Identification of highly responsive kidney transplant recipients using pretransplant soluble CD30

Monitoring of Soluble Forms of BAFF System (BAFF, APRIL, sR-BAFF, sTACI and sBCMA) in Kidney Transplantation

BAFF system plays an essential role in B cells homeostasis and tolerance, although it has widely not been tested in transplantation with doubtful results. The main purpose was to study the BAFF soluble forms and their correlation with acute rejection (AR) and donor-specific antibodies production. Serum levels of BAFF, APRIL, and soluble forms of their receptors were analyzed in renal recipients with and without acute rejection (AR/NAR) appearance. All molecules were evaluated at pre- and post-transplantation. sTACI showed a significant correlation with BAFF and sR-BAFF levels, and sBCMA also showed a positive correlation with sAPRIL levels. A significant increase in sAPRIL levels in patients suffering AR was also found, and ROC curves analysis showed an AUC = 0.724, a concentration of 6.05 ng/ml (sensitivity: 66.7%; specificity: 73.3%), the best cutoff point for predicting AR. In the post-transplant dynamics of sAPRIL levels in the longitudinal cohort, we observed a significant decrease at 3 and 6 month post-transplantation compared to pretransplantation status. We also observed that recipients with high pre-transplant levels of sAPRIL generated antibodies earlier than those with lower sAPRIL levels, although their long-term post-transplantation was not different. Our results show that elevated serum levels of APRIL may be helpful as a biomarker for the diagnosis of AR, although the longitudinal study shows that it is not helpful as a prognostic biomarker.

Increased Levels of sCD30 Have No Impact on the Incidence of Early ABMR and Long-Term Outcome in Intermediate-Risk Renal Transplant Patients With Preformed DSA

Background: It is still incompletely understood why some patients with preformed donor-specific anti-HLA antibodies (DSA) have reduced kidney allograft survival secondary to antibody-mediated rejection (ABMR), whereas many DSA-positive patients have favorable long-term outcomes. Elevated levels of soluble CD30 (sCD30) have emerged as a promising biomarker indicating deleterious T-cell help in conjunction with DSA in immunologically high-risk patients. We hypothesized that this would also be true in intermediate-risk patients.

Methods: We retrospectively analyzed pre-transplant sera from 287 CDC-crossmatch negative patients treated with basiliximab induction and tacrolimus-based maintenance therapy for the presence of DSA and sCD30. The incidence of ABMR according to the Banff 2019 classification and death-censored allograft survival were determined.

Results: During a median follow-up of 7.4 years, allograft survival was significantly lower in DSA-positive as compared to DSA-negative patients (p < 0.001). In DSA-positive patients, most pronounced in those with strong DSA (MFI > 5,000), increased levels of sCD30 were associated with accelerated graft loss compared to patients with low sCD30 (3-year allograft survival 75 vs. 95%). Long-term survival, however, was comparable in DSA-positive patients irrespective of sCD30 status. Likewise, the incidence of early ABMR and lesion score characteristics were comparable between sCD30-positive and sCD30-negative patients with DSA. Finally, increased sCD30 levels were not predictive for early persistence of DSA.

Conclusion: Preformed DSA are associated with an increased risk for ABMR and long-term graft loss independent of sCD30 levels in intermediate-risk kidney transplant patients.

Pre-existing Alloreactive T and B Cells and Their Possible Relevance for Pre-transplant Risk Estimation in Kidney Transplant Recipients

In allogeneic transplantation, genetic disparities between patient and donor may lead to cellular and humoral immune responses mediated by both naïve and memory alloreactive cells of the adaptive immune system. This review will focus on alloreactive T and B cells with emphasis on the memory compartment, their role in relation to kidney rejection, and in vitro assays to detect these alloreactive cells. Finally, the potential additional value of utilizing donor-specific memory T and B cell assays supplementary to current routine pre-transplant risk assessment of kidney transplant recipients will be discussed.

The Dynamic Changes in Soluble CD30 and Regulatory T Cells Before and After Solid Organ Transplantations: A Pilot Study

Among multiple parameters, applied in the immunologic monitoring of transplantation, the levels of serum soluble CD30 (sCD30) and peripheral regulatory T cells (Tregs) are very promising. These are relatively new biomarkers, considered to reflect immune activation and tolerance in solid organ transplantation. Results are shown here from a preliminary study on the relevance of sCD30 and Tregs in the monitoring of the early post-transplantation period. Sixteen patients with chronic liver or kidney disease were examined. Nine of them were further selected for transplantation. Follow-up of sCD30 and Tregs was carried out during the first month after transplantation. Until day 30 (D30) after transplantation, a progressive decrease in sCD30 levels was observed in all patients. Conversely, the dynamic of Tregs was dependent on the transplanted organ: in liver recipients, an increase of Tregs was detected at day 7 (D7) followed by a gradual decrease until D30, whereas in kidney recipients, a sustained downward trend starting on D7 was observed. In liver recipients, the increase in Tregs preceded albumin normalization, whereas in kidney recipients, sCD30 was found to have predictive significance for the creatinine levels. Our results demonstrated that peripheral blood sCD30 and Tregs are valuable parameters in the immunologic monitoring of transplanted patients.

