Quantifying infection risks in incompatible living donor kidney transplant recipients

Evaluation and Long-Term Follow-Up of Living Kidney Donors

The evaluation of living kidney donor candidates is a complex and lengthy process. Donor candidates face geographic and socioeconomic barriers to completing donor evaluation. Inequities in access to living donations persist. With a growing demand for kidney transplants and a shortage of living donors, transplant centers are more permissive of accepting less-than-ideal donor candidates. Donors have an increased lifetime risk of kidney failure, but the absolute risk increase is small. Efforts are needed to support donor candidates to complete donor nephrectomy safely and efficiently and receive optimal follow-up care to prevent risk factors for kidney disease and detect complications early. In this article, the authors address key elements of donor kidney evaluation, including current living donation policy requirements and transplant center practices. The authors present a simplified comprehensive practical approach to help guide providers in completing donor evaluation and follow-up care with best outcomes possible.

The Second International Consensus Guidelines on the Management of BK Polyomavirus in Kidney Transplantation

BK polyomavirus (BKPyV) remains a significant challenge after kidney transplantation. International experts reviewed current evidence and updated recommendations according to Grading of Recommendations, Assessment, Development, and Evaluations (GRADE). Risk factors for BKPyV-DNAemia and biopsy-proven BKPyV-nephropathy include recipient older age, male sex, donor BKPyV-viruria, BKPyV-seropositive donor/-seronegative recipient, tacrolimus, acute rejection, and higher steroid exposure. To facilitate early intervention with limited allograft damage, all kidney transplant recipients should be screened monthly for plasma BKPyV-DNAemia loads until month 9, then every 3 mo until 2 y posttransplant (3 y for children). In resource-limited settings, urine cytology screening at similar time points can exclude BKPyV-nephropathy, and testing for plasma BKPyV-DNAemia when decoy cells are detectable. For patients with BKPyV-DNAemia loads persisting >1000 copies/mL, or exceeding 10 000 copies/mL (or equivalent), or with biopsy-proven BKPyV-nephropathy, immunosuppression should be reduced according to predefined steps targeting antiproliferative drugs, calcineurin inhibitors, or both. In adults without graft dysfunction, kidney allograft biopsy is not required unless the immunological risk is high. For children with persisting BKPyV-DNAemia, allograft biopsy may be considered even without graft dysfunction. Allograft biopsies should be interpreted in the context of all clinical and laboratory findings, including plasma BKPyV-DNAemia. Immunohistochemistry is preferred for diagnosing biopsy-proven BKPyV-nephropathy. Routine screening using the proposed strategies is cost-effective, improves clinical outcomes and quality of life. Kidney retransplantation subsequent to BKPyV-nephropathy is feasible in otherwise eligible recipients if BKPyV-DNAemia is undetectable; routine graft nephrectomy is not recommended. Current studies do not support the usage of leflunomide, cidofovir, quinolones, or IVIGs. Patients considered for experimental treatments (antivirals, vaccines, neutralizing antibodies, and adoptive T cells) should be enrolled in clinical trials.

Biomarkers in Kidney Transplantation: A Rapidly Evolving Landscape

The last decade has seen an explosion in clinical research focusing on the use of noninvasive biomarkers in kidney transplantation. Much of the published literature focuses on donor-derived cell-free DNA (dd-cfDNA). Although initially studied as a noninvasive means of identifying acute rejection, it is now clear that dd-cfDNA is more appropriately described as a marker of severe injury and irrespective of the etiology, elevated dd-cfDNA ≥0.5% portends worse graft outcomes. Blood gene expression profiling is also commercially available and has mostly been studied in the context of early identification of subclinical rejection, although additional data is needed to validate these findings. Torque teno virus, a ubiquitous DNA virus, has emerged as a biomarker of immunosuppression exposure as peripheral blood Torque teno virus copy numbers might mirror the intensity of host immunosuppression. Urinary chemokine tests including C-X-C motif chemokine ligand 9 and C-X-C motif chemokine ligand 10 have recently been assessed in large clinical trials and hold promising potential for early diagnosis of both subclinical and acute rejection, as well as, for long-term prognosis. Urinary cellular messenger RNA and exosome vesicular RNA based studies require additional validation. Although current data does not lend itself to conclusion, future studies on multimodality testing may reveal the utility of serial surveillance for individualization of immunosuppression and identify windows of opportunity to intervene early and before the irreversible allograft injury sets in.

