is very important for successful transplantation of solid organs. In this paper, we focused on the humoral arm of immunity in the clinical setting of organ transplantation: how HLA antibodies develop, how they can be detected, and what they can do to injure organ transplants. Specifically, we explore the technical perspectives of detecting donor-specific antibodies (DSA) in HLA laboratories, and use real-life clinical cases to explain the principles. Currently there are many tools in our HLA antibody detection toolbox: conventional cytotoxicity cross match, flow cross match, and solid phase assays using beads conjugated with single or multiple HLA antigens. Single antigen bead (SAB) assay is the most sensitive tool available for detecting HLA antibodies and assessing the immunological risk for organ transplant. However, there are intrinsic limitations to solid-phase assays and they are prone to both false negativity and importantly, false positivity. Denatured antigens on single antigen beads might be the most prominent source of false positive reactivity, and may have been underestimated by many HLA experts. No single assay is perfect and therefore multiple methods, including the less sensitive assays, should be employed to determine the clinical relevance of detected HLA antibodies. Thoughtful process, including knowledge of HLA systems, cross reactivity, epitopes, and the patient's clinical history should be employed to correctly interpret data. The clinical team should work closely with HLA laboratories to ensure accurate interpretation of information and optimal management of patients before and after organ transplantation.

Identification of risk epitope mismatches associated with de novo donor-specific HLA antibody development in cardiothoracic transplantation

The development of de novo donor-specific HLA antibodies (dnDSA) after transplantation is associated with graft failure, mortality, and cost. There is no effective therapeutic intervention to prevent dnDSA or ameliorate associated injury. The aims of this study were to identify specific HLA factors associated with dnDSA development and to propose primary prevention strategies that could reduce the incidence of dnDSA without prohibitively limiting access to transplant. The investigation cohort included heart transplant recipients from 2008 to 2015 (n = 265). HLA typing was performed and HLA antibody testing was undertaken before and after transplantation. HLAMatchmaker analysis was performed for persistent dnDSA to identify potentially more immunogenic eplet differences. Validation was performed in recipients of lung transplants from 2008 to 2013 (n = 433). The majority of recipients with dnDSA had antibodies to identical eplet positions on DQ2 and DQ7. A high-risk epitope mismatch (found in DQA1*05 +  DQB1*02/DQB1*03:01(7)) was associated with a 4.2- and 4.9-fold increased risk of dnDSA in heart and lung recipients respectively. HLA electrostatic potential modeling provided a plausible explanation for this observed immunogenicity. A theoretical allocation algorithm avoiding high-risk epitope mismatches was generated and predicted to reduce dnDSA by up to 72% without additional testing, eplet analysis, or cost.

Does human leukocyte antigens sensitization matter for xenotransplantation?

The major histocompatibility complex class I and class II human leukocyte antigens (HLA) play a central role in adaptive immunity but are also the dominant polymorphic proteins targeted in allograft rejection. Sensitized patients with high levels of panel-reactive anti-HLA antibody (PRA) are at risk of early allograft injury, rejection, reduced allograft survival and often experience prolonged waiting times prior to transplantation. Xenotransplantation, using genetically modified porcine organs, offers a unique source of donor organs for these highly sensitized patients if the anti-HLA antibody, which places the allograft at risk, does not also enhance anti-pig antibody reactivity responsible for xenograft rejection. Recent improvements in xenotransplantation efficacy have occurred due to improved immune suppression, identification of additional xenogeneic glycans, and continued improvements in donor pig genetic modification. Genetically engineered pig cells, devoid of the known xenogeneic glycans, minimize human antibody reactivity in 90% of human serum samples. For waitlisted patients, early comparisons of patient PRA and anti-pig antibody reactivity found no correlation suggesting that patients with high PRA levels were not at increased risk of xenograft rejection. Subsequent studies have found that some, but not all, highly sensitized patients express anti-HLA class I antibody which cross-reacts with swine leukocyte antigen (SLA) class I proteins. Recent detailed antigen-specific analysis suggests that porcine-specific anti-SLA antibody from sensitized patients binds cross-reactive groups present in a limited subset of HLA antigens. This suggests that using modern genetic methods, a program to eliminate specific SLA alleles through donor genetic engineering or stringent donor selection is possible to minimize recipient antibody reactivity even for highly sensitized individuals.