Immune function as predictor of infectious complications and clinical outcome in patients undergoing solid organ transplantation (the ImmuneMo:SOT study): a prospective non-interventional observational trial

Background

Solid organ transplantation (SOT) is a well-established and life-saving treatment for patients with end-stage organ failure. Organ rejection and infections are among the main complications to SOT and largely determines the clinical outcome. The correct level of immunosuppression is of major importance to prevent these complications. However, it is a consistent observation that in recipients on the same immunosuppressive regimens the clinical outcome varies, and no reliable marker exists to monitor immune function.

Methods

In a prospective, observational study, we plan to enroll 630 adult patients with a planned organ transplantation at Rigshospitalet, University of Copenhagen, Denmark. Prior to and on different time points up to two years after transplantation we will perform a complete immunological profile on the recipients. This profile will consist of classical descriptive immune phenotyping (flow cytometry and circulating biomarkers) and the functional assay TruCulture®. In TruCulture® whole blood is incubated ex vivo with stimulants imitating bacterial, viral and fungal infections, where after a panel of selected cytokines is quantified. Clinical data from electronic health records will be obtained from the PERSIMUNE (Centre of Excellence for Personalized Medicine of Infections Complications in Immune Deficiency at Rigshospitalet, Copenhagen) data repository, a warehouse of data generated as part of routine care including vital signs, biochemistry, microbiology, pathology as well as medication, demographics, diagnoses, hospital contacts, surgical procedures and mortality.

Discussion

This will be the first large scale study to determine several aspects of immune function and perform a complete immunological profiling in SOT recipients. It is expected that knowledge generated will provide information to generate prediction models identifying patients at increased risk of infection and/or rejection. If the study is successful, we will subsequently use the generated prediction models to propose personalized immunosuppressive regimens to be tested in future randomized controlled trials.

Trial registration

This study has been approved by the Regional ethical committee (H-17024315), the Danish Data Protection Agency (RH-2016-47, RH-2015-04, I-Suite 03605) and the Danish National board of Health (3–3013-1060/1). The trial is retrospectively registered at clinicaltrials.gov (NCT03847285) the 20th February 2019.

Immunological Alterations due to Hemodialysis Might Interfere with Early Complications in Renal Transplantation

Background

Chronic or intercurrent alterations of the immune system in patients with end-stage renal disease (CKD) and intermittent hemodialysis (CKD5D, HD) have been attributed to an acute rejection of renal allograft.

Methods

Leukocyte subsets in flow cytometry, complement activation, and concentrations of TGFβ, sCD30 (ELISA), and interleukins (CBA) of fifteen patients eligible for renal transplantation were analyzed before, during, and after a regular HD.

Results

Before HD, the median proportion of CD8+ effector cells, CD8+ CCR5+ effector cells, and HLA-DR+ regulatory T cells as well as the median concentration of soluble CD30 increased and naive CD8+ T cells decreased. During HD, there was a significant decrease in CD4- CD8- T cells (p < 0.001) and an increase in CD25+ T cells (p = 0.026), sCD30 (p < 0.001), HLA-DR+ regulatory T cells (p = 0.005), and regulatory T cells (p = 0.003). TGFβ and sCD30 increased significantly over time. The activity of the classical complement pathway started to slightly increase after the first hour of HD and lasted until fifteen minutes after finishing dialysis. The decrease in the functional activity of the alternative pathway was only transient and was followed by a significant increase within 15 minutes after finishing the treatment.

Conclusion

HD might interact with the allograft outcome by influencing T cell subsets and activation of the complement system in a biphasic course.

Soluble CD30, Acute Rejection, and Graft Survival: Pre- and 6-Month Post-Transplant Determinations-When Is the Best Time to Measure?

BACKGROUND

Pretransplantation soluble CD30 (sCD30) has been shown to be a good predictor of acute rejection (AR) and graft loss. This study aimed to evaluate the effectiveness of sCD30 measured pretransplant and up to 6 months after transplantation as a predictor of AR, graft loss, and survival at 5 years post-transplantation. Subjects were patients receiving living donor renal transplants at Bonsucesso Federal Hospital (Rio de Janeiro) in 2006 and between August 2010 and May 2011.

METHODS

sCD30 was analyzed in samples collected pretransplantation and 7, 14, and 21, 28 days and 3, 4, 5, and 6 months post-transplantation from 73 kidney recipients.

RESULTS

Patients in the AR group did not present a positive correlation with the sCD30 levels pretransplant (P = .54); in the post-transplant period, the 7- to 14-day samples showed patients with AR had higher levels of this biomarker (P = .036). The graft survival in 5 years of follow-up was not different between groups.

CONCLUSIONS

The best time to predict AR using sCD30 is the 7- to 14-day sample; however, identifying and following the decrease of this biomarker from pre- to post-transplant seems to be better than just 1 measurement. The sCD30 post-transplant is another tool that may be used in monitoring patients after renal transplantation.

