Objective: The innate immune response to viral infection is crucial in the host control of infection through production of the interferons (IFN) and expression of interferon stimulated genes (ISGs). The expression of the IFNs and ISGs are orchestrated through complex cellular viral recognition and signalling cascades. While these cascades are well characterised, there is a lack of understanding the interaction with other cellular pathways. In this study we investigate activation of the xenobiotic activated transcription factor, Aryl Hydrocarbon Receptor (AhR), following flavivirus and coronavirus infections and subsequent differential regulation of cellular innate antiviral responses.
Methods: To investigate the role of AhR following virus infection we infected various cell types with the flaviviruses ZIKV, WNVKUN and DENV and human coronavirus 229E and assessed AhR activation by qRT-PCR of specific AhR target gene expression. Innate responses were monitored by qRT-PCR of key innate response genes (IFNb, IFITM1, IFI6, IRF1) and Illumina RNASeq analysis of AhR CRISPR knockout cell lines, and the effect of AhR KO on viral replication was assessed by qRT-PCR and plaque assay.
Results: We have demonstrated that RNA virus infection can trigger AhR activation (CYP1A1, TIPARP) and increase AhR mRNA expression in a multitude of cell types. Interestingly, PolyI:C stimulation of cells also activates AhR, while CRISPR mediated AhR KO results in a decrease in virus replication in comparison to AhR positive cells. Importantly, in AhR KO cells there was a significant increase in ISG and immune signalling gene expression in response to Poly I:C stimulation as determined by RNASeq analysis.
Conclusions: Our study demonstrates that expression of the transcription factor AhR can be enhanced and activated by flavivirus infection possibly via cytosolic RNA receptors. Furthermore, KO of AhR and resulting decreases in viral replication suggest that AhR is an important regulator of innate antiviral responses.