MiR-155 induction in microglial cells suppresses Japanese encephalitis virus replication and negatively modulates innate immune responses.

Siddhika Pareek,Sudhanshu Vrati,Bharti Kumari,Saugata Roy,Pratistha Jain,Arup Banerjee

doi:10.1186/1742-2094-11-97

Siddhika Pareek, Sudhanshu Vrati + Show 4 more

Open Access

https://doi.org/10.1186/1742-2094-11-97

Copy DOI

Abstract

BackgroundMicroglial cells, which are resident macrophages of the central nervous system, play important roles in immune responses and pathogenesis. Japanese encephalitis virus (JEV) is a neurotropic virus that infects microglial cells in brain. Several microRNAs including miR-155 and miR-146a play an important role in defining the microglia inflammatory profile. In this study, we have investigated the effect of miR-155 and miR-146a modulation on JEV infection as well as innate immune responses in human microglial cells.MethodsIn vitro studies were performed in JEV-infected human microglial CHME3 cells. miR-155 or miR-146a were overexpressed and total RNA and protein were extracted following JEV-infection. Expression of genes involved in innate immune responses was studied by PCR array, quantitative real-time PCR (qPCR), western blot and Fluorescence activated cell sorter (FACS). JEV replication was monitored by studying the viral RNA by qPCR, protein by western blot, and titres by plaque assay.ResultsOverexpression of miR-155 in CHME3 cells resulted in significantly reduced JEV replication whereas miR-146a overexpression had an insignificant effect. Additionally, interferon regulatory factor 8 (IRF8) and complement factor H (CFH) were induced during JEV infection; however, this induction was attenuated in miR-155 overexpressing cells following JEV infection. Further, JEV-induced NF-κB regulated downstream gene expression was attenuated. Interestingly, an increased level of CD45, a negative regulator of microglia activation and a reduced phosphorylated-Signal Transducers and Activators of Transcription (p-STAT1) expression was observed in miR-155 overexpressing cells upon JEV infection.ConclusionInduction of miR-155 in human microglial cells may negatively modulate JEV-induced innate immune gene expression and may have a beneficial role in limiting JEV replication in human microglial cells.

Highlights

Microglial cells, which are resident macrophages of the central nervous system, play important roles in immune responses and pathogenesis
Japanese encephalitis (JE) is an acute central nervous system (CNS) inflammatory disease caused by infection with Japanese encephalitis virus (JEV); a small, enveloped, plus-strand RNA virus belonging to the Flaviviridae family
JEV infection modulates expression of NeurimmiRs in microglial cells In order to understand how JEV infection modulates immune pathogenesis-related miRNAs, we carried out a global human miRNA array study to identify differentially expressed miRNAs in human microglial CHME3 cells in response to JEV infection

Summary

Introduction

Microglial cells, which are resident macrophages of the central nervous system, play important roles in immune responses and pathogenesis. Japanese encephalitis (JE) is an acute central nervous system (CNS) inflammatory disease caused by infection with Japanese encephalitis virus (JEV); a small, enveloped, plus-strand RNA virus belonging to the Flaviviridae family. A new class of regulatory RNAs, called microRNAs (miRNAs) have emerged that modulate immune response and play key regulatory roles in virushost interactions These miRNAs serve as universal regulators of differentiation, activation, and polarization of mammalian cells including microglia and macrophages in normal and diseased CNS [6]. MiR155 and miR-146a modulate Toll-like receptors (TLRs)-mediated innate immune response, and target complement regulatory proteins and facilitate complement activation [17,18,19] This phenomenon is very important to eliminate the virus from infected cells. Wu et al [20] reported an increased dengue virus 2 (DENV2) replication in miR-146a overexpressing cells, whereas overexpression of miR-155 significantly suppressed human immunodeficiency virus (HIV) infection in activated macrophages [21]

Methods

Results

Conclusion