An integrated view of immune monitoring in vascularized composite allotransplantation

PURPOSE OF REVIEW

Vascularized composite allotransplantation (VCA) has several immunological peculiarities that imply a specific immune monitoring. Here, we provide an integrated view of current procedures of immune monitoring in VCA and potential complementary approaches learned from organ transplantation.

RECENT FINDINGS

Because the skin is highly immunogenic and is the main target of the alloimmune response, immune monitoring in VCA essentially relies on visual inspection and pathological examination of for-causes and protocol skin biopsies. Light microscopical and immunohistochemical analyses enable us to identify skin lesions that are characteristic, but not specific, of allograft rejection. Complementary approaches of immunological assessment may assist in reinforcing the diagnosis of rejection and preventing over-immunosuppression or under-immunosuppression. Such approaches can inform either on the patient's global immune status or more specifically on the B-cell-mediated or T-cell-mediated immune responses against donor antigens.

SUMMARY

Strategies that integrate both the current 'gold standards' of monitoring in VCA and a complementary multilayer immunological assessment are likely to provide the highest precision for the personalized determination of the recipients' immunological status. The objective is a tailored adaptation of immunosuppressive treatment.

Immune monitoring as prerequisite for transplantation tolerance trials

Ever since its first application in clinical medicine, scientists have been urged to induce tolerance towards foreign allogeneic transplants and thus avoid rejection by the recipient's immune system. This would circumvent chronic use of immunosuppressive drugs (IS) and thus avoid development of IS-induced side effects, which are contributing to the still unsatisfactory long-term graft and patient survival after solid organ transplantation. Although manifold strategies of tolerance induction have been described in preclinical models, only three therapeutic approaches have been utilized successfully in a still small number of patients. These approaches are based on (i) IS withdrawal in spontaneous operational tolerant (SOT) patients, (ii) induction of a mixed chimerism and (iii) adoptive transfer of regulatory cells. Results of clinical trials utilizing these approaches show that tolerance induction does not work in all patients. Thus, there is a need for reliable biomarkers, which can be used for patient selection and post-therapeutic immune monitoring of safety, success and failure. In this review, we summarize recent achievements in the identification and validation of such immunological assays and biomarkers, focusing mainly on kidney and liver transplantation. From the published findings so far, it has become clear that indicative biomarkers may vary between different therapeutic approaches applied and organs transplanted. Also, patient numbers studied so far are very small. This is the main reason why nearly all described parameters lack validation and reproducibility testing in large clinical trials, and are therefore not yet suitable for clinical practice.

Peritransplant Soluble CD30 as a Risk Factor for Slow Kidney Allograft Function, Early Acute Rejection, Worse Long-Term Allograft Function, and Patients' Survival

BACKGROUND

We aimed to determine whether serum soluble CD30 (sCD30) could identify recipients at high risk for unfavorable early and late kidney transplant outcomes.

METHODS

Serum sCD30 was measured on the day of kidney transplantation and on the 4th day posttransplant. We assessed the value of these measurements in predicting delayed graft function, slow graft function (SGF), acute rejection (AR), pyelonephritis, decline of allograft function after 6 months, and graft and patient survival during 5 years of follow-up in 45 recipients.

RESULTS

We found the association between low pretransplant serum levels of sCD30 and SGF. The absence of significant decrease of sCD30 on the 4th day posttransplant was characteristic for SGF, early AR (the 8th day-6 months), late AR (>6 months), and early pyelonephritis (the 8th day-2 months). Lower pretransplant and posttransplant sCD30 predicted worse allograft function at 6 months and 2 years, respectively. Higher pretransplant sCD30 was associated with higher frequency of early AR, and worse patients' survival, but only in the recipients of deceased-donor graft. Pretransplant sCD30 also allowed to differentiate patients with early pyelonephritis and early AR.

CONCLUSIONS

Peritransplant sCD30 is useful in identifying patients at risk for unfavorable early and late transplant outcomes.

Clinical Relevance of HLA Antibodies in Kidney Transplantation: Recent Data from the Heidelberg Transplant Center and the Collaborative Transplant Study

Herein, we summarize our recent findings from the international Collaborative Transplant Study (CTS) and Heidelberg Transplant Center regarding the role of HLA antibodies in kidney transplantation and their application into the clinical routine. Based on the antibody findings from the CTS serum study, an algorithm was developed in 2006 for the transplantation of high-risk sensitized patients at the Heidelberg Transplant Center which includes seven different pre- and posttransplant measures. Using this algorithm, the number of transplantations could be increased in high-risk presensitized patients and the previously existing impact of antibodies on graft survival could greatly be diminished but not totally eliminated. More recent findings led to the hypothesis that T cell help from a preactivated immune system supports the harmful effects of pretransplant donor-specific HLA antibodies that otherwise disappear in many cases after transplantation without any consequence.

Serum sCD30: A promising biomarker for predicting the risk of bacterial infection after kidney transplantation

BACKGROUND

The transmembrane glycoprotein CD30 contributes to regulate the balance between Th₁ and Th₂ responses. Previous studies have reported conflicting results on the utility of its soluble form (sCD30) to predict post-transplant infection.

