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

Background: microglial 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.methods: in 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.results: overexpression 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.conclusion: induction 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. © 2014 pareek et al.; licensee biomed central ltd.