Limits...
Escherichia coli α-hemolysin counteracts the anti-virulence innate immune response triggered by the Rho GTPase activating toxin CNF1 during bacteremia.

Diabate M, Munro P, Garcia E, Jacquel A, Michel G, Obba S, Goncalves D, Luci C, Marchetti S, Demon D, Degos C, Bechah Y, Mege JL, Lamkanfi M, Auberger P, Gorvel JP, Stuart LM, Landraud L, Lemichez E, Boyer L - PLoS Pathog. (2015)

Bottom Line: In vitro experiments further revealed the synergistic effects of CNF1 and LPS in promoting the maturation/secretion of IL-1β and establishing the roles of Rac, ASC and caspase-1 in this pathway.Furthermore, we found that the α-hemolysin toxin inhibits IL-1β secretion without affecting the recruitment of Gr1+ cells.Here, we report the first example of anti-virulence-triggered immunity counteracted by a pore-forming toxin during bacteremia.

View Article: PubMed Central - PubMed

Affiliation: INSERM, U1065, Centre Méditerranéen de Médecine Moléculaire, C3M, Toxines Microbiennes dans la relation hôte pathogènes, Nice, France; Université de Nice-Sophia-Antipolis, UFR Médecine, Nice, France; Laboratoire de Bactériologie, CHU de Nice, Hôpital l'Archet, Nice, France.

ABSTRACT
The detection of the activities of pathogen-encoded virulence factors by the innate immune system has emerged as a new paradigm of pathogen recognition. Much remains to be determined with regard to the molecular and cellular components contributing to this defense mechanism in mammals and importance during infection. Here, we reveal the central role of the IL-1β signaling axis and Gr1+ cells in controlling the Escherichia coli burden in the blood in response to the sensing of the Rho GTPase-activating toxin CNF1. Consistently, this innate immune response is abrogated in caspase-1/11-impaired mice or following the treatment of infected mice with an IL-1β antagonist. In vitro experiments further revealed the synergistic effects of CNF1 and LPS in promoting the maturation/secretion of IL-1β and establishing the roles of Rac, ASC and caspase-1 in this pathway. Furthermore, we found that the α-hemolysin toxin inhibits IL-1β secretion without affecting the recruitment of Gr1+ cells. Here, we report the first example of anti-virulence-triggered immunity counteracted by a pore-forming toxin during bacteremia.

Show MeSH

Related in: MedlinePlus

Infection with E. coli encoding CNF1 triggers clearance of bacteria from blood and mouse survival.(A) Female BALB/c mice were intravenously infected with 107 CFUs of E. coli expressing CNF1, E. coli UTI89ΔhlyA (E. coliCNF1+), or with the isogenic mutant UTI89ΔhlyA/Δcnf1 (E. coliCNF1-) or the parental strain UTI89 (E. coliUTI89) prior to the collection of peripheral blood at 3, 6, 24 and 48 h for the measurement of bacteremia (n = 25–30). The red line indicates the mean values. (B) Female BALB/c mice were intravenously infected with 107 CFUs of the E. coliCNF1- strain transformed with a control empty plasmid (E. coliCNF1- pempty), with a plasmid encoding the CNF1-inactive mutant C866S (E. coliCNF1- pcnf1 C866S) or with a plasmid encoding E. coli CNF1 WT (E. coliCNF1-pcnf1 WT) prior to the collection of peripheral blood at 3, 6, 24 and 48 h for the measurement of bacteremia (n = 6–12). For both (A) and (B), the data are expressed as the mean ± SEM (n = 6–30) at a *p<0.05. (C) BALB/c mouse survival was monitored for 52 h after intravenous injection of 2.108 CFUs of E. coliCNF1+ or the isogenic mutant, E. coliCNF1- (n = 20). *p<0.05 using the Gehan-Breslow-Wilcoxon chi-squared test.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4363529&req=5

