Immune activation, immune senescence and levels of Epstein Barr Virus in kidney transplant patients: Impact of mTOR inhibitors

Outcomes of Older Primary Kidney Transplant Recipients by Induction Agent and High-risk Viral Discordance Status in the United States

Background

The impact of induction type or high-risk viral discordance on older kidney transplant recipients is unclear. Herein, we analyzed the association between induction type, viral discordance, and outcomes for older recipients.

Methods

We analyzed the Scientific Registry of Transplant Recipients standard analysis file for all primary kidney transplant recipients older than 55 y who were transplanted between 2005 and 2022. All transplants were crossmatch negative and ABO-compatible. Recipients were discharged on tacrolimus and mycophenolate ± steroids. Recipients were categorized into 3 groups by induction received: rabbit antithymocyte globulin (r-ATG; N = 51 079), interleukin-2 receptor antagonist (IL-2RA; N = 22 752), and alemtuzumab (N = 13 465). Kaplan-Meier curves were generated for recipient and graft survival, and follow-up was censored at 10 y. Mixed-effect Cox proportional hazard models examined the association between induction type, high-risk viral discordance, and outcomes of interest. Models were adjusted for pertinent recipient and donor characteristics.

Results

Induction type did not predict recipient survival in the multivariable model, whereas Epstein-Barr virus high-risk discordance predicted 14% higher mortality (1.14 [1.07-1.21], P < 0.01). In the multivariable model for death-censored graft survival, alemtuzumab, but not IL-2RA, was associated with an increased risk of graft loss (1.18 [1.06-1.29], P < 0.01) compared with r-ATG. High-risk cytomegalovirus discordance predicted 10% lower death-censored graft survival (1.10 [1.01-1.19], P < 0.02). Live donor and preemptive transplantation were favorable predictors of survival.

Conclusions

In this large cohort of older transplant recipients, alemtuzumab, but not IL-2RA, induction was associated with an increased risk of graft loss compared with r-ATG. Cytomegalovirus and Epstein-Barr virus high-risk viral discordance portended poor graft and recipient survival, respectively.

BCR signaling is required for posttransplant lymphoproliferative disease in immunodeficient mice receiving human B cells

Posttransplant lymphoproliferative disease (PTLD) is a major therapeutic challenge that has been difficult to study using human cells because of a lack of suitable models for mechanistic characterization. Here, we show that ex vivo-differentiated B cells isolated from a subset of healthy donors can elicit pathologies similar to PTLD when transferred into immunodeficient mice. The primary driver of PTLD-like pathologies were IgM-producing plasmablasts with Epstein-Barr virus (EBV) genomes that expressed genes commonly associated with EBV latency. We show that a small subset of EBV+ peripheral blood-derived B cells expressing self-reactive, nonmutated B cell receptors (BCRs) expand rapidly in culture in the absence of BCR stimulation. Furthermore, we found that in vitro and in vivo expansion of EBV+ plasmablasts required BCR signaling. Last, treatment of immunodeficient mice with the BCR pathway inhibitor, ibrutinib, delays onset of PTLD-like pathologies in vivo. These data have implications for the diagnosis and care of transplant recipients who are at risk of developing PTLD.

Impact of Immunosenescence in Older Kidney Transplant Recipients: Associated Clinical Outcomes and Possible Risk Stratification for Immunosuppression Reduction

