Angiotensin II type 1-receptor activating antibodies in renal-allograft rejection

Bariatric surgery modulates plasma levels of antibodies against angiotensin II type 1 and endothelin 1 type A receptor in severe obesity

PURPOSE

The contribution of endothelial-targeted autoantibodies against the angiotensin II type 1 receptor (anti-AT1R) and the anti-endothelin 1 type A receptor (anti-ETAR1) has been proposed in the development of cardiovascular diseases. However, no data have been reported yet in obesity. In this observational study we evaluated the relationship between anthropometric and metabolic parameters and anti-AT1R and anti-ETAR1 concentrations in a cohort of patients with severe obesity and associated comorbidities undergoing bariatric surgery.

METHODS

Clinical evaluation and metabolic assessment were performed in 36 subjects referring to our Center for the Study and Integrated Treatment of Obesity at the University Hospital of Padova. Circulating inflammatory adipocytokines and the endothelial dysfunction marker asymmetric dimethylarginine (ADMA) were evaluated; plasma levels of anti-AT1R and anti-ETAR1 were also determined. 10 normal-weight subjects were considered as a control group. 29 patients out of 36 were re-evaluated after surgery.

RESULTS

With respect to normal-weight controls patients showed significantly higher plasma levels of anti-AT1R (28 ± 20.4 vs 13.5 ± 2.8 U/mL, p < 0.005) and ADMA (0.8 ± 0.1 vs 0.54 ± 0.08 uM/L, p < 0.0001) but not anti-ETAR1 (14.2 ± 1.3 vs 13.3 ± 2 U/mL, p = 0.1). Anti-AT1R concentration showed an increasing trend with the worsening of glycemic status, while the presence of arterial hypertension among the patients did not affect autoantibodies levels. One year after surgery, a significant improvement in body weight and metabolic and inflammatory parameters was observed, along with a significant reduction of anti-AT1R (28.1 ± 20.4 U/mL vs 22.6 ± 16 U/mL, p < 0.05) and anti-ETAR1 (14.2 ± 1.3 U/L vs 13 ± 1.6 U/L, p < 0.01).

CONCLUSIONS

Subjects with obesity present higher plasma levels of anti-AT1R which are more related to glycemic profile than blood pressure levels, and are reduced by bariatric surgery. Considering the detrimental effects of these autoantibodies on vascular health, they should be assessed as potential biomarkers in obesity and metabolic diseases.

Immune monitoring in pediatric kidney transplant

BACKGROUND

Long-term outcomes in pediatric kidney transplantation remain suboptimal, largely related to chronic rejection. Creatinine is a late marker of renal injury, and more sensitive, early markers of allograft injury are an active area of current research.

METHODS

This is an educational review summarizing existing strategies for monitoring for rejection in kidney transplant recipients.

RESULTS

We summarize supporting currently available clinical tests, including surveillance biopsy, donor specific antibodies, and donor-derived cell free DNA, as well as the potential limitations of these studies. In addition, we review the current avenues of active research, including transcriptomics, proteomics, metabolomics, and torque tenovirus levels.

CONCLUSION

Advancing the use of noninvasive immune monitoring will depend on well-designed multicenter trials that include patients with stable graft function, include biopsy results on all patients, and can demonstrate both association with a patient-relevant clinical endpoint such as graft survival or change in glomerular filtration rate and a potential timepoint for intervention.

Non-HLA angiotensin-type-1 receptor autoantibodies mediate the long-term loss of grafted neurons in Parkinson's disease models

BACKGROUND

Clinical trials have provided evidence that transplants of dopaminergic precursors, which may be replaced by new in vitro stem cell sources, can integrate into the host tissue, and alleviate motor symptoms in Parkinson´s disease (PD). In some patients, deterioration of graft function occurred several months after observing a graft-derived functional improvement. Rejection of peripheral organs was initially related to HLA-specific antibodies. However, the role of non-HLA antibodies is now considered also relevant for rejection. Angiotensin-II type-1 receptor autoantibodies (AT1-AA) act as agonists of the AT1 receptors. AT1-AA are the non-HLA antibodies most widely associated with graft dysfunction or rejection after transplantation of different solid organs and hematopoietic stem cells. However, it is not known about the presence and possible functional effects of AT1-AA in dopaminergic grafts, and the effects of treatment with AT1 receptor blockers (ARBs) such as candesartan on graft survival.

METHODS

In a 6-hydroxydopamine PD rat model, we studied the short-term (10 days)- and long-term (3 months) effects of chronic treatment with the ARB candesartan on survival of grafted dopaminergic neurons and microglial graft infiltration, as well as the effects of dopaminergic denervation and grafting on serum and CSF AT1-AA levels. The expression of AT1 receptors in grafted neurons was determined by laser capture microdissection.

RESULTS

At the early period post-grafting, the number of grafted dopaminergic neurons that survived was not significantly different between treated and untreated hosts (i.e., control rats and rats treated with candesartan), probably because, just after grafting, other deleterious factors are predominant for dopaminergic cell death, such as mechanical trauma, lack of growth factors/nutrients and ischemia. However, several months post-grafting, we observed a significantly higher number of surviving dopaminergic neurons and a higher density of striatal dopaminergic terminals in the candesartan-treated group. For several months, grafted rats showed blood and cerebrospinal fluid levels of AT1-AA higher than normal controls, and also higher AT1-AA levels than non-grafted parkinsonian rats.

CONCLUSIONS

The results suggest the use of ARBs such as candesartan in PD patients, particularly before and after dopaminergic grafts, and the need to monitor AT1-AA levels in PD patients, particularly in those candidates for dopaminergic grafting.

Clinical conundrums in pediatric kidney transplantation: What we know about the role of angiotensin II type I receptor antibodies in pediatric kidney transplantation and the path forward

Antibodies to angiotensin II type 1 receptor (AT1R-Abs) are among the most well-studied non-HLA antibodies in renal transplantation. These antibodies have been shown to be common in pediatric kidney transplantation and associated with antibody-mediated rejection (AMR), vascular inflammation, development of human leukocyte donor-specific antibodies (HLA DSA), and allograft loss. As AT1R-Ab testing becomes more readily accessible, evidence to guide clinical practice for testing and treating AT1R-Ab positivity in pediatric kidney transplant recipients remains limited. This review discusses the clinical complexities of evaluating AT1R-Abs given the current available evidence.

Selective Elimination and Rationalization of Cell-based Assays in Deceased Donor Kidney Transplant Crossmatching

Background

While there is increasing reliance on a negative virtual crossmatch to proceed with deceased donor kidney transplantation, a flow cytometry crossmatch (FCXM) is still usually performed after the transplant has already occurred. Our center has eliminated pretransplant physical crossmatches for most patients, and since 2018, we have eliminated the systematic performance of posttransplant FCXMs.

Methods

We studied all deceased donor kidney transplants in our program between June 1, 2018, and March 31, 2021, to evaluate the impact of eliminating retrospective FCXMs on resource utilization and graft outcomes (ie, the occurrence of antibody-mediated rejection [AMR] in the first 3-mo posttransplant).

Results

A total of 358 kidney transplants occurred during the study period, and approximately 70% of these transplants proceeded without the performance of any FCXM. Incidence rates of AMR were low (9.63 per 1000 person-months), which compared favorably with the incidence rate of AMR during the 3-y period preceding the policy (4.82 per 1000 person-months, P = 0.21).

Conclusions

Our results suggest that moving away from retrospective FCXM and relying exclusively on the virtual crossmatch is safe and efficient for kidney allocation.

Translating B cell immunology to the treatment of antibody-mediated allograft rejection

Antibody-mediated rejection (AMR), including chronic AMR (cAMR), causes ~50% of kidney allograft losses each year. Despite attempts to develop well-tolerated and effective therapeutics for the management of AMR, to date, none has obtained FDA approval, thereby highlighting an urgent unmet medical need. Discoveries over the past decade from basic, translational and clinical studies of transplant recipients have provided a foundation for developing novel therapeutic approaches to preventing and treating AMR and cAMR. These interventions are aimed at reducing donor-specific antibody levels, decreasing graft injury and fibrosis, and preserving kidney function. Innovative approaches emerging from basic science findings include targeting interactions between alloreactive T cells and B cells, and depleting alloreactive memory B cells, as well as donor-specific antibody-producing plasmablasts and plasma cells. Therapies aimed at reducing the cytotoxic antibody effector functions mediated by natural killer cells and the complement system, and their associated pro-inflammatory cytokines, are also undergoing evaluation. The complexity of the pathogenesis of AMR and cAMR suggest that multiple approaches will probably be required to treat these disease processes effectively. Definitive answers await results from large, double-blind, multicentre, randomized controlled clinical trials.

Dynamics of HLA and angiotensin II type 1 receptor antibodies during pregnancy

BACKGROUND

Alloantibodies, especially anti-human leukocyte antigen antibodies (HLA antibodies), and autoantibodies, as angiotensin II type 1 receptor antibodies (AT1R antibodies), may complicate the access and the course of transplantation. Pregnancy is a known source of HLA antibodies, with most studies evaluating pregnancy-induced sensitization by complement-dependent cytotoxicity assays, mainly after childbirth. AT1R antibodies have been evaluated in the context of preeclampsia. We aimed to evaluate pregnancy as a natural source of HLA antibodies and AT1R antibodies, their dynamics along gestation and the potential factors involved in antibody appearance.

METHODS

Serum samples from pregnant women were collected during the three trimesters of pregnancy (1T, 2T, 3T). Presence of HLA antibodies was assessed by screening beads on Luminex and AT1R antibodies by ELISA.

RESULTS

A cohort of 138 pregnant women were included. Samples from all were tested in 1T, 127 in 2T and 102 in 3T. HLA antibodies increased from 29.7 % (1T) to 38.2 % (3T). AT1R antibodies were stable around 30 % along pregnancy. Up to 43.2 % multiparous women had HLA antibodies, with a similar proportion of class I and class II antibodies. In primiparous women HLA antibodies increased along pregnancy (from 17.6 % to 34.1 %), with predominance of class II HLA antibodies. AT1R antibodies were not different in primiparous and multiparous women.

