Hcp2b of T6SS affects colonization of avian pathogenic Escherichia coli and host keratin filament expression.

T6SS (type VI secretion system) is a type of nano-syringe that exists in APEC (avian pathogenic Escherichia coli). Hcp (haemolysin-coregulated protein) of T6SS participates in the regulation of virulence during APEC infection. However, whether hcp plays a role in bacterial colonization by expression in host cells remains unclear. In this study, we analysed the biological characteristics of the mutant hcp2b strain. Our results showed that the hcp2b gene was involved in the regulation of bacterial motility, biofilm formation, anti-serum and anti-oxidative stress. Moreover, our data indicate that the colonization of the hcp2b mutation strain (Δhcp2b) in the lung, liver and kidney of chickens decreased significantly. Hence, overexpression of Hcp2b protein in DF-1 cells was used to analyse the effect of Hcp2b on colonization of APEC. Proteomics analysis showed that overexpression of Hcp2b induced differentially expressed proteins in DF-1 cells (230 were significantly upregulated and 96 were significantly downregulated) and differentially expressed proteins were enriched in keratin filament. In conclusion, our data indicated that hcp2b promoted the colonization of APEC by affecting the expression of keratin filament.