The number of older individuals receiving a kidney transplant as replacement therapy has significantly increased in the past decades and this increase is expected to continue. Older patients have a lower rate of acute rejection but an increased incidence of death with a functioning graft. Several factors, including an increased incidence of infections, post-transplant malignancy and cardiovascular comorbidity and mortality, contribute to this increased risk. Notwithstanding, kidney transplantation is still the best form of kidney replacement therapy in all patients with chronic kidney disease, including in older individuals. The best form of immunosuppression and the optimal dose of these medications in older recipients remains a topic of discussion. Pharmacological studies have usually excluded older patients and when included, patients were highly selected and their numbers insignificant to draw a reasonable conclusion. The reduced incidence of acute rejection in older recipients has largely been attributed to immunosenescence. Immunosenescence refers to the aging of the innate and adaptive immunity, accumulating in phenotypic and functional changes. These changes influences the response of the immune system to new challenges. In older individuals, immunosenescence is associated with increased susceptibility to infectious pathogens, a decreased response after vaccinations, increased risk of malignancies and cardiovascular morbidity and mortality. Chronic kidney disease is associated with premature immunosenescent changes, and these are independent of aging. The immunosenescent state is associated with low-grade sterile inflammation termed inflammaging. This chronic low-grade inflammation triggers a compensatory immunosuppressive state to avoid further tissue damage, leaving older individuals with chronic kidney disease in an immune-impaired state before kidney transplantation. Immunosuppression after transplantation may further enhance progression of this immunosenescent state. This review covers the role of immunosenescence in older kidney transplant recipients and it details present knowledge of the changes in chronic kidney disease and after transplantation. The impact of immunosuppression on the progression and complications of an immunosenescent state are discussed, and the future direction of a possible clinical implementation of immunosenescence to individualize/reduce immunosuppression in older recipients is laid out.

The case for the therapeutic use of mechanistic/mammalian target of rapamycin (mTOR) inhibitors in xenotransplantation

The mechanistic/mammalian target of rapamycin (mTOR) is one of the systems that are necessary to maintain cell homeostasis, such as survival, proliferation, and differentiation. mTOR inhibitors (mTOR-Is) are utilized as immunosuppressants and anti-cancer drugs. In organ allotransplantation, current regimens infrequently include an mTOR-I, which are positioned more commonly as alternative immunosuppressants. In clinical allotransplantation, long-term efficacy has been established, but there is a significant incidence of adverse events, for example, inhibition of wound healing, buccal ulceration, anemia, hyperglycemia, dyslipidemia, and thrombocytopenia, some of which are dose-dependent. mTOR-Is have properties that may be especially beneficial in xenotransplantation. These include suppression of T cell proliferation, increases in the number of T regulatory cells, inhibition of pig graft growth, and anti-inflammatory, anti-viral, and anti-cancer effects. We here review the potential benefits and risks of mTOR-Is in xenotransplantation and suggest that the benefits exceed the adverse effects.

In vitro and in vivo evidence that the switch from calcineurin to mTOR inhibitors may be a strategy for immunosuppression in Epstein-Barr virus-associated post-transplant lymphoproliferative disorder

Post-transplant lymphoproliferative disorder is a life-threatening complication of immunosuppression following transplantation mediated by failure of T cells to control Epstein-Barr virus (EBV)-infected and transformed B cells. Typically, a modification or reduction of immunosuppression is recommended, but insufficiently defined thus far. In order to help delineate this, we characterized EBV-antigen-specific T cells and lymphoblastoid cell lines from healthy donors and in patients with a kidney transplant in the absence or presence of the standard immunosuppressants tacrolimus, cyclosporin A, prednisolone, rapamycin, and mycophenolic acid. Phenotypes of lymphoblastoid cell-lines and T cells, T cell-receptor-repertoire diversity, and T-cell reactivity upon co-culture with autologous lymphoblastoid cell lines were analyzed. Rapamycin and mycophenolic acid inhibited lymphoblastoid cell-line proliferation. T cells treated with prednisolone and rapamycin showed nearly normal cytokine production. Proliferation and the viability of T cells were decreased by mycophenolic acid, while tacrolimus and cyclosporin A were strong suppressors of T-cell function including their killing activity. Overall, our study provides a basis for the clinical decision for the modification and reduction of immunosuppression and adds information to the complex balance of maintaining anti-viral immunity while preventing acute rejection. Thus, an immunosuppressive regime based on mTOR inhibition and reduced or withdrawn calcineurin inhibitors could be a promising strategy for patients with increased risk of or manifested EBV-associated post-transplant lymphoproliferative disorder.

