Pathogen-specific cell-mediated immunity to guide the management of cytomegalovirus in solid organ transplantation: state of the art clinical review

INTRODUCTION

Cytomegalovirus (CMV) is a common opportunistic infection after solid organ transplantation, with significant impact on morbidity and long-term survival. Despite advances in diagnostics and therapeutics, the management of CMV remains very challenging.

AREAS COVERED

This article reviews emerging data on the clinical utility of laboratory assays that quantify cell-mediated immune responses to CMV. Observational studies have consistently demonstrated that a deficiency in pathogen-specific cell-mediated immunity is correlated with a heightened risk of primary, reactivation or recurrent CMV after transplantation. A limited number of interventional studies have recently investigated cell-mediated immune assays in guiding the prevention and treatment of CMV infection after solid organ transplantation.

EXPERT OPINION

The pathogenesis and outcome of CMV after solid organ transplantion reflect the interplay between viral replication and CMV-specific immune reconstitution. Research in CMV-specific cell-mediated immunity paved way for the development of several laboratory assays that may assist clinicians in predicting the risk of CMV after transplantation, individualize the approach to CMV disease prevention, guide the need and duration of treatment of CMV infection, and predict the risk of relapse after treatment. More interventional studies are needed to further solidify the role of cell-mediated immune assays in various clinical situations after transplantation.

Unintended Consequences: Risk of Opportunistic Infections Associated With Long-term Glucocorticoid Therapies in Adults

Glucocorticoids are widespread anti-inflammatory medications used in medical practice. The immunosuppressive effects of systemic glucocorticoids and increased susceptibility to infections are widely appreciated. However, the dose-dependent model frequently used may not accurately predict the risk of infection in all patients treated with long-term glucocorticoids. In this review, we examine the risks of opportunistic infections (OIs) in patients requiring glucocorticoid therapy by evaluating the influence of the glucocorticoid dose, duration, and potency, combined with biological and host clinical factors and concomitant immunosuppressive therapy. We propose strategies to prevent OIs, which involve screening, antimicrobial prophylaxis, and immunizations. While this review focuses on patients with autoimmune, inflammatory, or neoplastic diseases, the potential risks and preventative strategies are likely applicable to other populations. Clinicians should actively assess the benefit-harm ratios of systemic glucocorticoids and implement preventive efforts to decrease their associated infections complications.

Interferon-Gamma-Release assay and absolute CD8 lymphocyte count for acquired immunosuppression monitoring in critically ill patients

Guided biomarker-personalized immunotherapy is advancing rapidly as a means to rejuvenate immune function in injured patients who are the most immunosuppressed. A recent study introduced a fully automated interferon-γ release assay (IGRA) for monitoring the functionality of T lymphocytes in patients with septic shock. While a significant decrease in IFN-γ release capacity was observed, a significant correlation with CD8 lymphocyte absolute count was also reported, raising the question of whether ex-vivo IFN-γ production would be only a surrogate marker for lymphocyte count or if these two parameters conveyed distinct and complementary information. In a large cohort of more than 353 critically ill patients following various injuries (sepsis, trauma, major surgery), the primary objective of the present study was to simultaneously evaluate the association between ex vivo IFN-γ release and CD8 cell count with regard to adverse outcome. Our findings provide a clear-cut result, as they distinctly demonstrate that IGRA offers higher-quality information than CD8 count in terms of an independent association with the occurrence of an adverse outcome. These results strengthen the case for incorporating IGRA into the array of biomarkers of interest for defining endotypes in sepsis. This holds especially true given that fully automated tests are now readily available and could be used in routine clinical practice.

Utility of the Interferon-Gamma Enzyme-Linked Immunosorbent Spot Assay to Predict Risk of Cytomegalovirus Infection in Kidney Transplant Recipients

Non-specific interferon-gamma (IFN-γ) enzyme-linked immunosorbent (ELISpot) responses after solid organ transplant (SOT) and their relationship with cytomegalovirus (CMV) reactivation have hardly been investigated. Adult kidney transplant (KT) recipients underwent measurement of IFN-γ-producing T cells using the ELISpot assay before and 1 month after transplantation. Data for CMV infection episodes were collected. Risk factors for post-transplant CMV infection, based on IFN-γ responses, were analyzed using a Cox proportional hazards model. A total of 93 KT recipients were enrolled in the study and 84 evaluable participants remained at 1 month post KT. Thirty-three (39%) recipients developed subsequent CMV infection within 6 months post-transplant. At 1-month post-transplant, IFN-γ-producing T cells with <250 spot-forming units (SFUs)/2.5 × 105 peripheral blood mononuclear cells (PBMCs) were significantly associated with CMV infection (HR 3.1, 95% CI 1.4-7.1, p = 0.007). On multivariable analysis, posttransplant IFN-γ-producing T cells with <250 SFUs/2.5 × 105 PBMCs remained independently associated with CMV infection (HR 3.1, 95% CI 1.2-7.8, p = 0.019). Conclusions: KT recipients with low IFN-γ-producing T cells measured by the ELISpot assay are more likely to develop CMV infection after transplantation. Therefore, measurement of nonspecific cell-mediated immunity ELISpot responses could potentially stratify recipients at risk of CMV infection (Thai Clinical Trials Registry, TCTR20210216004).