METHODS

Serum sCD30 was measured by a commercial ELISA assay at baseline and post-transplant months 1, 3, and 6 in 100 kidney transplant (KT) recipients (279 monitoring points). The impact of sCD30 levels on the incidence of overall, bacterial and opportunistic infection during the first 12 months after transplantation was assessed by Cox regression.

RESULTS

There were no differences in serum sCD30 according to the occurrence of overall or opportunistic infection. However, sCD30 levels were higher in patients with bacterial infection compared to those without at baseline (P=.038) and months 1 (P<.0001), 3 (P=.043), and 6 after transplantation (P=.006). Patients with baseline sCD30 levels ≥13.5 ng/mL had lower 12-month bacterial infection-free survival (35.0% vs 80.0%; P<.0001). After adjusting for potential confounders, baseline sCD30 levels ≥13.5 ng/mL remained as an independent risk factor for bacterial infection (adjusted hazard ratio [aHR]: 4.65; 95% confidence interval [CI]: 2.05-10.53; <.001). Analogously, sCD30 levels ≥6.0 ng/mL at month 1 acted as a risk factor for subsequent bacterial infection (aHR: 5.29; 95% CI: 1.11-25.14; P=.036).

CONCLUSION

Higher serum sCD30 levels were associated with an increased risk of bacterial infection after KT. We hypothesize that this biomarker reflects a Th₂ -polarized T-cell response, which exerts a detrimental effect on the immunity against bacterial pathogens.

High soluble CD30 levels and associated anti-HLA antibodies in patients with failed renal allografts

INTRODUCTION

Serum soluble CD30 (sCD30), a 120-kD glycoprotein that belongs to the tumor necrosis factor receptor family, has been suggested as a marker of rejection in kidney transplant patients. The aim of this study was to evaluate the relationship between sCD30 levels and anti-HLA antibodies, and to compare sCD30 levels in patients undergoing hemodialysis (HD) with and without failed renal allografts and transplant recipients with functioning grafts.

METHODS

100 patients undergoing HD with failed grafts (group 1), 100 patients undergoing HD who had never undergone transplantation (group 2), and 100 kidney transplant recipients (group 3) were included in this study. Associations of serum sCD30 levels and anti-HLA antibody status were analyzed in these groups.

RESULTS

The sCD30 levels of group 1 and group 2 (154 ± 71 U/mL and 103 ± 55 U/mL, respectively) were significantly higher than those of the transplant recipients (group 3) (39 ± 21 U/mL) (p&lt;0.001 and p&lt;0.001). The serum sCD30 levels in group 1 (154 ± 71 U/mL) were also significantly higher than group 2 (103 ± 55 U/mL) (p&lt;0.001). Anti-HLA antibodies were detected in 81 (81%) and 5 (5%) of patients in groups 1 and 2, respectively (p&lt;0.001). When multiple regression analysis was performed to predict sCD30 levels, the independent variables in group 1 were the presence of class I anti-HLA antibodies (β = 0.295; p = 0.003) and age (β = -0.272; p = 0.005), and serum creatinine (β = 0.218; p = 0.027) and presence of class II anti-HLA antibodies (standardized β = 0.194; p = 0.046) in group 3.

CONCLUSIONS

Higher sCD30 levels and anti-HLA antibodies in patients undergoing HD with failed renal allografts may be related to higher inflammatory status in these patients.

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.

Donor-specific antibodies require preactivated immune system to harm renal transplant

•

Pretransplant DSA have a deleterious impact on graft survival only in the presence of high pretransplant serum levels of sCD30.

•

The majority of patients with pretransplant DSA might be transplanted safely without special pretreatment measures.

Kidney transplantation in the presence of donor-specific HLA antibodies (DSA) is associated with a high failure rate due to antibody-mediated rejection. Many centers avoid transplantations if DSA are present. Others perform such transplantations after removal of DSA by apheresis under potent immunosuppression.

We provide strong evidence that DSA positive recipients reject their grafts at a high rate only if the immune activation marker sCD30 is also high, suggesting that T-cell help from an activated immune system is necessary for pretransplant DSA to exert a deleterious effect on the graft.

High-risk patients with DSA and sCD30 may benefit from special treatment measures. The presence of DSA alone may not be deleterious.

Background

It is an unresolved issue why some kidney transplant recipients with pretransplant donor-specific HLA antibodies (DSA) show a high transplant failure rate, whereas in other patients DSA do not harm the graft. We investigated whether help from preactivated T-cells might be necessary for DSA to exert a deleterious effect.

Methods

The impact of pretransplant DSA and immune activation marker soluble CD30 (sCD30) on 3-year graft survival was analyzed in 385 presensitized kidney transplant recipients.

Findings

A deleterious influence of pretransplant DSA on graft survival was evident only in patients who were positive for the immune activation marker sCD30. In the absence of sCD30 positivity, 3-year graft survival was virtually identical in patients with or without DSA (83.1 ± 3.9% and 84.3 ± 2.8%, P = 0.81). A strikingly lower 3-year graft survival rate of 62.1 ± 6.4% was observed in patients who were both sCD30 and DSA positive (HR 2.92, P < 0.001). Even in the presence of strong DSA with ≥ 5000 MFI, the 3-year graft survival rate was high if the recipients were sCD30 negative.

