Biomarkers as a tool for management of immunosuppression in transplant patients. Ther Drug Monit. 2010;32:560-572. [PMID: 20814352 DOI: 10.1097/ftd.0b013e3181efb3d2]

Torque Teno Virus: A Promising Biomarker in Kidney Transplant Recipients

Torque Teno Virus (TTV) is a ubiquitous component of the human virome, not associated with any disease. As its load increases when the immune system is compromised, such as in kidney transplant (KT) recipients, TTV load monitoring has been proposed as a method to assess immunosuppression. In this prospective study, TTV load was measured in plasma and urine samples from 42 KT recipients, immediately before KT and in the first 150 days after it. Data obtained suggest that TTV could be a relevant marker for evaluating immune status and could be used as a guide to predict the onset of infectious complications in the follow-up of KT recipients. Since we observed no differences considering distance from transplantation, while we found a changing trend in days before viral infections, we suggest to consider changes over time in the same subjects, irrespective of time distance from transplantation.

Lymphocyte function based on IFN-γ secretion assay may be a promising indicator for assessing different immune status in renal transplant recipients

BACKGROUND

Immunological monitoring plays a crucial role in organ recipients for allowing tailoring of immunosuppression. However, there is still a paucity of promising indicators for detecting immune status in recipients.

METHODS

We conducted a prospective study to characterize the immune status by detecting dynamically lymphocyte subsets and function (represented by the abilities to secrete IFN-γ) in the first 6 months posttransplant in renal recipients. Participants were classified into an immune stable group, infected group, and rejected group.

RESULTS

In the stable group, our study suggested that the counts and function of CD4+ T, CD8+ T, and NK lymphocytes decreased to their nadir at week 2, and thereafter these indicators were gradually restored. The counts exceeded pre-operative levels, whereas function did not reach the pre-transplant levels by 6 months. We demonstrated that function of lymphocytes was considerably decreased in infected recipients compared with the stable group when infection occurred. By contrast, the function of lymphocytes was obviously increased at the point of rejection. Receiver operating characteristic (ROC) analysis in the combination of subsets and function of lymphocytes presented a superior clinical value with an area under the curve (AUC) of 0.903 in the diagnosis of infected receivers, and IFN-γ+CD8+ T cells% is the highest indicator with the auROC curve of 0.862. Another ROC analysis confirmed that IFN-γ+CD4  T cells% presented a preferable diagnostic value with an area of 0.887 for rejected recipients.

CONCLUSIONS

In conclusion, the ability of lymphocyte subsets secreting IFN-γ may provide a promising assessment of immune status in recipients and allow timely modifying immunosuppression.

CYP3A5 and UGT1A9 Polymorphisms Influence Immunosuppressive Therapy in Pediatric Kidney Transplant Recipients

Background: Tacrolimus (TAC) and mycophenolic acid (MPA) are the main immunosuppressive drugs used in pediatric kidney transplantation. Single nucleotide polymorphisms (SNPs) in metabolizing enzymes and transporters might influence plasma levels of these drugs. Herein, we sought to determine the influence of SNPs on CYP3A5, MRP2 and UGT1A9 genes in Chilean pediatric kidney recipients using TAC and MPA. Patients and Methods: A prospective study was performed on 104 pediatric kidney recipients that used TAC and MPA for immunosuppression. The median age at the time of transplantation was 8.1 years [Q1-Q3 4.5-11.6 years] and the main clinical diagnosis was a structural anomaly. In a subgroup of patients, a complete steroid withdrawal was made at day 7. The CYP3A5 polymorphism (ancestral allele *1; variant allele *3) was determined in the entire cohort, while MRP2 -24G > A, UGT1A9 -275T > A, and UGT1A9 -2152C > T polymorphisms were determined in 53 patients. Genotypes were associated with trough drug concentrations (C₀), dose requirements normalized by weight (TAC-D mg/kg) or body surface (MPA-D mg/m2), trough levels normalized by dose requirements (C₀/D), and area under the curve in 12 h normalized by dose requirements (AUC_0-12h/D). Results: The frequencies of the variant alleles CYP3A5*3, MRP2-24A, UGT1A9-275A, and UGT1A9-2152T were 76.9, 22.1, 6.6, and 2.9%, respectively. AUC_0-12h/TAC-D were 1.6-fold higher in CYP3A5*3/*3 patients than in CYP3A5*1 carriers (CYP3A5*1/*3 and CYP3A5*1/*1). When analyzing patients with steroid withdrawal, CYP3A5*3/*3 patients had 1.7-fold higher AUC_0-12h/TAC-D than the other genotypes. Patients carrying the CYP3A5*3/*3 genotype had higher TAC-C₀, lower TAC-D and higher TAC-C₀/D, consistently in a 6-months follow-up. Creatinine clearance was stable during the follow-up, regardless of the genotype. No significant differences between MRP2 and UGT1A9 genotypes were observed in MPA-C₀, MPA-D or MPA-C₀/D. However, patients carrying the UGT1A9-275A allele had lower AUC_0-12h/MPA-D than those carrying the UGT1A9-275T ancestral allele. Conclusions: These results support that CYP3A5 and UGT1A9 genotyping in pediatric recipients might be useful and advisable to guide TAC and MPA dosing and monitoring in children that undergo kidney transplantation.