ppat.1004732.g001: Infection with E. coli encoding CNF1 triggers clearance of bacteria from blood and mouse survival.(A) Female BALB/c mice were intravenously infected with 107 CFUs of E. coli expressing CNF1, E. coli UTI89ΔhlyA (E. coliCNF1+), or with the isogenic mutant UTI89ΔhlyA/Δcnf1 (E. coliCNF1-) or the parental strain UTI89 (E. coliUTI89) prior to the collection of peripheral blood at 3, 6, 24 and 48 h for the measurement of bacteremia (n = 25–30). The red line indicates the mean values. (B) Female BALB/c mice were intravenously infected with 107 CFUs of the E. coliCNF1- strain transformed with a control empty plasmid (E. coliCNF1- pempty), with a plasmid encoding the CNF1-inactive mutant C866S (E. coliCNF1- pcnf1 C866S) or with a plasmid encoding E. coli CNF1 WT (E. coliCNF1-pcnf1 WT) prior to the collection of peripheral blood at 3, 6, 24 and 48 h for the measurement of bacteremia (n = 6–12). For both (A) and (B), the data are expressed as the mean ± SEM (n = 6–30) at a *p<0.05. (C) BALB/c mouse survival was monitored for 52 h after intravenous injection of 2.108 CFUs of E. coliCNF1+ or the isogenic mutant, E. coliCNF1- (n = 20). *p<0.05 using the Gehan-Breslow-Wilcoxon chi-squared test.

Mentions: We first assessed the role of the CNF1 toxin in determining E. coli burden during the course of bacteremia in the absence of interference from the other toxin, HlyA. For this purpose, we generated both an hlyA- deletion mutant (referred to as E. coliCNF1+) and an hlyA-cnf1- double deletion mutant (referred to as E. coliCNF1-) from E. coliWT UTI89. By characterizing the strains at the genetic and functional levels, we determined that the two mutants and the wild-type strain had identical growth properties (S1 and S2 Figs). BALB/c mice were then infected intravenously with E. coliCNF1+ or E. coliCNF1- isogenic strains, and the pathogen load was monitored by the serial dilution of blood samples and the enumeration of CFUs (Fig. 1A). We found that the kinetics of clearance from the bloodstream of the E. coliCNF1+ strain was very different (Fig. 1A). The E. coliCNF1+ strain was rapidly cleared, with no bacteria detectable at 48 h p.i. compared with E. coliWT and E. coliCNF1-, which produced 104 and 103 CFU/mouse, respectively, at 48 h p.i. (Fig. 1A). We next assessed whether the rapid clearance of the E. coliCNF1+ strain was actually due to the enzymatic activity of CNF1. We tested this hypothesis by complementing the E. coliCNF1- strain with either an expression vector of wild-type CNF1 (E. coliCNF1- pcnf1) or an expression vector of the catalytically inactive mutant CNF1 C866S (E. coliCNF1- pcnf1 C866S) (Fig. 1B). We found that E. coliCNF1- pcnf1 bacteria were cleared more rapidly from the blood than E. coliCNF1- pcnf1 C866S (Fig. 1B). Together, these results indicate that CNF1 activity promotes the eradication of bacteria from the bloodstream.


Escherichia coli α-hemolysin counteracts the anti-virulence innate immune response triggered by the Rho GTPase activating toxin CNF1 during bacteremia.

Diabate M, Munro P, Garcia E, Jacquel A, Michel G, Obba S, Goncalves D, Luci C, Marchetti S, Demon D, Degos C, Bechah Y, Mege JL, Lamkanfi M, Auberger P, Gorvel JP, Stuart LM, Landraud L, Lemichez E, Boyer L - PLoS Pathog. (2015)

Infection with E. coli encoding CNF1 triggers clearance of bacteria from blood and mouse survival.(A) Female BALB/c mice were intravenously infected with 107 CFUs of E. coli expressing CNF1, E. coli UTI89ΔhlyA (E. coliCNF1+), or with the isogenic mutant UTI89ΔhlyA/Δcnf1 (E. coliCNF1-) or the parental strain UTI89 (E. coliUTI89) prior to the collection of peripheral blood at 3, 6, 24 and 48 h for the measurement of bacteremia (n = 25–30). The red line indicates the mean values. (B) Female BALB/c mice were intravenously infected with 107 CFUs of the E. coliCNF1- strain transformed with a control empty plasmid (E. coliCNF1- pempty), with a plasmid encoding the CNF1-inactive mutant C866S (E. coliCNF1- pcnf1 C866S) or with a plasmid encoding E. coli CNF1 WT (E. coliCNF1-pcnf1 WT) prior to the collection of peripheral blood at 3, 6, 24 and 48 h for the measurement of bacteremia (n = 6–12). For both (A) and (B), the data are expressed as the mean ± SEM (n = 6–30) at a *p<0.05. (C) BALB/c mouse survival was monitored for 52 h after intravenous injection of 2.108 CFUs of E. coliCNF1+ or the isogenic mutant, E. coliCNF1- (n = 20). *p<0.05 using the Gehan-Breslow-Wilcoxon chi-squared test.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4363529&req=5