Meet in the middle: Could cell mediated-immunity assays be the answer for ideal Cytomegalovirus prophylaxis after lung transplantation? Observational study from a single center with intermittent antiviral prophylaxis

BACKGROUND

Cytomegalovirus (CMV) can cause tissue-invasive disease and indirect effects after lung transplantation (LTx) such as acute rejection episodes and chronic lung allograft dysfunction. Monitoring CMV-specific cell immune recovery (CMV-CIR) after LTx can individualize CMV risks and establish better antiviral approach. This study evaluated the dynamics of CMV-CIR, using QuantiFERON-CMV assay (Qiagen Group), in the first year after LTx.

METHODS

Prospective observational cohort study included lung transplant recipients from December/2015 to December/2016. Universal antiviral prophylaxis with intravenous ganciclovir 5 mg/kg/day 3 days/week for 3 months was given for CMV-seropositive recipients (R+) and only CMV-seropositive donor and negative recipient (D+/R-) received a 6-month-prophylaxis with ganciclovir and valganciclovir, on alternate days, in the first 3 months and then, 3 more months of valganciclovir. QuantiFERON-CMV was measured at the same time points of surveillance bronchoscopies. CMV infection was defined as any DNAemia detected and CMV disease with proven biopsy or antigenemia pp65 above 10 cells/300.000 neutrophils.

RESULTS

Thirty-eight patients were included. On days 45, 90, and 365 days post-LTx, 60%, 72%, and 81% QuantiFERON-CMV were reactive, respectively. Eleven patients (28.9%) presented CMV-disease and 27 DNAemia/CMV infections. Reactive tests were able to predict CMV disease only at 90 days after LTx (p = .027) but failed on DNAemia/CMV infection (p = .148). Daily prophylaxis, for D+/R- patients (13.2%), remained as an independently associated factor for not achieving reactive QuantiFERON-CMV (adjusted OR .27, 95%CI .12-.60, p = .02).

CONCLUSION

QuantiFERON-CMV may be another diagnostic tool to help stratify CMV-disease risk and individualized antiviral prophylaxis after LTx.

Infections after organ transplantation and immune response

Organ transplantation has provided another chance of survival for end-stage organ failure patients. Yet, transplant rejection is still a main challenging factor. Immunosuppressive drugs have been used to avoid rejection and suppress the immune response against allografts. Thus, immunosuppressants increase the risk of infection in immunocompromised organ transplant recipients. The infection risk reflects the relationship between the nature and severity of immunosuppression and infectious diseases. Furthermore, immunosuppressants show an immunological impact on the genetics of innate and adaptive immune responses. This effect usually reactivates the post-transplant infection in the donor and recipient tissues since T-cell activation has a substantial role in allograft rejection. Meanwhile, different infections have been found to activate the T-cells into CD₄⁺ helper T-cell subset and CD₈⁺ cytotoxic T-lymphocyte that affect the infection and the allograft. Therefore, the best management and preventive strategies of immunosuppression, antimicrobial prophylaxis, and intensive medical care are required for successful organ transplantation. This review addresses the activation of immune responses against different infections in immunocompromised individuals after organ transplantation.

A multicentre, patient- and assessor-blinded, non-inferiority, randomised and controlled phase II trial to compare standard and torque teno virus-guided immunosuppression in kidney transplant recipients in the first year after transplantation: TTVguideIT

BACKGROUND

Immunosuppression after kidney transplantation is mainly guided via plasma tacrolimus trough level, which cannot sufficiently predict allograft rejection and infection. The plasma load of the non-pathogenic and highly prevalent torque teno virus (TTV) is associated with the immunosuppression of its host. Non-interventional studies suggest the use of TTV load to predict allograft rejection and infection. The primary objective of the current trial is to demonstrate the safety, tolerability and preliminary efficacy of TTV-guided immunosuppression.

METHODS

For this purpose, a randomised, controlled, interventional, two-arm, non-inferiority, patient- and assessor-blinded, investigator-driven phase II trial was designed. A total of 260 stable, low-immunological-risk adult recipients of a kidney graft with tacrolimus-based immunosuppression and TTV infection after month 3 post-transplantation will be recruited in 13 academic centres in six European countries. Subjects will be randomised in a 1:1 ratio (allocation concealment) to receive tacrolimus either guided by TTV load or according to the local centre standard for 9 months. The primary composite endpoint includes the occurrence of infections, biopsy-proven allograft rejection, graft loss, or death. The main secondary endpoints include estimated glomerular filtration rate, graft rejection detected by protocol biopsy at month 12 post-transplantation (including molecular microscopy), development of de novo donor-specific antibodies, health-related quality of life, and drug adherence. In parallel, a comprehensive biobank will be established including plasma, serum, urine and whole blood. The date of the first enrolment was August 2022 and the planned end is April 2025.