CONCLUSIONS

Pregnancy is a relevant source of HLA antibodies sensitization, but not of AT1R antibodies. HLA antibodies increased clearly in primiparous women with predominance of class II. The use of newer solid-phase techniques on Luminex evidence a higher degree of HLA sensitization during pregnancy.

Association of Angiotensin II Receptor Type 1 and Endothelin-1 Receptor Type A Agonistic Autoantibodies With Adverse Remodeling and Cardiovascular Events After Acute Myocardial Infarction

BACKGROUND

The left ventricular remodeling (LVR) process has limited the effectiveness of therapies after myocardial infarction. The relationship between autoantibodies activating AT1R-AAs (angiotensin II receptor type 1-AAs) and ETAR-AAs (autoantibodies activating endothelin-1 receptor type A) with myocardial infarction has been described. Among patients with ST-segment-elevation myocardial infarction, we investigated the relationship between these autoantibodies with LVR and subsequent major adverse cardiac events.

METHODS AND RESULTS

In this prospective observational study, we included 131 patients with ST-segment-elevation myocardial infarction (61±11 years of age, 112 men) treated with primary percutaneous coronary intervention. Within 48 hours of admission, 2-dimensional transthoracic echocardiography was performed, and blood samples were obtained. The seropositive threshold for AT1R-AAs and ETAR-AAs was >10 U/mL. Patients were followed up at 6 months, when repeat transthoracic echocardiography was performed. The primary end points were LVR, defined as a 20% increase in left ventricular end-diastolic volume index, and major adverse cardiac event occurrence at follow-up, defined as cardiac death, nonfatal re-myocardial infarction, and hospitalization for heart failure. Forty-one (31%) patients experienced LVR. The prevalence of AT1R-AAs and ETAR-AAs seropositivity was higher in patients with versus without LVR (39% versus 11%, P<0.001 and 37% versus 12%, P=0.001, respectively). In multivariable analysis, AT1R-AAs seropositivity was significantly associated with LVR (odds ratio [OR], 4.66; P=0.002) and represented a risk factor for subsequent major adverse cardiac events (OR, 19.6; P=0.002).

CONCLUSIONS

AT1R-AAs and ETAR-AAs are associated with LVR in patients with ST-segment-elevation myocardial infarction. AT1R-AAs are also significantly associated with recurrent major adverse cardiac events. These initial observations may set the stage for a better pathophysiological understanding of the mechanisms contributing to LVR and ST-segment-elevation myocardial infarction prognosis.

Improved Graft Function following Desensitization of Anti-AT1R and Autoantibodies in a Heart Transplant Recipient Negative for Donor-Specific Antibodies with Antibody-Mediated Rejection: A Case Report

HLA donor-specific antibodies (DSAs) pre and post transplant increase the risk of antibody-mediated rejection (AMR) and lead to poor graft survival. Increasing data exist to support the involvement of non-HLA antibodies in triggering an immunological response. The development of non-HLA antibodies specific for AT1R is associated with poor clinical outcomes in orthotopic heart transplant recipients. This case presents an investigation of non-HLA antibodies in a 56-year-old female heart transplant recipient diagnosed with AMR in the absence of DSAs.

Tissue transglutaminase: a multifunctional and multisite regulator in health and disease

Tissue transglutaminase (TG2) is a widely distributed multifunctional protein involved in a broad range of cellular and metabolic functions carried out in a variety of cellular compartments. In addition to transamidation, TG2 also functions as a Gα signaling protein, a protein disulfide isomerase (PDI), a protein kinase, and a scaffolding protein. In the nucleus, TG2 modifies histones and transcription factors. The PDI function catalyzes the trimerization and activation of heat shock factor-1 in the nucleus and regulates the oxidation state of several mitochondrial complexes. Cytosolic TG2 modifies proteins by the addition of serotonin or other primary amines and in this way affects cell signaling. Modification of protein-bound glutamines reduces ubiquitin-dependent proteasomal degradation. At the cell membrane, TG2 is associated with G protein-coupled receptors (GPCRs), where it functions in transmembrane signaling. TG2 is also found in the extracellular space, where it functions in protein cross-linking and extracellular matrix stabilization. Of particular importance in transglutaminase research are recent findings concerning the role of TG2 in gene expression, protein homeostasis, cell signaling, autoimmunity, inflammation, and hypoxia. Thus, TG2 performs a multitude of functions in multiple cellular compartments, making it one of the most versatile cellular proteins. Additional evidence links TG2 with multiple human diseases including preeclampsia, hypertension, cardiovascular disease, organ fibrosis, cancer, neurodegenerative diseases, and celiac disease. In conclusion, TG2 provides a multifunctional and multisite response to physiological stress.

Non-HLA Antibodies to G Protein-coupled Receptors in Pediatric Kidney Transplant Recipients: Short- and Long-term Clinical Outcomes

BACKGROUND

Angiotensin II type 1 receptor antibodies (AT1R-Abs) and endothelin-type A receptor antibodies (ETAR-Abs) are G protein-coupled receptor activating autoantibodies associated with antibody-mediated rejection, vascular pathology, increased cytokines, allograft dysfunction, and allograft loss in pediatric kidney transplant recipients in the first 2 y posttransplantation. The impact of AT1R-Ab and ETAR-Ab positivity on longer-term 5-y transplant outcomes is unknown.

METHODS

One hundred pediatric kidney transplant recipients were tested for ETAR-Ab and AT1R-Ab on serially collected blood samples in the first 2 y posttransplant. Biopsies were collected per protocol and 6, 12, and 24 mo posttransplant and at any time during the 5-y follow-up period for clinical indication. Clinical outcomes, including renal dysfunction, rejection, HLA donor-specific antibodies, and allograft loss, were assessed through 5 y posttransplantation.

RESULTS

AT1R-Ab or ETAR-Ab were positive in 59% of patients. AT1R-Ab or ETAR-Ab positivity was associated with greater declines in estimated glomerular filtration rate, and de novo AT1R-Ab or ETAR-Ab was associated with allograft loss in the first 2 y posttransplant. There was no association between antibody positivity and rejection, antibody-mediated rejection, or allograft loss in the first 5 y posttransplant. In a model controlled for age, sex, immunosuppression, and HLA mismatch, AT1R-Ab or ETAR-Ab positivity was significantly associated with the development of HLA donor-specific antibodies at 5 y posttransplant (odds ratio 2.87, P  = 0.034).

CONCLUSIONS

Our findings suggest temporally distinct clinical complications associated with AT1R-Ab or ETAR-Ab positivity in pediatric patients; these injury patterns are of significant interest for developing effective treatment strategies.

Vasoregulatory Autoantibodies and Clinical Outcome After Ischemic Stroke-PROSCIS-B

BACKGROUND

Vasoregulatory autoantibodies including autoantibodies targeting G-protein-coupled receptors might play a functional role in vascular diseases. We investigated the impact of vasoregulatory autoantibodies on clinical outcome after ischemic stroke.

METHODS AND RESULTS

Data were used from the PROSCIS-B (Prospective Cohort With Incident Stroke-Berlin). Autoantibody-targeting receptors such as angiotensin II type 1 receptor (AT1R), endothelin-1 type A receptor, complement factor-3 and -5 receptors, vascular endothelial growth factor receptor-1 and -2, vascular endothelial growth factor A and factor B were measured. We explored associations of high antibody levels with (1) poor functional outcome defined as modified Rankin Scale >2 or Barthel Index <60 at 1 year after stroke, (2) Barthel Index scores over time using general estimating equations, and (3) secondary vascular events (recurrent stroke, myocardial infarction) or death up to 3 years using Cox proportional hazard models. We included 491 patients with ischemic stroke with data on autoantibody levels and outcome. In models adjusted for demographics and vascular risk factors, high autoantibody concentrations (quartile 4) targeting complement factor C3a receptor, vascular endothelial growth factor receptor-2, and vascular endothelial growth factor B were associated with poor functional outcome at 1 year: (odds ratio, 2.0 [95% CI, 1.1-3.6]; odds ratio, 1.8 [95% CI, 1.1-3.2]; and odds ratio, 2.1 [95% CI, 1.2-3.6], respectively) and with lower Barthel Index scores over 3 years (complement factor C3a receptor: adjusted β=-3.3 [95% CI, -5.7 to -0.5]; VEGF-B: adjusted β=-2.4 [95% CI, -4.8 to -0.06]). Patients with high autoantibody levels were not at higher risk for secondary vascular events or death.

CONCLUSIONS

High levels of autoantibodies against vascular endothelial growth factor receptor-2, vascular endothelial growth factor B, and complement factor C3a receptor measured are associated with poor functional outcome after stroke but not with recurrent vascular events or death.

REGISTRATION

URL: https://www.clinicaltrials.gov; Unique identifier: NCT01363856.

Angiotensin II type 1 receptor antibodies and native kidney function in pediatric liver and intestinal transplant recipients

BACKGROUND

Angiotensin II type-1 receptor antibody (AT1R-Ab) has been associated with vascular injury and kidney dysfunction in pediatric kidney transplant recipients. The role of AT1R-Ab in the development of chronic kidney disease in pediatric liver and intestinal transplant recipients has not been explored.

METHODS

Twenty-five pediatric intestinal transplant recipients and 79 pediatric liver transplant recipients had AT1R-Ab levels measured at varying time points in the post-transplant period. Estimated glomerular filtration rate (eGFR) was determined using creatinine based CKiD U25 equation and measured at time of AT1R-Ab measurement, at 1 year post-AT1R-Ab measurement, at 5 years post-AT1R-Ab measurement, and at the most recent routine clinic visit. The prevalence of hypertension and antihypertensive medication use were also evaluated.