Immune cell function assays in the diagnosis of infection in pediatric liver transplantation: an open-labeled, two center prospective cohort study

BACKGROUND

Limited studies have been performed in assessment of immune status of pediatric liver transplants (PLTs). We conducted this study to evaluate Cylex immune cell function assay in diagnosis of infection and its potential clinical application in Chinese infant PLTs.

METHODS

In this prospective cohort study, 227 infant PLTs from two medical centers were enrolled, and 216 completed the study. Cylex ATP values were measured before and after liver transplantation (LT) at week 1, 2, 3, 4, 8, 12 and 24 respectively. Accordingly, patients' clinical records, including demographic data, liver function results, tacrolimus dosages and concentrations were collected and analyzed.

RESULTS

One hundred and sixty of 216 PLTs (74.1%) were diagnosed infection based on the parameters including abnormal vital signs, imaging changes, and pathogens detection, while 44 (20.4%) were clinically stable and 12 (5.6%) experienced acute rejection. The median Cylex ATP value in infant PLTs post-surgery reduced significantly in infection group compared to stable group (median, 137 vs. 269 ng/mL, P<0.001). Receiver operating characteristic (ROC) curve analysis determined that the cut-off value of Cylex ATP was 152 ng/mL in diagnosis of infection [area under the curve (AUC): 0.784, 95% CI: 0.720-0.848]. Meanwhile, Cylex ATP value showed no correlation to tacrolimus dosage, blood concentration, dose-normalized concentration/dose ratio or Kaup index. However, it tended to correlate weakly with the white blood cell (WBC) number (R =0.462, P<0.0001) and lymphocyte counts (R =0.363, P<0.0001).

CONCLUSIONS

In this study, we demonstrated that low Cylex ATP represented partly over-immunosuppression and had diagnostic value in infant PLTs with infections, which might assist individualized immunosuppression in PLT patients.

Organ donation and transplantation: a multi-stakeholder call to action

Although overall donation and transplantation activity is higher in Europe than on other continents, differences between European countries in almost every aspect of transplantation activity (for example, in the number of transplantations, the number of people with a functioning graft, in rates of living versus deceased donation, and in the use of expanded criteria donors) suggest that there is ample room for improvement. Herein we review the policy and clinical measures that should be considered to increase access to transplantation and improve post-transplantation outcomes. This Roadmap, generated by a group of major European stakeholders collaborating within a Thematic Network, presents an outline of the challenges to increasing transplantation rates and proposes 12 key areas along with specific measures that should be considered to promote transplantation. This framework can be adopted by countries and institutions that are interested in advancing transplantation, both within and outside the European Union. Within this framework, a priority ranking of initiatives is suggested that could serve as the basis for a new European Union Action Plan on Organ Donation and Transplantation.

Torque Teno Virus as a Novel Biomarker Targeting the Efficacy of Immunosuppression After Lung Transplantation

Torque teno viruses (TTV) are small DNA-viruses, of the genus Alphatorquevirus, whose replication is linked to immune status. TTV load may be an indicator for efficacy of IS in lung transplant recipients (LTRs). In a prospective single-center-study 143 LTRs were followed up and tested by quantitative TTV-DNA PCR. Using multivariate Cox-regression contribution of TTV-load to the occurrence of severe infections, chronic lung allograft dysfunction (CLAD), acute cellular rejection (ACR), and death was assessed. During follow-up 28 (20%) patients developed infections with a rate of 7.7 per 100 patient-years (PY). The hazard-ratio (HR) associated with a one-log10 increase of TTV-load before the event was 5.05. CLAD occurred with a rate of 6.0%-PY. HR for a 1 log10 increase of the lowest TTV level before the event was 0.71 (CI: 0.54-0.93). TTV-load predicts clinical events and may be useful to optimize IS during the first years of follow-up of LTRs.

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.

