Porcine Reproductive and Respiratory Syndrome (PRRS) causes significant economic losses in the swine industry. Circular RNAs (circRNAs), a class of stable non-coding RNAs, are increasingly recognized as regulators in immune responses and host–virus interactions. This study investigated the genome-wide circRNA responses in porcine alveolar macrophages (PAMs), key cell targets of PRRSV, following treatment with a modified live virus (MLV) vaccine or two interferon (IFN) subtypes (IFN-α1, IFN-ω5). Using RNA sequencing, we identified over 1000 differentially expressed circRNAs across treatment groups, revealing both conserved and distinct expression profiles. Gene Ontology and KEGG pathway analyses indicated that circRNA-associated genes are significantly enriched in immune-related processes and pathways, including cytokine signaling and antiviral defense. Notably, IFN-ω5 treatment induced a pronounced circRNA response, aligning with its potent antiviral activity. We further explored the regulatory potential of these circRNAs by predicting miRNA binding sites, revealing complex circRNA-miRNA interaction networks. Additionally, we assessed the coding potential of differentially expressed circRNAs by identifying open reading frames (ORFs), internal ribosome entry sites (IRESs), and N6-methyladenosine (m⁶A) modification sites, suggesting a subset may undergo non-canonical translation. These findings provide a comprehensive landscape of circRNA expression in PAMs under different antiviral conditions, highlighting their potential roles as immune regulators and novel players in interferon-mediated antiviral responses, particularly downstream of IFN-ω5. This work contributes to understanding the non-coding RNA landscape in the PRRSV-swine model and suggests circRNAs as potential targets for future antiviral strategies.

Porcine reproductive and respiratory syndrome virus (PRRSV) is a major threat to the global swine industry. Long non-coding RNAs (lncRNAs) are emerging as crucial regulators of antiviral immunity, but their roles in porcine alveolar macrophages (PAMs)—the primary target of PRRSV—remain poorly characterized. This study presents a genome-wide analysis of lncRNA expression in PAMs stimulated with a PRRS modified live virus (MLV) vaccine and two type I interferons, IFN-α1 and IFN-ω5. Whole-transcriptome sequencing identified over 2000 differentially expressed lncRNAs, with IFN-ω5 inducing the most extensive transcriptional reprogramming. Weighted gene co-expression network analysis (WGCNA) revealed interferon-specific lncRNA-mRNA modules, and functional enrichment showed these lncRNAs are involved in key immune and metabolic pathways, including chemokine signaling, MAPK, and mTOR. Our findings establish a comprehensive landscape of lncRNA regulation in PAMs, highlighting their role in fine-tuning the antiviral responses and suggesting novel targets for interferon-based antiviral interventions against PRRSV.