DotU expression is highly induced during in vivo infection and responsible for virulence and Hcp1 secretion in avian pathogenic Escherichia coli

Abstract

Type VI secretion systems (T6SSs) contribute to pathogenicity in many pathogenic bacteria. Three distinguishable T6SS loci have been discovered in avian pathogenic Escherichia coli (APEC). The sequence of APEC T6SS2 locus is highly similar to the sequence of the newborn meningitis Escherichia coli (NMEC) RS218 T6SS locus, which might contribute to meningitis pathogenesis. However, little is known about the function of APEC T6SS2. We showed that the APEC T6SS2 component organelle trafficking protein (DotU) could elicit antibodies in infected ducks, suggesting that DotU might be involved in APEC pathogenicity. To investigate DotU in APEC pathogenesis, mutant and complemented strains were constructed and characterized. Inactivation of the APEC dotU gene attenuated virulence in ducks, diminished resistance to normal duck serum, and reduced survival in macrophage cells and ducks. Furthermore, deletion of the dotU gene abolished hemolysin-coregulated protein (Hcp) 1 secretion, leading to decreased interleukin (IL)-6 and IL-8 gene expression in HD-11 chicken macrophages. These functions were restored for the complementation strain. Our results demonstrated that DotU plays key roles in the APEC pathogenesis, Hcp1 secretion, and intracellular host response modulation.

The CpxR regulates type VI secretion system 2 expression and facilitates the interbacterial competition activity and virulence of avian pathogenic Escherichia coli

“…The strains and plasmids used in this study are listed in Table 1. The APEC strain DE719 (O2:K1) causes severe colibacillosis symptoms and high mortality in ducks and mice [14]. Bacteria were grown routinely in Luria–Bertani (LB) medium at 37 °C with aeration.…”

“…Three distinct T6SSs have been identified in APEC genomes. Among them, the APEC T6SS2, similar to NMEC T6SS, is responsible for the binding and invasion to host cells, survival, interbacterial competition and pathogenesis of APEC and NMEC [11, 14–16]. As contact-dependent pathways, the T6SSs are tightly regulated by various regulatory mechanisms to ensure successful bacterial infection [17].…”

A Novel PhoP/PhoQ Regulation Pathway Modulates the Survival of Extraintestinal Pathogenic Escherichia coli in Macrophages

“…HD11 cells (chicken macrophage-like cell line) were derived from chicken bone marrow macrophages by transforming the avian leukemia virus ( 34 ). HD11 macrophages were kindly provided by Shaohui Wang (Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences) and cultured as the previously described ( 15 , 35 ). HD11 cells were cultured in RPMI 1640 media (Gibco) (at a humidified incubator for 41.5°C and 5% CO 2 ), supplemented with 10% heat-inactivated fetal bovine serum (FBS), 2 mM l -glutamine (Gibco), 1 mM of sodium pyruvate 0.1 mM of NEAA, and 10 mM HEPES.…”

Expression of Immune-Related Genes of Ducks Infected with Avian Pathogenic Escherichia coli (APEC)

“…For instance, the APEC T6SS2 component organelle trafficking protein (DotU) could elicit antibodies in infected ducks. Deletion of the dotU gene of APEC abolished hemolysin-coregulated protein 1 secretion, leading to the decreased expression of interleukin (IL)-6 and IL-8 genes in HD-11 chicken macrophages ( Wang et al, 2014 ). Another study has shown that E. coli type three effectors can manipulate PAMP/MAMP-triggered immune signaling components and acting on the evolutionary conserved cellular hubs of immune responses ( Fraiture and Brunner, 2015 ).…”