The Pre-Transplant Drop in Panel-Reactive Antibodies Titer Evaluated Using Complement-Dependent Cytotoxicity (PRA-CDC) and the Risk of Early Acute Rejection in Sensitized Kidney Transplant Recipients

Background: The panel-reactive antibodies that use the complement-dependent cytotoxicity test (PRA-CDC) are still a standard method for monitoring the degree of immunization in kidney transplant candidates on active waiting lists in some countries, including Poland. The aim of this study was to analyze the relationship between the maximum and the last pre-transplant PRA titer on the percentage of positive cross-matches and rate of early acute rejection episodes. Material and methods: The retrospective analysis included 528 patients from two transplant centers. All patients were divided into three groups, depending on their peak and last pre-transplant PRA titers. There were 437 (82.8%) patients with peak PRA <20% (non-sensitized group, non-ST) and 91 (17.2%) patients with peak PRA >20%. Among the latter group, 38 had maintained PRA level >20% at the time of transplantation (sensitized patients, ST), whereas 53 had pre-transplant PRA ≤20% (previously sensitized patients, prev-ST). Results: The percentages of positive crossmatches were 76.9% in ST and 53.7% in prev-ST groups versus 18.4 in non-ST group (both p < 0.001). The acute rejection rates were 18.9, 17.6 and 6.8%, respectively (p < 0.001 for ST or prev-ST versus non-ST). The pre-transplant PRA titer drop did not decrease the risk of early acute rejection [OR = 1.09 (95% CI: 0.31–3.85)] in a multiple logistic regression analysis. The occurrences of primary graft non-function and delayed graft function were similar in all study groups. Conclusions: Previously immunized kidney transplant candidates even with substantial decrease in pre-transplant PRA-CDC levels are still at high immunological risk when compared with non-immunized patients, and they should receive lymphocyte-depleting induction therapy.

Factors Influencing Long-Term Survival of Kidney Grafts Transplanted From Deceased Donors-Analysis Based on a Single-Center Experience

BACKGROUND

Kidney transplantation is a routine procedure in the treatment of patients with kidney failure and requires collaboration of experts from different disciplines. Improvements in the procedure result from numerous factors.

METHODS

The analyzed group consisted of 150 patients divided into 2 equal subgroups: long-term (>15 years) and short-term (<6 years) graft survival. The following factors were taken into consideration: graft survival time, HLA mismatches, recipient sex, sex compatibility, panel reactive antibodies (PRA), cold ischemia time (CIT), and cause of kidney insufficiency. Factors were analyzed in groups with the use of Student t and chi-square tests, Kruskal-Wallis analysis of variance (ANOVA), and multifactorial ANOVA.

RESULTS

Basic statistical analysis revealed no significance between long-term and short-term survival groups in HLA mismatches, recipient sex, or sex compatibility. There was a very significant difference in CIT. ANOVA revealed no statistical difference between groups in recipient sex, sex compatibility, or recipient disease. There were more patients in the group with long-term survival with lower PRA. There were more women in the group with long-term survival who received kidneys from men. Multifactorial analysis revealed no interactions or independent influence of the selected factors.

CONCLUSIONS

CIT was a strong independent factor influencing graft survival. Recipient sex and cause of kidney insufficiency seemed to have no impact. Lower PRA was positively correlated with long-term survival. Women who received kidneys from men lived longer with functioning grafts.

