Is the intracellular ATP concentration of CD4+ T-Cells a predictive biomarker of immune status in stable transplant recipients?

Immune monitoring of allograft status in kidney transplant recipients

Kidney transplant patients require careful management of immunosuppression to avoid rejection while minimizing the risk of infection and malignancy for the best long-term outcome. The gold standard for monitoring allograft status and immunosuppression adequacy is a kidney biopsy, but this is invasive and costly. Conventional methods of allograft monitoring, such as serum creatinine level, are non-specific. Although they alert physicians to the need to evaluate graft dysfunction, by the time there is a clinical abnormality, allograft damage may have already occurred. The development of novel and non-invasive methods of evaluating allograft status are important to improving graft outcomes. This review summarizes the available conventional and novel methods for monitoring allograft status after kidney transplant. Novel and less invasive methods include gene expression, cell-free DNA, urinary biomarkers, and the use of artificial intelligence. The optimal method to manage patients after kidney transplant is still being investigated. The development of less invasive methods to assess allograft function has the potential to improve patient outcomes and allow for a more personalized approach to immunosuppression management.

Serum extracellular vesicle MicroRNAs as candidate biomarkers for acute rejection in patients subjected to liver transplant

Acute rejection (AR) is a common and grave complication of liver transplantation (LT). The diagnosis of AR is challenging because it has nonspecific clinical features and requires invasive procedures. Since extracellular vesicles (EVs) are promising candidates as indicators for diagnosis of various diseases, this study aimed to identify serum EV microRNAs (miRNAs) as potential biomarkers for AR in patients subjected to LT. We collected clinical information and serum samples from the liver transplant recipients with and without AR (non-AR). EVs from the serum were isolated via ultracentrifugation and identified using transmission electron microscopy, nanoparticle tracking analysis, and western blotting. EV RNA was extracted and sequenced on an Illumina HiSeq 2500/2000 platform to identify differentially expressed miRNAs between the groups. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were performed on the target gene candidates of the differentially expressed miRNAs to test their functions in biological systems. Then, we validated 12 differentially expressed miRNAs by quantitative real-time PCR. The results demonstrated that 614 EV miRNAs were significantly altered (387 up regulated and 227 down regulated) between non-AR and AR patients. GO enrichment analysis revealed that these target genes were related to cellular processes, single-organism processes, biological regulation, metabolic processes, cells, cell parts, protein-binding processes, nucleoid binding, and catalytic activity. Furthermore, KEGG pathway analysis demonstrated that the target genes of the differentially expressed miRNAs were primarily involved in ubiquitin-mediated proteolysis, lysosomes, and protein processing in the endoplasmic reticulum. miR-223 and let-7e-5p in AR patients were significantly up-regulated compared to those in non-AR patients, whereas miR-199a-3p was significantly down-regulated, which was consistent with sequencing results. The expression of serum EV miRNAs (up-regulated: miR-223 and let-7e-5p and miR-486-3p; down regulated: miR-199a-3p, miR-148a-3p and miR-152-3p) in AR patients was significantly different from that in non-AR patients, and these miRNAs can serve as promising diagnostic biomarkers for AR in patients subjected to liver transplant.

Non-invasive diagnosis and follow-up in liver transplantation

The field of liver transplantation directly or indirectly embodies all liver diseases, in addition to specific ones related to organ rejection (cellular and humoral). The recommended non-invasive methods for determining the indication for liver transplantation are the Model for End-stage Liver Disease score, and the alpha-foetoprotein score in case of hepatocellular carcinoma. Radiological methods are the cornerstones for the diagnosis of vascular and biliary complications after liver transplantation. The possible diseases of the liver graft after transplantation are multiple and often intertwined. Non-invasive diagnostic methods have been poorly evaluated in this context, apart from the recurrence of hepatitis C. Liver biopsy remains the gold standard for evaluating graft lesions in the majority of cases, especially graft rejection.

Evaluation of cell-mediated immune response by QuantiFERON Monitor Assay in kidney transplant recipients presenting with infective complications

The net level of immunosuppression in kidney transplant recipients is difficult to assess. QuantiFERON Monitor (QFM) is an in vitro diagnostic test that detects interferon-γ (IFN-γ) release in peripheral blood. The aim of our study was to compare QFM testing results in stable kidney transplant recipients and kidney transplant recipients with infection, in a single-centre cohort.We enrolled 71 kidney transplant recipients from our transplantation centre. They were divided into 2 groups according to clinical presentation (Stable kidney transplant recipients or Infection).There were no significant differences in interferon-γ release between the 2 groups (Stable kidney transplant recipients 140.59 ± 215.28 IU/ml, Infection group 78.37 ± 197.03 IU/ml, P = .24). A further analysis revealed that kidney transplant recipients presenting with bacterial infection had significantly lower IFN-γ release when compared to stable kidney transplant recipients (26.52 ± 42.46 IU/ml vs 140.59 ± 215.28 IU/ml, P = .04).Kidney transplant recipients presenting with bacterial infection had lower IFN-γ release when compared to stable kidney transplant recipients. The QFM test may be useful as a tool to help guide immunosuppression dosing in kidney transplant recipients, but further studies are required to confirm its diagnostic value.