RESULTS

Younger age at time of AT1R-Ab measurement was associated with AT1R-Ab positivity in liver transplant recipients. There was no association between AT1R-Ab status and change in eGFR, prevalence of hypertension, or use of antihypertensive medications at the described time points.

CONCLUSIONS

AT1R-Ab positivity was not associated with a decline in eGFR or hypertension in pediatric liver and intestinal transplant recipients. Further studies are needed using other markers of kidney function, such as cystatin C, to validate this finding. A higher resolution version of the Graphical abstract is available as Supplementary information.

Impact of everolimus plus calcineurin inhibitor on formation of non-HLA antibodies and graft outcomes in kidney transplant recipients: 12-month results from the ATHENA substudy

Background

Non-human leukocyte antigen (non-HLA) antibodies including antibodies targeting Angiotensin II type 1 (AT1R) and Endothelin-1 type A (ETAR) receptors represent a topic of interest in kidney transplantation (KTx). This exploratory substudy evaluated the impact of everolimus (EVR) or mycophenolic acid (MPA) in combination with tacrolimus (TAC) or cyclosporine A (CsA) in patients with preformed non-HLA antibodies, potentially associated rejections and/or their impact on renal function over 1 year.

Methods

All eligible patients were randomized (1:1:1) before transplantation to receive either EVR/TAC, EVR/CsA, or MPA/TAC regimen. The effect of these regimens on the formation of non-HLA antibodies within one year post de novo KTx and the association with clinical events was evaluated descriptively in randomized (n = 268) population.

Results

At Month 12, in EVR/TAC group, higher incidence of patients negative for AT1R- and ETAR-antibodies (82.2% and 76.7%, respectively) was noted, whereas the incidence of AT1R- and ETAR-antibodies positivity (28.1% and 34.7%, respectively) was higher in the MPA/TAC group. Non-HLA antibodies had no influence on clinical outcomes in any treatment group and no graft loss or death was reported.

Conclusions

The studied combinations of immunosuppressants were safe with no influence on clinical outcomes and suggested minimal exposure of calcineurin inhibitors for better patient management.

Clinical Trial Registration

https://clinicaltrials.gov/ (NCT01843348; EudraCT number: 2011-005238-21).

Autoantibodies from patients with kidney allograft vasculopathy stimulate a proinflammatory switch in endothelial cells and monocytes mediated via GPCR-directed PAR1-TNF-α signaling

Non-HLA-directed regulatory autoantibodies (RABs) are known to target G-protein coupled receptors (GPCRs) and thereby contribute to kidney transplant vasculopathy and failure. However, the detailed underlying signaling mechanisms in human microvascular endothelial cells (HMECs) and immune cells need to be clarified in more detail. In this study, we compared the immune stimulatory effects and concomitant intracellular and extracellular signaling mechanisms of immunoglobulin G (IgG)-fractions from kidney transplant patients with allograft vasculopathy (KTx-IgG), to that from patients without vasculopathy, or matched healthy controls (Con-IgG). We found that KTx-IgG from patients with vasculopathy, but not KTx-IgG from patients without vasculopathy or Con-IgG, elicits HMEC activation and subsequent upregulation and secretion of tumor necrosis factor alpha (TNF-α) from HMECs, which was amplified in the presence of the protease-activated thrombin receptor 1 (PAR1) activator thrombin, but could be omitted by selectively blocking the PAR1 receptor. The amount and activity of the TNF-α secreted by HMECs stimulated with KTx-IgG from patients with vasculopathy was sufficient to induce subsequent THP-1 monocytic cell activation. Furthermore, AP-1/c-FOS, was identified as crucial transcription factor complex controlling the KTx-IgG-induced endothelial TNF-α synthesis, and mircoRNA-let-7f-5p as a regulatory element in modulating the underlying signaling cascade. In conclusion, exposure of HMECs to KTx-IgG from patients with allograft vasculopathy, but not KTx-IgG from patients without vasculopathy or healthy Con-IgG, triggers signaling through the PAR1-AP-1/c-FOS-miRNA-let7-axis, to control TNF-α gene transcription and TNF-α-induced monocyte activation. These observations offer a greater mechanistic understanding of endothelial cells and subsequent immune cell activation in the clinical setting of transplant vasculopathy that can eventually lead to transplant failure, irrespective of alloantigen-directed responses.

Chronic Fatigue and Dysautonomia following COVID-19 Vaccination Is Distinguished from Normal Vaccination Response by Altered Blood Markers

SARS-CoV-2 mRNA vaccination can entail chronic fatigue/dysautonomia tentatively termed post-acute COVID-19 vaccination syndrome (PACVS). We explored receptor autoantibodies and interleukin-6 (IL-6) as somatic correlates of PACVS. Blood markers determined before and six months after first-time SARS-CoV-2 vaccination of healthy controls (N = 89; 71 females; mean/median age: 39/49 years) were compared with corresponding values of PACVS-affected persons (N = 191; 159 females; mean/median age: 40/39 years) exhibiting chronic fatigue/dysautonomia (≥three symptoms for ≥five months after the last SARS-CoV-2 mRNA vaccination) not due to SARS-CoV-2 infection and/or confounding diseases/medications. Normal vaccination response encompassed decreases in 11 receptor antibodies (by 25-50%, p < 0.0001), increases in two receptor antibodies (by 15-25%, p < 0.0001) and normal IL-6. In PACVS, serological vaccination-response appeared significantly (p < 0.0001) altered, allowing discrimination from normal post-vaccination state (sensitivity = 90%, p < 0.0001) by increased Angiotensin II type 1 receptor antibodies (cut-off ≤ 10.7 U/mL, ROC-AUC = 0.824 ± 0.027), decreased alpha-2B adrenergic receptor antibodies (cut-off ≥ 25.2 U/mL, ROC-AUC = 0.828 ± 0.025) and increased IL-6 (cut-off ≤ 2.3 pg/mL, ROC-AUC = 0.850 ± 0.022). PACVS is thus indicated as a somatic syndrome delineated/detectable by diagnostic blood markers.

A bibliometric and knowledge-map analysis of antibody-mediated rejection in kidney transplantation

OBJECTIVES

Antibody-mediated rejection (AMR) is a large obstacle to the long-term survival of allograft kidneys. It is urgent to find novel strategies for its prevention and treatment. Bibliometric analysis is helpful in understanding the directions of one field. Hence, this study aims to analyze the state and emerging trends of AMR in kidney transplantation.

METHODS

Literature on AMR in kidney transplantation from 1999 to 2022 was collected from the Web of Science Core Collection. HistCite (version 12.03.17), CiteSpace (version 6.2.R2), Bibliometrix 4.1.0 Package from R language, and Gephi (https://gephi.org) were applied to the bibliometric analysis of the annual publications, leading countries/regions, core journals, references, keywords, and trend topics.

RESULTS

A total of 2522 articles related to AMR in kidney transplantation were included in the analysis and the annual publications increased year by year. There were 10874 authors from 118 institutions located in 70 countries/regions contributing to AMR studies, and the United States took the leading position in both articles and citation scores. Halloran PF from Canada made the most contribution to AMR in kidney transplantation. The top 3 productive journals, American Journal of Transplantation, Transplantation, and Transplantation Proceedings, were associated with transplantation. Moreover, the recent trend topics mainly focused on transplant outcomes, survival, and clinical research.

CONCLUSIONS

North American and European countries/regions played central roles in AMR of kidney transplantation. Importantly, the prognosis of AMR is the hotspot in the future. Noninvasive strategies like plasma and urine dd-cfDNA may be the most potential direction in the AMR field.

COVID-19, G protein-coupled receptor, and renin-angiotensin system autoantibodies: Systematic review and meta-analysis

INTRODUCTION

There are an increasing number of reports of autoantibodies (AAbs) against host proteins such as G-protein coupled receptors (GPCRs) and the renin-angiotensin system (RAS) in COVID-19 disease. Here we have undertaken a systematic review and meta-analysis of all reports of AAbs against GPCRs and RAS in COVID-19 patients including those with long-COVID or post-COVID symptoms.

METHODS

PubMed, Embase, Web of Science, and Scopus databases were searched to find papers on the role of GPCR and RAS AAbs in the presence and severity of COVID-19 or post- COVID symptoms available through March 21, 2023. Data on the prevalence of AngII or ACE, comparing AngII or ACE between COVID-19 and non-COVID-19, or comparing AngII or ACE between COVID-19 patients with different disease stages were pooled and a meta-analysed using random- or fixed-effects models were undertaken.

RESULTS

The search yielded a total of 1042 articles, of which 68 studies were included in this systematic review and nine in the meta-analysis. Among 18 studies that investigated GPCRs and COVID-19 severity, 18 distinct AAbs were detected. In addition, nine AAbs were found in case reports that assessed post- COVID, and 19 AAbs were found in other studies that assessed post- COVID or long- COVID symptoms. Meta-analysis revealed a significantly higher number of seropositive ACE2 AAbs in COVID-19 patients (odds ratio = 7.766 [2.056, 29.208], p = 0.002) and particularly in severe disease (odds ratio = 11.49 [1.04, 126.86], p = 0.046), whereas AngII-AAbs seropositivity was no different between COVID-19 and control subjects (odds ratio = 2.890 [0.546-15.283], p = 0.21).

CONCLUSIONS

GPCR and RAS AAbs may play an important role in COVID-19 severity, the development of disease progression, long-term symptoms COVID and post- COVID symptoms.