Impact of Preformed Donor-Specific Anti-Human Leukocyte Antigen Antibody C1q-Binding Ability on Kidney Allograft Outcome

The consolidation of single antigen beads (SAB-panIgG) assay in the detection of preformed anti-human leukocyte antigen (HLA) antibodies has improved transplantation success. However, its high sensitivity has limited the allograft allocation for sensitized patients, increasing their waiting time. A modification of the standard SAB-panIgG assay allows the detection of that subset of antibodies capable of binding C1q (SAB-C1q assay). However, the clinical usefulness of SAB-C1q assay for determining the unacceptable mismatches is under discussion. We retrospectively analyzed the impact of preformed donor-specific anti-HLA antibodies (DSA) according to the C1q-binding ability on allograft outcome, examining 389 single-kidney transplanted patients from deceased donors. Recipients with preformed C1q-binding DSA showed the lowest allograft survival up to 7 years (40.7%) compared to patients with preformed non-C1q-binding DSA (73.4%; p = 0.001) and without DSA (79.1%; p < 0.001). Allograft survival rate was similar between patients with preformed non-C1q-binding DSA and patients without preformed DSA (p = 0.403). Interestingly, among the high-mean fluorescence intensity DSA (≥10,000) population (n = 46), those patients whose DSA were further capable of binding C1q showed a poorer allograft outcome (38.4 vs. 68.9%; p = 0.041). Moreover, in our multivariate predictive model for assessing the risk of allograft loss, the presence of C1q-binding DSA (HR 4.012; CI 95% 2.326–6.919; p < 0.001) but not of non-C1q-binding DSA (HR 1.389; CI 95% 0.784–2.461; p = 0.260) remained an independent predictor after stratifying the DSA population according to the C1q-binding ability and adjusting the model for other pre-transplantation predictive factors including donor age, cold-ischemia time, and HLA-DR mismatches. In conclusion, the unacceptable mismatch definition according to the SAB-C1q assay would improve the risk stratification of allograft loss and increase the limited allograft allocation of highly sensitized patients, shortening their waiting time.

Graft immunologic events in deceased donor kidney transplant recipients with preformed HLA-donor specific antibodies

INTRODUCTION

Pretransplant donor-specific HLA alloantibodies detected with the Single Antigen Bead (SAB) assay reflect an increased risk for acute antibody-mediated rejection (AMR). We herein report the incidence of both acute AMR and acute cellular rejection (ACR) during the first year posttransplantation, in a cohort of kidney transplant recipients (KTR) of deceased donor (DD) grafts, according to their DSA status. Pretransplant DSA do not preclude DD-KT in negative CDC-XM recipients at our center.

PATIENTS AND METHODS

246 KT were performed at our center between 01/2012 and 12/2015 and 100 KTR obtained from a DD were analyzed; 24% harbored DSA by SAB assay, MFI values >500 were considered positive. All recipients received thymoglobulin induction and generic tacrolimus-based maintenance therapy. Graft biopsies were performed by protocol on months 3 and 12 as well as per indication. The incidence of AMR and ACR was correlated with the existence of pretransplant DSA.

RESULTS

Overall, 34% of patients developed an acute rejection episode, 54.2% in the DSA group versus 27.6% in the non-DSA group (p=0.032), and most of these events were detected as subclinical conditions in protocol biopsies. AMR events developed in 33.3% and 19.7% (p=0.176) in the DSA and the non-DSA groups, respectively. ACR events were found in 16.6% and 6.6% (p=0.127) in the DSA and non-DSA groups, respectively. Graft function was similar between groups at the end of the 1st year posttransplant and no immunological graft loss occurred.

CONCLUSION

Despite the use of depleting induction therapy and adequate tacrolimus trough levels along with MMF and steroids, a high rate of rejection events was observed during the first year post-transplantation.

Effect of Single Sensitization Event on Human Leukocyte Antigen Alloimmunization in Kidney Transplant Candidates: A Single-Center Experience

OBJECTIVES

Human leukocyte antigen alloimmunization is caused by exposure to HLA antigens through transfusion, pregnancy, or transplant. Our study objective was to present the rate of positivity of anti-HLA antibody considering the effects of a single sensitization event in kidney transplant candidates at our center.

MATERIALS AND METHODS

Our study reviewed 606 kidney transplant candidates. Patient sera were analyzed using Luminex xMAP technology. Panel reactive antibody positivity rates and antibody strengths in patients were analyzed according to a single sensitization event.

