Usefulness of BK virus-specific interferon-γ enzyme-linked immunospot assay for predicting the outcome of BK virus infection in kidney transplant recipients

The value and complexity of studying cellular immunity against BK Polyomavirus in kidney transplant recipients

BK Polyomavirus is of particular concern for kidney transplant recipients, due to their immunosuppression. This problem is exacerbated by the high effectiveness of antirejection therapies, which also compromise the organism's ability to fight viral infections. The long-term risk is loss of graft function through BKPyV-associated nephropathy (BKPyVAN). The assessment of host immunity and its link to the control of viral infections is a major challenge. In terms of humoral immunity, researchers have highlighted the prognostic value of the pre-transplantation anti-BKPyV immunoglobulin G titer. However, humoral immunity alone does not guarantee viral clearance, and the correlation between the humoral response and the time course of the infection remains weak. In contrast, cellular immunity variables appear to be more closely associated with viral clearance, given that the cellular immune response to the kidney transplant is the main target of immunosuppressive treatments in recipients. However, the assessment of the cellular immune response to BK Polyomavirus is complex, and many details still need to be characterized. Here, we review the current state of knowledge about BKPyV cellular immunity, as well as the difficulties that may be encountered in studying it in kidney transplant recipient. This is an essential area of research for optimizing the management of transplant recipients and minimizing the risks associated with insidious BKPyV disease.

Pretransplant BKV-IgG serostatus and BKV-specific ELISPOT assays to predict BKV infection after kidney transplantation

Introduction

Polyomavirus (BKV) infection can lead to major complications and damage to the graft in kidney transplant recipients (KTRs). We investigated whether pretransplant BK serostatus and BK-specific cell-mediated immunity (CMI) predicts post-transplant BK infection.

Methods

A total of 93 donor-recipient pairs who underwent kidney transplantation (KT) and 44 healthy controls were examined. Assessment of donor and recipient BKV serostatus and BKV-CMI in recipients was performed prior to transplantation using BKV-IgG ELISA and BKV-specific IFN-g ELISPOT assays against five BK viral antigens (LT, St, VP1, VP2, and VP3). BK viremia was diagnosed when blood BKV-DNA of 104 copies/mL or more was detected during follow-up periods.

Results

Anti-BKV IgG antibody was detected in 74 (79.6%) of 93 KTRs and in 68 (73.1%) of 93 KT donors. A greater percentage of KTRs who received allograft from donors with high levels of anti-BKV IgG had posttransplant BK viremia (+) than KTRs from donors with low anti-BKV IgG (25.5% [12/47] vs. 4.3% [2/46], respectively; P = 0.007). Pretransplant total BKV-ELISPOT results were lower in BK viremia (+) patients than in patients without viremia (-) 20.5 [range 9.9-63.6] vs. 72.0 [43.2 - 110.8]; P = 0. 027). The sensitivity and specificity of the total BKV-ELISPOT assay (cut-off ≤ 53 spots/3×105 cells) for prediction of posttransplant BK viremia were 71.4 (95% CI: 41.9-91.6) and 54.4 (42.8-65.7), respectively. The combination of high donor BKV-IgG, low recipient BKV-IgG, and low total BKV-ELISPOT results improved specificity to 91.1%.

Discussion

Our study highlights the importance of pretransplant BKV-IgG serostatus and BKV-specific CMI in predicting posttransplant BKV infection in KTRs. The combination of high donor BKV-IgG, low recipient BKV-IgG, and low total BKV-ELISPOT results predicted BK viremia after KT. Pretransplant identification of patients at highrisk for BK viremia could enable timely interventions and improve clinical outcomes of KTRs.

Omics-based biomarkers for diagnosis and prediction of kidney allograft rejection

Kidney transplantation is the preferred treatment for patients with end-stage kidney disease, because it prolongs survival and improves quality of life. Allograft biopsy is the gold standard for diagnosing allograft rejection. However, it is invasive and reactive, and continuous monitoring is unrealistic. Various biomarkers for diagnosing allograft rejection have been developed over the last two decades based on omics technologies to overcome these limitations. Omics technologies are based on a holistic view of the molecules that constitute an individual. They include genomics, transcriptomics, proteomics, and metabolomics. The omics approach has dramatically accelerated biomarker discovery and enhanced our understanding of multifactorial biological processes in the field of transplantation. However, clinical application of omics-based biomarkers is limited by several issues. First, no large-scale prospective randomized controlled trial has been conducted to compare omics-based biomarkers with traditional biomarkers for rejection. Second, given the variety and complexity of injuries that a kidney allograft may experience, it is likely that no single omics approach will suffice to predict rejection or outcome. Therefore, integrated methods using multiomics technologies are needed. Herein, we introduce omics technologies and review the latest literature on omics biomarkers predictive of allograft rejection in kidney transplant recipients.

Getting immunosuppression just right: the role of clinical biomarkers in predicting patient response post solid organ transplantation

INTRODUCTION

Actually, immunosuppression selection isn't based on individual immune alloreactivity, and immunosuppressive drug dosing is mainly based on the development of toxicity and the achievement of specific target concentrations. Since a successful outcome requires optimal patient risk stratification and treatment, several groups have evaluated candidate biomarkers that have shown promise in the assessment of individual immune responses, the prediction of personal pharmacodynamic effects of immunosuppressive drugs and the prognosis and diagnosis of graft outcomes..

AREAS COVERED

This review includes biomarkers that the Scientific Community in Solid Organ Transplantation currently considers to have potential as diagnostic and prognostic biomarkers of graft evolution. We have focused on recent scientific advances and expert recommendations regarding the role of specific and non-specific pharmacodynamic biomarkers that are mainly involved in the T-cell-mediated response.

EXPERT OPINION

Integral pharmacologic monitoring that combines pharmacokinetics, pharmacogenetics and predictive pharmacodynamic biomarkers may provide crucial information and allow personal adjustment of immunosuppressive drugs at an early stage before severe adverse events ensue. Multicentre, randomized, prospective and interventional trials are needed to fine tune the established cut-off values for each biomarker and the optimal monitoring frequency for each biomarker and to accurately evaluate possible clinical confounding factors to enable correct clinical qualification.

Indoleamine 2,3-Dioxygenase Is Involved in Interferon Gamma's Anti-BKPyV Activity in Renal Cells

Reactivation of BK polyomavirus (BKPyV) infection is frequently increasing in transplant recipients treated with potent immunosuppressants and highlights the importance of immune system components in controlling viral reactivation. However, the immune response to BKPyV in general and the role of antiviral cytokines in infection control in particular are poorly understood. Here, we investigated the efficacy of interferons (IFN) alpha, lambda and gamma with regard to the BKPyV multiplication in Vero cells. Treatment with IFN-gamma inhibited the expression of the viral protein VP1 in a dose-dependent manner and decreased the expression of early and late viral transcripts. Viral inhibition by IFN-gamma was confirmed in human cells (Caki-1 cells and renal proximal tubular epithelial cells). One of the IFN-stimulated genes most strongly induced by IFN-gamma was the coding for the enzyme indoleamine 2,3 dioxygenase (IDO), which is known to limit viral replication and regulates the host immune system. The antiviral activity induced by IFN-gamma could be reversed by the addition of an IDO inhibitor, indicating that IDO has a specific role in anti-BKPyV activity. A better understanding of the action mechanism of these IFN-gamma-induced antiviral proteins might facilitate the development of novel therapeutic strategies.