Biomarkers of over-immunosuppression

A Sequential Two-Step Cell-Based Assay Predicts Immunosuppression-Related Adverse Events

Immunosuppressants are associated with serious and often life-threatening adverse effects. To optimize immunotherapy, a tool that measures the immune reserve is necessary. We validated that a cell-based assay that measures TNF-α production by CD14⁺16⁺ intermediate monocytes following stimulation with EBV peptides has high sensitivity for the detection of over-immunosuppression (OIS) events. To develop a sequential, two-step assay with high specificity, we used PBMCs from kidney recipients (n = 87). Patients were classified as cases or controls, according to the occurrence of opportunistic infection, recurring bacterial infections, or de novo neoplasia. Patients who tested positive in the first step were randomly allocated to a training or a testing set for the development of the second step. In the discovery phase, an assay based on the examination of early mature B (eBm5) cells was able to discriminate OIS patients from controls with a specificity of 88%. The testing set also revealed a specificity of 88%. The interassay coefficient of variability between the experiments was 6.1%. Stratified analyses showed good diagnostic accuracy across tertiles of age and time posttransplant. In the adjusted model, the risk of OIS was more than 12 times higher in patients classified as positive than in those who tested negative (adjusted hazard ratio, 12.2; 95% confidence interval: 4.3-34.6). This sequential cell-based assay, which examines the monocyte and eBm5 cell response to EBV peptides, may be useful for identifying OIS in immunosuppressed patients.

Association of Pretransplant BK Polyomavirus Antibody Status with BK Polyomavirus Infection After Kidney Transplantation: A Prospective Cohort Pilot Study of 47 Transplant Recipients

BACKGROUND

Prevention and early detection of BK polyomavirus (BKV) infection is important for long-term kidney graft survival; hence, pretransplant screening methods are essential to identify recipients at high risk for BKV infection. This study investigated the association of pretransplant donor and recipient BKV antibody status with the occurrence of post-transplant BKV infection.

METHODS

We prospectively enrolled 47 adult living donor kidney transplant pairs from December 2014 to January 2016. Recipient and donor pretransplant BKV antibody titer was measured by hemagglutination inhibition (HI) test. Donor and recipient median HI titer of 1:20 was used as a cutoff to define seropositivity. Recipients were divided into 2 groups (BKV antibody donor-seropositive/recipient-seronegative (D+/R-) and non-D+/R-). Urinary cytology was used to screen for BKV infection. Plasma polymerase chain reaction testing for BKV DNA was used when decoy cells in urine were persistently detected.

RESULTS

Nine (19.2%) of 47 patients belonged to the D+/R- group. Decoy cells were observed in 32 recipients (68.1%) during follow-up. BK viremia occurred in 3 (6.4%) cases. The maximum decoy cell count was significantly higher in the D+/R- group than in the non-D+/R- group (P = .0002). Decoy-cell-free survival was significantly shorter in the D+/R- group (P = .0220). Multivariate analysis identified only BKV antibody serostatus as an independent risk factor for decoy cell appearance (P = .0491).

CONCLUSIONS

Pretransplant donor and recipient BKV antibody status was associated with higher maximum decoy cell count and shorter decoy-cell-free survival after kidney transplantation.

TNF-α Production by Monocytes Stimulated With Epstein-Barr Virus-Peptides as a Marker of Immunosuppression-Related Adverse Events in Kidney Transplant Recipients

Introduction

Infections and cancers now outnumber rejection as a cause of morbidity in transplant recipients, likely as a result of over-immunosuppression. Currently, there is no clinical tool to detect over-immunosuppression. We recently reported that tumor necrosis factor alpha (TNF-α) production by CD14⁺CD16⁺ intermediate monocytes, following ex vivo stimulation by Epstein-Barr virus–peptides, could identify over-immunosuppressed patients.

Methods

We conducted a pilot study the assay using 142 peripheral blood mononuclear samples from a cohort of 71 kidney transplant recipients. Patients were classified as cases or controls according to the occurrence of opportunistic infection, recurring bacterial infections or de novo neoplasia in the 12 months following blood collection. We used both the classifier rule and a threshold of <73% of CD14⁺CD16⁺TNFα⁺ cells developed in a previous training set.