Development of an immune function assay by measuring intracellular adenosine triphosphate (iATP) levels in mitogen-stimulated CD4+ T lymphocytes

We developed an immune function assay for monitoring CD4+ T cells activity based on changes in intracellular adenosine triphosphate (iATP) levels after phytohemagglutinin (PHA) stimulation. Blood samples were obtained from 40 healthy subjects and 30 RTRs and incubated with 5 µg/mL of PHA for 15-18 hr at 37°C and 5% CO2. Afterward, the CD4+ T cells were separated by antibody-coated magnetic beads and lysed. Then, iATP content in unstimulated and stimulated conditions was measured by luciferin-luciferase reaction using a log-log standard curve. The iATP levels showed significant increase in CD4+ T cells in both healthy persons (mean: 550 ± 142 ng/mL vs. 109 ± 54 ng/mL) and RTRs (mean: 394 ± 160 ng/mL vs. 52 ± 37 ng/mL) after PHA stimulation (P < 0.001). However, the iATP production in RTRs was significantly lower than that in healthy individuals; both prior to and after stimulation with PHA (P < 0.001). No gender-specific difference in iATP production was observed between women and men subjects. This rapid and low-cost assay reflects the degree of immune cell function through assessment of CD4+ T cells activation. Thus, it can be used for evaluation of immune system status in immunodeficient individuals as well as in immunosuppressed transplant recipients who needs drug adjustment.

Barcelona Consensus on Biomarker-Based Immunosuppressive Drugs Management in Solid Organ Transplantation

With current treatment regimens, a relatively high proportion of transplant recipients experience underimmunosuppression or overimmunosuppression. Recently, several promising biomarkers have been identified for determining patient alloreactivity, which help in assessing the risk of rejection and personal response to the drug; others correlate with graft dysfunction and clinical outcome, offering a realistic opportunity for personalized immunosuppression. This consensus document aims to help tailor immunosuppression to the needs of the individual patient. It examines current knowledge on biomarkers associated with patient risk stratification and immunosuppression requirements that have been generally accepted as promising. It is based on a comprehensive review of the literature and the expert opinion of the Biomarker Working Group of the International Association of Therapeutic Drug Monitoring and Clinical Toxicology. The quality of evidence was systematically weighted, and the strength of recommendations was rated according to the GRADE system. Three types of biomarkers are discussed: (1) those associated with the risk of rejection (alloreactivity/tolerance), (2) those reflecting individual response to immunosuppressants, and (3) those associated with graft dysfunction. Analytical aspects of biomarker measurement and novel pharmacokinetic-pharmacodynamic models accessible to the transplant community are also addressed. Conventional pharmacokinetic biomarkers may be used in combination with those discussed in this article to achieve better outcomes and improve long-term graft survival. Our group of experts has made recommendations for the most appropriate analysis of a proposed panel of preliminary biomarkers, most of which are currently under clinical evaluation in ongoing multicentre clinical trials. A section of Next Steps was also included, in which the Expert Committee is committed to sharing this knowledge with the Transplant Community in the form of triennial updates.

Nuclear Factor of Activated T Cells-Regulated Gene Expression as Predictive Biomarker of Personal Response to Calcineurin Inhibitors

BACKGROUND

Calcineurin inhibitors (CNIs) represent the most widely used immunosuppressive agents in kidney transplantation. Both CNIs show a narrow therapeutic window; thus, monitoring is necessary to balance efficacy and toxicity. Several approaches have been undertaken to measure the biological effects of CNI-based immunosuppression.

METHODS

A quantitative analysis of gene expression was established to calculate the functional effects of calcineurin inhibition, the assessment of nuclear factor of activated T cells (NFAT)-regulated gene expression. This assay is based on the quantitative analysis of interleukin-2, interferon-γ, and granulocyte macrophage colony-stimulating factor gene expression in whole blood samples collected at the time cyclosporine A/tacrolimus troughs (C0) and 2 hours after oral uptake (C2).

RESULTS

In this comprehensive review, analytical aspects of the assay and also clinical benefits and limitations are presented and discussed. Several observational studies underline the beneficial effect of NFAT-regulated gene expression as biomarker of personal response on CNI therapy, especially in infectious complications, malignancies, and acute rejection episodes. Data are more comprehensive in cyclosporine A compared with tacrolimus therapy. However, results on prospective interventional studies are sparse. A randomized controlled study evaluating the opportunity for NFAT-guided immunosuppression is ongoing.

CONCLUSIONS

NFAT-regulated gene expression is a promising biomarker in CNI therapy concerning infectious complications, malignancies, and acute rejection. Prospective interventional studies and randomized controlled studies are ongoing to confirm the encouraging results.

The pharmacokinetics and pharmacodynamics of mycophenolate mofetil in younger and elderly renal transplant recipients

AIMS

Elderly transplant recipients have a lower incidence of acute rejection, and a higher risk to die from infectious complications. A potential cause may be differences in the pharmacokinetics (PK) or pharmacodynamics (PD) of the immunosuppressive drugs they are taking. This study was designed to comprehensively evaluate the influence of age on the PK and PD of mycophenolic acid (MPA).

METHODS

In this study the PK and PD of MPA was studied in 26 elderly and 54 younger renal transplant recipients treated with mycophenolate mofetil and tacrolimus. Patients were sampled repetitively, both before and during the first 6 months after kidney transplantation. Age-related variability in MPA PK, baseline IMPDH activity, as well as MPA-induced IMPDH inhibition were studied.