Autoantibodies against DNA topoisomerase I promote renal allograft rejection by increasing alloreactive T cell responses

Antibodies reactive to self-antigens are an important component of posttransplant immune responses. The generation requirements and functions of autoantibodies, as well as the mechanisms of their influence on alloimmune responses, still remain to be determined. Our study investigated the contribution of autoimmunity during rejection of renal allografts. We have previously characterized a mouse model in which the acute rejection of a life-supporting kidney allograft is mediated by antibodies. At rejection, recipient sera screening against >4000 potential autoantigens revealed DNA topoisomerase I peptide 205-219 (TI-I205-219) as the most prominent epitope. Subsequent analysis showed TI-I205-219-reactive autoantibodies are induced in nonsensitized recipients of major histocompatibility complex-mismatched kidney allografts in a T cell-dependent manner. Immunization with TI-I205-219 broke self-tolerance, elicited TI-I205-219 immunoglobin G autoantibodies, and resulted in acute rejection of allogeneic but not syngeneic renal transplants. The graft loss was associated with increased priming of donor-reactive T cells but not with donor-specific alloantibodies elevation. Similarly, passive transfer of anti-TI-I205-219 sera following transplantation increased donor-reactive T cell activation with minimal effects on donor-specific alloantibody levels. The results identify DNA topoisomerase I as a novel self-antigen in transplant settings and demonstrate that autoantibodies enhance activation of donor-reactive T cells following renal transplantation.

Functional autoantibodies: Definition, mechanisms, origin and contributions to autoimmune and non-autoimmune disorders

A growing body of evidence underscores the relevance of functional autoantibodies in the development of various pathogenic conditions but also in the regulation of homeostasis. However, the definition of functional autoantibodies varies among studies and a comprehensive overview on this emerging topic is missing. Here, we do not only explain functional autoantibodies but also summarize the mechanisms underlying the effect of such autoantibodies including receptor activation or blockade, induction of receptor internalization, neutralization of ligands or other soluble extracellular antigens, and disruption of protein-protein interactions. In addition, in this review article we discuss potential triggers of production of functional autoantibodies, including infections, immune deficiency and tumor development. Finally, we describe the contribution of functional autoantibodies to autoimmune diseases including autoimmune thyroid diseases, myasthenia gravis, autoimmune pulmonary alveolar proteinosis, autoimmune autonomic ganglionopathy, pure red cell aplasia, autoimmune encephalitis, pemphigus, acquired thrombotic thrombocytopenic purpura, idiopathic dilated cardiomyopathy and systemic sclerosis, as well as non-autoimmune disorders such as allograft rejection, infectious diseases and asthma.

Rejection markers in kidney transplantation: do new technologies help children?

Recent insights in allorecognition and graft rejection mechanisms revealed a more complex picture than originally considered, involving multiple pathways of both adaptive and innate immune response, supplied by efficient inflammatory synergies. Current pillars of transplant monitoring are serum creatinine, proteinuria, and drug blood levels, which are considered as traditional markers, due to consolidated experience, low cost, and widespread availability. The most diffuse immunological biomarkers are donor-specific antibodies, which are included in routine post-transplant monitoring in many centers, although with some reproducibility issues and interpretation difficulties. Confirmed abnormalities in these traditional biomarkers raise the suspicion for rejection and guide the indication for graft biopsy, which is still considered the gold standard for rejection monitoring. Rapidly evolving new "omic" technologies have led to the identification of several novel biomarkers, which may change the landscape of transplant monitoring should their potential be confirmed. Among them, urinary chemokines and measurement of cell-free DNA of donor origin are perhaps the most promising. However, at the moment, these approaches remain highly expensive and cost-prohibitive in most settings, with limited clinical applicability; approachable costs upon technology investments would speed their integration. In addition, transcriptomics, metabolomics, proteomics, and the study of blood and urinary extracellular vesicles have the potential for early identification of subclinical rejection with high sensitivity and specificity, good reproducibility, and for gaining predictive value in an affordable cost setting. In the near future, information derived from these new biomarkers is expected to integrate traditional tools in routine use, allowing identification of rejection prior to clinical manifestations and timely therapeutic intervention. This review will discuss traditional, novel, and invasive and non-invasive biomarkers, underlining their strengths, limitations, and present or future applications in children.

Antibodies against angiotensin II receptor type 1 and endothelin A receptor are increased in COVID-19 patients

Background

Increased titers of autoantibodies targeting the G-protein-coupled receptors angiotensin II type 1 receptor (AT1R) and endotelin-1 type A receptor (ETAR) are associated with severe coronavirus disease 2019 (COVID-19) infection. The aim of this study was to determine whether 1) these antibodies are specifically related to COVID-19 disease pathogenesis or increased during any severe respiratory illness, 2) if they are formed during illness, and 3) if they correlate with inflammatory markers or long-term symptoms.

Methods

Antibodies against AT1R, ETAR, and antinuclear antibodies (ANAs) were measured in n=40 prospectively enrolled COVID-19 patients and n=207 COVID-19 patients included in a biobank. Clinical and laboratory findings were prospectively and retrospectively assessed in both cohorts, and results were combined for analysis. The presence of auto-antibodies against AT1R or ETAR in peripheral blood was compared between hospitalized patients with COVID-19 and controls (n=39). Additionally, AT1R and ETAR titers were compared between patients with an unfavorable disease course, defined as intensive care admission and/or death during hospital admission (n=121), to those with a favorable disease course (n=126). A subset of intubated patients with severe COVID-19 were compared to intubated patients with acute respiratory distress syndrome (ARDS) due to any other cause.

Results

Significantly increased AT1R and ETAR antibody titers were found in COVID-19 patients compared to controls, while titers were equal between favorable and unfavorable COVID-19 disease course groups. On ICU, intubated patients with COVID-19 had significantly increased AT1R and ETAR titers compared to patients with ARDS due to any other cause. The titers did not correlate with baseline inflammatory markers during admission or with diffusion capacity, cognitive impairment, or fatigue measured at 3 months follow-up.

Conclusions

In patients hospitalized for COVID-19, antibodies against AT1R and ETAR are increased compared to controls and patients with ARDS due to other causes than COVID-19. The baseline antibody titers do not correlate with inflammatory markers or long-term symptoms in this study.

Association between anti-endothelial antigen antibodies and allograft rejection in kidney transplantation

BACKGROUND

Endothelial cells are vital in the transplant immune system as semiprofessional antigen-presenting cells. Few studies have investigated the importance of anti-endothelin subtype A receptor (ETAR) antibodies in kidney transplantation. Here, we aimed to analyze the association between anti-angiotensin II type I receptor (AT1R) and anti-ETAR antibodies and the association between the presence of anti-endothelial antibodies and the risk of allograft rejection in kidney transplantation.

METHODS

In total, 252 patients who underwent kidney transplantation were enrolled in this study. Antibodies for human leukocyte antigens (HLAs) and non-HLAs were analyzed immediately before transplantation. Patients were categorized based on the occurrence of antibody-mediated rejection (AMR) or T-cell-mediated rejection (TCMR) by 2017 Banff classification. All p-values were two-tailed, and statistical significance was set at p < 0.05.

RESULTS

Patients with anti-AT1R antibodies had a 3.49-fold higher risk of TCMR than those without anti-AT1R antibodies. Patients with anti-ETAR antibodies had a 5.84-fold higher risk of AMR than those without anti-ETAR antibodies. The hazard ratio of AMR in patients with both HLA DSAs and anti-ETAR antibodies, relative to patients without anti-ETAR antibodies and HLA DSAs, was 32.85 (95% CI = 1.82-592.91).

CONCLUSION

Our findings indicated that anti-ETAR antibodies are associated with AMR, and patients with both anti-ETAR antibodies and de novo HLA DSAs were at a high risk of AMR.

Kidney Allograft Monitoring by Combining Donor-Derived Cell-Free DNA and Molecular Gene Expression: A Clinical Management Perspective

Donor-derived cell-free DNA (dd-cfDNA) may safely assess kidney allograft rejection. Molecular Microscope (MMDx®) gene expression may offer increased precision to histology. This single-center retrospective study monitored kidney transplant recipients for rejection at specified time intervals by utilizing creatinine (SCr), proteinuria, donor-specific antibodies (DSAs), and dd-cfDNA. A clinically indicated biopsy sample was sent for histopathology and MMDx®. Patients were categorized into rejection (Rej) and non-rejection (NRej) groups, and further grouped according to antibody-mediated rejection (ABMR) subtypes. Rej and NRej groups included 52 and 37 biopsies, respectively. Median follow-up duration was 506 days. DSAs were positive in 53% and 22% of patients in both groups, respectively (p = 0.01). Among these groups, pre- and post-intervention median SCr, proteinuria, and dd-cfDNA at 1 month, 2 months, and at the last follow-up revealed significant difference for dd-cfDNA (all p = 0.01), however, no difference was found for SCr and proteinuria (p > 0.05). The AUC was 0.80 (95% CI: 0.69-0.91), with an optimal dd-cfDNA criterion of 2.2%. Compared to histology, MMDx® was more likely to diagnose ABMR (79% vs. 100%) with either C4d positivity or negativity and/or DSA positivity or negativity. Hence, a pre- and post-intervention allograft monitoring protocol in combination with dd-cfDNA, MMDx®, and histology has aided in early diagnosis and timely individualized intervention.

Current Therapies in Kidney Transplant Rejection

Despite significant advancements in immunosuppressive therapies, kidney transplant rejection continues to pose a substantial challenge, impacting the long-term survival of grafts. This article provides an overview of the diagnosis, current therapies, and management strategies for acute T-cell-mediated rejection (TCMR) and antibody-mediated rejection (ABMR). TCMR is diagnosed through histological examination of kidney biopsy samples, which reveal the infiltration of mononuclear cells into the allograft tissue. Corticosteroids serve as the primary treatment for TCMR, while severe or steroid-resistant cases may require T-cell-depleting agents, like Thymoglobulin. ABMR occurs due to the binding of antibodies to graft endothelial cells. The most common treatment for ABMR is plasmapheresis, although its efficacy is still a subject of debate. Other current therapies, such as intravenous immunoglobulins, anti-CD20 antibodies, complement inhibitors, and proteasome inhibitors, are also utilized to varying degrees, but their efficacy remains questionable. Management decisions for ABMR depend on the timing of the rejection episode and the presence of chronic changes. In managing both TCMR and ABMR, it is crucial to optimize immunosuppression and address adherence. However, further research is needed to explore newer therapeutics and evaluate their efficacy.