Results

Cases were detected with 83% sensitivity and 68% specificity. The negative predictive value of the assay was 89%. The hazard ratio for the occurrence of the endpoint was 6.8 (95% confidence interval 2.0–23.9; P = 0.003) in patients with a positive test. Multivariable linear regression analysis revealed that the association was independent of baseline clinical characteristics, renal function, and immunosuppressive regimen.

Conclusion

These data validate this cell-based assay as a promising tool for personalizing immunotherapy. Studies are under way for a 2-step assay with improved specificity.

Evidence for Persistent Immune Suppression in Patients Who Develop Chronic Critical Illness After Sepsis

BACKGROUND

Many sepsis survivors develop chronic critical illness (CCI) and are assumed to be immunosuppressed, but there is limited clinical evidence to support this. We sought to determine whether the incidence of secondary infections and immunosuppressive biomarker profiles of patients with CCI differ from those with rapid recovery (RAP) after sepsis.

METHODS

This prospective observational study evaluated 88 critically ill patients with sepsis and 20 healthy controls. Cohorts were defined based on clinical trajectory (early death, RAP, or CCI), whereas immunosuppression was clinically determined by the presence of a postsepsis secondary infection. Serial blood samples were collected for absolute lymphocyte counts (ALCs), monocytic human leukocyte antigen-DR (mHLA-DR) expression, and plasma-soluble programmed death-ligand 1 (sPD-L1) concentrations.

RESULTS

Of the 88 patients with sepsis, 3 (3%) died within 14 days of sepsis onset, 50 (57%) experienced RAP, and 35 (40%) developed CCI. Compared with RAP patients, CCI patients exhibited a higher incidence and overall number of infections adjusted for hospital length of stay. ALC and mHLA-DR levels were dramatically reduced at the time of sepsis diagnosis when compared with healthy controls, whereas sPD-L1 concentrations were significantly elevated. There were no differences between RAP and CCI patients in ALC, sPD-L1, or mHLA-DR at the time of diagnosis or within 24 h after sepsis diagnosis. However, in contrast to the RAP group, CCI patients failed to exhibit any trend toward restoration of normal values of ALC, HLA-DR, and sPD-L1.

CONCLUSIONS

Septic patients demonstrate clinical and biological evidence to suggest they are immunosuppressed at the time of sepsis diagnosis. Those who develop CCI have a greater incidence of secondary infections and persistently aberrant markers of impaired host immunity, although measurements at the time of sepsis onset did not distinguish between subjects with RAP and CCI.

Management of BK Polyomavirus Infection in Kidney and Kidney-Pancreas Transplant Recipients: A Review Article

BK virus (BKV) can cause graft dysfunction or failure in kidney transplant recipients and hemorrhagic cystitis in allogeneic hematopoietic stem cell transplant patients. BKV-associated nephropathy (BKVAN) emerged as a common complication in the late 1990s, probably due to the introduction of potent immunosuppressive agents. BKVAN occurred in up to 5% of kidney transplant recipients, with graft failure in up to 70%. Since universal implementation of effective screening and treatment strategies, BKV is no longer a common cause of graft failure; reported graft loss is only 0% to 5%. This article briefly describes BK virology, epidemiology, diagnosis, and management.

BK viremia is not associated with adverse outcomes in the absence of BK nephropathy

There are limited data regarding the association of different levels of BK viremia and BK nephropathy (BKN), and graft outcomes. We studied the BK plasma PCR levels of all kidney transplant recipients (KTR) transplanted at our institution between 01/01/2006 and 06/30/2014. Patients were divided into groups based on their highest BK plasma PCR level within the first year following transplantation: undetectable, low (<1000 copies/mL), moderate (1000-10 000 copies/mL), high (>10 000-100 000 copies/mL), very high (>100 000 copies/mL), and those that had biopsy-proven BKN. There were a total of 1146 KTR during the study period: 813 with undetectable BK levels and 333 with any detectable BK level (87 with low, 79 with moderate, 88 with high, 34 with very high level BK, and 45 that had BKN). Compared to KTR with an undetectable BK level, incidence of mortality, graft failure, rejections,and infections were not significantly different for those with low, moderate, high, or very high BK level. Patients with BKN had a higher rate of infection and higher rates of total graft failure or death-censored graft failure compared to those with undetectable BK levels. BK viremia in the absence of BKN does not significantly increase the risk of rejection, infections, or graft failure compared to an undetectable BK level.

