miR-146a facilitates replication of dengue virus by dampening interferon induction by targeting TRAF6

Objectives: To investigate the role of miR-146a in dengue virus (DENV) replication. Methods: Expression levels of miR-146a were measured by real-time PCR and Northern blot. Role of miR-146a was tested by overexpression and inhibition assays. Real-time PCR and 50% tissue culture infective dose (TCID50) assays were used to detect RNA levels and extracellular yields of DENV respectively. Interferon (IFN) levels induced by DENV infection were measured by real-time PCR and ELISA respectively. IFN-beta neutralization and RNAi were used to test the involvement of IFN-beta in the effects of miR-146a. TNFR-associated factor 6 (TRAF6) level was measured by Western-blot. Results: miR-146a expression was significantly increased in primary human monocytes and THP-1 cells upon DENV infection. Overexpression of miR-146a increased DENV2 replication, while inhibition of miR-146a decreased the viral replication. miR-146a impaired the IFN production and the DENV2 replication suppressed by miR-146a inhibition was partially restored by neutralization of IFN-beta or depletion of interferon receptor (IFNAR) 1 or 2. Furthermore, miR-146a targets TRAF6 and overexpression of TRAF6 reversed the effects of miR-146a on IFN-beta induction and viral replication. Conclusions: DENV infection significantly induced the expression of miR-146a, which facilitated viral replication by targeting TRAF6 and dampening IFN-beta production. (C) 2013 The British Infection Association. Published by Elsevier Ltd. All rights reserved.