Chicken miR-148a-3p regulates immune responses against AIV by targeting the MAPK signalling pathway and IFN-γ

MicroRNAs are involved in the immune systems of host animals and play essential roles in several immune-related pathways. In the current study, we investigated the systemic biological function of the chicken miRNA gga-miR-148a-3p on immune responses in chicken lines resistant and susceptible to HPAIV-H5N1. We found that gga-miR-148a expression in the lung tissue of H5N1-resistant chickens was significantly downregulated during HPAIV-H5N1 infection. Overexpression of gga-miR-148a and a reporter construct with wild type or mutant IFN-gamma, MAPK11, and TGF-beta 2 3 ' untranslated region (3 ' UTR)-luciferase in chicken fibroblasts showed that gga-miR-148a acted as a direct translational repressor of IFN-gamma, MAPK11, and TGF-beta 2 by targeting their 3 ' UTRs. Furthermore, miR-148a directly and negatively influenced the expression of signalling molecules related to the MAPK signalling pathway, including MAPK11, TGF-beta 2, and Jun, and regulated antiviral responses through interferon-stimulated genes and MHC class I and class II genes by targeting IFN-gamma. Downstream of the MAPK signalling pathway, several proinflammatory cytokines such as IL-1 beta, IFN-gamma, IL-6, TNF-alpha, IFN-beta, and interferon-stimulated genes were downregulated by the overexpression of gga-miR-148a. Our data suggest that gga-miR-148a-3p is an important regulator of the MAPK signalling pathway and antiviral response. These findings improve our understanding of the biological functions of gga-miR-148a-3p, the mechanisms underlying the MAPK signalling pathway, and the antiviral response to HPAIV-H5N1 infection in chickens as well as the role of gga-miR-148a-3p in improving the overall performance of chicken immune responses for breeding disease-resistant chickens.