Low T-Cell Responses to Mitogen Stimulation Predicts Poor Survival in Recipients of Allogeneic Hematopoietic Stem Cell Transplantation

Background

Successful engraftment and reconstitution of the innate and adaptive immune system are associated with improved outcomes in recipients of allogeneic hematopoietic stem cell transplantation (HSCT). A clinically meaningful and simple biomarker of immunosuppression could potentially assist clinicians in their decision-making. We aimed to determine the relationship between T-cell production of interferon gamma (IFN-γ) in response to phytohemagglutinin (PHA) to clinical outcomes in HSCT recipients.

Methods

A prospective observational multicenter study of 73 adult allogeneic HSCT recipients was conducted in Melbourne, Australia. Eligible participants were >18 years and at risk of cytomegalovirus disease. T-cell responses to PHA were assessed at 3, 6, 9, and 12 months post-HSCT using the commercial quantiferon-cytomegalovirus assay, which quantifies IFN-γ production by ELISA following stimulation with PHA. A low response was defined as IFN-γ <0.5 IU/ml following stimulation with PHA.

Results

At 3 months post-HSCT, high responses to PHA (median IFN-γ 7.68 IU/ml) were seen in 63% of participants and low responses to PHA (median IFN-γ 0.06 IU/ml) in 37%. IFN-γ responses to PHA were significantly associated with the severity of acute graft versus host disease (AGVHD) (spearman r = −0.53, p < 0.001) and correlated with blood lymphocyte count (spearman r = 0.52, p < 0.001). Twelve month overall survival was greater in individuals with high compared to low IFN-γ response to PHA at 3 months [92 vs. 62%, respectively, Cox proportional hazard ratio (HR): 4.12 95% CI: 1.2–13.7, p = 0.02]. Non-relapse mortality (NRM) was higher in individuals with low IFN-γ response to PHA (competing risk regression HR 11.6 p = 0.02). In individuals with no AGVHD compared to AGVHD and high IFN-γ response to PHA compared to AGVHD and low IFN-γ response to PHA, 12-month survival was 100 vs. 80 vs. 52%, respectively (log rank test p < 0.0001).

Conclusion

Low IFN-γ response to PHA at the 3-month time-point following allogeneic HSCT was predictive of reduced 12-month overall survival, increased NRM, and reduced survival in recipients with AGVHD. Assessing IFN-γ response to PHA post-HSCT may be a clinically useful immune biomarker.

Biomarkers in solid organ transplantation

Recipients of solid organs such as the kidney and heart are treated with standard immunosuppressive regimens, and personalized medicine has not yet reached the clinic for this patient population. Biomarkers potentially will allow treatment regimens to be adjusted, according to the needs of the individual patient. Biomarkers may reflect the degree of immunosuppression of the immune system, or they may reflect early damage to the transplanted organ.

Practical Recommendations for Long-term Management of Modifiable Risks in Kidney and Liver Transplant Recipients: A Guidance Report and Clinical Checklist by the Consensus on Managing Modifiable Risk in Transplantation (COMMIT) Group

