Abstract
Porcine reproductive and respiratory syndrome (PRRS) caused by PRRS virus (PRRSV) has been recognized as one of the severest epidemics in pigs worldwide. microRNAs (miRNAs) play important roles in a variety of biological processes, including cell differentiation, proliferation and death, as well as viral infections and antiviral immune responses. In this study, we found that miR-142-3p was expressed lower in cells susceptible to PRRSV infection than in cells less or no permissive to PRRSV infection. Subsequently, we showed that overexpression of miR-142-3p remarkably inhibited PRRSV infection in PAMs, while blockage of endogenous miR-142-3p significantly enhanced PRRSV replication. Then, we demonstrated that miR-142-3p directly targeted Ras-related C3 botulinum toxin substrate 1 (Rac1), a member of Rho GTPases family, by using luciferase reporter assay and UV cross-linking and immunoprecipitation (CLIP) assay. Importantly, we verified that miR-142-3p inhibited PRRSV entry into PAMs and accordingly suppressed PRRSV infection by downregulating Rac1 expression. These findings reveal an important role of miR-142-3p in modulating PRRSV infection and provide us with some ideas for developing novel antiviral therapy against PRRSV infection.