RESULTS

The IMPDH activity pre-transplantation did not differ between elderly and younger patients. Neither IMPDH activity pre-transplantation nor maximum IMPDH inhibition was significantly correlated with the patients' age. The area under the MPA plasma concentration-time curve (AUC_0-12h ) and the area under the effect (IMPDH activity)-time curve (AEC_0-12h ) from 0 to 12 h were also not significantly different between the two groups. We found no significant differences in EC₅₀ and E_max between elderly and younger patients.

CONCLUSIONS

Age did not significantly affect the PK or PD of MPA. It is unlikely that the lower incidence of acute rejection in elderly patients, or the higher risk to die from a severe infection in elderly patients is due to different handling of MPA in the elderly.

Relationship between immune function recovery and infectious complications in patients following living donor liver transplantation

AIM

The ImmuKnow (IK) assay enables the evaluation of peripheral blood CD4(+) adenosine triphosphate activity to facilitate an objective assessment of the cellular immune function in immunosuppressed patients. However, it is unclear whether the IK assay is utilized during the acute postoperative periods following living donor liver transplantation (LDLT).

METHODS

The IK values of 43 LDLT recipients were measured during the month following LDLT to evaluate the relationship between the measured IK values and infectious events.

RESULTS

The IK values after LDLT were significantly increased compared with the IK values before LDLT ( P < 0.01). During the month following transplantation, the rate of bacterial infection in the recipients with IK values of more than 225 ng/mL was significantly lower than that in the recipients with IK values of 225 ng/mL or less ( 42.1% vs 91.7%, respectively; P < 0.01). The rate of severe infections among the recipients who maintained IK values of more than 150 ng/mL was significantly lower than that among the recipients with IK values of 150 ng/mL or less during the month following transplantation ( 3.7% vs 56.3%, respectively; P < 0.01).

CONCLUSION

The immune system of LDLT recipients dramatically improved following transplantation. The IK values of LDLT recipients were associated with the incidence of infectious events during the perioperative period after LDLT. Monitoring IK values was useful during both the acute and long-term postoperative periods.

Monitoring pharmacologically induced immunosuppression by immune repertoire sequencing to detect acute allograft rejection in heart transplant patients: a proof-of-concept diagnostic accuracy study

BACKGROUND

It remains difficult to predict and to measure the efficacy of pharmacological immunosuppression. We hypothesized that measuring the B-cell repertoire would enable assessment of the overall level of immunosuppression after heart transplantation.

METHODS AND FINDINGS

In this proof-of-concept study, we implemented a molecular-barcode-based immune repertoire sequencing assay that sensitively and accurately measures the isotype and clonal composition of the circulating B cell repertoire. We used this assay to measure the temporal response of the B cell repertoire to immunosuppression after heart transplantation. We selected a subset of 12 participants from a larger prospective cohort study (ClinicalTrials.gov NCT01985412) that is ongoing at Stanford Medical Center and for which enrollment started in March 2010. This subset of 12 participants was selected to represent post-heart-transplant events, with and without acute rejection (six participants with moderate-to-severe rejection and six without). We analyzed 130 samples from these patients, with an average follow-up period of 15 mo. Immune repertoire sequencing enables the measurement of a patient's net state of immunosuppression (correlation with tacrolimus level, r = -0.867, 95% CI -0.968 to -0.523, p = 0.0014), as well as the diagnosis of acute allograft rejection, which is preceded by increased immune activity with a sensitivity of 71.4% (95% CI 30.3% to 94.9%) and a specificity of 82.0% (95% CI 72.1% to 89.1%) (cell-free donor-derived DNA as noninvasive gold standard). To illustrate the potential of immune repertoire sequencing to monitor atypical post-transplant trajectories, we analyzed two more patients, one with chronic infections and one with amyloidosis. A larger, prospective study will be needed to validate the power of immune repertoire sequencing to predict rejection events, as this proof-of-concept study is limited to a small number of patients who were selected based on several criteria including the availability of a large number of samples and the absence or presence of rejection events.

CONCLUSIONS

If confirmed in larger, prospective studies, the method described here has potential applications in the tailored management of post-transplant immunosuppression and, more broadly, as a method for assessing the overall activity of the immune system.

P70S6 kinase phosphorylation: a new site to assess pharmacodynamy of sirolimus

Background:

The phosphorylation of p70S6 kinase (p70S6K) represents an important target for sensitive detection on pharmacodynamic effects of sirolimus, but the methods of assessing p70S6K phosphorylation are still unclear. The aim of this study was to investigate p70S6K phosphorylation located down-stream of the mammalian target of rapamycin (mTOR) pathway in peripheral blood mononuclear cells (PBMCs) of liver transplant patients through different methods.

