Infectious Bronchitis Virus Activates the Aryl Hydrocarbon Receptor During In Vitro Infection.

Coronaviruses, including avian infectious bronchitis virus (IBV), utilize host cellular pathways to evade the host immune response. The aryl hydrocarbon receptor (AhR), a key antiviral regulator exploited by mammalian coronaviruses like SARS-CoV-2, remains unclear in avian coronavirus pathogenesis. This study examined AhR's involvement during IBV infection using H1299 and Vero cells with pharmacological modulation (AhR antagonist CH223191/agonist kynurenine) and shRNA-mediated silencing. Viral replication was quantified through plaque assays, qRT-PCR, and Western blot. The results reveal IBV-induced AhR activation, driving downstream CYP1A1 expression and pro-inflammatory cytokine production. CH223191 treatment reduced IBV titers, RNA loads, and N protein expression dose-dependently, while kynurenine showed no effect. AhR knockdown similarly reduced N protein expression, confirming its proviral role. An IBV-encoded noncoding RNA was identified as a modulator of AhR activation, suggesting viral balancing of immune evasion and replication efficiency. These results establish AhR as a conserved host factor co-opted by IBV, and highlight AhR antagonism as a promising therapeutic strategy. By bridging insights from avian and mammalian coronaviruses, this work informs strategies to address IBV's genetic variability and supports development of broad-spectrum antiviral therapies.