DISCUSSION

The assessment of individual kidney transplant recipient immune function might enable clinicians to personalise immunosuppression, thereby reducing infection and rejection. Moreover, the trial might act as a proof of principle for TTV-guided immunosuppression and thus pave the way for broader clinical applications, including as guidance for immune modulators or disease-modifying agents.

TRIAL REGISTRATION

EU CT-Number: 2022-500024-30-00.

Conventional and Novel Approaches to Immunosuppression in Lung Transplantation

Most therapeutic advances in immunosuppression have occurred over the past few decades. Although modern strategies have been effective in reducing acute cellular rejection, excess immunosuppression comes at the price of toxicity, opportunistic infection, and malignancy. As our understanding of the immune system and allograft rejection becomes more nuanced, there is an opportunity to evolve immunosuppression protocols to optimize longer term outcomes while mitigating the deleterious effects of traditional protocols.

Integrated Immunologic Monitoring in Solid Organ Transplantation: The Road Toward Torque Teno Virus-guided Immunosuppression

Potent immunosuppressive drugs have been introduced into clinical care for solid organ transplant recipients. It is now time to guide these drugs on an individual level to optimize their efficacy. An ideal tool simultaneously detects overimmunosuppression and underimmunosuppression, is highly standardized, and is straightforward to implement into routine. Randomized controlled interventional trials are crucial to demonstrate clinical value. To date, proposed assays have mainly focused on the prediction of rejection and were based on the assessment of few immune compartments. Recently, novel tools have been introduced based on a more integrated approach to characterize the immune function and cover a broader spectrum of the immune system. In this respect, the quantification of the plasma load of a highly prevalent and apathogenic virus that might reflect the immune function of its host has been proposed: the torque teno virus (TTV). Although TTV control is driven by T cells, other major immune compartments might contribute to the hosts' response. A standardized in-house polymerase chain reaction and a conformité européenne-certified commercially available polymerase chain reaction are available for TTV quantification. TTV load is associated with rejection and infection in solid organ transplant recipients, and cutoff values for risk stratification of such events have been proposed for lung and kidney transplantation. Test performance of TTV load does not allow for the diagnosis of rejection and infection but is able to define at-risk patients. Hitherto TTV load has not been used in interventional settings, but two interventional randomized controlled trials are currently testing the safety and efficacy of TTV-guided immunosuppression.

Prognostic Value of Mid-Region Proadrenomedullin and In Vitro Interferon Gamma Production for In-Hospital Mortality in Patients with COVID-19 Pneumonia and Respiratory Failure: An Observational Prospective Study

Coagulopathy and immune dysregulation have been identified as important causes of adverse outcomes in coronavirus disease (COVID-19). Mid-region proadrenomedullin (MR-proADM) is associated with endothelial damage and has recently been proposed as a prognostic factor in COVID-19. In non-COVID-19 immunocompromised patients, low in vitro interferon gamma (IFNγ) production correlates with infection risk and mortality. This prospective, monocentric, observational study included adult patients consecutively admitted with radiologic evidence of COVID-19 pneumonia and respiratory failure. MR-proADM and in vitro IFNγ production were measured at T0 (day 1 from admission) and T1 (day 7 from enrollment). One hundred patients were enrolled. Thirty-six percent were females, median age 65 (Q1−Q3 54.5−75) years, and 58% had ≥1 comorbidity. Only 16 patients had received COVID-19 vaccination before hospitalization. At admission, the median PaO2:FiO2 ratio was 241 (157−309) mmHg. In-hospital mortality was 13%. MR-proADM levels differed significantly between deceased and survivors both at T0 (1.41 (1.12−1.77) nmol/L vs. 0.79 (0.63−1.03) nmol/L, p < 0.001) and T1 (1.67 (1.08−1.96) nmol/L vs. 0.66 (0.53−0.95) nmol/L, p < 0.001). In vitro IFNγ production at T0 and T1 did not vary between groups. When only the subset of non-vaccinated patients was considered, both biomarkers at T1 resulted significantly associated with in-hospital mortality. AUROC for MR-proADM at T0 to predict in-hospital mortality was 0.87 (95%CI 0.79−0.94), with the best cut-off point at 1.04 nmol/L (92% sensitivity, 75% specificity and 98% negative predictive value). In patients with COVID-19 pneumonia and different degrees of respiratory failure, MR-proADM at admission and during hospitalization resulted strongly associated with in-hospital mortality. Low in vitro IFNγ production after the first week of hospitalization was associated with mortality in non-vaccinated patients possibly identifying the subgroup characterized by a higher degree of immune suppression.