Telomere therapy for chronic kidney disease

Chronic kidney disease (CKD) is estimated to affect almost 10% of individuals worldwide and is one of the leading causes of morbidity and mortality. Renal fibrosis, a central pathway in CKD progression (irrespective of etiology), is associated with shortened or dysfunctional telomeres in animal studies. Telomeres are specialized nucleoprotein structures located at the chromosome end that maintain genomic integrity. The mechanisms of associations between telomere length and CKD have not yet been fully elucidated, however, CKD patients with shorter telomere length may have decreased renal function and a higher mortality rate. A plethora of ongoing research has focused on possible therapeutic applications of telomeres with the overall goal to preserve telomere length as a therapy to treat CKD.

Immune Activation, Exhaustion and Senescence Profiles as Possible Predictors of Cancer in Liver Transplanted Patients

Liver transplanted (LT) patients for hepatocellular carcinoma (LT-HCC) or for other causes (LT-no-HCC) may develop post-transplantation malignancies. Although immune activation and senescence are frequently implicated in cancer development, no data is available on their possible role as biomarkers predictive of tumor onset in this setting. A total of 116 patients were investigated: the 45 LT-HCC patients were older than the 71 LT-non-HCC (p=0.011), but comparable for sex, HCV, HBV infection and immunosuppressive treatment. At baseline, the numbers of activated and senescent-like circulating cells were significantly higher in LT-HCC patients than in LT-no-HCC ones. After a median follow-up of 26.8 months, 6 post-transplant malignancies (PTM) occurred: 4 in LT-HCC (8.9%) and 2 in LT-no-HCC (2.8%) patients. Overall, subjects with high percentages of activated and exhausted T and B cells at baseline were at higher risk of PTM. Notably, within the LT-HCC group, a higher percentage of senescence-like T cells was also associated with cancer development. Moreover, patients with PTM had higher telomere erosion and higher levels of circulating PAMPs (16S rDNA) and DAMPs (mtDNA) when compared with matched patients without PTM. Overall, these findings suggest that immune activation and exhaustion may be useful to predict the risk of PTM occurrence, regardless of the cause of transplantation. In LT-HCC, T-cell senescence represents an additional risk factor for tumor onset.

Biological Predictors of De Novo Tumors in Solid Organ Transplanted Patients During Oncological Surveillance: Potential Role of Circulating TERT mRNA

Background

De novo tumors are a major cause of morbidity and mortality after long-term solid organ transplantation. Chronic immunosuppression strongly affects solid organ transplanted (SOT) patients' immune system by promoting immune evasion strategies and reactivations of viruses with oncogenic potential, ultimately leading to cancer onset. In this scenario, an oncological Surveillance Protocol integrated with biobanking of peripheral blood samples and evaluation of immunovirological and molecular parameters was activated for SOT patients at CRO-IRCCS Aviano, with the aim of identifying suitable biomarkers of cancer development.

Methods

An exploratory longitudinal study was designed based on two serial peripheral blood samples collected at least three months apart. Forty nine SOT patients were selected and stratified by tumor onset during follow-up. Spontaneous T-cell responses to EBV, CMV and tumor associated antigens, EBV-DNA and CMV-DNA loads, and circulating TERT mRNA levels were investigated.

Results

Significantly higher levels of circulating TERT mRNA were observed 3.5-23.5 months before and close to the diagnosis of cancer as compared to tumor-free patients. Plasmatic TERT mRNA levels >97.73 copies/mL at baseline were significantly associated with the risk of developing de novo tumors (HR=4.0, 95%C.I. = 1.4-11.5, p=0.01). In particular, the risk significantly increased by 4% with every ten-unit increment in TERT mRNA (HR=1.04, 95%C.I. = 1.01-1.07, p=0.01).

Conclusions

Although obtained in an exploratory study, our data support the importance of identifying early biomarkers of tumor onset in SOT patients useful to modulate the pace of surveillance visits.

Asymptomatic and Mild SARS-CoV-2 Infections Elicit Lower Immune Activation and Higher Specific Neutralizing Antibodies in Children Than in Adults

Background

The immune response plays a pivotal role in dictating the clinical outcome in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-infected adults, but it is still poorly investigated in the pediatric population.