Short-term patient and graft outcomes continue to improve after kidney and liver transplantation, with 1-year survival rates over 80%; however, improving longer-term outcomes remains a challenge. Improving the function of grafts and health of recipients would not only enhance quality and length of life, but would also reduce the need for retransplantation, and thus increase the number of organs available for transplant. The clinical transplant community needs to identify and manage those patient modifiable factors, to decrease the risk of graft failure, and improve longer-term outcomes.COMMIT was formed in 2015 and is composed of 20 leading kidney and liver transplant specialists from 9 countries across Europe. The group's remit is to provide expert guidance for the long-term management of kidney and liver transplant patients, with the aim of improving outcomes by minimizing modifiable risks associated with poor graft and patient survival posttransplant.The objective of this supplement is to provide specific, practical recommendations, through the discussion of current evidence and best practice, for the management of modifiable risks in those kidney and liver transplant patients who have survived the first postoperative year. In addition, the provision of a checklist increases the clinical utility and accessibility of these recommendations, by offering a systematic and efficient way to implement screening and monitoring of modifiable risks in the clinical setting.

A Rationale for Age-Adapted Immunosuppression in Organ Transplantation

Demographic changes are associated with a steady increase of older patients with end-stage organ failure in need for transplantation. As a result, the majority of transplant recipients are currently older than 50 years, and organs from elderly donors are more frequently used. Nevertheless, the benefit of transplantation in older patients is well recognized, whereas the most frequent causes of death among older recipients are potentially linked to side effects of their immunosuppressants.Immunosenescence is a physiological part of aging linked to higher rates of diabetes, bacterial infections, and malignancies representing the major causes of death in older patients. These age-related changes impact older transplant candidates and may have significant implications for an age-adapted immunosuppression. For instance, immunosenescence is linked to lower rates of acute rejections in older recipients, whereas the engraftment of older organs has been associated with higher rejection rates. Moreover, new-onset diabetes mellitus after transplantation is more frequent in the elderly, potentially related to corticosteroids, calcineurin inhibitors, and mechanistic target of rapamycin inhibitors.This review presents current knowledge for an age-adapted immunosuppression based on both, experimental and clinical studies in and beyond transplantation. Recommendations of maintenance and induction therapy may help to improve graft function and to design future clinical trials in the elderly.

Risk Stratification for Rejection and Infection after Kidney Transplantation

BACKGROUND AND OBJECTIVES

Definition of individual risk profile is the first step to implement strategies to keep the delicate balance between under- and overimmunosuppression after kidney transplantation.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We used data from the Efficacy Limiting Toxicity Elimination Symphony Study (1190 patients between 2002 and 2004) to model risk of rejection and infection in the first year after kidney transplantation. External validation was performed in a study population from the Fixed-Dose Concentration-Controlled Trial (630 patients between 2003 and 2006).

RESULTS

Despite different temporal dynamics, rejections and severe infections had similar overall incidences in the first year after transplantation (23.4% and 25.5%, respectively), and infections were the principal cause of death (43.2% of all deaths). Recipient older age, deceased donor, higher number of HLA mismatches, and high risk for cytomegalovirus disease were associated with infection; deceased donor, higher number of HLA mismatches, and immunosuppressive therapy including cyclosporin A (compared with tacrolimus), with rejection. These factors were integrated into a two-dimensional risk stratification model, which defined four risk groups: low risk for infection and rejection (30.8%), isolated risk for rejection (36.1%), isolated risk for infection (7.0%), and high risk for infection and rejection (26.1%). In internal validation, this model significantly discriminated the subgroups in terms of composite end point (low risk for infection/rejection, 24.4%; isolated risk for rejection and isolated risk for infection, 31.3%; high risk for infection/rejection, 54.4%; P<0.001), rejection episodes (isolated risk for infection and low risk for infection/rejection, 13.0%; isolated risk for rejection and high risk for infection/rejection, 24.2%; P=0.001), and infection episodes (low risk for infection/rejection and isolated risk for rejection, 12.0%; isolated risk for infection and high risk for infection/rejection, 37.6%; P<0.001). External validation confirmed the applicability of the model to an independent cohort.

CONCLUSIONS

We propose a two-dimensional risk stratification model able to disentangle the individual risk for rejection and infection in the first year after kidney transplantation. This concept can be applied to implement a personalized immunosuppressive and antimicrobial treatment approach.