Clinical relevance of a CD4+ T cell immune function assay in the diagnosis of infection in pediatric living-donor liver transplantation

The aim of the present study was to investigate the potential of the Immuknow immune cell function assay for the diagnosis of infection after pediatric living-donor liver transplantation (LDLT). Based on clinical data obtained following liver transplantation, 66 patients were divided into infection (n=28) and non-infection (n=38) groups. The following factors were considered in the present analysis: Primary disease, lymphocyte count, tacrolimus plasma concentration/dose (C0/D) ratio, CD4+ T lymphocyte ATP levels, at pre-transplant stage and at weeks 1-4, and 2 and 3 months post-transplant. The CD4+ T lymphocyte ATP values were plotted in a receiver operating characteristic (ROC) curve. The CD4+ T lymphocyte ATP value of the infection group was significantly lower compared with that of the non-infection group (188.6±93.5 vs. 424.4±198.1 ng/ml, respectively; P<0.05). No correlation was observed between the ATP value and tacrolimus plasma C0/D ratio (R2=0.0001484); however, a correlation was reported between the ATP value and lymphocyte count (R2=0.2149). Analysis of the ROC curve indicated that the ATP levels of CD4+ T cells were significantly associated with the diagnostic value of infection (area under the curve=0.866). These findings suggest that low CD4+ T lymphocyte ATP levels may be an independent risk factor for infection following pediatric LDLT, and that the Immuknow assay may be used as a tool to evaluate T lymphocyte function in such patients to predict the risk of infection.

Monitoring cellular immune function of renal transplant recipients based on adenosine triphosphate (ATP) production by mitogen-induced CD4+ T helper cells

Maintaining the balance between over- and under-immunosuppression has a critical role for successful immunosuppressive therapy after renal transplantation. We studied the predictive value of our functional immune assay, which works based on adenosine triphosphate (ATP) levels, in determining risk of infection and rejection among renal transplant recipients (RTRs). A total of 65 RTRs with less than 1 month (RTRL1) and 48 RTRs with more than 6 months (RTRM6) of post-transplant time, and 56 healthy individuals were included. Upon lymphocyte activation by phytohemagglutinin (PHA), CD4+ T cells were separated using magnetic beads (Dynabeads), the intracellular ATP (iATP) concentrations were measured by luciferin-luciferase reaction, and compared within and between the groups. Activated CD4+ cells iATP production directly correlated with post-transplant time (r = 0.32, P = 0.011). The iATP levels were significantly lower in both RTRL1 and RTRM6 groups compared to control (P < 0.001), and in the RTRL1 group compared to the RTRM6 (P < 0.05). The iATP concentrations were significantly lower in patients who suffered from infection versus the RTRs with stable graft function (SGF). However, the iATP levels were higher in those with allograft rejection episode (ARE). Our optimization experiments showed that best iATP levels cutoffs were 472.5 and 572.5 ng/ml for predicting risk of ARE, and 218.5 and 300.5 ng/ml for predicting risk of developing infection in RTRL1 and RTRM6 patients, respectively. iATP levels measured by immune function assay might be a promising predictive tool for identifying RTRs who are at risk of developing infection or allograft rejection.

Blood biomarkers of kidney transplant rejection, an endless search?

INTRODUCTION

The tailoring of immunosuppressive treatment is recognized as a promising strategy to improve long-term kidney graft outcome. To guide the standard care of transplant recipients, physicians need objective biomarkers that can identify an ongoing pathology with the graft or low intensity signals that will be later evolved to accelerated transplant rejection. The early identification of 'high-risk /low-risk' patients enables the adjustment of standard of caring, including managing the frequency of clinical visits and the immunosuppression dosing. Given their ease of availability and the compatibility with a large technical array, blood-based biomarkers have been widely scrutinized for use as potential predictive and diagnostic biomarkers. Areas covered: Here, the authors report on non-invasive biomarkers, such as modification of immune cell subsets and mRNA and miRNA profiles, identified in the blood of kidney transplant recipients collected before or after transplantation. Expert commentary: Combined with functional tests, the identification of biomarkers will improve our understanding of pathological processes and will contribute to a global improvement in clinical management.

Correlation Between Immunosuppressive Therapy and CD4(+) T-Cell Intracellular Adenosine Triphosphate Levels in Liver Transplant Recipients

OBJECTIVE

The aim of this work was to analyze the correlation between immunosuppressive therapy and CD4(+) T-cell intracellular adenosine triphosphate (iATP) levels after liver transplantation and to describe the distribution characteristics of iATP in CD4(+) T cells among liver transplant recipients.