A Multicenter Retrospective Cohort Study on Management Protocols and Clinical Outcomes After ABO-incompatible Kidney Transplantation in India

BACKGROUND

There is no robust evidence-based data for ABO-incompatible kidney transplantation (ABOiKT) from emerging countries.

METHODS

Data from 1759 living donor ABOiKT and 33 157 ABO-compatible kidney transplantations (ABOcKT) performed in India between March 5, 2011, and July 2, 2022, were included in this retrospective, multicenter (n = 25) study. The primary outcomes included management protocols, mortality, graft loss, and biopsy-proven acute rejection (BPAR).

RESULTS

Protocol included rituximab 100 (232 [13.18%]), 200 (877 [49.85%]), and 500 mg (569 [32.34%]); immunoadsorption (IA) (145 [8.24%]), IVIG (663 [37.69%]), and no induction 200 (11.37%). Mortality, graft loss, and BPAR were reported in 167 (9.49%), 136 (7.73%), and 228 (12.96%) patients, respectively, over a median follow-up of 36.3 mo. In cox proportional hazard model, mortality was higher with IA (hazard ratio [HR]: 2.53 [1.62-3.97]; P  < 0.001), BPAR (HR: 1.83 [1.25-2.69]; P  = 0.0020), and graft loss (HR: 1.66 [1.05-2.64]; P  = 0.0310); improved graft survival was associated with IVIG (HR: 0.44 [0.26-0.72]; P  = 0.0010); higher BPAR was reported with conventional tube method (HR: 3.22 [1.9-5.46]; P  < 0.0001) and IA use (HR: 2 [1.37-2.92]; P  < 0.0001), whereas lower BPAR was reported in the prepandemic era (HR: 0.61 [0.43-0.88]; P  = 0.008). Primary outcomes were not associated with rituximab dosing or high preconditioning/presurgery anti-A/anti-B titers. Incidence of overall infection 306 (17.39%), cytomegalovirus 66 (3.75%), and BK virus polyoma virus 20 (1.13%) was low. In unmatched univariate analysis, the outcomes between ABOiKT and ABOcKT were comparable.

CONCLUSIONS

Our largest multicenter study on ABOiKT provides insights into various protocols and management strategies with results comparable to those of ABOcKT.

Cancer Risk Following HLA-Incompatible Living Donor Kidney Transplantation

Incompatible living donor kidney transplant recipients (ILDKTr) require desensitization to facilitate transplantation, and this substantial upfront immunosuppression may result in serious complications, including cancer.

Methods

To characterize cancer risk in ILDKTr, we evaluated 858 ILDKTr and 12 239 compatible living donor kidney transplant recipients (CLDKTr) from a multicenter cohort with linkage to the US transplant registry and 33 cancer registries (1997-2016). Cancer incidence was compared using weighted Cox regression.

Results

Among ILDKTr, the median follow-up time was 6.7 y (maximum 16.1 y) for invasive cancers (ascertained via cancer registry linkage) and 5.0 y (maximum 16.1 y) for basal and squamous cell carcinomas (ascertained via the transplant registry and censored for transplant center loss to follow-up). Invasive cancers occurred in 53 ILDKTr (6.2%) and 811 CLDKTr (6.6%; weighted hazard ratio [wHR] 1.01; 95% confidence interval [CI], 0.76-1.35). Basal and squamous cell carcinomas occurred in 41 ILDKTr (4.8%) and 737 CLDKTr (6.0%) (wHR 0.99; 95% CI, 0.69-1.40). Cancer risk did not vary according to donor-specific antibody strength, and in an exploratory analysis, was similar between CLDKTr and ILDKTr for most cancer types and according to cancer stage, except ILDKTr had a suggestively increased risk of colorectal cancer (wHR 3.27; 95% CI, 1.23-8.71); however, this elevation was not significant after correction for multiple comparisons.