Methods:

Seventy-five liver transplant recipients from Beijing Chaoyang Hospital of the Capital Medical University were analyzed in this study. Patients were divided into three groups, patient treated with sirolimus (n = 22), patient treated with tacrolimus (n = 30), patient treated with cyclosporine (n = 23). The p70S6K phosphorylation of PBMCs in patients and healthy control (HC, n = 12) were analyzed by phospho-flow cytometry and Western blotting. A correlation analysis of data from phospho-flow cytometry and Western blotting was performed. Intra-assay variability of p70S6K phosphorylation in HC and different patients were measured.

Results:

Intra-assay variability of p70S6K phosphorylation in phospho-flow cytometry was from 4.1% to 8.4% and in Western blotting was from 8.2% to 18%. The p70S6K phosphorylation in patients receiving a sirolimus (19.5 ± 7.7) was significantly lower than in HC (50.1 ± 11.3, P < 0.001), tacrolimus (37.7 ± 15.7, P < 0.001) or cyclosporine treated patients (41.7 ± 11.7, P < 0.001). The p70S6K phosphorylation in HC (50.1 ± 11.3) was significantly higher than in tacrolimus (37.7 ± 15.7, P < 0.01) or cyclosporine-treated patients (41.7 ± 11.7, P < 0.01). There was correlation between data from phospho-flow cytometry and data from Western blotting (r = 0.88, P < 0.001).

Conclusions:

The degree of mTOR inhibition by assessing p70S6K phosphorylation was established by phospho-flow cytometry and Western blotting. Assessment of p70S6K phosphorylation may play an adjunct role to on pharmacodynamically guide and individualize sirolimus based on immunosuppression.

Lymphocyte surface molecules as immune activation biomarkers

Immunosuppression is mandatory after solid organ transplantation between HLA mismatched individuals. It is a lifelong therapy that needs to be closely monitored to avoid under- and over-immunosuppression. For many drugs, pharmacokinetic monitoring has been proven to be beneficial. However, the therapeutic ranges are statistically derived surrogate markers for the effects that cannot predict the individual response of single patients. Better tailored immunosuppression biomarkers are needed that indicate immune activation. T cells are critically involved in organ rejection, and the means to assess their activation state may be promising to individualize immunosuppressive therapies. Activated T cells can be monitored with flow cytometry based on surface molecules that are typically up regulated or with molecules that are cleaved off the cell surface. Among these molecules are the interleukin-2 receptor (CD25); transferrin receptor (CD71); the T cell co-stimulatory molecules CD28, CD69, and CD154 and sCD30, which is a member of the TNF-alpha family. The effect of immunosuppressive drugs on T cell activation can be recorded with indirect cell function assays or by directly monitoring activated T cells in whole blood. Soluble proteins can be measured with immunoassays. This review provides a summary of the experimental and clinical studies investigating the potential of surface molecules as a tool for immune monitoring. It critically discusses the obstacles and shortcomings from an analytical and diagnostic perspective that are currently preventing their use in multicenter trials and clinical routine monitoring of transplant patients.

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.

Immune cell function assay does not identify biopsy-proven pediatric renal allograft rejection or infection

Management of pediatric renal transplant patients involves multifactorial monitoring modalities to ensure allograft survival and prevent opportunistic infection secondary to immunosuppression. An ICFA, which utilizes CD4 T-cell production of ATP to assess immune system status, has been used to monitor transplant recipients and predict susceptibility of patients to rejection or infection. However, the validity of this assay to reflect immune status remains unanswered. In a two-yr retrospective study that included 31 pediatric renal transplant recipients, 42 patient blood samples were analyzed for immune cell function levels, creatinine, WBC (white blood cell) count, immunosuppressive drug levels, and viremia, concurrent with renal biopsy. T-cell ATP production as assessed by ICFA levels did not correlate with allograft rejection or with the presence or absence of viremia. ICFA levels did not correlate with serum creatinine or immunosuppressive drug levels, but did correlate with WBC count. The ICFA is unreliable in its ability to reflect immune system status in pediatric renal transplantation. Further investigation is necessary to develop methods that will accurately predict susceptibility of pediatric renal transplant recipients to allograft rejection and infection.

Role of dendritic cells in the context of acute cellular rejection: comparison between tacrolimus- or cyclosporine A-treated heart transplanted recipients

BACKGROUND

In the last years many studies have been designed to predict risk of acute rejection and to adapt the immunosuppressive therapy. The importance of dendritic cells (DCs) in the immune response, especially their role in tolerance is known. Thus, we investigated the influence of tacrolimus (TAC)-based and of cyclosporine A (CsA)-based immunosuppressive therapies on dendritic cells and the incidence of rejection in heart transplant recipients.