Bacterial and Viral Infections in Liver Transplantation: New Insights from Clinical and Surgical Perspectives

End-stage liver disease patients undergoing liver transplantation are prone to develop numerous infectious complications because of immunosuppression, surgical interventions, and malnutrition. Infections in transplant recipients account for the main cause of mortality and morbidity with rates of up to 80%. The challenges faced in the early post-transplant period tend to be linked to transplant procedures and nosocomial infections commonly in bloodstream, surgical, and intra-abdominal sites. Viral infections represent an additional complication of immunosuppression; they can be donor-derived, reactivated from a latent virus, nosocomial or community-acquired. Bacterial and viral infections in solid organ transplantation are managed by prophylaxis, multi-drug resistant screening, risk assessment, vaccination, infection control and antimicrobial stewardship. The aim of this review was to discuss the epidemiology of bacterial and viral infections in liver transplants, infection control issues, as well as surgical frontiers of ex situ liver perfusion.

Bacterial and Viral Infection and Sepsis in Kidney Transplanted Patients

Kidney transplanted patients are a unique population with intrinsic susceptibility to viral and bacterial infections, mainly (but not exclusively) due to continuous immunosuppression. In this setting, infectious episodes remain among the most important causes of death, with different risks according to the degree of immunosuppression, time after transplantation, type of infection, and patient conditions. Prevention, early diagnosis, and appropriate therapy are the goals of infective management, taking into account that some specific characteristics of transplanted patients may cause a delay (the absence of fever or inflammatory symptoms, the negativity of serological tests commonly adopted for the general population, or the atypical anatomical presentation depending on the surgical site and graft implantation). This review considers the recent available findings of the most common viral and bacterial infection in kidney transplanted patients and explores risk factors and outcomes in septic evolution.

Review: immunosuppression for the lung transplant patient

Lung transplantation (LTx) has evolved significantly since its inception and the improvement in LTx outcomes over the last three decades has predominantly been driven by advances in immunosuppression management. Despite the lack of new classes of immunosuppression medications, immunosuppressive strategies have evolved significantly from a universal method to a more targeted approach, reflecting a greater understanding of the need for individualized therapy and careful consideration of all factors that are influenced by immunosuppression choice. This has become increasingly important as the demographics of lung transplant recipients have changed over time, with older and more medically complex candidates being accepted and undergoing LTx. Furthermore, improved survival post lung transplant has translated into more immunosuppression related comorbidities long-term, predominantly chronic kidney disease (CKD) and malignancy, which has required further nuanced management approaches. This review provides an update on current traditional lung transplant immunosuppression strategies, with modifications based on pre-existing recipient factors and comorbidities, peri-operative challenges and long term complications, balanced against the perpetual challenge of chronic lung allograft dysfunction (CLAD). As we continue to explore and understand the complexity of LTx immunology and the interplay of different factors, immunosuppression strategies will require ongoing critical evaluation and personalization in order to continue to improve lung transplant outcomes.

Novel ways to monitor immunosuppression in pediatric kidney transplant recipients-underlying concepts and emerging data

After pediatric kidney transplantation, immunosuppressive therapy is given to avoid acute and chronic rejections. However, the immunosuppression causes an increased risk of severe viral complications and bacterial infections and is associated with serious side effects. It is therefore crucial to achieve the optimal individual balance between over- and under-immunosuppression and thereby avoid unnecessary exposure to immunosuppressive drugs. In routine use, steering of immunosuppressants is performed primarily by monitoring of trough levels that mirror pharmacokinetics (although not, however, pharmacodynamics). Other diagnostic and prognostic markers to assess the individual intensity of immunosuppression are missing. Potential methods to determine immune function and grade of immunosuppression, such as analysis of the torque teno virus (TTV) load, QuantiFERON Monitor®, and ImmuKnow® as well as virus-specific T cells (Tvis), are currently being evaluated. In some studies TTV load, QuantiFERON Monitor® and ImmuKnow® were associated with the risk for post-transplant rejections and infections, but randomized controlled trials after pediatric kidney transplantation are not available. Post-transplant monitoring of Tvis levels seem to be promising because Tvis control virus replication and have been shown to correlate with virus-specific as well as general cellular immune defense, which represents the individual’s susceptibility to infections. Additional Tvis-monitoring provides an innovative opportunity to personalize the antiviral management and the dosing of the immunosuppressive therapy after pediatric kidney transplantation to avoid unnecessary therapeutic interventions and identify over-immunosuppression.

Immunosuppression-related neurological disorders in kidney transplantation

A large number of neurological disorders can affect renal transplant recipients, potentially leading to disabling or life-threatening complications. Prevention, early diagnosis and appropriate management of these conditions are critical to avoid irreversible lesions. A pivotal role in the pathogenesis of common post-transplant neurological disorders is played by immunosuppressive therapy. The most frequently administered regimen consists of triple immunosuppression, which comprises a calcineurin inhibitor (CNI), a purine synthesis inhibitor and glucocorticoids. Some of these immunosuppressive drugs may lead to neurological signs and symptoms through direct neurotoxic effects, and all of them may be responsible for the development of tumors or opportunistic infections. In this review, after a brief summary of neurotoxic pathogenetic mechanisms encompassing recent advances in the field, we focus on the clinical presentation of more common and severe immunosuppression-related neurological complications, classifying them by characteristics of urgency and anatomic site. Our goal is to provide a general framework that addresses such clinical issues with a multidisciplinary approach, as these conditions require.