The Clinical Utility of Post-Transplant Monitoring of Donor-Specific Antibodies in Stable Renal Transplant Recipients: A Consensus Report With Guideline Statements for Clinical Practice

Solid phase immunoassays improved the detection and determination of the antigen-specificity of donor-specific antibodies (DSA) to human leukocyte antigens (HLA). The widespread use of SPI in kidney transplantation also introduced new clinical dilemmas, such as whether patients should be monitored for DSA pre- or post-transplantation. Pretransplant screening through SPI has become standard practice and DSA are readily determined in case of suspected rejection. However, DSA monitoring in recipients with stable graft function has not been universally established as standard of care. This may be related to uncertainty regarding the clinical utility of DSA monitoring as a screening tool. This consensus report aims to appraise the clinical utility of DSA monitoring in recipients without overt signs of graft dysfunction, using the Wilson & Junger criteria for assessing the validity of a screening practice. To assess the evidence on DSA monitoring, the European Society for Organ Transplantation (ESOT) convened a dedicated workgroup, comprised of experts in transplantation nephrology and immunology, to review relevant literature. Guidelines and statements were developed during a consensus conference by Delphi methodology that took place in person in November 2022 in Prague. The findings and recommendations of the workgroup on subclinical DSA monitoring are presented in this article.

Immune surveillance and humoral immune responses in kidney transplantation - A look back at T follicular helper cells

T follicular helper cells comprise a specialized, heterogeneous subset of immune-competent T helper cells capable of influencing B cell responses in lymphoid tissues. In physiology, for example in response to microbial challenges or vaccination, this interaction chiefly results in the production of protecting antibodies and humoral memory. In the context of kidney transplantation, however, immune surveillance provided by T follicular helper cells can take a life of its own despite matching of human leukocyte antigens and employing the latest immunosuppressive regiments. This puts kidney transplant recipients at risk of subclinical and clinical rejection episodes with a potential risk for allograft loss. In this review, the current understanding of immune surveillance provided by T follicular helper cells is briefly described in physiological responses to contrast those pathological responses observed after kidney transplantation. Sensitization of T follicular helper cells with the subsequent emergence of detectable donor-specific human leukocyte antigen antibodies, non-human leukocyte antigen antibodies their implication for kidney transplantation and lessons learnt from other transplantation "settings" with special attention to antibody-mediated rejection will be addressed.

Natural Antibodies Are Associated With Rejection and Long-term Renal Allograft Loss in a Multicenter International Cohort

BACKGROUND

Potentially harmful nonhuman leukocyte antigen antibodies have been identified in renal transplantation, including natural immunoglobulin G antibodies (Nabs) reactive to varied antigenic structures, including apoptotic cells.

METHODS

In this retrospective, multicenter study, we assessed Nabs by reactivity to apoptotic cells in sera collected from 980 kidney transplant recipients across 4 centers to determine their association with graft outcomes.

RESULTS

Elevated pretransplant Nabs were associated with graft loss (hazard ratio [HR] 2.71; 95% confidence interval [CI], 1.15-6.39; P   =  0.0232), the composite endpoint of graft loss or severe graft dysfunction (HR 2.40; 95% CI, 1.13-5.10; P  = 0.0232), and T cell-mediated rejection (odds ratio [OR] 1.77; 95% CI, 1.07-3.02; P  = 0.0310). High pretransplant Nabs together with donor-specific antibodies (DSAs) were associated with increased risk of composite outcomes (HR 6.31; 95% CI, 1.81-22.0; P  = 0.0039). In patients with high pretransplant Nabs, the subsequent development of posttransplant Nabs was associated with both T cell-mediated rejection (OR 3.64; 95% CI, 1.61-8.36; P  = 0.0021) and mixed rejection (OR 3.10; 95% CI, 1.02-9.75; P  = 0.0473). Finally, elevated pre- and posttransplant Nabs combined with DSAs were associated with increased risk of composite outcomes (HR 3.97; 95% CI, 1.51-10.43; P  = 0.0052) and T cell-mediated rejection (OR 7.28; 95% CI, 2.16-25.96; P  = 0.0016).

CONCLUSIONS

The presence of pre- and posttransplant Nabs, together with DSAs, was associated with increased risk of poor graft outcomes and rejection after renal transplantation.

Vascular and Non-HLA autoantibody profiles in hospitalized patients with COVID-19

Introduction

Severe COVID-19 illness is characterized by an overwhelming immune hyperactivation. Autoantibodies against vascular, tissue, and cytokine antigens have been detected across the spectrum of COVID-19. How these autoantibodies correlate with COVID-19 severity is not fully defined.

Methods

We performed an exploratory study to investigate the expression of vascular and non-HLA autoantibodies in 110 hospitalized patients with COVID-19 ranging from moderate to critically ill. Relationships between autoantibodies and COVID- 19 severity and clinical risk factors were examined using logistic regression analysis.

Results

There were no absolute differences in levels of expression of autoantibodies against angiotensin II receptor type 1 (AT1R) or endothelial cell proteins between COVID-19 severity groups. AT1R autoantibody expression also did not differ by age, sex, or diabetes status. Using a multiplex panel of 60 non- HLA autoantigens we did identify seven autoantibodies that differed by COVID-19 severity including myosin (myosin; p=0.02), SHC-transforming protein 3 (shc3; p=0.07), peroxisome proliferator-activated receptor gamma coactivator 1-beta (perc; p=0.05), glial-cell derived neurotrophic factor (gdnf; p=0.07), enolase 1 (eno1; p=0.08), latrophilin-1 (lphn1; p=0.08), and collagen VI (coll6; p=0.05) with greater breadth and higher expression levels seen in less severe COVID-19.

Discussion

Overall, we found that patients hospitalized with COVID-19 demonstrate evidence of auto-reactive antibodies targeting endothelial cells, angiotensin II receptors, and numerous structural proteins including collagens. Phenotypic severity did not correlate with specific autoantibodies. This exploratory study underscores the importance of better understanding of the role of autoimmunity in COVID-19 disease and sequelae.

When natural antibodies become pathogenic: autoantibodies targeted against G protein-coupled receptors in the pathogenesis of systemic sclerosis

Systemic sclerosis (SSc) is a chronic, multisystem connective tissue, and autoimmune disease with the highest case-specific mortality and complications among rheumatic diseases. It is characterized by complex and variable features such as autoimmunity and inflammation, vasculopathy, and fibrosis, which pose challenges in understanding the pathogenesis of the disease. Among the large variety of autoantibodies (Abs) present in the sera of patients suffering from SSc, functionally active Abs against G protein-coupled receptors (GPCRs), the most abundant integral membrane proteins, have drawn much attention over the last decades. These Abs play an essential role in regulating the immune system, and their functions are dysregulated in diverse pathological conditions. Emerging evidence indicates that functional Abs targeting GPCRs, such as angiotensin II type 1 receptor (AT1R) and the endothelin-1 type A receptor (ETAR), are altered in SSc. These Abs are part of a network with several GPCR Abs, such as those directed to the chemokine receptors or coagulative thrombin receptors. In this review, we summarize the effects of Abs against GPCRs in SSc pathologies. Extending the knowledge on pathophysiological roles of Abs against GPCRs could provide insights into a better understanding of GPCR contribution to SSc pathogenesis and therefore help in developing potential therapeutic strategies that intervene with pathological functions of these receptors.

Angiotensin II Type 1 Receptor Antibody-Mediated Kidney Rejection Unresponsive to Treatment

Allograft rejection is a significant cause of renal transplant failure which needs prompt diagnosis and treatment for graft salvage. Angiotensin II type 1 receptor antibody-mediated rejection (AT1R-AMR) is increasingly being identified as the etiology of antibody-mediated rejection in kidney transplant recipients with allograft rejection but without detectable human leukocyte antigen (HLA) antibodies. While some reports have suggested that AT1R-AMR may be refractory to standard therapy, others have reported improvement or stabilization of graft function. We present two patients in which anti-rejection therapy including therapeutic plasma exchange was unable to salvage the allograft.

Case Report: Suspected Hyperacute Rejection During Living Kidney Transplantation

BACKGROUND

We report a case of suspected hyperacute rejection during living kidney transplantation.

CASE REPORT

A 61-year-old man underwent kidney transplantation in November 2019. Before the transplantation, immunologic tests revealed the presence of anti-HLA antibodies but not donor-specific HLA antibodies. The patient was intravenously administered 500 mg of methylprednisolone (MP) and basiliximab before perioperative blood flow reperfusion. After blood flow restoration, the transplanted kidney turned bright red and then blue. Hyperacute rejection was suspected. After the intravenous administration of 500 mg of MP and 30 g of intravenous immunoglobulin, the transplanted kidney gradually changed from blue to bright red. The initial postoperative urine output was good. On the 22nd day after the renal transplantation, the patient was discharged with a serum creatinine level of 2.38 mg/dL, and the function of the transplanted kidney gradually improved.

CONCLUSIONS

In this study, non-HLA antibodies may have been a cause of the hyperacute rejection, which was managed with additional perioperative therapies.