METHODS

We studied 172 patients who were followed regularly after liver transplantation with long-term stable conditions from July 2010 to October 2012. CD4(+) T-cell iATP levels were detected with the use of the Cylex Immuknow Assay method and analyzed retrospectively according to immunosuppressive therapy protocol.

RESULTS

There was a significant difference in CD4(+) T-cell iATP level among the recipients receiving different immunosuppressive therapy protocols after liver transplantation. CD4(+) T-cell iATP level in the FK506 group and FK506 + prednisone (Pred) groups was higher than in the FK506 + mycophenolate mofetil (MMF), FK506 + MMF + Pred, and rapamycin (Rapa) groups. CD4(+) T-cell iATP level in patients receiving an MMF protocol was lower than in the group without MMF.

CONCLUSIONS

There is a relationship between distribution immunosuppressive therapy protocol and CD4(+) T-cell iATP level after liver transplantation. MMF and Rapa lower the CD4(+) T-cell iATP level significantly.

High proportion of CD95(+) and CD38(+) in cultured CD8(+) T cells predicts acute rejection and infection, respectively, in kidney recipients

The aim of this study was to find noninvasive T-cell markers able to predict rejection or infection risk after kidney transplantation. We prospectively examined T-lymphocyte subsets after cell culture stimulation (according to CD38, CD69, CD95, CD40L, and CD25 expression) in 79 first graft recipients from four centers, before and after transplantation. Patients were followed up for one year. Patients who rejected within month-1 (n=10) showed high pre-transplantation and week-1 post-transplantation percentages of CD95(+), in CD4(+) and CD8(+) T-cells (P<0.001 for all comparisons). These biomarkers conferred independent risk for early rejection (HR:5.05, P=0.061 and HR:75.31, P=0.004; respectively). The cut-off values were able to accurately discriminate between rejectors and non-rejectors and Kaplan-Meier curves showed significantly different free-of-rejection time rates (P<0.005). Patients who rejected after the month-1 (n=4) had a higher percentage of post-transplantation CD69(+) in CD8(+) T-cells than non-rejectors (P=0.002). Finally, patients with infection (n=41) previously showed higher percentage of CD38(+) in CD8(+) T-cells at all post-transplantation times evaluated, being this increase more marked in viral infections. A cut-off of 59% CD38(+) in CD8(+) T-cells at week-1, week-2 and month-2 reached 100% sensitivity for the detection of subsequent viral infections. In conclusion, predictive biomarkers of rejection and infection risk after transplantation were detected that could be useful for the personalized care of kidney recipients.

Biomarkers to assess donor-reactive T-cell responses in kidney transplant patients

Different to antibody-mediated rejection (ABMR), T-cell mediated rejection (TCMR) still unpredictably occurs after kidney transplantation in a great part because of a poor immunologic evaluation of the cellular allogeneic immune response. However, in the last years, important efforts have focused on the development of novel and more sensitive assays to monitor T-cell alloimmune responses at different biological levels that may improve the understanding of the functional status of the cellular immune compartment in patients undergoing organ transplantation. In this direction, immune assays evaluating T-cell proliferation, intracellular ATP release, multiparameter flow cytometry, profiling T-cell receptor repertoires and measurements of frequencies of cytokine-producing T-cells using an IFN-γ enzyme-linked immunospot assay (IFN-γ ELISPOT) have been reported showing interesting associations between the cellular alloimmune response and kidney transplant outcomes. In summary, an important progress has been made in the assessment of alloreactive T-cell responses in the context of organ transplantation using novel immune assays at different biological levels. However, there is an urgent need for prospective, randomized clinical studies to validate these encouraging preliminary data to ultimately introduce them in current clinical practice for refining current immune-risk stratification in kidney transplantation.

Adenosine triphosphate production by peripheral blood CD4⁺T cells in clinically stable renal transplant recipients

Previous studies have shown that intracellular adenosine triphosphate (iATP) in activated CD4 T cells in vitro may identify patients at risk of infection or rejection post-transplantation. In this study, we evaluated whether this test could identify the level of risk in 656 renal transplant recipients (RTRs) with good and stable graft function. Therefore, 1095 blood samples from RTRs and 200 from healthy blood donors (normal controls [NCs]) were collected in 2 years and analyzed using the Cylex(®) ImmuKnow™ assay (Cylex, Inc., Columbia, MD, USA). The classification of T cell responses into strong, moderate, and low revealed significant differences between patients and NCs in low and strong responses (P < .001 and P = .021, respectively). The majority of patient samples exhibited moderate immune response (72.2%) in comparison with NC (75%). One hundred twenty-eight patients had fluctuated T cell responses between the three response zones. All patients were clinically stable for at least 1 month after the test. T cell response was increased after time post-transplantation (P < .001) and was found higher in protocols using azathioprine versus other immunosuppression (P < .001) and cyclosporine instead of tacrolimus (P = .012). According to the results of this study, we are not able to support this assay as an immune monitoring test post-transplantation in clinically stable RTRs. In contrast, measuring of iATP in CD4 T cells is a valuable tool for estimating T cell activation capacity. Because T cell activation is mainly affected by immunosuppression, this test may give information regarding the strength of different immunosuppressive protocols or the strength of immunosuppression as it is associated with longer follow-up periods.