Evaluation of Quantiferon®-Monitor as a biomarker of immunosuppression and predictor of infection in lung transplant recipients

BACKGROUND

Optimizing immunosuppression in lung transplant recipients (LTR) is crucially important in minimizing the risk of infection and rejection. Quantiferon®-Monitor (QFM) is a candidate immune function biomarker which has not yet been rigorously evaluated in the lung transplant setting. The aim of this prospective cohort study was to explore relationships between QFM results, immunosuppression, and infection/rejection in LTR.

METHODS

QFM, which measures interferon-γ after stimulation with innate and adaptive immune antigens, was tested before and at 2, 6, 12, 24 and 52 weeks post-transplant. Immunosuppression relationships were assessed with linear mixed effects models. Clinical outcomes were analyzed based on the preceding QFM result.

RESULTS

Eighty LTR were included. Median pre-transplant QFM levels were 171 IU/mL (IQR 45-461), decreasing to 3 IU/mL (IQR 1-8) at 2 weeks post-transplant then progressively recovering toward baseline with time from transplant. Prednisolone was strongly inversely associated with QFM level (0.1 mg/kg dose increase correlating with 88 IU/mL QFM decrease, 95% CI 61-114, P < .001). Patients with QFM values <10 and <60 IU/mL were more likely to develop a serious opportunistic infection between 3 and 6 months (HR 6.38, 95% CI 1.37-29.66, P = .02) and 6-12 months (HR 3.25, 95% CI 1.11-9.49, P = .03) post-transplant, respectively.

CONCLUSIONS

QFM values declined significantly post-transplant, with patients recovering at different rates. Prednisolone dose significantly impacted QFM results. Low levels were associated with infection beyond 3 months post-transplant, suggesting that QFM may be able to identify overly immunosuppressed patients who could be targeted for dose reduction. Larger prospective studies are needed to further evaluate this promising assay.

Epidemiology and risk factors for varicella zoster virus reactivation in heart transplant recipients

Heart transplant (HT) recipients are at higher risk of varicella zoster virus (VZV) reactivation. Risk factors for VZV reactivation are currently not well defined, impeding the ability to design and implement strategies to minimize the burden of this illness in this population. Automated data extraction tools were used to retrieve data from the electronic health record (EHR) of all adult HT recipients at our center between 2010 and 2016. Information from the Organ Procurement and Transplantation Network Standard Analysis and Research Files was merged with the extracted data. Potential cases were manually reviewed and adjudicated using consensus definitions. Cumulative incidence and risk factors for VZV reactivation in HT recipients were assessed by the Kaplan-Meier method and Cox modeling, respectively. In 203 HT recipients, the cumulative incidence of VZV reactivation at 8-years post-transplantation was 26.4% (95% CI: 17.8-38.0). The median time to VZV reactivation was 2.1 years (IQR, 1.5-4.1). Half (14/28) of the cases experienced post-herpetic neuralgia (PHN). Post-transplant CMV infection (HR 9.05 [95% CI: 3.76-21.77) and post-transplant pulse-dose steroids (HR 3.19 [95% CI: 1.05-9.68]) were independently associated with a higher risk of VZV reactivation in multivariable modeling. Identification of risk factors will aid in the development of targeted preventive strategies.

Immunosuppressive Agents and Infectious Risk in Transplantation: Managing the "Net State of Immunosuppression"

Successful solid organ transplantation reflects meticulous attention to the details of immunosuppression, balancing risks for graft rejection against risks for infection. The 'net state of immune suppression' is a conceptual framework of all factors contributing to infectious risk. Assays which measure immune function in the immunosuppressed transplant recipient relative to infectious risk and allograft function are lacking. The best measures of integrated immune function may be quantitative viral loads to assess the individual's ability to control latent viral infections. Few studies address adjustment of immunosuppression during active infections. Thus, confronted with infection in solid organ recipients, the management of immunosuppression is based largely on clinical experience. This review examines known measures of immune function and the immunologic effects of common immunosuppressive drugs and available studies reporting modification of drug regimens for specific infections. These data provide a conceptual framework for the management of immunosuppression during infection in organ recipients.

Torque teno virus for risk stratification of graft rejection and infection in kidney transplant recipients-A prospective observational trial

The nonpathogenic and ubiquitous torque teno virus (TTV) is associated with immunosuppression in solid organ transplant recipients. Studies in kidney transplant patients proposed TTV quantification for risk stratification of graft rejection and infection. In this prospective trial (DRKS00012335) 386 consecutive kidney transplant recipients were subjected to longitudinal per-protocol monitoring of plasma TTV load by polymerase chain reaction for 12 months posttransplant. TTV load peaked at the end of month 3 posttransplant and reached steady state thereafter. TTV load after the end of month 3 was analyzed in the context of subsequent rejection diagnosed by indication biopsy and infection within the first year posttransplant, respectively. Each log increase in TTV load decreased the odds for rejection by 22% (odds ratio [OR] 0.78, 95% confidence interval [CI] 0.62-0.97; P = .027) and increased the odds for infection by 11% (OR 1.11, 95% CI 1.06-1.15; P < .001). TTV was quantified at a median of 14 days before rejection was diagnosed and 27 days before onset of infection, respectively. We defined a TTV load between 1 × 10⁶ and 1 × 10⁸ copies/mL as optimal range to minimize the risk for rejection and infection. These data support the initiation of an interventional trial assessing the efficacy of TTV-guided immunosuppression to reduce infection and graft rejection in kidney transplant recipients.