The Influence of Antibodies against Angiotensin II Type-1 Receptor on the Outcome of Kidney Transplantation: A Single-Center Retrospective Study

Allo- and autoimmune mechanisms are involved in kidney allograft rejection and loss. This study investigates the impact of anti-angiotensin II type-1 receptor antibodies (anti-AT1RAbs) detected alone or in association with HLA donor-specific antibodies (HLA-DSAs) on the outcome of kidney transplantation (KTx). Anti-AT1RAbs and HLA-DSAs were detected in 71 kidney transplant (KT) recipients who developed biopsy-proven acute or chronic active T-cell rejection (TCMR) (n = 51) or antibody-mediated rejection (ABMR) (n = 20), forming the rejection group (RG). The control group (CG) included 71 KTx recipients with comparable characteristics without rejection. All patients had been transplanted with negative T/B flow crossmatch (T/BFCXM). The median follow-up period was 3.7 years. Antibodies were determined pre- and periodically post-KTx by Luminex method for HLA-DSAs and enzyme-linked immunosorbent assay for anti-AT1RAbs. Before KTx, twenty-three (32.4%) patients in the RG, sixteen with TCMR and seven with ABMR, were found anti-AT1Rabs-positive (≥10 U/mL) versus eleven (15.5%) patients in the CG (p = 0.031). Simultaneous detection of preformed anti-AT1RAbs and HLA-DSAs was found in five patients of the RG versus two of the CG (p = 0.355). At the time of transplant biopsy, fifteen (21.1%) patients, four with ABMR and eleven with TCMR, were positive for anti-AT1RAbs. Anti-AT1RAbs and HLA-DSAs were detected simultaneously in 7/15 (46.7%) cases, three with ABMR and four with TCMR. During the follow-up, thirteen (18.3%) patients in the RG, eight with ABMR and five with TCMR, lost their graft compared to one patient (1.4%) in the CG (p = 0.001). Six out of thirteen (46.2%) RG patients who lost the graft were found positive for anti-AT1RAbs pretransplant. Patient survival with functioning graft did not differ significantly between anti-AT1Rabs-positive and negative KT recipients (log-rank p = 0.88). Simultaneous detection of anti-ATR1Abs and HLA-DSAs did not have a significant influence on patient survival with functioning graft (log-rank p = 0.96). Graft function at the end of the follow-up was better, but not significantly, in anti-AT1Rabs-negative patients, with serum creatinine 1.48 [1.20-1.98] mg/dL and eGFR (CKD-EPI) 48.5 [33.5-59.0] mL/min/1.73 m², compared to anti-AT1Rabs-positive ones who had serum creatinine 1.65 [1.24-2.02] mg/dL (p = 0.394) and eGFR (CKD-EPI) 47.0 [34.8-60.3] mL/min/1.73 m² (p = 0.966). Anti-AT1RAbs detection pretransplant characterizes KT recipients at increased risk of cellular or antibody-mediated rejection. Furthermore, anti-AT1RAbs, detected alone or simultaneously with HLA-DSAs, appear to be associated with impaired graft function, but their role in graft survival has not been documented in this study. Screening for these antibodies appears to complement pretransplant immunological risk assessment.

Endothelial Injury Syndromes after Allogeneic Hematopoietic Stem Cell Transplantation: Angiopetin-2 as a Novel Predictor of the Outcome and the Role of Functional Autoantibodies against Angiotensin II Type 1 and Endothelin A Receptor

Transplant-associated thrombotic microangiopathy (TMA) occurs in a significant percentage of patients after allogeneic stem cell transplantation (allo-SCT) and is associated with significant morbidity and mortality. The aim of the present study was to examine the association of serum angiopoetin-2 (Ang2) levels and the presence of antibodies against angiotensin II type 1 (AT1R) and ndothelin A Recreptor (ETAR) with the outcome of patients with TMA and/or graft-versus-host disease (GVHD) after allo-SCT. Analysis of our data showed that elevated serum Ang2 levels at the time of TMA diagnosis are significantly associated with increased non-relapse mortality and decreased overall survival. To our knowledge, this is the first study demonstrating an association between raised Ang2 levels and poor outcomes in patients with TMA. Antibodies against AT1R (AT1R-Abs) and ETAR (ETAR-Abs) were detected in 27% and 23% of the patients, respectively, but there was no association between the presence of autoantibodies and the outcome of patients with TMA. However, a significant finding was the strong positive correlation between the presence of AT1R-Abs with the occurrence of chronic fibrotic GVHD, such as scleroderma and cryptogenic organizing pneumonia, raising the possibility of the contribution of autoantibodies in the pathogenesis of fibrotic GVHD manifestations.

On a Long and Winding Road: Alloantibodies in Organ Transplantation

Today we know that both the humoral and the cellular arm of the immune system are engaged in severe immunological challenges. A close interaction between B and T cells can be observed in most "natural" challenges, including infections, malignancies, and autoimmune diseases. The importance and power of humoral immunity are impressively demonstrated by the current coronavirus disease 2019 pandemic. Organ transplant rejection is a normal immune response to a completely "artificial" challenge. It took a long time before the multifaceted action of different immunological forces was recognized and a unified, generally accepted opinion could be formed. Here, we address prominent paradigms and paradigm shifts in the field of transplantation immunology. We identify several instances in which the transplant community missed a timely paradigm shift because essential, available knowledge was ignored. Moreover, we discuss key findings that critically contributed to our understanding of transplant immunology but sometimes developed with delay and in a roundabout way, as was the case with antibody-mediated rejection-a main focus of this article. These include the discovery of the molecular principles of histocompatibility, the recognition of the microcirculation as a key interface of immune damage, the refinement of alloantibody detection, the description of C4d as a footmark of endothelium-bound antibody, and last but not least, the developments in biopsy-based diagnostics beyond conventional morphology, which only now give us a glimpse of the enormous complexity and pathogenetic diversity of rejection.

Nailfold Videocapillaroscopy for Non-Invasive Assessment of Microcirculation and Prognostic Correlation with Endothelial Dysfunction, Cardiovascular Risk Factors, and Non-HLA Antibodies in Heart Transplant Recipients: A Pilot Study

Early identification of allograft vasculopathy and the concomitant elimination of adverse risk factors is essential for improving the long-term prognosis of heart transplant (HTx) recipients with underlying cardiovascular disease (CVD). The major aim of this pilot study was to conduct a non-invasive imaging evaluation of the HTx patient microcirculation by employing nailfold video-capillaroscopy (NVC) in a well-characterized patient and control cohort, and to correlate these data with endothelial cell function, accompanied by studies of traditional cardiovascular risk factors and non-HLA antibodies in HTx recipients. Ten patients undergoing HTx (mean age of 38 ± 14 years) were recruited for the study and compared to a control group of 12 well-matched healthy volunteers (mean age 35 ± 5 years) with normal body mass index (BMI). Detailed medical records were collected from all individuals. NVC was performed using CapillaryScope 200 MEDL4N microscope. For functional readout and correlation analysis, endothelial cell network formation in conjunction with measurements of patient serum levels of vascular endothelial growth factor (VEGF) and non-HLA autoantibodies directed against the angiotensin II type-1-receptor (anti-AT1R-Ab), endothelin-1 type-A-receptor (anti-ETAR-Ab), protease-activated receptor-1 (anti-PAR-1-Ab), and VEGF-A (anti-VEGF-A-Ab) were studied. Our NVC analysis found that the average apical loop diameter of nailfold capillaries was significantly increased in HTx recipients (p = 0.001). In addition, HTx patients with more prominent changes in capillaroscopic patterns were characterized by the presence of traditional cardiovascular risk factors, and HTx patients had increased levels of anti-AT1R-ab, anti-ETAR-ab, and anti-VEGF-A-Ab (p = 0.017, p = 0.025, and p = 0.003, respectively). Capillary diameters most strongly correlated with elevated serum levels of troponin T and triglycerides (R = 0.69, p = 0.028 and R = 0.81, p = 0.004, respectively). In conclusion, we found that an abnormal NVC pattern in HTx patients is associated with traditional CVD risk factors and that NVC is a useful non-invasive tool to conveniently monitor changes in the microvasculature of HTx patients.

Autoantibodies targeting G protein-coupled receptors: An evolving history in autoimmunity. Report of the 4th international symposium

G protein-coupled receptors (GPCR) are involved in various physiological and pathophysiological processes. Functional autoantibodies targeting GPCRs have been associated with multiple disease manifestations in this context. Here we summarize and discuss the relevant findings and concepts presented in the biennial International Meeting on autoantibodies targeting GPCRs (the 4th Symposium), held in Lübeck, Germany, 15-16 September 2022. The symposium focused on the current knowledge of these autoantibodies' role in various diseases, such as cardiovascular, renal, infectious (COVID-19), and autoimmune diseases (e.g., systemic sclerosis and systemic lupus erythematosus). Beyond their association with disease phenotypes, intense research related to the mechanistic action of these autoantibodies on immune regulation and pathogenesis has been developed, underscoring the role of autoantibodies targeting GPCRs on disease outcomes and etiopathogenesis. The observation repeatedly highlighted that autoantibodies targeting GPCRs could also be present in healthy individuals, suggesting that anti-GPCR autoantibodies play a physiologic role in modeling the course of diseases. Since numerous therapies targeting GPCRs have been developed, including small molecules and monoclonal antibodies designed for treating cancer, infections, metabolic disorders, or inflammatory conditions, anti-GPCR autoantibodies themselves can serve as therapeutic targets to reduce patients' morbidity and mortality, representing a new area for the development of novel therapeutic interventions.

Association of MICA and AT1R antibodies with antibody-mediated rejection and cardiac allograft vasculopathy in a pediatric heart transplant recipient

BACKGROUND

Recipient antibodies against mismatched donor-specific human leukocyte antigens (HLA) are known to be associated with antibody-mediated rejection (AMR), posing increased risks of cardiac allograft vasculopathy (CAV), graft dysfunction, and graft loss after heart transplant (HTx). However, the impact of non-HLA antibodies on HTx outcome is not yet well defined.

CASE DESCRIPTION

Here we report a case of a pediatric patient, who was retransplanted after developing CAV in his first heart allograft. Five years post 2nd HTx, the patient presented with graft dysfunction and mild rejection (ACR 1R, AMR 1H, C4d Neg) in the cardiac biopsy in the absence of HLA donor-specific antibodies (DSAs). We detected strong antibodies against non-HLA antigens, including angiotensin II receptor type 1 (AT1R) and donor-specific MHC class I chain-related gene A (MICA), in the patient's serum that were implicated in the AMR and accelerated CAV of his second allograft, and likely played a role in the loss of his first allograft as well.