Interpretation

Pretransplant DSA have a significantly deleterious impact on graft survival only in the presence of high pretransplant levels of the activation marker sCD30.

Association of CD30 transcripts with Th1 responses and proinflammatory cytokines in patients with end-stage renal disease

High serum sCD30 levels are associated with inflammatory disorders and poor outcome in renal transplantation. The contribution to these phenomena of transcripts and proteins related to CD30-activation and -cleavage is unknown. We assessed in peripheral blood of end-stage renal disease patients (ESRDP) transcripts of CD30-activation proteins CD30 and CD30L, CD30-cleavage proteins ADAM10 and ADAM17, and Th1- and Th2-type immunity-related factors t-bet and GATA3. Additionally, we evaluated the same transcripts and release of sCD30 and 32 cytokines after allogeneic and polyclonal T-cell activation. In peripheral blood, ESRDP showed increased levels of t-bet and GATA3 transcripts compared to healthy controls (HC) (both P<0.01) whereas levels of CD30, CD30L, ADAM10 and ADAM17 transcripts were similar. Polyclonal and allogeneic stimulation induced higher levels of CD30 transcripts in ESRDP than in HC (both P<0.001). Principal component analysis (PCA) in allogeneic cultures of ESRDP identified two correlation clusters, one consisting of sCD30, the Th-1 cytokine IFN-γ, MIP-1α, RANTES, sIL-2Rα, MIP-1β, TNF-β, MDC, GM-CSF and IL-5, and another one consisting of CD30 and t-bet transcripts, IL-13 and proinflammatory proteins IP-10, IL-8, IL-1Rα and MCP-1. Reflecting an activated immune state, ESRDP exhibited after allostimulation upregulation of CD30 transcripts in T cells, which was associated with Th1 and proinflammatory responses.

T-Cell Surface Antigens and sCD30 as Biomarkers of the Risk of Rejection in Solid Organ Transplantation

T-cell activation is a characteristic of organ rejection. T cells, located in the draining lymph nodes of the transplant recipient, are faced with non-self-molecules presented by antigen presenting cells and become activated. Activated T cells are characterized by up-regulated surface antigens, such as costimulatory molecules, adhesion molecules, chemokine receptors, and major histocompatibility complex class II molecules. Surface antigen expression can be followed by flow cytometry using monoclonal antibodies in either cell function assays using donor-specific or nonspecific stimulation of isolated cells or whole blood and without stimulation on circulating lymphocytes. Molecules such as CD30 can be proteolytically cleaved off the surface of activated cells in vivo, and the determination of the soluble protein (sCD30) in serum or plasma is performed by immunoassays. As promising biomarkers for rejection and long-term transplant outcome, CD28 (costimulatory receptor for CD80 and CD86), CD154 (CD40 ligand), and sCD30 (tumor necrosis factor receptor superfamily, member 8) have been identified. Whereas cell function assays are time-consuming laboratory-developed tests which are difficult to standardize, commercial assays are frequently available for soluble proteins. Therefore, more data from clinical trials have been published for sCD30 compared with the surface antigens on activated T cells. This short review summarizes the association between selected surface antigens and immunosuppression, and rejection in solid organ transplantation.

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.

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.

Pre- and Posttransplant IgA Anti-Fab Antibodies to Predict Long-term Kidney Graft Survival

OBJECTIVES

Immunologic factors are reliable markers for allograft monitoring, because of their seminal role in rejection process. One of these factors is the immunoglobulin (Ig)A anti-Fab of the IgG antibody. This study aimed to evaluate the predictive value of pre- and posttransplant levels of this marker for kidney allograft function and survival.

METHODS

Sera samples of 59 living unrelated donor kidney recipients were collected before and after transplantation (days 7, 14, and 30) and investigated for IgA anti-Fab of IgG antibody levels using enzyme-linked immunosorbent assay in relation with allograft outcome.

RESULTS

Among 59 patients, 15 cases (25%) including 10 with acute rejection and 5 with chronic rejection episodes showed graft failure during a mean of 5 years of follow-up. High posttransplant levels of IgA anti-Fab antibodies were observed more frequently in patients with stable graft function (SGF) compared with patients with graft failure (P = 2 × 10(-6)). None of patients with acute or chronic rejection episodes had high levels of IgA anti-Fab antibodies at day 30 posttransplant compared with the SGF group (P = 10(-6) and P = .01, respectively). In addition, high levels of IgA anti-Fab antibody correlated with lesser concentration of serum creatinine at 1 month posttransplantation (P = .01). Five-year graft survival was associated with high levels of pre- and posttransplant IgA anti-Fab antibodies (P = .02 and P = .003, respectively).

CONCLUSIONS

Our findings indicate the protective effect of higher levels of IgA anti-Fab antibodies regarding to kidney allograft outcomes and long-term graft survival.

