Automated Urinary Chemokine Assays for Noninvasive Detection of Kidney Transplant Rejection: A Prospective Cohort Study

RATIONALE & OBJECTIVE

Prior studies have demonstrated the diagnostic potential of urinary chemokines C-X-C motif ligand 9 (CXCL9) and CXCL10 for kidney transplant rejection. However, their benefit in addition to clinical information has not been demonstrated. We evaluated the diagnostic performance for detecting acute rejection of urinary CXCL9 and CXCL10 when integrated with clinical information.

STUDY DESIGN

Single-center prospective cohort study.

SETTING & PARTICIPANTS

We analyzed 1,559 biopsy-paired urinary samples from 622 kidney transplants performed between April 2013 and July 2019 at a single transplant center in Belgium. External validation was performed in 986 biopsy-paired urinary samples.

TESTS COMPARED

We quantified urinary CXCL9 (uCXCL9) and CXCL10 (uCXCL10) using an automated immunoassay platform and normalized the values to urinary creatinine. Urinary chemokines were incorporated into a multivariable model with routine clinical markers (estimated glomerular filtration rate, donor-specific antibodies, and polyoma viremia) (integrated model). This model was then compared with the tissue diagnosis according to the Banff classification for acute rejection.

OUTCOME

Acute rejection detected on kidney biopsy using the Banff classification.

RESULTS

Chemokines integrated with routine clinical markers had high diagnostic value for detection of acute rejection (n=150) (receiver operating characteristic area under the curve 81.3% [95% CI, 77.6-85.0]). The integrated model would help avoid 59 protocol biopsies per 100 patients when the risk for rejection is predicted to be below 10%. The performance of the integrated model was similar in the external validation cohort.

LIMITATIONS

The cross-sectional nature obviates investigating the evolution over time and prediction of future rejection.

CONCLUSIONS

The use of an integrated model of urinary chemokines and clinical markers for noninvasive monitoring of rejection could enable a reduction in the number of biopsies. Urinary chemokines may be useful noninvasive biomarkers whose use should be further studied in prospective randomized trials to clarify their role in guiding clinical care and the use of biopsies to detect rejection after kidney transplantation.

PLAIN-LANGUAGE SUMMARY

Urinary chemokines CXCL9 and CXCL10 have been suggested to be good noninvasive biomarkers of kidney transplant rejection. However, defining a context of use and integration with clinical information is necessary before clinical implementation can begin. In this study, we demonstrated that urinary chemokines CXCL9 and CXCL10, together with clinical information, have substantial diagnostic accuracy for the detection of acute kidney transplant rejection. Application of urinary chemokines together with clinical information may guide biopsy practices following kidney transplantation and potentially reduce the need for kidney transplant biopsies.

Urine CXCL10 as a biomarker in kidney transplantation

PURPOSE OF REVIEW

Urine CXCL10 is a promising biomarker for posttransplant renal allograft monitoring but is currently not widely used for clinical management.

RECENT FINDINGS

Large retrospective studies and data from a prospective randomized trial as well as a prospective cohort study demonstrate that low urine CXCL10 levels are associated with a low risk of rejection and can exclude BK polyomavirus replication with high certainty. Urine CXCL10 can either be used as part of a multiparameter based risk assessment tool, or as an individual biomarker taking relevant confounders into account. A novel Luminex-based CXCL10 assay has been validated in a multicenter study, and proved to be robust, reproducible, and accurate.

SUMMARY

Urine CXCL10 is a well characterized inflammation biomarker, which can be used to guide performance of surveillance biopsies. Wide implementation into clinical practice depends on the availability of inexpensive, thoroughly validated assays with approval from regulatory authorities.

Urine CXCL10 to Assess BK Polyomavirus Replication After Kidney Transplantation

BACKGROUND

Urine CXCL10 is a biomarker for renal allograft inflammation induced by rejection, urinary tract infection, or BK polyomavirus (BKPyV) replication. This study aimed to compare urine CXCL10 levels in different stages of BKPyV reactivation and to investigate urine CXCL10 as a biomarker for BKPyV replication.