Monitoring T cell alloreactivity

Currently, immunosuppressive therapy in kidney transplant recipients is center-specific, protocol-driven, and adjusted according to functional or histological evaluation of the allograft and/or signs of drug toxicity or infection. As a result, a large fraction of patients receive too much or too little immunosuppression, exposing them to higher rates of infection, malignancy and drug toxicity, or increased risk of acute and chronic graft injury from rejection, respectively. The individualization of immunosuppression requires the development of assays able to reliably quantify and/or predict the magnitude of the recipient's immune response toward the allograft. As alloreactive T cells are central mediators of allograft rejection, monitoring T cell alloreactivity has become a priority for the transplant community. Among available assays, flow cytometry based phenotyping, T cell proliferation, T cell cytokine secretion, and ATP release (ImmuKnow), have been the most thoroughly tested. While numerous cross-sectional studies have found associations between the results of these assays and the presence of clinically relevant post-transplantation outcomes, data from prospective studies are still scanty, thereby preventing widespread implementation in the clinic. Future studies are required to test the hypothesis that tailoring immunosuppression on the basis of results offered by these biomarkers leads to better outcomes than current standard clinical practice.

Utility of an immune cell function assay to differentiate rejection from infectious enteritis in pediatric intestinal transplant recipients

The Cylex Immune Cell Function Assay measures cell-mediated immunity based on ATP production by stimulated CD4 + cells. We hypothesized that this test would discriminate acute cellular rejection (ACR) from infectious enteritis (IE) in pediatric intestinal transplant (ITx) recipients with allograft dysfunction. We retrospectively analyzed 224 Cylex assays drawn in 47 children who received 53 ITx. Samples were classified as stable, ACR, or IE based on clinical status. ATP values were analyzed using Kruskal-Wallis and t-tests. Overall, there was a statistically significant difference in ATP values based on clinical status (p = 0.03); however, overlap was observed between groups. The median ATP value during ACR was significantly greater than during stable periods (p = 0.02). No difference was seen in IE vs. stability (p = 0.8). The difference in median ATP value in ACR vs. IE approached significance (p = 0.1). Relative to previous levels, ACR episodes were associated with a median ATP increase of 101 ng/mL and IE episodes with a decrease of 3 ng/mL (p = 0.3). These data indicate that the Cylex assay has limited utility in differentiating ACR from IE, largely due to interpatient variability. Following longitudinal intrapatient trends may be an adjunctive tool in discriminating IE from ACR and guiding immunosuppression adjustments in select patients.

Trends in immune cell function assay and donor-specific HLA antibodies in kidney transplantation: A 3-year prospective study

The immune cell function assay (ICFA) and de novo anti-donor-specific HLA antibodies (DSA) have been proposed as assays for immune monitoring in renal transplantation, but longitudinal studies examining the modification of both parameters over time and their relation with clinical events are lacking. We prospectively measured longitudinal changes in ICFA and DSA levels in 55 kidney transplant recipients over 3-year follow-up (534 visits) and analyzed their relation with the risk of developing acute rejections or infections. Seven patients (12.7%) developed biopsy-proven acute rejection, and 20 (36.4%) developed viral infections. At 3 years posttransplant, 28% of the patients had developed de novo DSA. ICFA levels peaked at 1-2 months posttransplant (p = 0.005) and leveled off thereafter. They were not associated with the risk of acute rejections, viral infections or development of de novo DSA. Instead, the incidence of de novo DSA was higher in patients who previously had viral infections (adjusted-odds ratio of de novo DSA associated with prior infections: 6.03 [95% CI, 1.64-22.06; p = 0.007]). Our prospective, longitudinal study does not support using ICFA to quantify the immune risk in kidney transplantation. Further studies are needed to confirm the relationship between viral infections and the subsequent development of de novo DSA.

Comparison of several functional methods to evaluate the immune response on stable kidney transplant patients

The introduction of new immunosuppressive drugs in the last two decades has been associated with a significant decline in the prevalence of acute rejection and a huge improvement of graft survival. Monitoring blood levels of immunosuppressive drugs is the most common way to control drug doses in renal transplant patients. This approach is useful and widely used but doesn't give accurate information about the immune status of the patient. For this goal, there are many "in house" protocols which give more information, but cannot be standardized, limiting their applicability to compare results between different laboratories. In this study we compare three classical functional methods to evaluate the immune response: Mixed lymphocyte reaction (MLR), phytohemagglutinin stimulated peripheral blood lymphocytes (PBLs), and anti-CD3 monoclonal antibodies (mAbs) against PBL with the only FDA-labeled assay to measure the patient immune status: Cylex ImmuKnow® that measures the intracelullar ATP in CD4+ lymphocytes. We used n=111 stable renal transplant patients, all the patients with more than one year functioning grafts. We referred the results to a control population of healthy blood donors (n=125).