METHODS

Groups consisted of 14 CsA treated and 15 TAC treated patients. At different study time points (0, 3 and 6 months after study begin) peripheral blood from the patients was drawn to analyse (1) blood concentration of CsA or TAC (trough value) and (2) percentages of plasmacytoid and myeloid DC (p and mDC) subsets using flow cytometry. Histological rejection grading was performed of endomyocardial biopsies.

RESULTS

TAC treated patients had significantly higher values of pDCs (CsA group 53.9%±13.0%; TAC group 67.5%±8.4%; p<0.05) and significantly lower values of mDCs than CsA treated patients (CsA group 58%±19.0%; TAC group 45.2%±10.7%; p<0.05). In general, HTx patients with rejection grade of ≥2 had significant lower values of pDCs (55.1%±16.2%) compared to patients without rejection (63.6%±10.5%; p<0.05). TAC-treated patients had significantly less rejections CsA-treated patients (CsA group 0.86±0.95; TAC group 0.2±0.4; p<0.05).

CONCLUSIONS

Our results showed that HTx patients with high pDCs had a lower risk for rejection and that TAC-treated patients had higher pDCs values compared to CsA-treated patients. Future studies need to define individual pDC values to predict acute cellular rejection.

Immune monitoring post liver transplant

Many of the causes of short and late morbidity following liver transplantation are associated with immunosuppression or immunosuppressive medications. Current care often involves close monitoring of liver biochemistry as well as therapeutic drug levels. However, the postoperative course following liver transplantation can often be associated with significant complications including infection and rejection, suggesting an inadequacy in current immune function monitoring. Many assays have been tested in the research setting to identify possible biomarkers that may be used to predict clinical events such as acute cellular rejection, and therefore allow modification of a patient’s immunosuppressive regimen prior to a clinical event. However, these generally require significant laboratory processing and have had difficulty becoming established in common clinical use outside the research setting. One assay, Cylex ImmuKnow has been food and drug administration approved but has had variable results. In this review we discuss the assays that have been used to assess monitoring of immune function after liver transplantation and consider possible future directions.

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.

A quantitative assessment model of T-cell immune function for predicting risks of infection and rejection during the early stage after liver transplantation

Although more and more clinical studies indicated that ImmuKnow assay could efficiently assess the immune status of recipients, it still has the challenge to predict the occurrence of clinical adverse events. This study aimed to establish a quantitative assessment model, which could more efficiently predict immune function of T lymphocytes after liver transplantation based on three indexes: CD4+ T lymphocyte count (C), CD4+/CD8+ ratio (R), and ImmuKnow adenosine triphosphate (ATP) value (A). We selected 194 recipients and measured the A, C, and R index every week, then obtained the Fisher linear discriminant functions by SPSS 16.0. Next, we divided the recipients into three groups: infection, stable, and rejection groups according to clinical status. After calculating, the discriminant function, 0.012A + 0.019C + 1.322R (simplified into T = 2A + 3C + 200R), was selected to represent the T-cell-mediated immune function. Based on the model, the optimal cutoff T values for infection and rejection were 1415 (sensitivity = 80%, specificity = 79.9%,AUC = 92.3%) and 1939.5 (sensitivity = 93.9%, specificity = 77.6%, AUC = 88.6%), relatively (p < 0.001). In conclusion, this model may be a more feasible way to evaluate the cellular immune function status in liver transplantation recipients.

Inosine monophosphate dehydrogenase expression and activity are significantly lower in kidney transplant recipients with diabetes mellitus

BACKGROUND

Inosine 5'-monophosphate dehydrogenase (IMPDH) is a target of the immunosuppressive drug, mycophenolic acid (MPA). A 12-hour clinical pharmacokinetic and pharmacodynamic study was conducted to compare IMPDH1 and IMPDH2 gene expression, IMPDHI and IMPDHII protein levels, and enzyme activity between kidney transplant recipients with respect to diabetes status.

METHODS

Nondiabetic (ND, n = 11) and diabetic (D, n = 9) kidney transplant recipients and on nontransplant nondiabetic (n = 10) and diabetic (n = 10) volunteers were included in the study.

RESULTS

Area under the effect curve values for gene expression: IMPDH1 [ND: 22.1 (13.8-31.3) versus D: 4.5 (2.3-6.5), P < 0.001] and IMPDH2 [ND: 15.3 (11.0-21.7) versus D: 6.1 (4.6-8.6), P < 0.001], protein level: IMPDHI [ND: 1.0 (0.5-1.3) versus 0.5 (0.4-0.7), P = 0.002] and IMPDHII [ND: 1.0 (0.6-1.6) versus D: 0.7 (0.6-0.8) P < 0.001] and enzyme activity [ND: 180 (105-245) versus D: 29.9 (15.3-35.6) µmole·s(-1)·mole(-1) adenosine monophosphate, P < 0.001] was significantly lower in transplant recipients with diabetes. Similar results were observed in nontransplanted volunteers. Kinetic studies of MPA-mediated suppression of IMPDH activity in nontransplanted individuals revealed an approximately 2.5-fold lower half-maximum effective concentration (EC50) for diabetic as compared with nondiabetic [ND: 50.2 (49.8-50.7) versus D: 15.8 (15.6-16.3) nmole/L, P = 0.004] volunteers. This difference was not related to several IMPDH gene variants.

