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-β neutralization and RNAi were used to test the involvement of IFN-β 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-β 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-β induction and viral replication.

Conclusions: DENV infection significantly induced the expression of miR-146a, which facilitated viral replication by targeting TRAF6 and dampening IFN-β production.