Antibody-mediated rejection: prevention, monitoring and treatment dilemmas

A universal urinary cell gene signature of acute rejection in kidney allografts

INTRODUCTION

Acute rejection (AR) undermines the life-extending benefits of kidney transplantation and is diagnosed using the invasive biopsy procedure. T cell-mediated rejection (TCMR), antibody-mediated rejection (ABMR), or concurrent TCMR + ABMR (Mixed Rejection [MR]) are the three major types of AR. Development of noninvasive biomarkers diagnostic of AR due to any of the three types is a useful addition to the diagnostic armamentarium.

METHODS

We developed customized RT-qPCR assays and measured urinary cell mRNA copy numbers in 145 biopsy-matched urine samples from 126 kidney allograft recipients. We determined whether the urinary cell three-gene signature diagnostic of TCMR (Suthanthiran et al., 2013) discriminates patients with no rejection biopsies (NR, n = 50) from those with ABMR (n = 28) or MR (n = 20) biopsies.

RESULTS

The urinary cell three-gene signature discriminated all three types of rejection biopsies from NR biopsies (P < 0.0001, One-way ANOVA). Dunnett's multiple comparisons test yielded P < 0.0001 for NR vs. TCMR; P < 0.001 for NR vs. ABMR; and P < 0.0001 for NR vs. MR. By bootstrap resampling, optimism-corrected area under the receiver operating characteristic curve (AUC) was 0.749 (bias-corrected 95% confidence interval [CI], 0.638 to 0.840) for NR vs. TCMR (P < 0.0001); 0.780 (95% CI, 0.656 to 0.878) for NR vs. ABMR (P < 0.0001); and 0.857 (95% CI, 0.727 to 0.947) for NR vs. MR (P < 0.0001). All three rejection categories were distinguished from NR biopsies with similar accuracy (all AUC comparisons P > 0.05).

CONCLUSION

The urinary cell three-gene signature score discriminates AR due to TCMR, ABMR or MR from NR biopsies in human kidney allograft recipients.

Immunomodulatory Effect of COVID-19 on HLA-Antibody Profile in Renal Transplant Recipients

Background/Objectives: The novel coronavirus disease 2019 (COVID-19) has led to significant morbidity and mortality among kidney transplant recipients. SARS-CoV-2 has been hypothesized to cause an unusual immunological dysregulation triggering alloimmunity and leading to graft rejection. Methods: This prospective observational cohort study assessed 321 kidney transplant recipients who had COVID-19 infection. After the infection, patients' sera were tested for the presence of anti-HLA de novo DSA and non-DSA specificities. Logistic regression analysis and a stepwise multivariable logistic regression analysis were used to analyze the independent risk factors associated with the development of antibodies, adjusting for known confounders. The variables evaluated were acute COVID-19 characteristics (i.e., presentation, and need for hospitalization), demographic characteristics (i.e., age, gender, and primary renal disease), clinical characteristics (i.e., various comorbidities), and post-COVID-19 sequelae. Results: Anti-HLA de novo DSA developed in 18.7% of patients, while anti-HLA class I and class II non-DSA antibodies developed de novo in 84 (26.3%) and 83 (25.9%) patients, respectively. The development of DSA, HLA-DQ, and HLA-DR antibodies was predicted by the history of graft rejection. Obesity appeared to be protective against the emergence of de novo DSA. De novo DSA and HLA-DR antibody formation was positively linked with intravenous immunoglobulin use, CMV-hyperimmune globulin use, and decreased doses of immunosuppression during acute infection. Better allograft function during the acute disease was a protective factor against the formation of HLA-DQ and HLA-DR antibodies. Positive predictors of de novo DSA development were graft biopsy and the reactivation of EBV after infection. Conclusions: These findings suggest that the SARS-CoV-2 virus has an immunomodulatory effect and may be associated with an increased mortality in this population.

Nanoparticle-assisted Targeting Delivery Technologies for Preventing Organ Rejection

Although organ transplantation is a life-saving medical procedure, the challenge of posttransplant rejection necessitates safe and effective immune modulation strategies. Nanodelivery approaches may have the potential to overcome the limitations of small-molecule immunosuppressive drugs, achieving efficacious treatment options for transplant tolerance without compromising overall host immunity. This review highlights recent advances in biomaterial-assisted formulations and technologies for targeted nanodrug delivery with transplant organ- or immune cell-level precision for treating graft rejection after transplantation. We provide an overview of the mechanism of transplantation rejection, current clinically approved immunosuppressive drugs, and their relevant limitations. Finally, we discuss the targeting principles and advantages of organ- and immune cell-specific delivery technologies. The development of biomaterial-assisted novel therapeutic strategies holds considerable promise for treating organ rejection and clinical translation.