Clinical laboratory diagnostics of immunosuppressants: One laboratory’s journey

Laboratory support for the organ transplant patient is the provision of the best testing technology for a specific and accurate determination of immunosuppressive drug level. This translates to better management with the therapeutic cocktail of immunosuppressive drugs used with a lesser incidence of organ rejection and side effects. Over the years, development of automated immunoassay/chemistry test platforms with standardization of test protocols has demonstrated great improvements. The present clinical laboratory services with tandem mass spectrometry in our hospital present more precise and specific therapeutic drug monitoring so necessary still for the patient. This article follows the evolving testing technologies over the years for immunosuppressive drug monitoring following the organ transplants programme (renal in general) in Singapore General Hospital.

The need for minimization strategies: current problems of immunosuppression

New immunosuppressants and the better use of immunosuppressant combination therapy have led to significant improvements in renal allograft outcomes over the last decades. Yet, despite dramatic reduction in rejection rates and improvement in 1-year graft survival, long-term graft attrition rates remained rather constant. Current immunosuppressant combinations are frequently leading to overimmunosuppression and are increasing cardiovascular risk. Importantly, calcineurin inhibitors are nephrotoxic, contribute to cardiovascular risk and chronic allograft dysfunction. Furthermore, immunosuppressant-associated toxicities aggravate immune-mediated nephron injury and side effects lead to nonadherence, an identified important reason for late acute and chronic antibody-mediated rejections. The frequent development of a chronic humoral response indicates rather insufficient immunosuppression of current combinations than simple under-immunosuppression. While there is no evidence that increasing immunosuppressive doses will improve outcomes or reduce de novo HLA-antibody formation, there is clear evidence that adequate minimization strategies will reduce side effect burden. Because of low rejection risk, but frequent side effects, drug minimization is particularly relevant for the many maintenance patients. In summary, new therapeutic strategies need to be developed from adequately powered clinical trials for reduction of the many side effects of immunosuppressants. Such evidence-based and time-dependent immunosuppressive minimization strategies are needed to achieve better long-term outcomes in the future.

The use of novel diagnostics to individualize immunosuppression following transplantation

Despite major improvements in short-term survival of organ allografts, long-term graft survival has not changed significantly. It is also known that toxic side effects of current immunosuppressive drugs (IS) especially calcineurin inhibitors (CNI) contribute to the unsatisfactory graft and patient survival following transplantation. Thus, clinicians strive to reduce or wean IS in potentially eligible patients. Research in the last 10 years has focussed on identification of biomarkers suitable for patient stratification in minimization or weaning trials. Most of the described biomarkers have been run retrospectively on samples collected within single-centre trials. Thus, often their performance has not been validated in other potentially multicentre clinical trials. Ultimately, the utility of biomarkers to identify potential weaning candidates should be investigated in large randomized prospective trials. In particular, for testing in such trials, we need more information about the accuracy, reproducibility, stability and limitations of the described biomarkers. Also, data repositories summarizing crucial information on biomarker performance in age- and gender-matched healthy individuals of different ethnicity are missing. This together with improved bioinformatics tools might help in developing better scores for patient stratification. Here, we will summarize the current results, knowledge and limitations on biomarkers for drug minimization or weaning trials.

Temporal response of the human virome to immunosuppression and antiviral therapy

There are few substantive methods to measure the health of the immune system, and the connection between immune strength and the viral component of the microbiome is poorly understood. Organ transplant recipients are treated with posttransplant therapies that combine immunosuppressive and antiviral drugs, offering a window into the effects of immune modulation on the virome. We used sequencing of cell-free DNA in plasma to investigate drug-virome interactions in a cohort of organ transplant recipients (656 samples, 96 patients) and find that antivirals and immunosuppressants strongly affect the structure of the virome in plasma. We observe marked virome compositional dynamics at the onset of the therapy and find that the total viral load increases with immunosuppression, whereas the bacterial component of the microbiome remains largely unaffected. The data provide insight into the relationship between the human virome, the state of the immune system, and the effects of pharmacological treatment and offer a potential application of the virome state to predict immunocompetence.

Update on the long-term complications of renal transplantation

INTRODUCTION

Powerful immunosuppressive regimens have reduced rejection risk, leading to an expanding cohort of long-term kidney transplant recipients who are likely to encounter practitioners in other specialties.

