Chemokines induced by PEDV infection and chemotactic effects on monocyte, T and B cells

Porcine epidemic diarrhea virus (PEDV) is a re-emerging pathogen that causes severe economic loss in the pig industry. The host's innate immune system is the first line of defense on virus invasion of the small intestinal epithelial cells. Chemokines, as a part of the innate immune system, play an important role in host immunity against infection, however, and their expression and chemotactic effect on key immune cells in PEDV infection remains unclear. In this study, cDNA microarray was firstly performed to analyzed ileum tissue of piglets on the third day after PEDV infection. The differentially expressed genes mainly involved in multiple biological processes, chemokine signaling pathway and cytokine receptor interaction signaling pathway had the highest enrichment according to GO and KEGG enrichment analysis. The expression levels of chemokines MCP-1, MIP-1β, IL-8, CXCL9, CXCL10 and CXCL13 in ileum of PEDV- infected piglets were significantly higher than those in the control group. The expression of chemokines in vivo experiment was further verified by RT-qPCR and ELISA using PEDV-infected IPEC-J2 cells. The results showed that the PEDV-infected IPEC-J2 cells had significantly induced protein expression of MCP-1, MIP-1β, IL-8, CXCL9, CXCL-10 and CXCL13. These results indicated that the changes of chemokines expressed in the ileum of piglets (in vivo) were consistent with those in IPEC-J2 cells (in vitro) after PEDV infection. Finally, the role of chemokines in immune cell migration during PEDV infection was illustrated by siRNA-mediated knock down method and the co-culture model of IPEC-J2 cells with peripheral blood leukocyte cells (PBLCs). The FACS analysis showed that MCP-1 induced by PEDV infection played a chemotactic effect on CD14⁺ cells, CXCL9 on CD3⁺CD4^-CD8^-γδ T, CD3⁺CD4^-CD8⁺ Tc, CD3⁺CD4⁺CD8^- Th and CD3⁺CD4⁺CD8⁺ Tm subsets, and CXCL13 on CD19⁺ B cells. Collectively, our findings first indicate that PEDV-induced chemokines MCP-1, CXCL-9 and CXCL-13 attracted CD14⁺ cells, T cells and B cells, respectively. These results provide a theoretical basis for studying the mechanism of anti-PEDV infection in piglets.