Bortezomib-Induced Superficial Vasculitis in a Kidney Transplant Recipient: A Rare Case

Bortezomib is a frequently administered immunosuppressive agent in kidney transplantation. A 30-year-old male kidney transplant recipient developed an atypical reaction on the left hand in terms of spider-like extensions, indicating erythematous inflammation along the superficial veins after bortezomib intravenous administration. The inflammation spontaneously resolved after three weeks with a bortezomib dose reduction. Nephrologists must be familiar with the potential cutaneous bortezomib-induced adverse effects.

Transcriptomic signatures of chronic active antibody-mediated rejection deciphered by RNA sequencing of human kidney allografts

Natural killer (NK) cells mediate spontaneous cell-mediated cytotoxicity and antibody-dependent cell-mediated cytotoxicity. This dual functionality could enable their participation in chronic active antibody-mediated rejection (CA-ABMR). Earlier microarray profiling studies have not subcategorized antibody-mediated rejection into CA-ABMR and active-ABMR, and the gene expression pattern of CA-ABMR has not been compared with that of T cell-mediated rejection (TCMR). To fill these gaps, we RNA sequenced human kidney allograft biopsies categorized as CA-ABMR, active-ABMR, TCMR, or No Rejection (NR). Among the 15,910 genes identified in the biopsies, 60, 114, and 231 genes were uniquely overexpressed in CA-ABMR, TCMR, and active-ABMR, respectively; compared to NR, 50 genes were shared between CA-ABMR and active-ABMR, and 164 genes between CA-ABMR and TCMR. The overexpressed genes were annotated to NK cells and T cells in CA-ABMR and TCMR, and to neutrophils and monocytes in active-ABMR. The NK cell cytotoxicity and allograft rejection pathways were enriched in CA-ABMR. Genes encoding perforin, granzymes, and death receptor were overexpressed in CA-ABMR versus active-ABMR but not compared to TCMR. NK cell cytotoxicity pathway gene set variation analysis score was higher in CA-ABMR compared to active-ABMR but not in TCMR. Principal component analysis of the deconvolved immune cellular transcriptomes separated CA-ABMR and TCMR from active-ABMR and NR. Immunohistochemistry of kidney allograft biopsies validated a higher proportion of CD56+ NK cells in CA-ABMR than in active-ABMR. Thus, CA-ABMR was exemplified by the overexpression of the NK cell cytotoxicity pathway gene set and, surprisingly, molecularly more like TCMR than active-ABMR.

Development and performance of a next generation sequencing (NGS) assay for monitoring of dd-cfDNA post solid organ transplantation

The aim of this study was to evaluate the analytical performance of a novel NGS assay, intended for monitoring of donor-derived cell-free DNA (dd-cfDNA), and describe its validity in clinical plasma samples from kidney transplanted patients. Artificial and clinical samples with increasing amounts of patient DNA were evaluated using NGS analysis of indel markers. Monitoring of dd-cfDNA with the NGS assay presented herein demonstrated a sensitivity of ≥0.1% dd-cfDNA and excellent accuracy (R2 0.99) throughout an extensive range of dd-cfDNA (0.1-30%). The precision of the test was determined for two levels (0.1% (LoD) and 1%) of dd-cfDNA. The between run precision (CV%) for the respective level was 16% and 9% and the corresponding result for the within run precision was 19% and 7%. To evaluate performance of the assay in clinical samples, 507 retrospective monitoring samples from 21 patients transplanted either with kidneys from living or deceased donors were analyzed. Monitoring samples were sampled at multiple time points from 24 h up to 90 days post-transplantation. We show that in one patient, increase of dd-cfDNA preceded increase of creatinine caused by acute cellular rejection by several days. In conclusion, the NGS assay displayed a combination of high sensitivity with good accuracy and precision in both artificial and clinical dd-cfDNA samples.