Soluble CD30 does not predict late acute rejection or safe tapering of immunosuppression in renal transplantation

BACKGROUND

Previous reports revealed the potential value of the soluble CD30 level (sCD30) as biomarker for the risk of acute rejection and graft failure after renal transplantation, here we examined its use for the prediction of safe tapering of calcineurin inhibitors as well as late acute rejection.

METHODS

In a cohort of renal transplant patients receiving triple immunosuppressive therapy we examined whether sCD30 can be used as a marker for safe (rejection-free) discontinuation of tacrolimus at six months after transplantation (TDS cohort: 24 rejectors and 44 non-rejecting controls). Also, in a second cohort of patients (n=22, rejectors n=11 and non-rejectors n=11), participating in a clinical trial of rituximab as induction therapy after renal transplantation (RITS cohort), we examined whether sCD30 could predict the occurrence of late (>3months post-transplant) acute rejection episodes. sCD30 was measured by ELISA in serum taken before and at several time points after transplantation.

RESULTS

Overall, in the TDS cohort sCD30 decreased after transplantation. No difference in sCD30 was observed between rejectors and non-rejecting controls at any of the time points measured. In addition, in the RITS cohort, sCD30 measured at three months after transplantation were not indicative for the occurrence of late acute rejection.

CONCLUSION

In two prospectively followed cohorts of renal transplant patients we found no association between sCD30 and the occurrence of either late acute rejection or acute rejection after reduction of immunosuppression.

Pre-transplant immune state defined by serum markers and alloreactivity predicts acute rejection after living donor kidney transplantation

Acute rejection (AR) remains a major cause for long-term kidney allograft failure. Reliable immunological parameters suitable to define the pre-transplant immune state and hence the individual risk of graft rejection are highly desired to preferably adapt the immunosuppressive regimen in advance. Donor and third party alloreactivities were determined by mixed lymphocyte cultures. Soluble forms of CD25, CD30, and CD44 were detected in patients' serum by ELISA. Various lymphocyte subpopulations were measured using flow cytometry. All patients received triple immunosuppression (tacrolimus/mycophenolate mofetil/steroids) and were grouped according to biopsy results within the first year: rejection-free (RF, n = 13), borderline (BL, n = 5), or acute rejection (AR, n = 7). Patients with AR showed the highest pre-transplant alloreactivities and serum levels (sCD25/sCD30/sCD44) according to the pattern RF < BL < AR. Relying on serum analysis only, multivariate logistic regression (logit link function) yielded a prognostic score for prediction of rejection with 75.0% sensitivity and 69.2% specificity. Patients with rejection showed markedly higher pre-transplant frequencies of CD4(+) /CD8(+) T cells lacking CD28, but lower numbers of CD8(+) CD161(bright) T cells and NK cells than RF individuals. Pre-transplant immune state defined by alloreactivity, serum markers, and particular lymphocyte subsets seems to correlate with occurrence of graft rejection after kidney transplantation. A prognostic score based on pre-transplant serum levels has shown great potential for prediction of rejection episodes and should be further evaluated.

Clinical immune-monitoring strategies for predicting infection risk in solid organ transplantation

Infectious complications remain a leading cause of morbidity and mortality after solid organ transplantation (SOT), and largely depend on the net state of immunosuppression achieved with current regimens. Cytomegalovirus (CMV) is a major opportunistic viral pathogen in this setting. The application of strategies of immunological monitoring in SOT recipients would allow tailoring of immunosuppression and prophylaxis practices according to the individual's actual risk of infection. Immune monitoring may be pathogen-specific or nonspecific. Nonspecific immune monitoring may rely on either the quantification of peripheral blood biomarkers that reflect the status of a given arm of the immune response (serum immunoglobulins and complement factors, lymphocyte sub-populations, soluble form of CD30), or on the functional assessment of T-cell responsiveness (release of intracellular adenosine triphosphate following a mitogenic stimulus). In addition, various methods are currently available for monitoring pathogen-specific responses, such as CMV-specific T-cell-mediated immune response, based on interferon-γ release assays, intracellular cytokine staining or main histocompatibility complex-tetramer technology. This review summarizes the clinical evidence to date supporting the use of these approaches to the post-transplant immune status, as well as their potential limitations. Intervention studies based on validated strategies for immune monitoring still need to be performed.

Early post-transplant immune monitoring can predict long-term kidney graft survival: soluble CD30 levels, anti-HLA antibodies and IgA-anti-Fab autoantibodies

This study aimed to investigate the predictive power of anti-HLA antibodies, sCD30 levels and IgA-anti-Fab autoantibody before and early after transplantation in relation to long-term kidney allograft survival. Pre- and post-transplant sera samples of 59 living-unrelated donor kidney recipients were tested for above risk factors by enzyme-linked immunoabsorbent assay. 15 out of 59 cases experienced rejection episodes (failure group). Pre- and post-transplant high sCD30 levels were significantly associated with graft failure (P=0.02 and P=0.004) and decreased 4 year graft survival (P = 0.009 and P = 0.001). Higher frequency of post-transplant HLA class-II antibody in the absence of class-I antibody was observed in failure group (P=0.007). Patients with post-transplant HLA class-I and class-II antibodies either alone or in combination showed significant lower 4 year graft survival. Recipients with high sCD30 levels in the presence of HLA class-I or class-II antibodies within 2 weeks post-transplant had poor graft survival (P = 0.004 and P = 0.002, respectively). High levels of post-transplant IgA-anti-Fab antibody was more frequent in functioning-graft patients (P = 0.00001), correlated with decreased serum creatinine levels (P = 0.01) and associated with improved graft survival (P = 0.008). Our findings indicate the deleterious effect of early post-transplant HLA antibodies and increased sCD30 levels dependently and protective effect of IgA-anti-Fab antibodies on long-term renal graft outcomes.

