Interferon Regulatory Factors: IRF1 and IRF7 directly regulate gene expression in bats in response to viral infection.

Bat cells and tissue have elevated basal expression levels of antiviral genes commonly associated with IFNα signalling. Here we show IRF1,3 and 7 levels are elevated in most bat tissues and that basally, IRFs contribute to the expression of type I IFN ligands and high expression of Interferon Regulated Genes (IRGs). CRISPR KO of IRF 1/3/7 in cells reveal distinct subsets of genes affected by each IRF in an IFN-ligand signalling dependent and largely independent manner. As the master regulators of innate immunity, the IRFs, control the kinetics and maintenance of the IRG response and play essential roles in response to IAV, HSV1, PRV3M and MERS-CoV infection. With its differential expression compared to human, this highlights a critical role for basal IRF expression in viral responses and potentially immune cell development in bats with relevance for IRF function in human biology.