Induction of IFN-β through TLR-3- and RIG-I-Mediated Signaling Pathways in Canine Respiratory Epithelial Cells Infected with H3N2 Canine Influenza Virus

• Published in: Journal of microbiology and biotechnology Vol. 31; no. 7; pp. 942 - 948
• Main Authors: Park, Woo-Jung, Han, Sang-Hoon, Kim, Dong-Hwi, Song, Young-Jo, Lee, Joong-Bok, Park, Seung-Yong, Song, Chang-Seon, Lee, Sang-Won, Choi, In-Soo
• Format: Journal Article
• Language: Korean
• Published: 한국미생물생명공학회 31.07.2021
• Subjects: Canine influenza virus; IFN-β; MX1; RIG-I; TLR3; RIG-I; IFN- ${\beta}; TLR3; Canine influenza virus; MX1
• ISSN: 1017-7825; 1738-8872

Canine influenza virus (CIV) induces acute respiratory disease in dogs. In this study, we aimed to determine the signaling pathways leading to the induction of IFN-β in a canine respiratory epithelial cell line (KU-CBE) infected with the H3N2 subtype of CIV. Small interfering RNAs (siRNAs) specific to pattern recognition receptors (PRRs) and transcription factors were used to block the IFN-β induction signals in H3N2 CIV-infected KU-CBE cells. Among the PRRs, only the TLR3 and RIG-I expression levels significantly (p < 0.001) increased in CIV-infected cells. Following transfection with siRNA specific to TLR3 (siTLR3) or RIG-I (siRIG-I), the mRNA expression levels of IFN-β significantly (p < 0.001) decreased, and the protein expression of IFN-β also decreased in infected cells. In addition, co-transfection with both siTLR3 and siRIG-I significantly reduced IRF3 (p < 0.001) and IFN-β (p < 0.001) mRNA levels. Moreover, the protein concentration of IFN-β was significantly (p < 0.01) lower in cells co-transfected with both siTLR3 and siRIG-I than in cells transfected with either siTLR3 or siRIG-I alone. Also, the antiviral protein MX1 was only expressed in KU-CBE cells infected with CIV or treated with IFN-β or IFN-α. Thus, we speculate that IFN-β further induces MX1 expression, which might suppress CIV replication. Taken together, these data indicate that TLR3 and RIG-I synergistically induce IFN-β expression via the activation of IRF3, and the produced IFN-β further induces the production of MX1, which would suppress CIV replication in CIV-infected cells.