Conclusions

These findings indicate that the risk of cancer is not increased for ILDKTr compared with CLDKTr. The possible elevation in colorectal cancer risk is unexplained and might suggest a need for tailored screening or prevention.

Impact of Low-Level Donor-Specific Anti-HLA Antibody on Posttransplant Clinical Outcomes in Kidney Transplant Recipients

Background

The clinical significance of low-level donor-specific anti-HLA antibody (low-DSA) remains controversial. We investigated the impact of low-DSA on posttransplant clinical outcomes in kidney transplant (KT) recipients.

Methods

We retrospectively reviewed 1,027 KT recipients, namely, 629 living donor KT (LDKT) recipients and 398 deceased donor KT (DDKT) recipients, in Seoul St. Mary's Hospital (Seoul, Korea) between 2010 and 2018. Low-DSA was defined as a positive anti-HLA-DSA result in the Luminex single antigen assay (LABScreen single antigen HLA class I - combi and class II - group 1 kits; One Lambda, Canoga Park, CA, USA) but a negative result in a crossmatch test. We compared the incidence of biopsy-proven allograft rejection (BPAR), changes in allograft function, allograft survival, patient survival, and posttransplant infections between subgroups according to pretransplant low-DSA.

Results

The incidence of overall BPAR and T cell-mediated rejection did not differ between the subgroups. However, antibody-mediated rejection (ABMR) developed more frequently in patients with low-DSA than in those without low-DSA in the total cohort and the LDKT and DDKT subgroups. In multivariate analysis, low-DSA was identified as a risk factor for ABMR development. Its impact was more pronounced in DDKT (odds ratio [OR]: 9.60, 95% confidence interval [CI]: 1.79-51.56) than in LDKT (OR: 3.76, 95% CI: 0.99-14.26) recipients. There were no significant differences in other outcomes according to pretransplant low-DSA.

Conclusions

Pretransplant low-DSA has a significant impact on the development of ABMR, and more so in DDKT recipients than in LDKT recipients, but not on long-term outcomes.

Imlifidase for Kidney Transplantation of Highly Sensitized Patients With a Positive Crossmatch: The French Consensus Guidelines

Imlifidase recently received early access authorization for highly sensitized adult kidney transplant candidates with a positive crossmatch against an ABO-compatible deceased donor. These French consensus guidelines have been generated by an expert working group, in order to homogenize patient selection, associated treatments and follow-up. This initiative is part of an international effort to analyze properly the benefits and tolerance of this new costly treatment in real-life. Eligible patients must meet the following screening criteria: cPRA ≥ 98%, ≤ 65-year of age, ≥ 3 years on the waiting list, and a low risk of biopsy-related complications. The final decision to use Imlifidase will be based on the two following criteria. First, the results of a virtual crossmatch on recent serum, which shall show a MFI for the immunodominant donor-specific antibodies (DSA) > 6,000 but the value of which does not exceed 5,000 after 1:10 dilution. Second, the post-Imlifidase complement-dependent cytotoxicity crossmatch must be negative. Patients treated with Imlifidase will receive an immunosuppressive regimen based on steroids, rATG, high dose IVIg, rituximab, tacrolimus and mycophenolic acid. Frequent post-transplant testing for DSA and systematic surveillance kidney biopsies are highly recommended to monitor post-transplant DSA rebound and subclinical rejection.