RESULTS

Measurement of intracellular ATP in CD4+ lymphocytes is able to differentiate immunosuppressed populations in renal transplant patients from health controls (242.30±21.62 vs. 386.43±25.12, p 0.0001). By contrary, there were no differences between controls and renal recipients when functional response was measured by MLR, PHA and anti-CD3 mAbs (2.48±0.45 vs. 2.37±0.41; 2.84±0.76 vs. 2.37±0.32; 2.32±0.34 vs. 1.89±0.38 respectively). In summary, our results show that the measurement of ATP in CD4+ lymphocytes gives more accurate information in comparison to the classical methods.

Clinical value of a single determination of intracellular ATP levels in stimulated CD4+ T lymphocytes in pediatric patients with stable liver transplantation

In the follow-up of transplanted patients under immunosupression, the functional assessment of CD4+ T cells activation by measuring intracellular ATP levels in vitro, using the Immuknow test give information on how immune system is functioning. Therefore, it has been reported that low levels of ATP correlate with the risk of opportunistic infection. Although limited, comprehensive results in adult recipients as well as in pediatric transplanted patients have been reported. Forty stable liver pediatric transplanted patients (mean age: 11.0 years [SD 5.65]), within at least 1 year of transplant were selected for a scheduled review, and an unique determination of Immuknow was performed. Average ATP levels were 317 ng/mL (200-400 ng/mL) which were similar to the values observed in adult population. ATP values among patients with monotherapy Cyclosporin A (CSA) or tacrolimus (TAC) were significantly higher (P = .005) than in patients with double immunosupressive therapy using either CSA/TAC + Mycophenolate Mofetil (MMF). In CSA treatment, there are significant differences (P = .0003) between monotherapy and double therapy, but in the case of TAC we did not find differences (P > .1). A single determination of levels of ATP on CD4+ lymphocytes, can provide additional information that could be used as a complementary test to guide immunosuppressive therapy in paediatric liver transplant recipients.

Intracellular ATP production in CD4+ T cells as a predictor for infection and allograft rejection in trough-level guided pediatric liver transplant recipients under calcineurin-inhibitor therapy

BACKGROUND

The assessment of cell-mediated immune responses through the measurement of intracellular adenosine-tri-phosphate (iATP) production (Cylex ImmuKnow) as a pharmacodynamic biomarker of immune function represents a potential tool to optimize individual immunosuppressive therapy independent of drug dosage or trough levels. This study aims to investigate the correlations between iATP and adverse events, immunosuppression, calcineurin-inhibitor-trough levels, and age.

METHODS

In this prospective trial, 31 nontransplant pediatric subjects and 50 consecutive children were included after they underwent liver transplantation (LTX). During the study period, 4 allograft rejections and 3 acute infections occurred. The patients were treated with cyclosporine, tacrolimus, mycophenolate mofetil, and everolimus either as monotherapy or in combinations. The reactivity of the immune system was measured as iATP concentration in CD4+ T-cells after in vitro stimulation by phytohemagglutinin.

RESULTS

The iATP concentrations in patients with intercurrent, clinically significant infections were in the low immune response range (median iATP 181 versus 251 ng/mL, P = 0.308), whereas the patients with incidental allograft rejection had significantly higher iATP concentrations as compared with the event-free group (median iATP 444 versus 251 ng/mL, P = 0.017). However, there was a wide range of iATP concentrations in both nontransplant and LTX patient groups, and no clear iATP cut-off values for an increased risk of infection or rejection could be defined. Post LTX, stable-phase patients showed a significantly lower iATP compared with respective controls (median iATP 297 versus 384 ng/mL, P = 0.013). No significant correlation between calcineurin-inhibitor-trough concentrations and iATP was found. iATP was not correlated with age, but was inversely correlated with time after transplantation.

CONCLUSIONS

The observed correlation between clinical events and iATP concentrations is similar to the findings previously reported in adult patients who underwent transplantation. The lack of correlation of iATP with trough drug concentrations suggests that the ImmuKnow assay provides independent information that may be useful to guide immunosuppressive therapy in pediatric (liver) transplant patients. However, the wide range of iATP levels in event-free patients suggests that serial iATP measurements will be necessary to assess and guide the individual immunosuppressive therapy. Further investigations are needed to evaluate and extend these findings.