Urinary Cell Gene Signature of Acute Rejection in Kidney Allografts

Introduction

A kidney allograft biopsy may display acute T cell-mediated rejection (TCMR), antibody-mediated rejection (ABMR), or concurrent TCMR + ABMR (MR). Development of noninvasive biomarkers diagnostic of all three types of acute rejection is a useful addition to the diagnostic armamentarium.

Methods

We developed customized RT-qPCR assays and measured urinary cell mRNA copy number in 145 biopsy-matched urine samples from 126 kidney allograft recipients and calculated urinary cell three-gene signature score from log 10 -transformed values for the 18S-normalized CD3E mRNA, 18S-normalized CXCL10 mRNA and 18S rRNA. We determined whether the signature score in biopsy-matched urine specimens discriminates biopsies without rejection (NR, n=50) from biopsies displaying TCMR (n=47), ABMR (n=28) or MR (n=20).

Results

Urinary cell three-gene signature discriminated TCMR, ABMR or MR biopsies from NR biopsies (P <0.0001, One-way ANOVA). Dunnett's multiple comparisons test yielded P<0.0001 for NR vs. TCMR; P <0.001 for NR vs. ABMR; and P <0.0001 for NR vs. MR. By bootstrap resampling, optimism-corrected area under the receiver operating characteristic curve (AUC) was 0.749 (bias-corrected 95% confidence interval [CI], 0.638 to 0.840) for NR vs. TCMR (P<0.0001); 0.780 (95% CI, 0.656 to 0.878) for NR vs. ABMR (P<0.0001); and 0.857 (95% CI, 0.727 to 0.947) for NR vs. MR (P<0.0001). All three rejection biopsy categories were distinguished from NR biopsies with similar accuracy (all AUC comparisons P>0.05).

Conclusion

Urinary cell three-gene signature score may serve as a universal diagnostic signature of acute rejection due to TCMR, ABMR or MR in human kidney allografts with similar performance characteristics.

Unrepresented human leucocyte antigen alleles in single-antigen bead assays: A single-centre cohort study

Human leucocyte antigen (HLA) alleles may generate antibodies that are undetectable by routine single-antigen beads (SABs) assays if their unique epitopes are unrepresented. We aimed to describe the prevalence and explore the potential impact of unrepresented HLA alleles in standard SAB kits in our cohort. All individuals who had undergone two-field HLA typing (HLA-A/B/C/DRB1/DQA1/-DQB1/-DPA1/-DPB1) from February 2021 to July 2023 were included. Two-field HLA-DRB3/4/5 typing was imputed. Each unrepresented allele was compared with the most similar represented allele in the standard LABScreen, LABScreen ExPlex (One Lambda) and the LIFECODES (Immucor) SAB kits. Differences in eplet expression (HLA Eplet Registry) were identified. Differences in three-dimensional molecular structures were visualized using generated models (SWISS-MODEL). Two-field HLA typing was performed for 116 individuals. Overall, 16.7% of all HLA alleles, found in 36.2% of individuals, were unrepresented by all SAB test kits. Four eplets, found in 12.9% of individuals, were unrepresented in at least 1 SAB kit. Non-Chinese individuals were more likely to have unrepresented HLA alleles and eplets than Chinese individuals. There were differences in HLA allele and eplet representation amongst the different SAB test kits. Use of supplementary SAB test kits may improve HLA allele and eplet representation. Although some HLA alleles were unrepresented, most epitopes were represented in current SAB kits. However, some unrepresented alleles may contain epitopes which may generate undetectable antibodies. Further studies may be needed to investigate the potential clinical impact of these unrepresented alleles and eplets, especially in certain ethnic populations or at-risk individuals.

Farnesyltransferase-inhibitors exert in vitro immunosuppressive capacity by inhibiting human B-cells

Objectives

Farnesyltransferase inhibitors (FTI), which inhibit the prenylation of Ras GTPases, were developed as anti-cancer drugs. As additional target proteins for prenylation were identified in the past, it is likely that FTI have potential value for therapeutic purposes beyond cancer. The effect of FTI on B-cells remains unclear. To address this issue, we investigated the effects of in vitro FTI treatment on effector and regulatory B-cells in healthy controls and renal transplant patients.

Methods

For this purpose, B-cells were isolated from the peripheral blood of healthy controls and renal transplant patients. Purified B-cells were stimulated via Toll-like-receptor 9 (TLR-9) in the presence or absence of FTI. Regulatory functions, such as IL-10 and Granzyme B (GrB) secretion, were assessed by flow cytometry. In addition, effector B-cell functions, such as plasma cell formation and IgG secretion, were studied.