METHODS

We included 763 urine samples (235 patients) from an interventional, randomized trial obtained in the context of regular screening for urine CXCL10 levels. All urine samples had a complete urine sediment analysis, no rejection episode noted within 30 d before urine collection, and a urine decoy cell analysis was conducted within ±3 d.

RESULTS

Urine CXCL10 levels were 2.31 ng/mmol in samples without BKPyV viruria, slightly rose to 4.35 ng/mmol with BKPyV viruria, and then markedly increased to 16.42 ng/mmol when decoy cells were detectable, but still in the absence of BKPyV DNAemia ( P  < 0.001). The highest urine CXCL10 values were observed in samples with BKPyV DNAemia (median 42.59 ng/mmol). The area under the curve of urine CXCL10 levels to detect ≥3 decoy cells was 0.816. At a CXCL10 cutoff of 3 ng/mmol, the negative predictive value was 97%. The area under the curve of urine CXCL10 levels to detect BKPyV DNAemia was 0.882, with a negative predictive value of 99% at a CXCL10 cutoff of 3 ng/mmol.

CONCLUSIONS

Urine CXCL10 levels are already significantly elevated in BKPyV viruria (especially with decoy cell shedding) and further increase with BKPyV DNAemia. Low urine CXCL10 values can rule out the presence of ≥3 decoy cells and BKPyV DNAemia with high certainty.

Interferon-Inducible Protein 10 and Disease Activity in Systemic Lupus Erythematosus and Lupus Nephritis: A Systematic Review and Meta-Analysis

There is increasing evidence of a correlation between interferon-inducible protein 10 (IP-10) and disease activity of systemic lupus erythematosus (SLE) and lupus nephritis (LN). We conducted a comprehensive search on IP-10 using MEDLINE, Scopus, and Cochrane electronic databases from the beginning to the end of December 2017. All studies that compared serum and/or urine IP-10 between active SLE/LN patients and any control groups were identified and included in this systematic review and meta-analysis. The mean difference (MD) of IP-10 level among active SLE and LN patients, as well as the correlation of IP-10 with disease activity, were meta-analyzed using a random-effects model. From 23 eligible studies, 15 provided adequate data for meta-analysis. Serum IP-10 was significantly elevated in patients with active SLE compared to non-active SLE patients (MD 356.5 pg/mL, 95% CI 59.6 to 653.4, p = 0.019). On the other hand, the levels of serum IP-10 was not different between active LN and non-active LN. However, serum IP-10 was positively correlated with disease activity like SLE disease activity index (SLEDAI) (pooled r = 0.29, 95% CI 0.22 to 0.35, p < 0.001). Furthermore, urine IP-10 tended to be higher in patients with active LN compared to non-active LN patients but this did not reach statistical significance (MD 3.47 pg/mgCr × 100, 95% CI -0.18 to 7.12, p = 0.06). Nevertheless, urine IP-10 was positively correlated with renal SLEDAI (pooled r = 0.29, 95% CI 0.05 to 0.50, p = 0.019). In conclusion, serum and urine IP-10 levels may be useful in monitoring the disease activity of SLE and LN. Serum IP-10 was correlated with systemic disease whereas urine IP-10 was a useful biomarker for detecting active LN.

Identification of inflammatory markers suitable for non-invasive, repeated measurement studies in biobehavioral research: A feasibility study

Introduction

Studying the role of the immune system in the interaction between mental and physical health is challenging. To study individuals with an intensive, longitudinal study design that requires repetitive sampling in their daily life, non-invasive sampling techniques are a necessity. Urine can be collected in a non-invasive way, but this may be demanding for participants and little is known about fluctuation of inflammatory markers in urine over time. The aim of this study was to investigate the feasibility of non-invasive sampling, and to explore intra-individual differences in inflammatory markers in urine.

Materials & methods

Ten healthy individuals collected 24-hour urine for 63 consecutive days. In a pilot analysis, 39 inflammatory markers were examined for detectability in urine, stability over time and under storage conditions, and daily fluctuations. Multiplex analyses were used to quantify levels of eight selected markers: C-reactive protein (CRP), Fractalkine, Interleukin-1 receptor-antagonist (IL-1RA), interferon-α (IFNα), interferon-γ (IFNγ), Interferon gamma-induced protein 10 (IP10), Macrophage inflammatory protein-1β (MIP-1β), and Vascular Endothelial Growth Factor (VEGF). Cross-correlations were calculated between the overnight and 24-hour samples were calculated, to examine whether 24-hour urine could be replaced by the overnight portion for better feasibility. We examined intra- and interindividual differences in the levels of inflammatory markers in urine and the fluctuations thereof.