CONCLUSION

This case report underscores the clinical relevance of non-HLA antibodies in heart transplantation and highlights the value of incorporating these tests in the immunological risk assessment and post-transplant monitoring of HTx recipients.

Loss of anti-AT1R reactivity in ELISA post-adsorption - False reactivity or interference in the assay?

Autoantibodies to Angiotensin II type 1 receptor (AT1R) are associated with detrimental outcomes in organ transplants. However, reports showed that adsorption with latex beads reduced positive anti-AT1R antibodies, suggesting possible false reactivity. To investigate this conundrum, we studied 11 samples positive for AT1R antibodies with an ELISA kit before and after adsorption. Adsorption significantly reduced the measurable level of AT1R antibodies (28.3 ± 9.8 vs. 6.3 ± 3.0 U/ml, p < 0.001). AT1R antibodies were lower when post-adsorption serum was added back at 1:1 ratio to the neat serum compared to the diluent control (8.6 ± 4.2 vs. 18.1 ± 10.3 U/ml, p = 0.02). Sham adsorption with the buffer from Adsorb Out™ kit without beads also suppressed the detection of anti-AT1R antibodies (32.7 ± 9.1 vs. 8.1 ± 3.9 U/ml, p < 0.001). Thus, rather than actively removing nonspecific antibodies by the beads, the adsorption process introduces soluble factors that interfere with the detection of anti-AT1R antibodies with the ELISA kit.

Rejection and graft outcomes in kidney transplant recipients with and without angiotensin II receptor type 1 antibodies

AIM

Angiotensin II type 1 receptor antibody (AT1R Ab) is a non-Human Leucocyte Antigen (HLA) antibody that is maybe associated with early severe kidney transplant rejection and worse graft outcomes. This study aimed to assess the association between AT1R Ab and kidney transplant rejection and graft outcomes.

METHODS

We performed a retrospective analysis of all adult kidney transplant recipients in an Australian centre who had an AT1R Ab test between 1 January 2015 to 30 June 2020. AT1R Ab positive patients were compared to AT1R Ab negative patients. Primary outcomes were rejection risk, type and histopathological severity scores. Secondary outcomes were 8-week graft function and graft loss.

RESULTS

Of 965 kidney transplants that were performed during the study period, 73 patients had AT1R Ab tested; 16 (22%) were positive and 57(78%) were negative. Positive patients were on average younger and had higher level of donor-specific HLA antibodies. Rejection occurred in 13 (81%) positive patients and 41 (72%) negative patients (P = 0.45). No significant differences in rejection type or severity were found. HLA mismatch and peak panel reactive antibody ≥80%, but not AT1R Ab, independently predicted rejection. Average (132 vs. 177 mmol/L, P = 0.302) and graft loss were not significantly different between groups.

CONCLUSION

The study found no evidence that AT1R Ab is associated with rejection type, severity or worse graft function. Future studies should assess its relationship with graft outcomes to help complement immunological risk assessment and potentially provide therapeutic options to alter outcomes.

AT1 receptor autoantibodies mediate effects of metabolic syndrome on dopaminergic vulnerability

The metabolic syndrome has been associated to chronic peripheral inflammation and related with neuroinflammation and neurodegeneration, including Parkinson's disease. However, the responsible mechanisms are unclear. Previous studies have involved the brain renin-angiotensin system in progression of Parkinson's disease and the angiotensin receptor type 1 (AT1) has been recently revealed as a major marker of dopaminergic vulnerability in humans. Dysregulation of tissue renin-angiotensin system is a key common mechanism for all major components of metabolic syndrome. Circulating AT1 agonistic autoantibodies have been observed in several inflammation-related peripheral processes, and activation of AT1 receptors of endothelial cells, dopaminergic neurons and glial cells have been observed to disrupt endothelial blood -brain barrier and induce neurodegeneration, respectively. Using a rat model, we observed that metabolic syndrome induces overactivity of nigral pro-inflammatory renin-angiotensin system axis, leading to increase in oxidative stress and neuroinflammation and enhancing dopaminergic neurodegeneration, which was inhibited by treatment with AT1 receptor blockers (ARBs). In rats, metabolic syndrome induced the increase in circulating levels of LIGHT and other major pro-inflammatory cytokines, and 27-hydroxycholesterol. Furthermore, the rats showed a significant increase in serum levels of proinflammatory AT1 and angiotensin converting enzyme 2 (ACE2) autoantibodies, which correlated with levels of several metabolic syndrome parameters. We also found AT1 and ACE2 autoantibodies in the CSF of these rats. Effects of circulating autoantibodies were confirmed by chronic infusion of AT1 autoantibodies, which induced blood-brain barrier disruption, an increase in the pro-inflammatory renin-angiotensin system activity in the substantia nigra and a significant enhancement in dopaminergic neuron death in two different rat models of Parkinson's disease. Observations in the rat models, were analyzed in a cohort of parkinsonian and non-parkinsonian patients with or without metabolic syndrome. Non-parkinsonian patients with metabolic syndrome showed significantly higher levels of AT1 autoantibodies than non-parkinsonian patients without metabolic syndrome. However, there was no significant difference between parkinsonian patients with metabolic syndrome or without metabolic syndrome, which showed higher levels of AT1 autoantibodies than non-parkinsonian controls. This is consistent with our recent studies, showing significant increase of AT1 and ACE2 autoantibodies in parkinsonian patients, which was related to dopaminergic degeneration and neuroinflammation. Altogether may lead to a vicious circle enhancing the progression of the disease that may be inhibited by strategies against production of these autoantibodies or AT1 receptor blockers (ARBs).

New immune horizons in therapeutics and diagnostic approaches to Preeclampsia

Hypertensive disorders of pregnancy (HDP) are one of the commonest maladies, affecting 5%-10% of pregnancies worldwide. The American College of Obstetricians and Gynecologists (ACOG) identifies four categories of HDP, namely gestational hypertension (GH), Preeclampsia (PE), chronic hypertension (CH), and CH with superimposed PE. PE is a multisystem, heterogeneous disorder that encompasses 2%-8% of all pregnancy-related complications, contributing to about 9% to 26% of maternal deaths in low-income countries and 16% in high-income countries. These translate to 50 000 maternal deaths and over 500 000 fetal deaths worldwide, therefore demanding high priority in understanding clinical presentation, screening, diagnostic criteria, and effective management. PE is accompanied by uteroplacental insufficiency leading to vascular and metabolic changes, vasoconstriction, and end-organ ischemia. PE is diagnosed after 20 weeks of pregnancy in women who were previously normotensive or hypertensive. Besides shallow trophoblast invasion and inadequate remodeling of uterine arteries, dysregulation of the nonimmune system has been the focal point in PE. This results from aberrant immune system activation and imbalanced differentiation of T cells. Further, a failure of tolerance toward the semi-allogenic fetus results due to altered distribution of Tregs such as CD4+FoxP3+ or CD4+CD25+CD127(low) FoxP3+ cells, thereby creating a cytotoxic environment by suboptimal production of immunosuppressive cytokines like IL-10, IL-4, and IL-13. Also, intracellular production of complement protein C5a may result in decreased FoxP3+ regulatory T cells. With immune system dysfunction as a major driver in PE pathogenesis, it is logical that therapeutic targeting of components of the immune system with pharmacologic agents like anti-inflammatory and immune-modulating molecules are either being used or under clinical trial. Cholesterol synthesis inhibitors like Pravastatin may improve placental perfusion in PE, while Eculizumab (monoclonal antibody inhibiting C5) and small molecular inhibitor of C5a, Zilucoplan are under investigation. Monoclonal antibody against IL-17(Secukinumab) has been proposed to alter the Th imbalance in PE. Autologous Treg therapy and immune checkpoint inhibitors like anti-CTLA-4 are emerging as new candidates in immune horizons for PE management in the future.

Double Pretransplant Positivity for Autoantibodies to LG3 and Angiotensin II Type 1 Receptor Is Associated With Alloimmune Vascular Injury in Kidney Transplant Recipients

Both angiotensin II receptor autoantibodies (ATRabs) and autoantibodies to LG3 have been linked to kidney graft rejection with alloimmune vascular injury (AVI). We aimed to examine whether positivity for both anti-LG3 and ATRabs is associated with rejection with AVI in kidney transplant recipients.

Methods

We performed a retrospective cohort study including consecutive kidney transplant recipients between 2013 and 2017 at a single center. The primary outcome was acute rejection with AVI (Banff grade 2 or 3 T-cell-mediated rejection and/or antibody-mediated rejection) in the first 3 mo posttransplant. The secondary outcome was death-censored allograft loss. The independent variables, anti-LG3 and ATRab, were measured pretransplant.

Results

Among the 328 study participants, 68 experienced acute rejection with AVI and 23 experienced graft loss over a median follow-up of 4.5 y. In a multivariable model, double pretransplant positivity for anti-LG3/ATRab was associated with acute rejection with AVI (odds ratio: 2.73, 95% confidence interval: 1.06-7.05). We did not observe an association between double positivity for anti-LG3/ATRab and death-censored graft loss.

Conclusions

Double positivity for anti-LG3/ATRabs pretransplant is associated with a higher risk of acute rejection with AVI. Whether therapies that remove antibodies could decrease that risk remains to be studied.Supplemental Visual Abtract: http://links.lww.com/TXD/A494.

Alloimmune risk assessment for antibody-mediated rejection in kidney transplantation: A practical proposal

Kidney transplantation is the treatment of choice for patients with end-stage renal disease. Although an improvement in graft survival has been observed in the last decades with the use of different immunosuppressive drugs, this is still limited in time with antibody-mediated rejection being a main cause of graft-loss. Immune monitoring and risk assessment of antibody-mediated rejection before and after kidney transplantation with useful biomarkers is key to tailoring treatments to achieve the best outcomes. Here, we provide a review of the rationale and several accessible tools for immune monitoring, from the most classic to the modern ones. Finally, we end up discussing a practical proposal for alloimmune risk assessment in kidney transplantation, including histocompatibility leukocyte antigen (HLA) and non-HLA antibodies, HLA molecular mismatch analysis and characterization of peripheral blood immune cells.

