Progressive multifocal leukoencephalopathy (PML) is a demyelinating disease induced by reactivation of Polyomavirus JC (JCPyV). Modulation of normal immune functions, as during longterm administration of disease-modifying therapies (DMTs) for Multiple Sclerosis (MS) treatment, plays a central role in JCPyV reactivation and PML development. The variability of JCPyV seroprevalence coupled with the intermittent nature of JCPyV infection, raises questions regarding the predictive value of assays currently used to assess PML risk. A risk stratification algorithm, applicable only for natalizumab (NZT) administration, has not led to a PML incidence reduction. Actually, other candidates such as L-selectin (CD62L) expression, T-cell response to JCPyV reactivation and JCPyV-DNA detection in blood (viremia) have been proposed. Recent studies signify the potential of JCPyV microRNAs (miRNAs) as biomarkers of JCPyV infection as they can be detected in plasma, urine and cerebrospinal fluid (CSF) of both JCPyV seropositive and seronegative healthy individuals and immunosuppressed patients. JCPyV encodes for two mature miRNAs, jcv-miR-J1-5p (5p-miRNA) and jcv-miR-J1-3p (3p-miRNA), that appear late in infection to downregulate early viral gene expression and target host factors aiding virus to escape immune elimination. The biomarker potential of miRNAs in blood has been studied for NTZ-associated PML, but studies in course of other DMTs are still lacking. In this project, we will characterize JCPyV miRNAs expression in plasma and urine of NTZ-treated MS patients as well as in patients treated with fingolimod (F), dimethyl fumarate (DF), ocrelizumab (OCRE), and in healthy controls (HCs) to evaluate the utility of these miRNAs in PML risk assessment. Moreover, a COS-7 cell-based model will be used to study and monitor miR-J1-5p expression during viral replication.
PML is a devastating and often fatal demyelinating disease of the CNS for which effective therapies are lacking. It is caused by the replication of JCPyV in the oligodendrocytes and astrocytes leading to their cytolytic death and loss of myelin from the subcortical white matter. While the virus is very common in human populations worldwide, the incidence of the disease is very low and confined almost exclusively to individuals with some form of immunological dysfunction. However, the number of people who constitute the at-risk population is growing larger and includes patients receiving DMTs such as MS patients treated with NTZ, F, DF and OCRE. Further adding to the public health significance of this disease are the difficulties encountered in the diagnosis of PML and the lack of useful biomarkers for PML progression. In the last two decades, several studies have been carried out in order to identify markers, which could improve safety and efficacy of NTZ therapy. JCPyV miRNAs has been proposed as a biomarker of JCPyV infection as it can be frequently detected in plasma, urine, and CSF of both JCPyV seropositive and seronegative healthy individuals and immunosuppressed patients [17,18] acting as a more sensitive biomarker of JCPyV infection than serology.
To date, for the best of our knowledge, JCPyV miRNAs expression was evaluated only in plasma of NTZ-treated MS patients. In the present project, we will evaluate the reliability and the utility of miRNAs as biomarkers in plasma and urine of patients treated not only with NTZ but also with F, DF and OCRE. JCPyV miRNAs circulating in biological fluid (urine and plasma) as a potential exhaustive marker of infection status are warranted to shed new light on their role in polyomavirus¿associated disease and to develop new antiviral strategies.
Moreover, using the in vitro COS-7 cells based-model, the expression of miR-J1-5p will be study and monitor during viral replication. Monitoring of miR-J1-5p may elucidate the mechanisms of virus reactivation and may help the clarification of the mechanisms responsible for severe side effects such as PML.