Results

This study showed that levels of selected inflammatory markers can be detected in urine. Cross-correlation analyses showed that correlations between levels of inflammatory markers in the night portion and the 24-hour urine sample varied widely between individuals. In addition, analyses of time series revealed striking inter- and intra-individual variation in levels of inflammatory markers and their fluctuations.

Conclusion

We show that the assessment of urinary inflammatory markers is feasible in an intensive day-to-day study in healthy individuals. However, 24-hour urine cannot be replaced by an overnight portion to alleviate the protocol burden. Levels of inflammatory markers show substantial variation between and within persons.

Multicentre randomised controlled trial protocol of urine CXCL10 monitoring strategy in kidney transplant recipients

INTRODUCTION

Subclinical inflammation is an important predictor of death-censored graft loss, and its treatment has been shown to improve graft outcomes. Urine CXCL10 outperforms standard post-transplant surveillance in observational studies, by detecting subclinical rejection and early clinical rejection before graft functional decline in kidney transplant recipients.

METHODS AND ANALYSIS

This is a phase ii/iii multicentre, international randomised controlled parallel group trial to determine if the early treatment of rejection, as detected by urine CXCL10, will improve kidney allograft outcomes. Incident adult kidney transplant patients (n~420) will be enrolled to undergo routine urine CXCL10 monitoring postkidney transplant. Patients at high risk of rejection, defined as confirmed elevated urine CXCL10 level, will be randomised 1:1 stratified by centre (n=250). The intervention arm (n=125) will undergo a study biopsy to check for subclinical rejection and biopsy-proven rejection will be treated per protocol. The control arm (n=125) will undergo routine post-transplant monitoring. The primary outcome at 12 months is a composite of death-censored graft loss, clinical biopsy-proven acute rejection, de novo donor-specific antibody, inflammation in areas of interstitial fibrosis and tubular atrophy (Banff i-IFTA, chronic active T-cell mediated rejection) and subclinical tubulitis on 12-month surveillance biopsy. The secondary outcomes include decline of graft function, microvascular inflammation at 12 months, development of IFTA at 12 months, days from transplantation to clinical biopsy-proven rejection, albuminuria, EuroQol five-dimension five-level instrument, cost-effectiveness analysis of the urine CXCL10 monitoring strategy and the urine CXCL10 kinetics in response to rejection therapy.

ETHICS AND DISSEMINATION

The study has been approved by the University of Manitoba Health Research Ethics Board (HS20861, B2017:076) and the local research ethics boards of participating centres. Recruitment commenced in March 2018 and results are expected to be published in 2023. De-identified data may be shared with other researchers according to international guidelines (International Committee of Medical Journal Editors [ICJME]).

TRIAL REGISTRATION NUMBER

NCT03206801; Pre-results.

First description of agonist and antagonist IP-10 in urine of patients with active TB

OBJECTIVES

Biomarkers for tuberculosis (TB) diagnosis and clinical management are needed to defeat TB. In chronic hepatitis, patients not responding to interferon/ribavirin treatment had high levels of an antagonist form of IP-10. Recently, antagonist IP-10 has been shown to be involved also in TB pathogenesis. Here, we investigated IP-10 agonist/antagonist forms as potential inflammatory biomarkers to support TB diagnosis and monitoring.

METHODS

Total IP-10 and its agonist/antagonist forms were measured by SIMOA digital ELISA in urine obtained from patients with active TB at baseline and after treatment. Healthy donors (HD) and patients with pneumonia were enrolled as controls.

RESULTS

Patients with active TB had significantly higher levels of total and agonist IP-10 at baseline compared to HD; conversely, no differences were observed between IP-10 levels in active TB vs pneumonia. Moreover, in active TB a decline of total urine IP-10 was observed at therapy completion; agonist/antagonist forms reflected this decline although their differences were not statistically significant.