CONCLUSIONS

This study indicates a significantly lower IMPDH gene expression, protein level, and enzyme activity in diabetic patients. Further clinical studies in a larger number of patients are warranted to verify whether MPA dosing must be optimized for kidney transplant recipients with diabetes mellitus.

CD4+ immune response as a potential biomarker of patient reported inflammatory bowel disease (IBD) activity

BACKGROUND

Crohn's disease (CD) and ulcerative colitis (UC) are inflammatory bowel diseases (IBDs) which are characterized by dysfunctional regulation of the immune system. A number of immune modifying drugs are used to treat CD and UC. Therapy is adjusted largely on the bases of subjective reports of disease activity and non-specific laboratory tests. Identification of a single or combination of immune markers of disease activity could be useful to select and monitor therapeutic responses. However, to date no reliable quantitative associations between IBD activity and laboratory measures of immune function have been identified. This study was designed to evaluate the usefulness of a commercially available laboratory measure of CD4(+) immune function, the Cylex® ImmuKnow®, as a surrogate marker of IBD activity.

METHODS

Adult IBD patients with either CD (N=55, 27 males, mean, SD age=38.5, 11.5 years) or UC (N=45, 24 males, mean, SD age=41.7, 15.4 years) were enrolled. Patients both in clinical remission and with active disease provided responses to structured, validated questionnaires (CDAI and HBI for CD patients and SCCAI for UC patients) used to monitor IBD activity. Whole blood and plasma samples were collected to quantify various markers of disease status including routine cell counts and differentials (CBCs), CRP, and albumin (Alb), as well as CD4(+) immune response (Cylex® ImmuKnow®, N=98). Results were compared between all IBD patients as well as between CD and UC subgroups.

RESULTS

There was a good correlation between the results of CDAI and HBI scores (r=0.811, p<0.01, Spearman-Rho) but HBI scores correlated slightly better (r=0.575, p<0.001) than the CDAI's (r=0.449, p=0.001) with CD patients' reported perception of their general condition. CDAI and HBI scores categorized 12/55 versus 36/55 of CD patients respectively as having active disease. SCCAI scores indicated that 25/45 of UC patients had active disease. Cylex® results (in ng/mL of ATP) were increased in 74/98 IBD subjects (≥525 ng/mL) but were influenced by the use of systemic corticosteroids (SCS) and infliximab. There were weak but statistically significant Spearman-Rho correlations between Alb concentrations and both CDAI (r=0.413, p=0.002) and HBI (r=0.325, p=0.017) scores as well as between CRP values and HBI scores (r=0.331, p=0.016). Correlations between CRP and both CDAI and SCCAI scores and between Alb and SCCAI scores were not significant and there were no significant positive associations between any of the three clinical scores and Cylex® results.

CONCLUSIONS

CD4(+) immune responses were significantly elevated in IBD patients whether or not they were in clinical remission but were influenced by treatment. There were some significant correlations between the clinical scores and CRP or Alb but not with the CD4(+) results. Both other clinical scoring systems, other measures of immune function, and CD4(+) immune response changes over time should be examined to see if this or other laboratory measures of immune response are predictive of actual disease activity or symptoms in CD or UC patients.

Intracellular IFN-γ and IL-2 expression monitoring as surrogate markers of the risk of acute rejection and personal drug response in de novo liver transplant recipients

Biomarker monitoring is needed in transplantation to reflect individual response to immunosuppressive drugs and graft outcome. We evaluated intracellular expression and soluble production of interferon-(IFN)-γ and interleukin-(IL)-2 as predictive biomarkers of acute rejection (AR) and personal drug response. Pharmacokinetic-pharmacodynamic profiles were determined in 47 de novo liver recipients treated with tacrolimus, mycophenolate mofetil and prednisone. Of the 47 patients, AR occurred in nine. There were no differences in drug concentrations between rejectors and non-rejectors. A pre-transplantation cut-off value of 55.80% for %CD8(+)-IFN-γ(+) identified patients at high risk of AR with a sensitivity of 75% and a specificity of 82%. In the first week post-transplantation, patients with a % inhibition for soluble IFN-γ, %CD8(+)-IFN-γ(+) and %CD8(+)-IL2(+) lower than 40% developed AR, showing low susceptibility to immunosuppressive drugs. Therefore, effector-T-cell response monitoring may help physicians to identify personal response to treatment and patients at high risk of AR.

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.

