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Background: Avian pathogenic Escherichia coli (APEC) causes tracheal damage and heterophilic granulocytic infiltration and inflammation in infected chicks. In this study, we infected chick tracheal tissue with strain AE17 and produced pathological sections with proteomic sequencing. We compared the results of pathological sections from the APEC-infected group with those from the PBS control group; the pathological sections from the experimental group showed hemorrhage, fibrinization, and infiltration of heterophilic granulocytes in the tracheal tissue. In order to explore the effect on proteomics on inflammation and to further search for the caus. Results: The tandem mass tag-based (TMT) sequencing analysis showed 224 upregulated and 140 downregulated proteins after infection with the AE17 strain. Based on the results of KEGG in Complement and coagulation cascades, differential protein expression in the Protein export pathway was upregulated. Conclusions: With these results, we found that chemokines produced by the Complement and coagulation cascades pathway may cause infiltration of heterophilic granulocytes involved in inflammation, as well as antimicrobial factors produced by the complement system to fight the infection together.These results suggest that APEC causes the infiltration of heterophilic granulocytes through the involvement of the complement system with serine protease inhibitors. [ABSTRACT FROM AUTHOR]

Background: Bacteria deliver effector proteins into the host cell via a secretory system that can directly act on the target to cause disease. As an important pipeline structural protein of the type VI secretion system (T6SS) complex, Hcp acts together with other virulence factors in the target cell. There is growing evidence that T6SS plays a key role in the pathogenic mechanism of APEC. However, the regulatory function played by the effector protein Hcp during its interaction with host cells is not clear. Here, tandem mass tag (TMT) analysis was used to quantify the proteins affected by increased expression of Hcp2a in DF-1 cells. Results: The host response was significantly different between the overexpression and null groups at the protein level. A total of 195 differentially expressed proteins (DEPs) were detected in the overexpression group (upregulated, n = 144, downregulated, n = 51). Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were performed to predict the biological functions and pathways of differentially expressed proteins. The results showed that these DEPs were mainly enriched in RNA degradation, spliceosome, and mRNA surveillance pathways. Conclusions: This study suggests that Hcp2a, the effector protein of APEC, plays an important role in regulating mRNA splicing and protein quality control in DF-1 cells. These findings provide useful clues to elucidate the pathogenic mechanism of effector protein Hcp2a on host target cells. [ABSTRACT FROM AUTHOR]