Infection Risk in the First Year After ABO-incompatible Kidney Transplantation: A Nationwide Prospective Cohort Study

BACKGROUND

ABO-incompatible (ABOi) kidney transplantation (KT) expands the kidney donor pool and may help to overcome organ shortage. Nonetheless, concerns about infectious complications associated with ABOi-KT have been raised.

METHODS

In a nationwide cohort (Swiss Transplant Cohort Study), we compared the risk for infectious complications among ABOi and ABO-compatible (ABOc) renal transplant recipients. Infections needed to fulfill rigorous, prespecified criteria to be classified as clinically relevant. Unadjusted and adjusted competing risk regression models were used to compare the time to the first clinically relevant infection among ABOi-KT and ABOc-KT recipients. Inverse probability weighted generalized mixed-effects Poisson regression was used to estimate incidence rate ratios for infection.

RESULTS

We included 757 living-donor KT recipients (639 ABOc; 118 ABOi) and identified 717 infection episodes. The spectrum of causative pathogens and the anatomical sites affected by infections were similar between ABOi-KT and ABOc-KT recipients. There was no significant difference in time to first posttransplant infection between ABOi-KT and ABOc-KT recipients (subhazard ratio, 1.24; 95% confidence interval [CI], 0.93-1.66; P = 0.142). At 1 y, the crude infection rate was 1.11 (95% CI, 0.93-1.33) episodes per patient-year for ABOi patients and 0.94 (95% CI, 0.86-1.01) for ABOc-KT recipients. Inverse probability weighted infection rates were similar between groups (adjusted incidence rate ratio, 1.12; 95% CI, 0.83-1.52; P = 0.461).

CONCLUSIONS

The burden of infections during the first year posttransplant was high but not relevantly different in ABOi-KT and ABOc-KT recipients. Our results highlight that concerns regarding infectious complications should not affect the implementation of ABOi-KT programs.

Approach to Highly Sensitized Kidney Transplant Candidates and a Positive Crossmatch

Human leukocyte antigen (HLA)-incompatible kidney transplantation offers survival benefit compared with ongoing dialysis. There have been considerable advances in the last decade to allow for increased access to transplant for the HLA-sensitized kidney transplant candidates. These include increased priority in the kidney allocation system, kidney paired donation, and novel desensitization strategies. A better understanding of the role of B cells, plasma cells, and complement and inflammatory cytokines in the pathophysiology of HLA antibody-mediated allograft injury has led to the use of novel therapeutics for desensitization and treatment of antibody-mediated rejection. Here we discuss current approaches to kidney transplantation in HLA-sensitized kidney transplant candidates.

Characteristics of Immunoglobulin M Type Antibodies of Different Origins from the Immunologic and Clinical Viewpoints and Their Application in Controlling Antibody-Mediated Allograft Rejection

Antibody-mediated allograft rejection (AMR) hinders patient prognosis after organ transplantation. Current studies concerning AMR have mainly focused on the diagnostic value of immunoglobulin G (IgG)-type donor-specific antihuman leukocyte antigen antibodies (DSAs), primarily because of their antigen specificity, whereas the clinical significance of immunoglobulin M (IgM)-type DSAs has not been thoroughly investigated in the context of organ transplantation because of their nonspecificity against antigens. Although consensus regarding the clinical significance and role of IgM antibodies is not clear, as discussed in this review, recent findings strongly suggest that they also have a huge potential in novel diagnostic as well as therapeutic application for the prevention of AMR. Most serum IgM antibodies are known to comprise natural antibodies with low affinity toward antigens, and this is derived from B-1 cells (innate B cells). However, some of the serum IgM-type antibodies reportedly also produced by B-2 cells (conventional B cells). The latter are known to have a high affinity for donor-specific antigens. In this review, we initially discuss how IgM-type antibodies of different origins participate in the pathology of various diseases, directly or through cell surface receptors, complement activation, or cytokine production. Then, we discuss the clinical applicability of B-1 and B-2 cell-derived IgM-type antibodies for controlling AMR with reference to the involvement of IgM antibodies in various pathological conditions.