SOURCES OF DATA

Key review papers and primary literature identified through searches of PubMed, Google Scholar and Medline.

AREAS OF AGREEMENT

Death from cardiovascular disease and malignancy remain the chief causes of transplant loss. Risk factors and phenotypes for these differ from the general population.

AREAS OF CONTROVERSY

Many guidelines for renal transplant recipients are based on extrapolation from studies on non-transplant cohorts and may not be appropriate. Emerging studies demonstrate that established interventions in the general population are less efficacious in transplant recipients.

GROWING POINTS

The influence of immunosuppression on the development of complications.

AREAS TIMELY FOR DEVELOPING RESEARCH

Markers to guide individualized optimal immunosuppression and predict the development of complications would allow for targeted early intervention.

ImmuKnow as a diagnostic tool for predicting infection and acute rejection in adult liver transplant recipients: a systematic review and meta-analysis

Immune status monitoring of transplant recipients could identify patients at risk of acute rejection, infection, and cancer, which are important sources of morbidity and mortality in these patients. The ImmuKnow assay provides an objective assessment of the cellular immune function of immunosuppressed patients. Inconclusive results concerning the ability of the ImmuKnow test to predict acute rejection and infection have raised concerns about the predictive value of ImmuKnow in liver transplant recipients. We conducted a systematic literature review to identify studies published up to March 2012 that documented the use of ImmuKnow for monitoring immune function in liver transplant recipients. The study quality was assessed with the Quality Assessment of Diagnostic Accuracy Studies 2 score. We identified 5 studies analyzing ImmuKnow performance for infection and 5 studies analyzing ImmuKnow performance for acute rejection. The pooled sensitivity, specificity, positive likelihood ratio, diagnostic odds ratio, and area under the summary receiver operating characteristic curve were 83.8% [95% confidence interval (CI) = 78.5%-88.3%], 75.3% (95% CI = 70.9%-79.4%), 3.3 (95% CI = 2.8-4.0), 14.6 (95% CI = 9.6-22.3), and 0.824 ± 0.034, respectively, for infection and 65.6% (95% CI = 55.0%-75.1%), 80.4% (95% CI = 76.4%-83.9%), 3.4 (95% CI = 2.4-4.7), 8.8 (95% CI = 3.1-24.8), and 0.835 ± 0.060, respectively, for acute rejection. Heterogeneity was low for infection studies and high for acute rejection studies. In conclusion, the ImmuKnow test is a valid tool for determining the risk of further infection in adult liver transplant recipients. Significant heterogeneity across studies precludes the conclusion that ImmuKnow identifies liver transplant patients at risk for rejection.

The influence of UGT polymorphisms as biomarkers in solid organ transplantation

In solid organ transplant patients, it is important to maintain a fine balance between preventing rejection and reducing adverse effects. Several immunosuppressive agents such tacrolimus, cyclosporine, sirolimus and everolimus require therapeutic drug monitoring. The study of germline variation of the genome has opened novel opportunities to individualize therapy. Among the currently available immunosuppressive agents, cyclosporine, tacrolimus and mycophenolic acid are in vitro substrates of the UGT1A and 2B families of glucuronidation enzymes. Mycophenolic acid, either given as mycophenolate mofetil or mycophenolate sodium, is the most frequently used antiproliferative immunosuppressant. Mycophenolic acid is a prodrug which is rapidly de-esterified in the gut wall, blood, liver and tissue to the active moiety, mycophenolic acid (MPA). MPA undergoes significant hepatic metabolism to several metabolites. The 7-hydroxyglucuronide MPA is the major metabolite and is inactive. This paper reviews the current status of the genetic associations between germline UGT variants and the pharmacokinetics and pharmacodynamics of mycophenolic acid. Our conclusive assessment of the studies conducted so far is that these germline markers are not ready to be used in the clinic to individualize mycophenolic acid dosing and improve outcome. Novel approaches are required to identify new genetic determinants of outcomes in transplantation.