[Functional immunoassays in the setting of infectious risk and immunosuppressive therapy of non-HIV immunocompromised patients]

The holistic approach of the human immune system is based on the study of its components collectively driving a functional response to an immunogenic stimulus. To appreciate a specific immune dysfunction, a condition is mimicked ex vivo and the immune response induced is assessed. The application field of such assays are broad and expanding, from the diagnosis of primary and secondary immunodeficiencies, immunotherapy for cancer to the management of patients at-risk for infections and vaccination. These assays are immune monitoring tools that may contribute to a personalised and precision medicine. The purpose of this review is to describe immune functional assays available in the setting of non-HIV acquired immune deficiency. First, we will address the use of theses assays in the diagnosis of opportunistic infections such as viral reactivation. Secondly, we will report the usefulness of these assays to assess vaccine efficacy and to manage immunosuppressive therapies.

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

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

A Polyclonal Immune Function Assay Allows Dose-Dependent Characterization of Immunosuppressive Drug Effects but Has Limited Clinical Utility for Predicting Infection on an Individual Basis

Dosage of immunosuppressive drugs after transplantation critically determines rejection and infection episodes. In this study, a global immune function assay was characterized among controls, dialysis-patients, and transplant-recipients to evaluate its utility for pharmacodynamic monitoring of immunosuppressive drugs and for predicting infections. Whole-blood samples were stimulated with anti-CD3/toll-like-receptor (TLR7/8)-agonist in the presence or absence of drugs and IFN-γ secretion was measured by ELISA. Additional stimulation-induced cytokines were characterized among T-, B-, and NK-cells using flow-cytometry. Cytokine-secretion was dominated by IFN-γ, and mainly observed in CD4, CD8, and NK-cells. Intra-assay variability was low (CV = 10.4 ± 6.2%), whereas variability over time was high, even in the absence of clinical events (CV = 65.0 ± 35.7%). Cyclosporine A, tacrolimus and steroids dose-dependently inhibited IFN-γ secretion, and reactivity was further reduced when calcineurin inhibitors were combined with steroids. Moreover, IFN-γ levels significantly differed between controls, dialysis-patients, and transplant-recipients, with lowest IFN-γ levels early after transplantation (p < 0.001). However, a single test had limited ability to predict infectious episodes. In conclusion, the assay may have potential for basic pharmacodynamic characterization of immunosuppressive drugs and their combinations, and for assessing loss of global immunocompetence after transplantation, but its application to guide drug-dosing and to predict infectious on an individual basis is limited.

Immunosuppressive strategies in lung transplantation

Lung transplantation is a viable option for those with end-stage lung disease which is evidenced by the continued increase in the number of lung transplantations worldwide. However, patients and clinicians are constantly faced with acute and chronic rejection, infectious complications, drug toxicities, and malignancies throughout the lifetime of the lung transplant recipient. Conventional maintenance immunosuppression therapy consisting of a calcineurin inhibitor (CNI), anti-metabolite, and corticosteroids have become the standard regimen but newer agents and modalities continue to be developed. Here we will review induction agents, maintenance immunosuppressives, adjunctive therapies and other strategies to improve long-term outcomes.

The QuantiFERON Monitor® assay is predictive of infection post allogeneic hematopoietic cell transplantation

INTRODUCTION

Following allogeneic hematopoietic stem cell transplantation (alloHCT), excessive immunosuppression can be complicated by infection, while inadequate immunosuppression can result in graft-vs-host disease (GVHD). An accurate method to assess overall immune status post HCT is lacking. The QuantiFERON Monitor^® (QFM) assay measures interferon gamma (IFN-γ) release from whole blood following incubation with both innate (Toll-like receptor 7, TLR7) and adaptive (CD3 antibody) stimulants and may result in a more complete assessment of the immune system.

METHODS

Whole blood samples were prospectively collected from alloHCT recipients at conditioning followed by days 10, 30, 60, 90, 120, and 180 post-transplant and assayed by the QFM test. IFN-γ levels were correlated to time post HCT and episodes of infection and GVHD.

RESULTS

Forty patients were enrolled in the study (68% male; median age 47 years; 58% matched related donors, 42% unrelated; 33% myeloablative). Post-stimulation IFN-γ levels rose steadily over the first 180 days post transplantation. IFN-γ levels were significantly lower in those with active infection compared to those without during the neutropenic period (P < .001). The assay was predictive of CMV reactivation (VL > 1000 copies/mL) post alloHCT (P = .001).

CONCLUSION

This is a promising assay to demonstrate immune recovery and predict risk of infection after alloHCT and may allow tailoring of immunosuppression, antimicrobial treatment, and prophylaxis.

