Abstract
In this study, we investigated the localized pathogenesis of infectious bronchitis virus (IBV) in chicken tracheal organ cultures (TOCs), focusing on the role of inducible cyclooxygenase (COX-2). Two divergent IBV strains, respiratory Connecticut (Conn) A5968 and nephropathogenic Delmarva (DMV)/1639, were studied at 6, 12, 24, and 48 hours post-infection (hpi). Various treatments including exogenous prostaglandin (PGE)2, a selective COX-2 antagonist (SC-236), and inhibitors of PGE2 receptors and Janus kinase (JAK) were administered. IBV genome load and antigen expression were quantified using real-time quantitative PCR and immunohistochemistry. COX-2, interferon (IFN)-α, IFN-β, interleukin (IL)-1β, IL-6, and inducible nitric oxide synthase (iNOS) expressions were measured, along with PGE2 and COX-2 concentrations. IBV genome load and protein expression peaked at 12 and 24 hpi, respectively. Conn A5968-infected TOCs exhibited continuous COX-2 expression for up to 24 hpi, extended PGE2 production up to 48 hpi, and reduced inflammatory cytokine expression. In contrast, DMV/1639-infected TOCs displayed heightened inflammatory cytokine expression, brief COX-2 expression, and PGE2 production. Treatment with IFN-γ, SC-236, PGE2 receptor inhibitors, or JAK inhibitors reduced IBV infection and lesion scores, whereas exogenous PGE2 or IFN-γ pretreatment with a JAK-2 inhibitor augmented infection. These findings shed light on the innate immune regulation of IBV infection in the trachea, highlighting the involvement of the COX-2/PGE2 pathway. Importance: Understanding the localized pathogenesis of infectious bronchitis virus (IBV) within the trachea of chickens is crucial for developing effective control strategies against this prevalent poultry pathogen. This study sheds light on the role of inducible cyclooxygenase (COX-2) and prostaglandin (PGE)2 in IBV pathogenesis using chicken tracheal organ culture (TOC) models. The findings reveal distinct patterns of COX-2 expression, PGE2 production, and immune responses associated with different IBV strains, highlighting the complexity of host-virus interactions. Furthermore, the identification of specific inhibitors targeting the COX-2/PGE2 pathway and Janus kinase-signal transducer and activator of transcription (JAK-STAT) signaling pathway provides potential therapeutic avenues for mitigating IBV infection in poultry. Overall, this study contributes to our understanding of the innate immune regulation of IBV infection within the trachea, laying the groundwork for the development of targeted interventions to control IBV outbreaks in poultry populations.