CONCLUSIONS

We showed for the first time that agonist/antagonist IP-10 forms are measurable in urine. IP-10 levels associate with TB and pneumonia disease, suggesting their association with acute inflammation. Further studies are needed to assess their role to monitor TB treatment efficacy.

Both absolute and relative quantification of urinary mRNA are useful for non-invasive diagnosis of acute kidney allograft rejection

Urinary mRNA analysis with three-gene set (18S rRNA, CD3ε, and IP-10) has been suggested as a non-invasive biomarker of acute rejection (AR) in kidney transplant recipients using quantitative real-time PCR (qPCR). Application of droplet digital PCR (ddPCR), which has been suggested to provide higher sensitivity, accuracy, and absolute quantification without standard curves, could be a useful method for the quantifying low concentration of urinary mRNA. We investigated the urinary expression of these three genes in Korean patients with kidney transplantation and also evaluated the usefulness of ddPCR. 90 urine samples were collected at time of allograft biopsy in kidney recipients (n = 67) and from patients with stable renal function more than 10 years (n = 23). Absolute quantification with both PCR system showed significant higher mRNA levels of CD3ε and IP-10 in AR patients compared with stable transplants (STA), but there was no difference in 18S rRNA expression across the patient groups. To evaluate discrimination between AR and STA, ROC curve analyses of CTOT-4 formula yielded area under the curve values of 0.72 (95% CI 0.60–0.83) and 0.77 (95% CI 0.66–0.88) for qPCR and ddPCR, respectively. However, 18S normalization of absolute quantification and relative quantification with 18S showed better discrimination of AR from STA than those of the absolute method. Our data indicate that ddPCR system without standard curve would be useful to determine the absolute quantification of urinary mRNA from kidney transplant recipients. However, comparative method also could be useful and convenient in both qPCR and ddPCR analysis.

Expressions of mRNA for innate immunity-associated functional molecules in urinary sediment in immunoglobulin A nephropathy

AIM

It has been reported that the innate immune system plays a pivotal role in the pathogenesis of immunoglobulin A nephropathy (IgAN). To explore non-invasive monitoring of disease activity in children with IgAN, we examined whether expressions of mRNA for innate immunity-associated functional molecules: CC ligand chemokine 5 (CCL5), fractalkine/CX3CL1, interferon-γ-induced protein 10 (IP-10), monocyte chemoattractant protein 1 (MCP-1), retinoic acid-inducible gene-I (RIG-I), and toll-like receptor 3 (TLR3) in urinary sediment from patients with IgAN correlate with histologic parameters.

METHODS

Twenty consecutive children with IgAN and four children with thin basement membrane disease (serving as a non-inflammatory control) were enrolled in this pilot study. Urinary mRNA expressions of target genes were examined real-time quantitative polymerase chain reaction.

RESULTS

The expressions of CCL5, fractalkine and RIG-I were significantly increased in IgAN (all P < 0.05). Although no significant correlation was observed between mRNA expressions of these three molecules and clinical parameters, such as levels of urinary protein excretion, degrees of occult blood in urine and serum albumin, the expression of fractalkine was significantly correlated with the histological activity index (P = 0.022) and the chronicity index (P = 0.005). Furthermore, intense glomerular immune activity of fractalkine was observed in biopsy specimens in patients with moderately to severe proliferative IgAN.

CONCLUSION

Regional expression of fractalkine may be involved in the pathogenesis of childhood IgAN. Although our present findings remain preliminary, measurement of mRNA expression of fractalkine in urinary sediment could be used as a non-invasive method for predicting histologic severity in IgAN in children. Further studies of this issue are needed.

Urine chemokines indicate pathogenic association of obesity with BPH/LUTS

OBJECTIVES

High prevalence of lower urinary tract symptoms (LUTS) consistent with benign prostate hyperplasia (BPH) is associated with obesity and prostatic inflammation. Here, we investigated whether chemokines associated with obesity and prostatic inflammation can be measured in normally voided urine of BPH/LUTS patients to demonstrate the mechanistic association between obesity and BPH/LUTS.