Autoimmune autonomic nervous system imbalance and conditions: Chronic fatigue syndrome, fibromyalgia, silicone breast implants, COVID and post-COVID syndrome, sick building syndrome, post-orthostatic tachycardia syndrome, autoimmune diseases and autoimmune/inflammatory syndrome induced by adjuvants

Chronic fatigue syndrome (CFS), fibromyalgia, silicone breast implants syndrome (SBIs), COVID and post-COVID syndrome (PCS), sick building syndrome (SBS), post-orthostatic tachycardia syndrome (POTS), autoimmune diseases and autoimmune/inflammatory syndrome induced by adjuvants (ASIA) are frequently accompanied by clinical symptoms characteristic for dysautonomia: severe fatigue, dizziness, fogginess, memory loss, dry mouth and eyes, hearing dysfunction, tachycardia etc. The recent discovery of an imbalance of autoantibodies against G protein-coupled receptors (GPCR) in some autoimmune diseases, post-COVID syndrome, SBIs allowed researchers to assume the novel mechanism in these conditions - autoimmune autonomic nervous system imbalance. In this review, all data published on an imbalance of autoantibodies against GPCR, clinical symptoms and pathogenic mechanisms in CFS, Fibromyalgia, SBIs, COVID and PCS, SBS, POTS, and some autoimmune diseases were analyzed. Possible criteria to diagnose the autoimmune autonomic nervous system imbalance were created.

Sensitization in transplantation: Assessment of Risk 2022 Working Group Meeting Report

The Sensitization in Transplantation: Assessment of Risk workgroup is a collaborative effort of the American Society of Transplantation and the American Society of Histocompatibility and Immunogenetics that aims at providing recommendations for clinical testing, highlights gaps in current knowledge, and proposes areas for further research to enhance histocompatibility testing in support of solid organ transplantation. This report provides updates on topics discussed by the previous Sensitization in Transplantation: Assessment of Risk working groups and introduces 2 areas of exploration: non-human leukocyte antigen antibodies and utilization of human leukocyte antigen antibody testing measurement to evaluate the efficacy of antibody-removal therapies.

Unraveling complexity of antibody-mediated rejections, the mandatory way towards an accurate diagnosis and a personalized treatment

Antibody-mediated rejection (ABMR) remains one of the most challenging issues after organ transplantation and particularly after kidney transplantation. Despite many progresses during the last decade, ABMR is still the main cause of kidney graft loss and this all over the post- transplant period. In this review, we describe the recent knowledge about molecular and cellular mechanisms involved in ABMR. We focused our report on the role of the complement pathway in the process of ABMR and we give some insights into the role of inflammatory cells, NK lymphocytes and the role of endothelial cells. We further describe the potential role of non-HLA antibodies, of which the importance has been increasingly emphasized in recent years. Overall, this report could be of interest for all physicians who are working in the field of organ transplantation or who are working in the field of immunology. It gives essential information to understand new diagnosis advances and further therapeutic approaches. Antibody-mediated rejection (ABMR) is the leading cause of graft failure ([1,2]). In contrast to T-cell mediated rejection usually sensitive to steroids, active ABMR remains a therapeutic challenge. ABMR diagnosis relies on the presence of renal injuries and donor-specific antibodies (DSA) (HLA and non HLA antibodies) with sometimes the evidence of interaction between DSA and graft endothelium. Regularly revised during expert conferences, ABMR definition is currently categorized as active or chronic active. [3] The emergence of validated molecular assays targeting a better phenotyping of ABMR and the recent advances regarding the detrimental effect of DSA directed against minor antigens open the way to a better assessment of the heterogeneity of ABMR. In this review, we will address new aspects of ABMR regarding its mechanisms, diagnosis and treatments.

Pre-transplant angiotensin II receptor type I antibodies in pediatric renal transplant recipients: An observational cohort study

BACKGROUND

The role of angiotensin II type 1 receptor antibodies (AT1R-Ab) in pediatric renal transplantation is unclear. Here, we evaluated pre-transplant AT1R-Ab on transplant outcomes in the first 5 years. Secondary analysis compared pre-transplant AT1R-Ab levels by age.

METHODS

Thirty-six patients, 2-20 years old, were divided into two groups: pre-transplant AT1R-Ab- (<17 U/ml; n = 18) and pre-transplant AT1R-Ab+ (≥17 U/ml; n = 18). eGFR was determined at 6-month, 1-, 2-, and 4-year post-transplant. Allograft biopsies were performed in the setting of strong HLA-DSA (MFI > 10 000), AT1R-Ab ≥17 U/ml, and/or elevated creatinine.

RESULTS

Mean age in pre-transplant AT1R-Ab- was 13.3 years vs. 11.0 in pre-transplant AT1R-Ab+ (p = 0.16). At 6 months, mean eGFR was 111.3 ml/min/1.73 m² in pre-transplant AT1R-Ab- vs. 100.2 in pre-transplant AT1R-Ab + at 1 year, 103.6 ml/min/1.73 m² vs. 100.5; at 2 years, 98.9 ml/min/1.73 m² vs. and 93.7; at 4 years, 72.6 ml/min/1.73 m² vs. 80.9. 11/36 patients had acute rejection (6 in pre-transplant AT1R-Ab-, 5 in pre-transplant AT1R-Ab + ). There was no difference in rejection rates. All 6 subjects with de novo HLA-DSA and AT1R-Ab ≥17 U/ml at the time of biopsy experienced rejection. Mean age in those with the AT1R-Ab ≥40 U/ml was 10.0 years vs. 13.2 in those <40 U/ml (p = 0.07).

CONCLUSION

In our small cohort, pre-transplant AT1R-Ab ≥17 U/ml was not associated with reduced graft function or rejection. The pathogenicity of pre-transplant AT1R-Ab in pediatric kidney transplantation requires further investigation.

Anti-glutathione S-transferase theta 1 antibodies correlate with graft loss in non-sensitized pediatric kidney recipients

Introduction

Immunity to Human leukocyte antigen (HLA) cannot explain all cases of ABMR, nor the differences observed in the outcome of kidney recipients with circulating DSAs endowed with similar biologic characteristics. Thus, increasing attention has recently been focused on the role of immunity to non-HLA antigenic targets.

Methods

We analyzed humoral auto- and alloimmune responses to the non-HLA antigen glutathione S-transferase theta 1 (GSTT1), along with development of de novo (dn)HLA-DSAs, in a cohort of 146 pediatric non-sensitized recipients of first kidney allograft, to analyze its role in ABMR and graft loss. A multiplex bead assay was employed to assess GSTT1 antibodies (Abs).

Results

We observed development of GSTT1 Abs in 71 recipients after transplantation, 16 with MFI &gt; 8031 (4th quartile: Q4 group). In univariate analyses, we found an association between Q4-GSTT1Abs and ABMR and graft loss, suggesting a potential role in inducing graft damage, as GSTT1 Abs were identified within ABMR biopsies of patients with graft function deterioration in the absence of concomitant intragraft HLA-DSAs. HLA-DSAs and GSTT1 Abs were independent predictors of graft loss in our cohort. As GSTT1 Ab development preceded or coincided with the appearance of dnHLA-DSAs, we tested and found that a model with the two combined parameters proved more fit to classify patients at risk of graft loss.

Discussion

Our observations on the harmful effects of GSTT1Abs, alone or in combination with HLA-DSAs, add to the evidence pointing to a negative role of allo- and auto-non-HLA Abs on kidney graft outcome.

An update on angiotensin-converting enzyme 2 structure/functions, polymorphism, and duplicitous nature in the pathophysiology of coronavirus disease 2019: Implications for vascular and coagulation disease associated with severe acute respiratory syndrome coronavirus infection

It has been known for many years that the angiotensin-converting enzyme 2 (ACE2) is a cell surface enzyme involved in the regulation of blood pressure. More recently, it was proven that the severe acute respiratory syndrome coronavirus (SARS-CoV-2) interacts with ACE2 to enter susceptible human cells. This functional duality of ACE2 tends to explain why this molecule plays such an important role in the clinical manifestations of coronavirus disease 2019 (COVID-19). At the very start of the pandemic, a publication from our Institute (entitled "ACE2 receptor polymorphism: susceptibility to SARS-CoV-2, hypertension, multi-organ failure, and COVID-19 disease outcome"), was one of the first reviews linking COVID-19 to the duplicitous nature of ACE2. However, even given that COVID-19 pathophysiology may be driven by an imbalance in the renin-angiotensin system (RAS), we were still far from understanding the complexity of the mechanisms which are controlled by ACE2 in different cell types. To gain insight into the physiopathology of SARS-CoV-2 infection, it is essential to consider the polymorphism and expression levels of the ACE2 gene (including its alternative isoforms). Over the past 2 years, an impressive amount of new results have come to shed light on the role of ACE2 in the pathophysiology of COVID-19, requiring us to update our analysis. Genetic linkage studies have been reported that highlight a relationship between ACE2 genetic variants and the risk of developing hypertension. Currently, many research efforts are being undertaken to understand the links between ACE2 polymorphism and the severity of COVID-19. In this review, we update the state of knowledge on the polymorphism of ACE2 and its consequences on the susceptibility of individuals to SARS-CoV-2. We also discuss the link between the increase of angiotensin II levels among SARS-CoV-2-infected patients and the development of a cytokine storm associated microvascular injury and obstructive thrombo-inflammatory syndrome, which represent the primary causes of severe forms of COVID-19 and lethality. Finally, we summarize the therapeutic strategies aimed at preventing the severe forms of COVID-19 that target ACE2. Changing paradigms may help improve patients' therapy.