Methods

Of 209 enrolled subjects, 155 patients were confirmed by PCR and/or serology as having coronavirus disease 2019 (COVID-19). Blood samples were obtained at a median of 2.8 (interquartile, 2.1–3.7) and 6.1 (5.3–7.2) months after baseline (symptom onset and/or first positive virus detection). The immune profiles of activation, senescence, exhaustion, and regulatory cells were analyzed by flow cytometry. Neutralizing antibodies (nAbs) were detected by a plaque reduction neutralization test. In available nasopharyngeal swabs at baseline, SARS-CoV-2 levels were quantified by digital droplet PCR (ddPCR).

Results

Overall, COVID-19 patients had higher levels of immune activation, exhaustion, and regulatory cells compared to non-COVID-19 subjects. Within the COVID-19 group, activated and senescent cells were higher in adults than in children and inversely correlated with the nAbs levels. Conversely, Tregs and Bregs regulatory cells were higher in COVID-19 children compared to adults and positively correlated with nAbs. Higher immune activation still persisted in adults after 6 months of infection, while children maintained higher levels of regulatory cells. SARS-CoV-2 levels did not differ among age classes.

Conclusions

Adults displayed higher immune activation and lower production of anti-SARS-CoV-2 nAbs than children. The different immune response was not related to different viral load. The higher expression of regulatory cells in children may contribute to reduce the immune activation, thus leading to a greater specific response against the virus.

Heterogeneous Manifestations of Posttransplant Lymphoma in Renal Transplant Recipients: A Case Series

Posttransplant lymphoproliferative disorder (PTLD) occurs in 1% to 3% of adult renal transplant recipients (RTRs). PTLD has a heterogeneous presentation and is often associated with Epstein-Barr virus (EBV) and immunosuppression. We present a descriptive case series of 16 RTRs who demonstrate a variety of PTLD manifestations. Fifty-six percent received rabbit antithymocyte globulin induction, and 37.5% received basiliximab. Maintenance immunosuppression included glucocorticoids, tacrolimus, and mycophenolate mofetil. Median time from transplantation to PTLD diagnosis was 96.5 months. PTLD involved a single site in 44% of RTRs and multiple sites in 56%. PTLD was localized to the gastrointestinal tract in 9 RTRs, in lymph nodes in 9, central nervous system in 4, bone marrow in 3, skin in 3, lungs in 2, perinephric space in 2, mediastinum in 1, and native kidney in 1. PTLD was EBV positive in 8 RTRs, monomorphic/monoclonal in 14, and of B-cell lineage in 13. Three RTRs had T-cell PTLD. Immunosuppressive agents, except glucocorticoids, were discontinued at diagnosis. Treatment was chemotherapy either alone (in 14 RTRs) or in combination with radiation. Complete remission was achieved in 62.5% of RTRs. Renal dysfunction developed in 62.5% of RTRs, and 4 received dialysis. The overall mortality rate was 62.5%, with median time of death 6.5 months after diagnosis. PTLD that was EBV negative and had T-cell involvement presented with aggressive disease and a higher mortality. Clinicians should be aware of the various PTLD manifestations. Early diagnosis and a multidisciplinary approach to treatment is crucial for improved patient outcomes.

Small Intestine Posttransplant Lymphoproliferative Disorder in a Kidney Transplant Recipient: A Case Report