Serum soluble interleukin 2 receptor (sIL-2R) as a marker of acute rejection in renal transplant children

The aim of the study was to evaluate whether or not serum levels of soluble interleukin 2 receptor (sIL-2R) predict acute rejection in pediatric recipients. We studied 51 pediatric renal transplant recipients divided into three groups: Group 1) Biopsy-proven cellular acute rejection (n = 19), Group 2) Graft dysfunction with histological diagnosis other than acute rejection (n = 8) and Group 3) Patients with stable graft function, no biopsy (n = 24). Serum samples for sIL-2R measurement by sandwich ELISA were obtained at the time of renal transplant and at the time of renal biopsy due to graft dysfunction (Groups 1 and 2) or at six months post-transplant in the case of Group 3. The mean ± s.e. serum values of sIL-2R were higher in patients during acute rejection (6539 ± 1802 pg/mL) compared to patients with other causes of graft dysfunction (2217 ± 256 pg/mL) or stable graft function at six months (2183 ± 283 pg/mL) (Kruskal-Wallis p = 0.004). When the sIL2-R levels at the time of transplant were compared to those at the time of biopsy (Groups 1 and 2) or at six months post-transplant in Group 3, there was no significant difference between baseline and biopsy in the acute rejection group (paired t-test = 0.07), whereas there was a significant reduction in Groups 2 and 3.

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.

Surface markers of lymphocyte activation and markers of cell proliferation

The individualization of immunosuppression is an approach for preventing rejection in the early phase after transplantation and for avoiding the long-term side effects of over immunosuppression. Pharmacodynamic markers, either specific or nonspecific, have been proposed as complementary tools to drug monitoring of immunosuppressive drugs. A key event in graft rejection is the activation and proliferation of the recipient's lymphocytes, particularly T cells. Activated T cells express surface receptors, such as CD25 (the IL-2 receptor) and CD71 (the transferrin receptor), or co-stimulatory molecules (CD26, CD27, CD28, CD30, CD154 or CD40L, and CD134). Both surface marker expression and cell proliferation are predominately assessed by flow cytometry. Protocols have been established and utilized for both in vitro and ex vivo investigations with either isolated lymphocytes or whole blood. This article reviews the current body of research regarding the use of lymphocyte proliferation and surface activation markers with an emphasis on T cells. Experimental and clinical results related to these markers, as well as methodological issues and open questions, are addressed.

The failure of immunosuppression withdrawal: patient benefit is not detectable, inducible, or reproducible

(1) Immunosuppression is responsible for excellent patient outcomes. (2) Immunosuppression withdrawal fails in most patients. (3) Patients who may benefit from immunosuppression withdrawal cannot currently be identified. (4) No data suggest that immunosuppression withdrawal decreases patient morbidity (ie, nephrotoxicity). (5) The minimization of immunosuppression instead of withdrawal may be adequate for improving patient outcomes.

Conventional and novel approaches to immunosuppression

Immunosuppressive therapy has contributed significantly to improved survival after solid organ transplantation. Nevertheless, treatment-related adverse events and persistently high risk of chronic graft rejection remain major obstacles to long-term survival after lung transplantation. The development of new agents, refinements in techniques to monitor immunosuppression, and enhanced understanding of transplant immunobiology are essential for further improvements in outcome. In this article, conventional immunosuppressive regimens, novel approaches to preventing graft rejection, and investigational agents for solid organ transplantation are reviewed.

HLA antigen and NK cell activating ligand expression in malignant cells: a story of loss or acquisition

Malignant transformation of cells is often associated with changes in classical and non-classical HLA class I antigen, HLA class II antigen as well as NK cell activating ligand (NKCAL) expression. These changes are believed to play a role in the clinical course of the disease since these molecules are critical to the interactions between tumor cells and components of both innate and adaptive immune system. For some time, it has been assumed that alterations in the expression profile of HLA antigens and NKCAL on malignant cells represented loss of classical HLA class I antigen and induction of HLA class II antigen, non-classical HLA class I antigen and/or NKCAL expression. In contrast to these assumptions, experimental evidence suggests that in some cases dysplastic and malignant cells can acquire classical HLA class I antigen expression and/or lose the ability to express HLA class II antigens. In light of the latter findings as well as of the revival of the cancer immune surveillance theory, a reevaluation of the interpretation of changes in HLA antigen and NKCAL expression in malignant lesions is warranted. In this article, we first briefly describe the conventional types of changes in HLA antigen and NKCAL expression that have been identified in malignant cells to date. Second, we discuss the evidence indicating that, in at least some cell types, classical HLA class I antigen expression can be acquired and/or the ability to express HLA class II antigens is lost. Third, we review the available evidence for the role of immune selective pressure in the generation of malignant lesions with changes in HLA antigen expression. This information contributes to our understanding of the role of the immune system in the control of tumor development and to the optimization of the design of immunotherapeutic strategies for the treatment of cancer.