Results

The two FTI Lonafarnib and tipifarnib both suppressed TLR-9-induced B-cell proliferation. Maturation of IL-10 producing B-cells was suppressed by FTI at high concentrations as well as induction of GrB-secreting B-cells. Plasma blast formation and IgG secretion were potently suppressed by FTI. Moreover, purified B-cells from immunosuppressed renal transplant patients were also susceptible to FTI-induced suppression of effector functions, evidenced by diminished IgG secretion.

Conclusion

FTI suppress in vitro B-cell proliferation and plasma cell formation while partially preserving IL-10 as well as GrB production of B-cells. Thus, FTI may have immunosuppressive capacity encouraging further studies to investigate the potential immunomodulatory value of this agent.

Novel Therapeutic Approaches in the Management of Chronic Kidney Disease

Chronic kidney disease (CKD) is a progressive and incurable disease that impairs kidney function. Its prevalence is estimated to affect up to 800 million individuals within the general population, and patients with diabetes and hypertension are particularly at risk. This disorder disrupts the physiological mechanisms of the body, including water and electrolyte balance, blood pressure regulation, the excretion of toxins, and vitamin D metabolism. Consequently, patients are exposed to risks such as hyperkalemia, hyperphosphatemia, metabolic acidosis, and blood pressure abnormalities. These risks can be reduced by implementing appropriate diagnostic methods, followed by non-pharmacological (such as physical activity, dietary, and lifestyle adjustment) and pharmacological strategies after diagnosis. Selecting the appropriate diet and suitable pharmacological treatment is imperative in maintaining kidney function as long as possible. Drugs such as finerenone, canakinumab, and pentoxifylline hold promise for improved outcomes among CKD patients. When these interventions prove insufficient, renal replacement therapy becomes essential. This is particularly critical in preserving residual renal function while awaiting renal transplantation or for patients deemed ineligible for such a procedure. The aim of this study is to present the current state of knowledge and recent advances, providing novel insights into the treatment of chronic kidney disease.

Clinical impact of early post-transplant red cell transfusions in kidney transplantation: a systematic review and meta-analysis

Introduction

Red blood cell transfusions (RBCT) represent a potentially modifiable risk factor for HLA sensitisation and adverse outcomes post transplantation. Evidence of the clinical impact of post-transplant RBCT has been infrequently reported. Herein, we performed a systematic review of available literature to assess the prevalence of RBCT post kidney transplant, and the effect of transfusion on transplant outcomes.

Methods

We included studies from 2000 to July 2022, published on Medline, Embase and the Transplant Library.

Results

Ten studies were analysed which included a total of 32,817 kidney transplant recipients, with a median transfusion prevalence of 40% (range 18-64%). There was significant heterogeneity between studies in terms of patient and allograft characteristics, immunological risk, and immunosuppression protocols. Analysis of unadjusted outcomes showed that post-transplant RBCTs are associated with inferior patient survival, allograft loss, rejection and donor specific antibodies. Adjusted outcomes were described where available, and supported the adverse associations seen in the unadjusted models in many studies.

Discussion

This review demonstrates that RBCT post-transplant are common and maybe associated with inferior outcomes, highlighting the urgent need for high quality prospective evidence of the effect of RBCTs on transplant outcomes.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/, identifier, CRD42022348763767.

An investigation of the primary immunosuppressive therapy's influence on kidney transplant survival at one month after transplantation

Immunosuppressive therapy is complex and challenging to do correctly due to on-target and off-target side effects. However, it is vital to successful allotransplantation. In this article, we analyzed the critical classes of immunosuppressants used in renal transplantation, highlighting the mechanisms of action and typical clinical applications used to develop predictive models for the diagnosis of various diseases, including the prediction of survival after kidney transplantation. In patients, the authors used a dataset with two immunosuppressants (tacrolimus and cyclosporin). The primary task was investigating critical risk factors associated with early transplant rejection. For this, the censored Kaplan-Meier survival estimation method was used . Our study shows a pairwise correlation between taking and not using a particular immunosuppressant. Therefore, the correct choice of immunosuppressive drugs is necessary to improve the prognosis of transplant survival.