METHODS

Frozen urine specimens of BPH/LUTS patients enrolled in the Nashville Men's Health Study were sent for blinded analysis to University of Pittsburgh. Thirty patients were blocked by their AUA-SI (>7 or ≤7) and prostatic enlargement (<40, 40-60, >60 cc). Clinical parameters including age, prostate size, and medications were derived from chart review. CXC chemokines (CXCL-1, CXCL-8, and CXCL-10), CC chemokines (CCL2 and CCL3), and sIL-1ra were measured in thawed urine using Luminex™ xMAP(®) technology and ELISA for NGF.

RESULTS

Urinary CCL2 levels were several fold higher compared with the other six proteins, of which CCL3 was detectable in less than one-fourth of patients. Urine levels of sIL-1ra and CXCL-8 were significantly associated with increasing BMI and waist circumference in BPH patients. CXCL-8 showed a marginal association with overall AUA-SI scores, as well as obstructive (p = 0.08) symptom subscores. Prostate volume was inversely and marginally associated with urinary CXCL-10 (p = 0.09).

CONCLUSIONS

Urine levels of CXCL-8, CXCL-10, and sIL-1ra were associated with varying degrees with LUTS severity, prostate size, and obesity, respectively. These findings in urine are consistent with past studies of chemokine levels from expressed prostatic secretions and demonstrate the potential of noninvasively measured chemokine in urine to objectively classify BPH/LUTS patients.

Serum and urinary MIP-1α and IP-10 levels in children with urinary tract infections

OBJECTIVES

Urinary tract infection (UTI) is a common bacterial disease in infants and children, with potentially serious complications, including kidney damage. The aim of this study was to test whether serum and urinary levels of interleukin-6 (IL-6), macrophage inflammatory protein-1a (MIP-1a) and interferon-γ-inducible protein-10 (IP-10) can be used as biomarkers in children with urinary tract infections.

MATERIAL AND METHODS

The study group consisted of 22 children with UTI and 20 controls. Blood and urine samples were collected in the acute phase and the convalescent phase, on the eighth day after the onset of antibiotic therapy. Serum and urine levels of MIP-1a, IP-10 and IL-6 were measured.

RESULTS

In children with UTI in the acute phase, serum MIP-1a and IL-6 levels were significantly higher compared to the controls (p<0.05 and p<0.005, respectively). A correlation between the serum levels of the chemokines MIP-1a and IP-10 in the acute phase was found.

CONCLUSIONS

The findings suggest that the chemokines MIP-1a or IP-10 respond to infection, but they cannot be used as biomarkers for UTI in childhood.

High urine IP-10 levels associate with chronic HCV infection

OBJECTIVES

Independent of IL-28B polymorphisms, blood IP-10 is a promising biomarker for predicting therapy response in chronic HCV infection. Urine IP-10 has been proposed as a biomarker in tuberculosis, but to date, no urine biomarkers for HCV infection have been evaluated. In this cross-sectional study, we assessed whether IP-10 is detectable in the urine of chronically HCV-infected patients, and if so, whether urine IP-10 correlates with serum IP-10 and HCV-specific clinical parameters.

METHODS

IP-10 was measured by ELISA in serum and urine concomitantly taken from 38 HCV-viremic patients, 10 cured-HCV subjects and 11 healthy donors enrolled as controls.

RESULTS

The urine of HCV-viremic patients showed measurable amounts of IP-10, although significantly lower than in serum (p < 0.0001). Urine IP-10 was normalized with creatinuria levels and we found that the urine IP-10/creatinuria ratio was significantly higher in HCV-viremic patients than in cured-HCV subjects (p = 0.002) and healthy donors (p = 0.008), and that it significantly correlated with transaminases (p = 0.01), although the correlation was low. Similarly, the serum IP-10 level significantly associated with HCV-viremic patients (p < 0.0001) and correlated with transaminases (p < 0.0001).

CONCLUSIONS

For the first time to our knowledge, we show that IP-10 is detected and increased in the urine of HCV-viremic patients compared to healthy donors and cured-HCV subjects.

Urinary-cell mRNA profile and acute cellular rejection in kidney allografts

BACKGROUND

The standard test for the diagnosis of acute rejection in kidney transplants is the renal biopsy. Noninvasive tests would be preferable.

METHODS

We prospectively collected 4300 urine specimens from 485 kidney-graft recipients from day 3 through month 12 after transplantation. Messenger RNA (mRNA) levels were measured in urinary cells and correlated with allograft-rejection status with the use of logistic regression.

