Lentivirus-mediated Bos taurus bta-miR-29b overexpression interferes with bovine viral diarrhoea virus replication and viral infection-related autophagy by directly targeting ATG14 and ATG9A in Madin-Darby bovine kidney cells.

MicroRNAs (miRNAs) are a class of short endogenous RNA molecules with the ability to control development, autophagy, apoptosis and the stress response in eukaryotes by pairing with partially complementary sites in the 3' UTRs of targeted genes. Recent studies have demonstrated that miRNAs serve as critical effectors in intricate networks of host-pathogen interactions. Notably, we found that Bos taurus bta-miR-29b (referred to as miR-29b herein) was significantly upregulated >2.3-fold in bovine viral diarrhoea virus (BVDV) strain NADL-infected Madin-Darby bovine kidney (MDBK) cells 6 h post-infection compared with normal MDBK cells. However, the roles of miR-29b in BVDV infection and pathogenesis remain unclear. Here, we report the inhibitory effects of miR-29b on BVDV NADL replication and viral infection-related autophagy. miR-29b overexpression mediated by miRNA precursor-expressing lentivirus resulted in the attenuation of BVDV NADL infection-related autophagy by directly downregulating the intracellular expression levels of two key autophagy-associated proteins, ATG14 and ATG9A. Moreover, ATG14 and ATG9A overexpression rescue not only reversed miR-29b-inhibited autophagy, but also increased BVDV NADL replication. In previous studies, we found that the early stages of autophagy contributed to BVDV NADL replication in MDBK cells and that the inhibition of autophagy repressed BVDV NADL replication, which was also proved in the present study. Collectively, our results establish a novel link between miR-29b and viral replication, and also provide a new pathway for the intimate interaction between host cells and pathogens.