Predictive tools to determine risk of infection in kidney transplant recipients

Introduction: Infection represents a major complication after kidney transplantation (KT). Therapeutic drug monitoring is essentially the only approach for the adjustment of immunosuppression in current practice, with suboptimal results. The implementation of immune monitoring strategies may contribute to minimizing the risk of adverse events attributable to over-immunosuppression without compromising graft outcomes.Areas covered: The present review (based on PubMed/MEDLINE searches from database inception to November 2019) is focused on immune biomarkers with no antigen specificity (non-pathogen-specific), including serum levels of immunoglobulins and complement factors, peripheral blood lymphocyte subpopulations, soluble CD30, intracellular ATP production by stimulated CD4⁺ T-cells, and other cell-based immune assays. We also summarized recent advances in the use of replication kinetics of latent viruses to assess the functionality of T-cell immunity, with focus on the nonpathogenic anelloviruses. Finally, the composite risk scores reported in the literature are critically discussed.Expert opinion: Notable efforts have been made to develop an enlarging repertoire of immune biomarkers and prediction models, although most of them still lack technical standardization and external validation. Preventive interventions based on these tools (prolongation of prophylaxis, tapering of immunosuppression, or immunoglobulin replacement therapy in hypogammaglobulinemic patients) remain to be defined, ideally in the context of controlled trials.

Torque Teno Virus for Risk Stratification of Acute Biopsy-Proven Alloreactivity in Kidney Transplant Recipients

Background

Drug-induced immunosuppression in kidney transplant recipients is crucial to prevent allograft rejection, but increases risk for infectious disease. Immunologic monitoring to tailor immunosuppressive drugs might prevent alloreactivity and adverse effects simultaneously. The apathogenic torque teno virus (TTV) reflects the immunocompetence of its host and might act as a potential candidate for a holistic monitoring.

Methods

We screened all 1010 consecutive patients from the prospective Vienna Kidney Transplant Cohort Study for availability of allograft biopsies and adequately stored sera for TTV quantification by polymerase chain reaction.

Results

Patients with acute biopsy-proven alloreactivity according to the Banff classification (n = 33) showed lower levels of TTV in the peripheral blood compared to patients without rejection (n = 80) at a median of 43 days before the biopsy. The risk for alloreactivity decreased by 10% per log level of TTV copies/mL (risk ratio, .90 [95% confidence interval, .84–.97]; P = .005). TTV levels >1 × 10⁶ copies/mL exclude rejection with a sensitivity of 94%. Multivariable generalized linear modeling suggests an independent association between TTV level and alloreactivity.

Conclusions

TTV is a prospective biomarker for risk stratification of acute biopsy-proven alloreactivity in kidney transplant recipients and might be a potential tool to tailor immunosuppressive drug therapy.

Monitoring cell-mediated immunity during immunosuppression reduction in heart transplant recipients with severe systemic infections

BACKGROUND

Treatment for severe systemic infections in heart transplantation is reduction in immunosuppression while treating the infection. An assay that measures adenosine triphosphate production in activated lymphocytes (ImmuKnow^® ) objectively monitors cellular immunity of transplant recipients. In this study, we used ImmuKnow^® to adjust immunosuppression in heart transplant recipients with severe systemic infections.

METHODS

Heart transplant recipients were followed with ImmuKnow^® at the time of biopsy and diagnosis of systemic infection. Patients who developed an infection were monitored by ImmuKnow^® assay with adjustments in immunosuppression based upon the results of the assay. Maintenance immunosuppression was reinstituted when the ImmuKnow^® increased to >225 ng/mL of ATP.

RESULTS

Two or more ImmuKnow^® assays were performed in 80 patients. Thirteen patients developed severe systemic infections. ImmuKnow^® mean value at the time of diagnosis of infection was 109 ± 49.2 ng/mL. Reduction in immunosuppression and treatment of infection resulted in normalization of ImmuKnow^® level, resolution of infection, and no episodes of rebound rejection.

CONCLUSION

Heart transplant recipients with severe systemic infections presented with a decreased ImmuKnow^® , suggesting over immunosuppression. ImmuKnow^® can be used as an objective measurement in withdrawing immunosuppression in heart transplant recipients with severe systemic infections.

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.

Diagnostic and therapeutic approach to infectious diseases in solid organ transplant recipients

Purpose

Prognosis of solid organ transplant (SOT) recipients has improved, mainly because of better prevention of rejection by immunosuppressive therapies. However, SOT recipients are highly susceptible to conventional and opportunistic infections, which represent a major cause of morbidity, graft dysfunction and mortality.

Methods

Narrative review.

Results

We cover the current epidemiology and main aspects of infections in SOT recipients including risk factors such as postoperative risks and specific risks for different transplant recipients, key points on anti-infective prophylaxis as well as diagnostic and therapeutic approaches. We provide an up-to-date guide for management of the main syndromes that can be encountered in SOT recipients including acute respiratory failure, sepsis or septic shock, and central nervous system infections as well as bacterial infections with multidrug-resistant strains, invasive fungal diseases, viral infections and less common pathogens that may impact this patient population.