Confronting the challenge: individualized immune monitoring after organ transplantation using the cellular immune function assay

The survival of a transplanted organ is dependent on avoidance of rejection, achieved through continuous immuno-suppression. Management of the transplant recipient confronts the clinician with a key challenge of post-transplant immune monitoring. Early detection of an activated allo-immune response is a harbinger of incipient rejection. Thus, timely intervention may prevent acute and chronic injury to the transplanted organ. Similarly, over immune-suppression can lead to infections or malignancies, hence the importance of early detection of the precarious suppression. The need for non-invasive systemic immune monitoring of the transplant recipient is therefore imperative. This review describes the cellular immune function assay--a non-invasive diagnostic method for evaluation of the net state of the recipient's cellular immune function. We describe the background that brought about the need for a reliable diagnostic tool for serial immune monitoring, and we overview the main mile-stones in the assimilation of the assay and its implementation in the clinic. The arising conclusion presents a novel non-invasive diagnostic bio-marker for post-transplant immune monitoring which enables the clinician to intervene prior to manifestation of clinical complications. The usefulness of the assay in detecting a state of over-suppression has been consensually described in multiple publications while its contribution in detection and management of under-suppression conditions remains to be determined by means of prospective interventional studies. The cellular immune function assay can be useful and beneficial for patient care only if used for longitudinal monitoring through serial testing.

Trends in immune function assay (ImmuKnow; Cylex™) results in the first year post-transplant and relationship to BK virus infection

BACKGROUND

The ImmuKnow assay is a functional T-cell assay (TCA) that may quantify cellular immune responsiveness following renal transplantation. Using a standard protocol of TCA sampling in the first year post-transplant, we examined changes in TCA values over time and tested for an association between TCA and BK virus (BKV) infection as a marker of over-immunosuppression.

METHODS

We performed a single-center retrospective analysis of 897 TCA results in 414 renal transplant recipients obtained at 0 (N = 122), 1 (N = 316), 6 (N = 258) and 12 (N = 201) months post-transplant from May 2005 to July 2009 with concurrent urine and blood BKV polymerase chain reaction measurements.

RESULTS

Nearly 40% of patients experienced a decrease in TCA of >150 ng/mL from 1 to 6 months (mean 466-356 ng/mL, P < 0.0001) and remained stable from 6 to 12 months (mean 357 versus 370 ng/mL, P = 0.33). Neither a change in TCA of >150 ng/mL nor a TCA value of ≤ 225 ng/mL were associated with a diagnosis of BKV infection at 1 or 6 months, while TCA ≤ 225 ng/mL was associated with BKV infection at 12 months (P = 0.005).

CONCLUSIONS

A reduction in TCA from 1 to 6 months post-transplant is common and is not associated with conditions of over-immunosuppression, rendering the interpretation of changes in TCA during this time period difficult. BKV infection is associated with low TCA values at 12 months, suggesting that patients with low TCA values after 6 months may benefit from potential tailoring of immunosuppression or more aggressive monitoring to prevent subsequent BKV infection.

Bone marrow-derived mesenchymal stem cells as immunosuppressants in liver transplantation: a review of current data

This article provides an overview of the current knowledge relating to the potential use of bone marrow-derived mesenchymal stem cells (BM-MSCs) acting as immunosuppressants after liver transplantation. Clinical use of BM-MSCs in liver transplantation remains experimental, as there is uncertainty as to their mechanism of action, conflicting studies in animal models, and the possibility of their cellular fusion with hepatocytes leading to potentially genetically unstable hepatocytes. These obstacles, to their underuse, have been decreasing, and BM-MSCs have elicited great interest for possible use in solid organ transplantation. Bone marrow-derived-MSCs, when transplanted systemically, might positively influence grafted organ outcome through cell-cell contact or the secretion of soluble factors that are immunomodulatory. Thus, the use of BM-MSCs to modulate organ rejection may directly or indirectly influence the survival properties of transplanted livers.

Peripheral blood sampling for the detection of allograft rejection: biomarker identification and validation

Currently, acute allograft rejection can only be detected reliably by deterioration of graft function confirmed by allograft biopsy. A huge drawback of this method of diagnosis is that substantial organ damage has already taken place at the time that rejection is diagnosed. Discovering and validating noninvasive biomarkers that predict acute rejection, and chronic allograft dysfunction, is of great importance. Many studies have investigated changes in the peripheral blood in an attempt to find biomarkers that reflect changes in the graft directly or indirectly. Herein, we will review the promises and limitations of the peripheral blood biomarkers that have been described in the literature so far.

