Effect of coiled-coil peptides on the in vitro function of the Type Three Secretion System dependent activity of Enterohemorragic Escherichia coli O157:H7 and Citrobacter rodentium

LARZÁBAL M; ZOTTA E; IBARRA C; VILTE D; RABINOVITZ BC; MERCADO EC; CATALDI A

Congreso; International Symposium on Shiga Toxin (verocytoxin) producing Escherichia coli Infections; 2012

Many animal and human pathogenic Gram-negative bacteria such as Salmonella, Yersinia, Enterohemorrhagic Escherichia coli (EHEC) and Enteropathogenic Escherichia coli (EPEC) possess a type III secretion system (TTSS) that is used to deliver virulence proteins directly into the host cell. In this study we assayed coiled-coil peptides, previously tested as effective against TTSS from EPEC and EHEC, in vitro correlates of TTSS action (RBC hemolysis and protein secretion) and in a mice model of C. rodentium infection. Coiled-coil peptides showed to be effective in reducing the RBC lysis mediated by EHEC O157:H7 and in vitro secretion of EspD by C. rodentium and EspB and EspD by EHEC O157:H7. For in vivo assay, a group of 5 C57BL/6J mice (Group 1) was orally treated daily with CoilA and CoilB peptides prior to challenge with C. rodentium and for 6 days post inoculation (dpi). Group 2 was the untreated control. Both groups were orally inoculated on day 8 with 5.109 CFU of a strain of C. rodentium. Stool samples were recovered at different dpi to determine the number of CFU/g of feces. Group 1 excreted a smaller amount of CFU/g during the first 3 dpi, compared to Group 2. After sacrifice at 13 dpi, large intestine samples were taken for histological analysis. Colon samples of Group 2 showed areas with loss of superficial epithelium, damaged cells and endoluminal mononuclear inflammatory infiltrate, consistent with histological lesion induced by C. rodentium. Mice treated with peptides CoilA and CoilB kept normal the surface epithelium showing a similar structure as an uninfected control group. These results suggest that pre-treatment with coiled-coil peptides prevent colon damage of mice inoculated with C. rodentium. These encouraging results prompted us to test coiled-coil peptides as treatment or vaccines in other models of bacterial infections.