Posttransplant lymphoproliferative disorder is a serious, life-threatening complication in organ transplant patients receiving immunosuppressive therapy. Isolated posttransplant lymphoproliferative disorder of the gastrointestinal tract is rare. Posttransplant lymphoproliferative disorder encompasses a spectrum of clinical manifestations, in addition to a wide range of histopathological findings, from B-cell hyperplasia to lymphoma. Renal transplant patients with small intestinal posttransplant lymphoproliferative disorder are more likely to be of younger age, but less frequently represent Hodgkin and Hodgkin-like lesions. They also have better patient survival compared with transplant recipients with posttransplant lymphoproliferative disorder in other locations. We report on the treatment of a kidney transplant recipient with confirmed isolated posttransplant lymphoproliferative disorder in the small intestine. The patient presented with acute abdomen and small intestine perforation, 17 years after kidney transplant, despite being without calcineurin inhibitor in immunosuppressive therapy, to mitigate previous ductal breast carcinoma. Pathological examinations revealed isolated EpsteinBarr virus-positive diffuse large B-cell non-Hodgkin lymphoma of small intestine, clinical stage IV A E. The patient was treated with reduction of immunosuppression, rituximab, and the CHOP regimen (ie, cyclophosphamide, doxorubicin, vincristine, and prednisone). A complete remission was achieved. Kidney allograft function was stable throughout the follow-up period. Physicians should consider isolated gastrointestinal posttransplant lymphoproliferative disorder as a possible etiology in posttransplant, immunocompromised patients who present with different gastrointestinal symptoms. Given good clinical response to treatment, early identification of posttransplant lymphoproliferative disorder has a key role in monitoring and treatment.

Immunosuppressive Drug-Associated Adverse Event Profiles in De Novo Kidney Transplant Recipients Receiving Everolimus and Reduced Tacrolimus Doses

BACKGROUND

The safety of immunosuppressive regimens is influenced by the induction agent, maintenance drug combination, and prophylactic strategy for cytomegalovirus (CMV) infection. Herein, this safety analysis compares rabbit antithymocyte globulin (r-ATG) or basiliximab (BAS) combined with everolimus (EVR) versus BAS combined with mycophenolate sodium (MPS) in kidney transplant recipients receiving tacrolimus, prednisone, and preemptive CMV therapy.

METHODS

In this single-center, prospective, randomized study, adverse events (AEs), serious AEs (SAEs), viral infections, laboratory abnormalities, dose reductions, and temporary or permanent discontinuation of the immunosuppressant were compared among patients receiving r-ATG/EVR (n = 85), BAS/EVR (n = 102), and BAS/MPS (n = 101).

RESULTS

A total of 2741 AEs and 344 SAEs were observed. There were no differences in the proportion of patients with at least one AE (96% versus 98% versus 96%, respectively; P > 0.05). The proportion of patients with at least one SAE was highest in the BAS/MPS group (33% versus 48% versus 69%, respectively; P < 0.05). This difference was due primarily to a high incidence of CMV infection in the BAS/MPS group (4.7% versus 10.8% versus 37.6%, respectively). The incidence of mild/moderate abnormalities in creatinine, cholesterol, and triglyceride levels was higher in both EVR groups. The cumulative freedom from dose reduction or treatment discontinuation due to an AE was higher in both EVR groups than in the BAS/MPS group (89.2% versus 92.8% versus 76.3%, respectively, P = 0.003). There was no difference in the incidence of biopsy-confirmed acute rejection (9.4% versus 18.6 versus 15.8%, respectively; P = 0.403).

CONCLUSIONS

This analysis suggests that r-ATG induction combined with EVR is associated with a comparable incidence of acute rejection, lower incidence of CMV infection, and fewer changes in initial immunosuppressive regimen due to AEs in kidney transplant recipients receiving tacrolimus, prednisone, and preemptive CMV therapy.

Post-transplant Lymphoproliferative Disorder in a Patient After Kidney Transplant, 5-Year Follow-up: A Case Report

INTRODUCTION

Post-transplant lymphoproliferative disorder (PTLD) is a serious, life-threatening complication in organ transplant patients receiving immunosuppressive therapy. The risk factors include Epstein-Barr virus infection and a cumulative dose of the immunosuppression.

CASE REPORT

We present a 5-year follow-up case of a 28-year-old patient with PTLD in the gastrointestinal tract. In the ninth month after kidney transplant, the patient was hospitalized for pain in the abdomen and diarrhea. Physical examination demonstrated tenderness in the area of the cecum, and colonoscopy revealed ulcerations in the large intestine. Polymorphic lymphoma (PTLD) was found in the collected samples. The patient received monotherapy treatment with anti-CD20 antibodies, resulting in complete remission of disease, confirmed by computed tomography scan and colonoscopy.

CONCLUSION

PTLD may have a different clinical course and should be considered in the differential diagnosis of patients after organ transplant.