CD28 and KIR2D receptors as sensors of the immune status in heart and liver transplantation

Viral infections and cellular acute rejection (AR) condition immunosuppressive therapy and compromise the evolution of allografts. Immune monitoring can be useful for ascertaining rejection and for differentiating allo-reaction from activation induced by infections. This work analyzes the usefulness of monitoring the expression of CD28 and KIR2D receptors in peripheral blood T lymphocytes by flow cytometry, to ascertain the immune response in heart and liver transplant recipients. In both types of transplant, the up-regulation of CD28 in CD4(+) lymphocytes in the periods of greatest AR frequency indicates an effective allo-response, whereas the post-transplantation emergence of circulating CD8(+)CD28(-) and CD8(+)CD28(-)KIR2D(+) T cells correlates with better early clinical results. Cytomegalovirus (CMV) infection, but not hepatitis C virus (HCV) or other infections, abrogated both CD28 up-regulation and CD8(+)CD28(-)KIR2D(+) T-cell expansion. Our results show that monitoring the expression of CD28 and KIR2D receptors on T lymphocytes might be considered as sensors of the immune status of heart and liver recipients.

Biomarker assessment of the immunomodulator effect of atorvastatin in stable renal transplant recipients and hypercholesterolemic patients

BACKGROUND

HMG-CoA reductase inhibitors (statins) have effects beyond lipid lowering, including immunomodulatory and anti-inflammatory properties. Statins are frequently combined with immunosuppressive agents in transplant recipients to modulate the hyperlipidemic side effects of the immunosuppressants. However, the role of statins in the immunosuppressive response that is achieved in individual patients remains to be assessed.

OBJECTIVE

The aim of this study was to evaluate the immunomodulatory effect of atorvastatin given alone and in combined treatment with tacrolimus and mycophenolate mofetil.

STUDY DESIGN

Two patient groups were studied: renal transplant recipients receiving tacrolimus and mycophenolate mofetil therapy, and hypercholesterolemic patients (the control group). Fasting blood samples were taken from participants before and 1 month after atorvastatin treatment was started to study a small battery of biomarkers that are able to reflect the range of the effects of immunosuppressive therapy and atorvastatin.

SETTING

All patients in the study were enrolled at the Hospital Clinic of Barcelona.

PATIENTS

All patients enrolled in the study were candidates for treatment with atorvastatin because of high cholesterol levels. One group consisted of 25 stable renal transplant recipients with low-density lipoprotein (LDL) cholesterol levels above 100 mg/dL after 3 months of therapeutic lifestyle changes, according to the guidelines of the National Kidney Foundation - Kidney Disease Outcomes Quality Initiative. The other group included 25 hypercholesterolemic patients with LDL cholesterol levels above target values for the patients' overall risk, as derived from the National Cholesterol Education Program Adult Treatment Panel III criteria.

INTERVENTION

Atorvastatin (Lipitor®) treatment was started at a fixed dose of 20 mg daily.

MAIN OUTCOME MEASURE

The studied biomarkers were lymphocyte proliferation, intracellular adenosine triphosphate (ATP) synthesis in CD4+ T cells, intralymphocytary cytokine expression (interleukin [IL]-2, interferon [IFN]-γ), soluble cytokine production (IL-2, IFN-γ, IL-10, IL-17, and transforming growth factor-β) and regulatory T (T(reg)) cells.

RESULTS

Atorvastatin proved to be an immunomodulatory agent, significantly decreasing lymphocyte proliferation by 15% (p = 0.001), increasing ATP levels by 16% (p = 0.0004), and showing a trend toward increasing T(reg) cells in hypercholesterolemic patients (p = 0.09). In the renal transplant recipients, atorvastatin therapy did not modify any of the biomarkers of immunosuppression that were studied.

CONCLUSION

Atorvastatin showed immunoregulatory effects on T cells in hypercholesterolemic patients. These effects were absent in renal transplant recipients, suggesting that the beneficial effects of atorvastatin in this patient group do not relate to immunoregulation. Therefore, statin treatment cannot be considered as a means to reduce the dose of immunosuppressive agents.

Biomarker assessment of the immunomodulator effect of atorvastatin in stable renal transplant recipients and hypercholesterolemic patients

BACKGROUND

HMG-CoA reductase inhibitors (statins) have effects beyond lipid lowering, including immunomodulatory and anti-inflammatory properties. Statins are frequently combined with immunosuppressive agents in transplant recipients to modulate the hyperlipidemic side effects of the immunosuppressants. However, the role of statins in the immunosuppressive response that is achieved in individual patients remains to be assessed.

OBJECTIVE

The aim of this study was to evaluate the immunomodulatory effect of atorvastatin given alone and in combined treatment with tacrolimus and mycophenolate mofetil.

STUDY DESIGN

Two patient groups were studied: renal transplant recipients receiving tacrolimus and mycophenolate mofetil therapy, and hypercholesterolemic patients (the control group). Fasting blood samples were taken from participants before and 1 month after atorvastatin treatment was started to study a small battery of biomarkers that are able to reflect the range of the effects of immunosuppressive therapy and atorvastatin.

SETTING

All patients in the study were enrolled at the Hospital Clinic of Barcelona.