Conclusion

We provide state-of the art review of available knowledge of critically ill SOT patients with infections.

Application of a New Paradigm for Cytomegalovirus Disease Prevention in Mayo Clinic's First Face Transplant

The optimal approach to preventing cytomegalovirus (CMV) disease after face transplant is unknown. We report an individualized hybrid approach, initially using valganciclovir prophylaxis followed by surveillance and preemptive therapy guided by viral and immunologic markers. A 31-year-old man received a near-total face allotransplant for gunshot injury-related severe facial deformities. He was CMV seronegative, and the donor was CMV seropositive (D+/R- mismatch), and he received intravenous ganciclovir followed by oral valganciclovir prophylaxis. Monthly CD8⁺ T-cell immune competence assay revealed no CMV-specific CD8⁺ T-cell immunity development during valganciclovir prophylaxis. Because of severe leukopenia, valganciclovir was discontinued at 7 months after transplant when the patient had recovered and sustained normal global CD8⁺ T-cell function. Weekly CMV polymerase chain reaction testing detected asymptomatic CMV replication (plasma CMV, 549 IU/mL) 3 months later. Short-course preemptive valganciclovir treatment resulted in sustained virologic clearance. The patient had development of CMV-specific CD8⁺ T cells (12 cells/μL) together with CMV IgM and IgG. No rejection or infection relapse was detected 20 months after transplant. In conclusion, viral and immunologic monitoring allowed for an individualized approach to effective CMV disease prevention after face transplant. This case highlights the importance of understanding the interplay between the host immunity and the pathogen in determining the clinical course and outcome of CMV and other infectious disease syndromes.

Strategies for Antimicrobial Stewardship in Solid Organ Transplant Recipients

Complications of antimicrobial therapy, such as multidrug-resistant organisms and Clostridium difficile, commonly affect solid-organ transplant recipients and have been associated with graft loss and mortality. Although opportunities are abundant, antimicrobial stewardship practices guiding appropriate therapy have been infrequently reported in transplant patients. A patient-centered, multidisciplinary structure, using established antimicrobial optimization principles, is needed to create nuanced approaches to protect patients and antimicrobials and improve outcomes.

Can immune biomarkers predict infections in solid organ transplant recipients? A review of current evidence

Despite improvements in graft survival, solid organ transplantation is still associated with considerable infection induced morbidity and mortality. If we were able to show that serious infection risk was associated with excessive suppression of immune capacity, we would be justified in "personalizing" the extent of immunosuppression by carefully monitored reduction to see if we can improve immune compromize without increasing the risk of rejection. Reliable biomarkers are needed to identify this patients at an increased risk of infection. This review focuses on the currently available evidence in solid organ transplant recipients for immune non-pathogen specific biomarkers to predict severe infections with the susceptibility to particular pathogens according to the component of the immune system that is suppressed. This review is categorized into immune biomarkers representative of the humoral, cellular, phagocytic, natural killer cell and complement system. Biomarkers humoral and cellular systems of the that have demonstrated an association with infections include immunoglobulins, lymphocyte number, lymphocyte subsets, intracellular concentrations of adenosine triphosphate in stimulated CD4⁺ cells and soluble CD30. Biomarkers of the innate immune system that have demonstrated an association with infections include natural killer cell numbers, complement and mannose binding lectin. Emerging evidence shows that quantification of viral nucleic acid (such as Epstein Barr Virus) can act as a biomarker to predict all-cause infections. Studies that show the most promise are those in which several immune biomarkers are assessed in combination. Ongoing research is required to validate non-pathogen specific immune biomarkers in multi-centre studies using standardized study designs.

Highlights in solid transplant infectious diseases 2015-2017

Solid organ transplant recipients have an increased risk of developing infections due to the lifelong treatment with immunosuppressive drugs. Herein we review recent (2015-2017) and relevant published advances in the field of bacterial, viral and fungal-infections in this population. We also address the most up-to-date immunological assays that can predict the risk of infection. Finally, we review current guidelines and how they improve the usual clinical care.

Immunosuppression for Lung Transplantation: Current and Future

Purpose of the review

The number of lung transplantations performed worldwide continues to increase. There is a growing need in these patients for more effective immunosuppressive medications with less toxicity.

Recent findings

This review article summarizes the recent studies and developments in lung transplant immunosuppression. Novel immunosuppressive medications and strategies used in other solid organ transplantations are being trialed in lung transplantation. This includes the use of co-stimulation blockers like belatacept and mTOR inhibitors like everolimus. Calcineurin sparing regimens have been described in an attempt to minimize nephrotoxicity. Assays to measure the bioactivity of immunosuppressive medications to determine the global immune competence, such as Immuknow assay and Gamma interferon response are gaining traction.

Summary

Immunosuppression in lung transplant is evolving with the development of newer drugs and promising strategies to optimize immunosuppression. Further studies with multicenter randomized trials are required to increase the strength of the evidence.