Regulation of influenza A virus induced CXCL-10 gene expression requires PI3K/Akt pathway and IRF3 transcription factor.

Influenza A virus infects human airway epithelial cells, and induces the CXC chemokine gamma interferon (IFN-γ)-inducible protein CXCL-10/IP-10 production. To understand the regulation of CXCL-10, we investigated the role of PI3K/AKT pathway in regulating virus induced CXCL-10 production. Previously we have shown that wild type (WT) influenza A virus infection activates PI3K/AKT pathway, whereas PR8-SH3-mf-1 mutant virus is unable to activate this pathway. Here we report that WT influenza A virus infection induced CXCL-10 production in A549 cells. PR8-SH3-mf-1 mutant virus infection led to reduced level of CXCL-10 mRNA transcription and protein expression. To define the transcriptional regulation factors that are important in this process, we performed studies using several mutant CXCL-10 promoter-luciferase constructs. Mutation of either of four Forkhead binding sites and two NF-κB response elements in CXCL-10 promoter did not alter promoter activity induced by WT virus. However, mutation of ISRE binding site markedly reduced luciferase activity. Our data suggested that PI3K/AKT pathway contributes to influenza A virus induced CXCL-10 production. This process is involved in binding of IRF3 to the ISRE binding site in CXCL-10 promoter region.