PATIENTS

All patients enrolled in the study were candidates for treatment with atorvastatin because of high cholesterol levels. One group consisted of 25 stable renal transplant recipients with low-density lipoprotein (LDL) cholesterol levels above 100 mg/dL after 3 months of therapeutic lifestyle changes, according to the guidelines of the National Kidney Foundation - Kidney Disease Outcomes Quality Initiative. The other group included 25 hypercholesterolemic patients with LDL cholesterol levels above target values for the patients' overall risk, as derived from the National Cholesterol Education Program Adult Treatment Panel III criteria.

INTERVENTION

Atorvastatin (Lipitor®) treatment was started at a fixed dose of 20 mg daily.

MAIN OUTCOME MEASURE

The studied biomarkers were lymphocyte proliferation, intracellular adenosine triphosphate (ATP) synthesis in CD4+ T cells, intralymphocytary cytokine expression (interleukin [IL]-2, interferon [IFN]-γ), soluble cytokine production (IL-2, IFN-γ, IL-10, IL-17, and transforming growth factor-β) and regulatory T (T(reg)) cells.

RESULTS

Atorvastatin proved to be an immunomodulatory agent, significantly decreasing lymphocyte proliferation by 15% (p = 0.001), increasing ATP levels by 16% (p = 0.0004), and showing a trend toward increasing T(reg) cells in hypercholesterolemic patients (p = 0.09). In the renal transplant recipients, atorvastatin therapy did not modify any of the biomarkers of immunosuppression that were studied.

CONCLUSION

Atorvastatin showed immunoregulatory effects on T cells in hypercholesterolemic patients. These effects were absent in renal transplant recipients, suggesting that the beneficial effects of atorvastatin in this patient group do not relate to immunoregulation. Therefore, statin treatment cannot be considered as a means to reduce the dose of immunosuppressive agents.

Biomarkers as a tool for management of immunosuppression in transplant patients

Therapeutic drug monitoring is a well-established approach in transplantation medicine to guide immunosuppressive therapy. However, it cannot always predict the effects of immunosuppressive drugs on immune cells, because it does not reflect any aspect of an individual patient's immune system. Pharmacodynamic monitoring is a more recent strategy to provide information about the biologic effect of a specific drug or drug combination on the individual transplant patient. Currently, there is a large number of different biomarkers that either directly (specific markers) or indirectly (global markers) relate to the pharmacodynamic effects of immunosuppressive drugs and are under investigation as potential candidates to be introduced in clinical practice. Such biomarkers may be useful to identify patients at risk of developing acute rejection, infection, or cancer as well as patients who are suitable for minimization of immunosuppressant therapy and may be helpful to manage the timing and rate of immunosuppressant weaning. Serial longitudinal monitoring may allow maintenance of an individualized immunosuppressive regimen. Thus, biomarker monitoring is a potential complementary tool to therapeutic drug monitoring. This review summarizes the current state of knowledge about the use of a number of global or drug-specific pharmacodynamic biomarkers. It is not a comprehensive overview of the literature available, but rather an evidence-based reflection by experts who are intensively involved in scientific work in this field.

Single time point immune function assay (ImmuKnow) testing does not aid in the prediction of future opportunistic infections or acute rejection

BACKGROUND AND OBJECTIVES

Current assays and tests that are used to determine the degree of immunosuppression in renal transplant recipients are suboptimal. The ImmuKnow assay (Cylex), a measure of intracellular CD4+ T cell ATP release proposed as a means to quantify cell-mediated immunity in transplant recipients, could be considered as a potential tool to identify patients at risk for opportunistic infections (OI) or acute rejection (AR).

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We retrospectively analyzed 1330 ImmuKnow assay values in 583 renal transplant recipients at a single center from 2004 to 2009 and correlated these values with episodes of OI and AR in the subsequent 90 days. Assay values were compared with a control population matched for age, gender, and time post-transplantation.

RESULTS

In patients with OI (n=94), there were no differences in prior mean assay values compared with matched controls (386 versus 417 ng/ml, P=0.24). In 47 patients with AR, again no differences were detected in prior assay results (390 versus 432 ng/ml, P=0.25) when compared with controls. "Low" values (≤225 ng/ml) lacked sensitivity and specificity as a predictive test for subsequent OI, as did "strong" (≥525 ng/ml) values as a predictive test for subsequent AR.

CONCLUSIONS

Our results fail to show an association between single time point ImmuKnow assay values and the subsequent development of an adverse event in the subsequent 90 days. The optimal use of the ImmuKnow assay in kidney transplantation has yet to be determined.

Novel strategies for immune monitoring in kidney transplant recipients

The ongoing quandary in kidney transplantation is discovering methods to prolong graft survival. To achieve this, there is a search for optimal methods to use immunosuppressive therapy, where rejection and chronic graft damage is minimized without causing an increased risk of infections, malignancy, or toxicities. The purpose of this review was to discuss the limitations of current immunosuppressant drug monitoring as well as the clinical application of novel methods of monitoring both immunosuppressants and the immune reaction within the allograft.