IBV QX affects the antigen presentation function of BMDCs through nonstructural protein16.

The gamma-coronavirus infectious bronchitis virus (IBV) has a high mutation rate and mainly invades the respiratory mucosa, making it difficult to prevent and causing great economic losses. Nonstructural protein 16 (NSP16) of IBV QX also not only plays an indispensable role in virus invading but also might hugely influence the antigen's recognition and presentation ability of host BMDCs. Hence, our study tries to illustrate the underline mechanism of how NSP16 influences the immune function of BMDCs. Initially, we found that NSP16 of the QX strain significantly inhibited the antigen presentation ability and immune response of mouse BMDCs, which was stimulated by Poly (I:C) or AIV RNA. Besides mouse BMDCs, we also found that NSP16 of the QX strain also significantly stimulated the chicken BMDCs to activate the interferon signaling pathway. Furthermore, we preliminarily demonstrated that IBV QX NSP16 inhibits the antiviral system by affecting the antigen-presenting function of BMDCs.

Gene Set Enrichment Analysis Reveals That Fucoidan Induces Type I IFN Pathways in BMDC.

Fucoidan, a sulfated polysaccharide extracted from brown seaweed, has been proposed to effectively treat and prevent various viral infections. However, the mechanisms behind its antiviral activity are not completely understood. We investigate here the global transcriptional changes in bone marrow-derived dendritic cells (BMDCs) using RNA-Seq technology. Through both analysis of differentially expressed genes (DEG) and gene set enrichment analysis (GSEA), we found that fucoidan-treated BMDCs were enriched in virus-specific response pathways, including that of SARS-CoV-2, as well as pathways associated with nucleic acid-sensing receptors (RLR, TLR, NLR, STING), and type I interferon (IFN) production. We show that these transcriptome changes are driven by well-known regulators of the inflammatory response against viruses, including IRF, NF-κB, and STAT family transcription factors. Furthermore, 435 of the 950 upregulated DEGs are classified as type I IFN-stimulated genes (ISGs). Flow cytometric analysis additionally showed that fucoidan increased MHCII, CD80, and CD40 surface markers in BMDCs, indicative of greater antigen presentation and co-stimulation functionality. Our current study suggests that fucoidan transcriptionally activates PRR signaling, type I IFN production and signaling, ISGs production, and DC maturation, highlighting a potential mechanism of fucoidan-induced antiviral activity.