Predictive biomarkers of renal allograft failure

BACKGROUND

Survival of renal allografts is limited by chronic allograft deterioration resulting from processes that are difficult to detect in their early stages, when therapeutic interventions would be most effective. Predictive biomarkers from easily accessible specimens, such as blood or urine, might improve early diagnosis of smoldering graft-damaging processes and help with the identification of patients at particularly high risk of sustained injury, thereby helping to tailor therapy and appropriate follow-up screening.

OBJECTIVE

This article reviews recently investigated biomarkers for the prediction of renal allograft failure, outlines the new '-omic' technologies as a potential source for the identification of new predictive biomarkers and judges the practical value of predictive biomarkers at the present timepoint.

METHODS

A literature search was performed using the medical database PubMed. No general restrictions (e.g., year of publication) were applied, but the focus was set on more recently published articles.

CONCLUSION

Despite a large number of interesting studies, none of the investigated candidate biomarkers is robustly established for widespread clinical use or able to replace biopsies for graft assessment.

Relation between pretransplant serum levels of soluble CD30 and acute rejection during the first 6 months after a kidney transplant

OBJECTIVES

The immunologic status of kidney allograft recipients affects transplant outcome. High levels of pretransplant serum soluble CD30 correlate with an increased risk of acute rejection. Studies show conflicting results. We evaluated the relation between pretransplant serum sCD30 levels with the risk of posttransplant acute kidney rejection in renal transplant recipients.

MATERIALS AND METHODS

This prospective cohort study was performed between March 2010 and March 2011 on 77 kidney transplant recipients (53 men [68.8%], 24 women [31.2%]; mean age, 41 ± 14 y). Serum samples were collected 24 hours before transplant and analyzed for soluble CD30 levels by enzyme-linked immunosorbent assay. Patients were followed for 6 months after transplant. Acute biopsy-proven rejection episodes were recorded, serum creatinine levels were measured, and glomerular filtration rates were calculated at the first and sixth months after transplant. Preoperative serum soluble CD30 levels were compared in patients with and without rejection.

RESULTS

The mean pretransplant serum soluble CD30 level was 92.1 ± 47.3 ng/mL. At 6 months' follow-up, 10 patients experienced acute rejection. Mean pretransplant soluble CD30 levels were 128.5 ± 84 ng/mL versus 86.7 ± 37 ng/mL in patients with and without acute rejection episodes (P = .008). At 100 ng/mL, the sensitivity, specificity, and positive and negative predictive values of pretransplant serum soluble CD30 level to predict acute rejection were 70%, 73.6%, 29.1%, and 94.3%.

CONCLUSIONS

We showed a significant relation between pretransplant serum soluble CD30 levels and acute allograft rejection. High pretransplant levels of serum soluble CD30 can be a risk factor for kidney transplant rejection, and its high negative predictive value at various cutoffs make it useful to find candidates with a low risk of acute rejection after transplant.

Alloantigen-stimulated induction and release of CD30 in patients with end-stage renal failure

High serum levels of soluble CD30 (sCD30) are associated with poor renal allograft survival, and regulatory T cells (Tregs) influence allograft survival depending on CD30 signaling. However, how sCD30 modulates alloimmune responses remains poorly understood. We measured the level of Tregs and sCD30 in patients with end-stage renal failure (ESRF) and analyzed whether allo- or polyclonal stimulation of the patients' T cells results in the expression and release of CD30. ESRF patients showed increased serum sCD30 levels and lower percentages of circulating Tregs as compared to healthy controls (HC) (p<0.001 and 0.024). Polyclonal and allogeneic stimulation resulted in higher expression of CD30, and after polyclonal stimulation, ESRF patients showed higher percentages of CD30-expressing T cells than HC (p<0.001). Compared to autologous stimulation, allogeneic stimulation induced significantly higher expression of CD30 on T cells of ESRF patients only. After polyclonal as well as allogeneic stimulation, an increased sCD30 content was found in culture supernatants of both ESRF patients and HC (p<0.001). Together with decreased Tregs, high serum sCD30 and increased induction of CD30 on T cells after polyclonal stimulation may explain exacerbated alloimmune responses and poor allograft survival in ESRF patients in whom immunosuppression is not able to control the alloimmune response.