RESULTS

A three-gene signature of 18S ribosomal (rRNA)-normalized measures of CD3ε mRNA and interferon-inducible protein 10 (IP-10) mRNA, and 18S rRNA discriminated between biopsy specimens showing acute cellular rejection and those not showing rejection (area under the curve [AUC], 0.85; 95% confidence interval [CI], 0.78 to 0.91; P<0.001 by receiver-operating-characteristic curve analysis). The cross-validation estimate of the AUC was 0.83 by bootstrap resampling, and the Hosmer-Lemeshow test indicated good fit (P=0.77). In an external-validation data set, the AUC was 0.74 (95% CI, 0.61 to 0.86; P<0.001) and did not differ significantly from the AUC in our primary data set (P=0.13). The signature distinguished acute cellular rejection from acute antibody-mediated rejection and borderline rejection (AUC, 0.78; 95% CI, 0.68 to 0.89; P<0.001). It also distinguished patients who received anti-interleukin-2 receptor antibodies from those who received T-cell-depleting antibodies (P<0.001) and was diagnostic of acute cellular rejection in both groups. Urinary tract infection did not affect the signature (P=0.69). The average trajectory of the signature in repeated urine samples remained below the diagnostic threshold for acute cellular rejection in the group of patients with no rejection, but in the group with rejection, there was a sharp rise during the weeks before the biopsy showing rejection (P<0.001).

CONCLUSIONS

A molecular signature of CD3ε mRNA, IP-10 mRNA, and 18S rRNA levels in urinary cells appears to be diagnostic and prognostic of acute cellular rejection in kidney allografts. (Funded by the National Institutes of Health and others.).

Urinary chemokines CXCL9 and CXCL10 are noninvasive markers of renal allograft rejection and BK viral infection

Renal transplant recipients require periodic surveillance for immune-based complications such as rejection and infection. Noninvasive monitoring methods are preferred, particularly for children, for whom invasive testing is problematic. We performed a cross-sectional analysis of adult and pediatric transplant recipients to determine whether a urine-based chemokine assay could noninvasively identify patients with rejection among other common clinical diagnoses. Urine was collected from 110 adults and 46 children with defined clinical conditions: healthy volunteers, stable renal transplant recipients, and recipients with clinical or subclinical acute rejection (AR) or BK infection (BKI), calcineurin inhibitor (CNI) toxicity or interstitial fibrosis (IFTA). Urine was analyzed using a solid-phase bead-array assay for the interferon gamma-induced chemokines CXCL9 and CXCL10. We found that urine CXCL9 and CXCL10 were markedly elevated in adults and children experiencing either AR or BKI (p = 0.0002), but not in stable allograft recipients or recipients with CNI toxicity or IFTA. The sensitivity and specificity of these chemokine assays exceeded that of serum creatinine. Neither chemokine distinguished between AR and BKI. These data show that urine chemokine monitoring identifies patients with renal allograft inflammation. This assay may be useful for noninvasively distinguishing those allograft recipients requiring more intensive surveillance from those with benign clinical courses.

Urinary biomarkers in lupus nephritis

Renal involvement in patients with systemic lupus erythematosus in the form of severe lupus nephritis is associated with a significant burden of morbidity and mortality. Conventional laboratory biomarkers in current use have not been very successful in anticipating disease flares, predicting renal histology, or decreasing unwanted outcomes. Since early treatment is associated with improved clinical results, it is thus essential to identify new biomarkers with substantial predictive power to reduce the serious sequelae of this difficult to control lupus manifestation. Indeed, considerable efforts and progress have been made over the last few years in the search for novel biomarkers. Since urinary biomarkers are more easily obtainable with much less risk to the patient than repeat renal biopsies, and these may more accurately discern between renal disease and other organ manifestations than their serum counterparts, there has been tremendous interest in studying new candidate urine biomarkers. Below, we review several promising urinary biomarkers under investigation, including total proteinuria and microalbuminuria, urinary proteomic signatures, and the individual inflammatory mediators interleukin-6, vascular cell adhesion molecule-1, CXCL16, IP-10, and tumor necrosis factor-like weak inducer of apoptosis.