RESULTS

Our findings showed 246 patients (40.6%) with a panel reactive antibody > 0, of which 97 (39.4%) were sensitized from a single event, 119 (48.4%) were sensitized by multiple events, and 30 (12.2%) had no known sensitizing event. Considering patients sensitized by a single event with a panel reactive antibody > 0, we found that 25.8% had received transplant only, 49.5% had previous pregnancy only, and 24.7% had received transfusion only. The strength of antibodies was significantly higher in patients with previous transplant procedures than in those with transfusion for HLA-A (P < .01), HLA-B (P < .05), HLA-C (P < .05), HLA-DR (P < .001), HLA-DQ (P < .05), and HLA-DP (P < .05). Similarly, we observed significantly higher median fluorescence intensity values for HLA-A, -DR, -DQ, and -DP loci in patients with a previous transplant procedure versus pregnancy. The strength of antibodies against HLA-DR was significantly higher in patients with a previous pregnancy compared with those with transfusion (P < .01).

CONCLUSIONS

This study documents the profile of HLA alloimmunization in kidney transplant candidates. In particular, transplant procedures appear to have a greater immunologic impact, followed by pregnancy and transfusion. Our data confirm and are in accordance with those of several studies in which the sensitization events were associated with higher prevalence of anti-HLA antibodies.

Successful living donor intestinal transplantation in cross-match positive recipients: Initial experience

Sensitized patients tend to have longer waiting times on the deceased donor list and are at increased risk of graft loss from acute or chronic rejection compared to non-sensitized candidates. Desensitization protocols are utilized to decrease the levels of alloantibodies and to convert an initial positive cross-match to prospective donors into a negative crossmatch. These procedures are mostly available in the setting of living donation. Due to the elective nature of the procedure, desensitization protocols can be extended until the desire result is obtained prior to transplantation. We present two cases of successful desensitization protocol applied to living donor intestinal transplant candidates that converted to negative cross-match to their donors. We present two cases of intestinal transplant candidates with a potential living donor to whom they are sensitized. Both cases underwent successful transplantation after desensitization protocol. No evidence of humoral rejection has occurred in either recipient. Living donor intestinal transplantation in sensitized recipients against the prospective donors provides the ability to implement a desensitization protocol to convert to negative cross-match.

Impact of donor mismatches at individual HLA-A, -B, -C, -DR, and -DQ loci on the development of HLA-specific antibodies in patients listed for repeat renal transplantation

We have analyzed the relationship between donor mismatches at each HLA locus and development of HLA locus-specific antibodies in patients listed for repeat transplantation. HLA antibody screening was undertaken using single-antigen beads in 131 kidney transplant recipients returning to the transplant waiting list following first graft failure. The number of HLA mismatches and the calculated reaction frequency of antibody reactivity against 10,000 consecutive deceased organ donors were determined for each HLA locus. Two-thirds of patients awaiting repeat transplantation were sensitized (calculated reaction frequency over 15%) and half were highly sensitized (calculated reaction frequency of 85% and greater). Antibody levels peaked after re-listing for repeat transplantation, were independent of graft nephrectomy and were associated with length of time on the waiting list (odds ratio 8.4) and with maintenance on dual immunosuppression (odds ratio 0.2). Sensitization was independently associated with increasing number of donor HLA mismatches (odds ratio 1.4). All mismatched HLA loci contributed to the development of HLA locus-specific antibodies (HLA-A: odds ratio 3.2, HLA-B: odds ratio 3.4, HLA-C: odds ratio 2.5, HLA-DRB1: odds ratio 3.5, HLA-DRB3/4/5: odds ratio 3.9, and HLA-DQ: odds ratio 3.0 (all significant)). Thus, the risk of allosensitization following failure of a first renal transplant increases incrementally with the number of mismatches at all HLA loci assessed. Maintenance of re-listed patients on dual immunosuppression was associated with a reduced risk of sensitization.