T-cell immune monitoring in organ transplantation

PURPOSE OF REVIEW

Chronic injury and late allograft loss remain major causes of morbidity in clinical transplantation. Biomarkers that can reliably assess the risk of posttransplant complications are required to direct and individualize therapy aimed at prolonging graft survival and improving patient health. The purpose of this review is to provide a framework for understanding how to use biomarkers in the context of clinical transplantation and to summarize current data on available noninvasive cellular-based immune monitoring methods to predict transplant outcome.

RECENT FINDINGS

New microarray and gene profiling data reveal peripheral blood cell gene expression patterns that identify operational tolerance, raising the possibility that the measurements can be used to direct immunosuppression withdrawal. Additional data support the use of selective urine gene products and soluble CD30 measurements in serum as reliable biomarkers of acute graft injury. Finally, recent studies demonstrate that measurement of T-cell alloimmunity by cytokine enzyme-linked immunospot is a promising, supplementary pretransplant risk assessment tool.

SUMMARY

Recently published studies in organ transplantation suggest that results derived from assays focused on markers of T-cell immunity can segregate transplant candidates or recipients into high and low-risk subgroups for posttransplant graft injury. Larger prospective studies are needed, however, before any proposed biomarker can be incorporated into the transplant physicians' armamentarium to guide individualized therapeutic decision-making.

Predicting renal graft failure by sCD30 levels and de novo HLA antibodies at 1year post-transplantation

HLA antibodies and sCD30 levels were detected in the serum sampled from 620 renal graft recipients at 1 year post-transplantation, which were followed up for 5 years. Six-year graft and patient survivals were 81.6% and 91.0%. HLA antibodies were detected in 45 recipients (7.3%), of whom there were 14 cases with class I antibodies, 26 cases with class II, and 5 cases with both class I and II. Much more graft loss was record in recipients with HLA antibodies than those without antibodies (60% vs. 15.1%, p<0.001). Significantly higher sCD30 levels were recorded in recipients suffering graft loss than the others (73.9±48.8 U/mL vs. 37.3±14.6 U/mL, p<0.001). Compared with those with high sCD30 levels, recipients with low sCD30 levels (<50 U/mL) had much better 6-year graft survival (92.4% vs. 46.6%, p<0.001). Further statistical analysis showed that detrimental effect of de novo HLA antibodies and high sCD30 on graft survival was not only independent but also additive. Therefore, post-transplantation monitoring of HLA antibodies and sCD30 levels is necessary and recipients with elevated sCD30 level and/or de novo HLA antibody should be paid more attention in order to achieve better graft survival.

Monitoring tolerance and rejection in organ transplant recipients

To avoid toxic side effects caused by permanent immunosuppressive treatment, research in transplantation focuses on new treatment strategies inducing tolerance or allowing drug weaning. Implementing drug minimization into clinical routine can be only safely achieved when guided by biomarkers reflecting the individual immune reactivity. We review recently described biomarkers and assays allowing identification of patients suitable for drug weaning or at risk of rejection. However, the majority of described biomarkers and assays have not been validated in prospective clinical trials. Thus, collaborative efforts are needed to design and perform prospective multicenter trials to validate the identified biomarkers across different laboratories.

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.

Pretransplant soluble CD30 serum concentration does not affect kidney graft outcomes 3 years after transplantation

INTRODUCTION

An elevated serum concentration of soluble the form of CD30 (sCD30), an activation marker of mainly T(H)2-type cytokines producing T lymphocytes, has been reported as a predictive factor for acute cellular rejection episodes and poor graft outcomes in kidney transplantation. This historic cohort study investigated the association of a pretransplant sCD30 serum concentrations with kidney graft function and graft survival 3 years posttransplantation in adult recipients of deceased donor kidney grafts, treated with monoclonal anti-CD25 antibodies as an induction treatment combined with a cyclosporine (CsA)-based maintenance triple therapy.

MATERIALS AND METHODS

The pretransplant sera of 296 recipients were tested for sCD30 content using a microsphere flow-cytometry assay. The estimated glomerular filtration rate (eGFR) was determined by the 4-variable Modification of Diet in Renal Disease equation. The incidences of graft loss were calculated with the use of Kaplan-Meier survival analysis and compared using the log-rank test.

RESULTS

According to the distribution of the pretransplant sCD30 levels concentration ≥2700 pg/mL was defined as high (n = 146) and concentration <2700 pg/mL as low (n = 150). Three years posttransplantation, the eGFR was not significantly different in the recipients in high and low sCD30 groups (65 ± 24 vs 67 ± 21 mL/min/1.73 m(2); P = .43); there was no association between the eGFR 3 years after transplantation and the pretransplant sCD30 levels (r(2) = 0.002; P = .49). Graft survival 3 years after transplantation was also not different in the recipients in high and low sCD30 groups (P = .52).

CONCLUSION

In our adult deceased-donor kidney graft recipients, the pretransplant sCD30 serum concentration was not a predictive factor of immunologic risk associated with the kidney graft function 3 years posttransplantation; neither did it affect graft survival 3 years after transplantation. The immunosuppression with anti-CD25 antibodies as an induction treatment combined with the CsA-based maintenance triple therapy could possibly be decisive for our findings.