ppat.1004732.g001: Infection with E. coli encoding CNF1 triggers clearance of bacteria from blood and mouse survival.(A) Female BALB/c mice were intravenously infected with 107 CFUs of E. coli expressing CNF1, E. coli UTI89ΔhlyA (E. coliCNF1+), or with the isogenic mutant UTI89ΔhlyA/Δcnf1 (E. coliCNF1-) or the parental strain UTI89 (E. coliUTI89) prior to the collection of peripheral blood at 3, 6, 24 and 48 h for the measurement of bacteremia (n = 25–30). The red line indicates the mean values. (B) Female BALB/c mice were intravenously infected with 107 CFUs of the E. coliCNF1- strain transformed with a control empty plasmid (E. coliCNF1- pempty), with a plasmid encoding the CNF1-inactive mutant C866S (E. coliCNF1- pcnf1 C866S) or with a plasmid encoding E. coli CNF1 WT (E. coliCNF1-pcnf1 WT) prior to the collection of peripheral blood at 3, 6, 24 and 48 h for the measurement of bacteremia (n = 6–12). For both (A) and (B), the data are expressed as the mean ± SEM (n = 6–30) at a *p<0.05. (C) BALB/c mouse survival was monitored for 52 h after intravenous injection of 2.108 CFUs of E. coliCNF1+ or the isogenic mutant, E. coliCNF1- (n = 20). *p<0.05 using the Gehan-Breslow-Wilcoxon chi-squared test.
Mentions: We first assessed the role of the CNF1 toxin in determining E. coli burden during the course of bacteremia in the absence of interference from the other toxin, HlyA. For this purpose, we generated both an hlyA- deletion mutant (referred to as E. coliCNF1+) and an hlyA-cnf1- double deletion mutant (referred to as E. coliCNF1-) from E. coliWT UTI89. By characterizing the strains at the genetic and functional levels, we determined that the two mutants and the wild-type strain had identical growth properties (S1 and S2 Figs). BALB/c mice were then infected intravenously with E. coliCNF1+ or E. coliCNF1- isogenic strains, and the pathogen load was monitored by the serial dilution of blood samples and the enumeration of CFUs (Fig. 1A). We found that the kinetics of clearance from the bloodstream of the E. coliCNF1+ strain was very different (Fig. 1A). The E. coliCNF1+ strain was rapidly cleared, with no bacteria detectable at 48 h p.i. compared with E. coliWT and E. coliCNF1-, which produced 104 and 103 CFU/mouse, respectively, at 48 h p.i. (Fig. 1A). We next assessed whether the rapid clearance of the E. coliCNF1+ strain was actually due to the enzymatic activity of CNF1. We tested this hypothesis by complementing the E. coliCNF1- strain with either an expression vector of wild-type CNF1 (E. coliCNF1- pcnf1) or an expression vector of the catalytically inactive mutant CNF1 C866S (E. coliCNF1- pcnf1 C866S) (Fig. 1B). We found that E. coliCNF1- pcnf1 bacteria were cleared more rapidly from the blood than E. coliCNF1- pcnf1 C866S (Fig. 1B). Together, these results indicate that CNF1 activity promotes the eradication of bacteria from the bloodstream.

Bottom Line: In vitro experiments further revealed the synergistic effects of CNF1 and LPS in promoting the maturation/secretion of IL-1β and establishing the roles of Rac, ASC and caspase-1 in this pathway.Furthermore, we found that the α-hemolysin toxin inhibits IL-1β secretion without affecting the recruitment of Gr1+ cells.Here, we report the first example of anti-virulence-triggered immunity counteracted by a pore-forming toxin during bacteremia.

View Article: PubMed Central - PubMed

Affiliation: INSERM, U1065, Centre Méditerranéen de Médecine Moléculaire, C3M, Toxines Microbiennes dans la relation hôte pathogènes, Nice, France; Université de Nice-Sophia-Antipolis, UFR Médecine, Nice, France; Laboratoire de Bactériologie, CHU de Nice, Hôpital l'Archet, Nice, France.

ABSTRACT
The detection of the activities of pathogen-encoded virulence factors by the innate immune system has emerged as a new paradigm of pathogen recognition. Much remains to be determined with regard to the molecular and cellular components contributing to this defense mechanism in mammals and importance during infection. Here, we reveal the central role of the IL-1β signaling axis and Gr1+ cells in controlling the Escherichia coli burden in the blood in response to the sensing of the Rho GTPase-activating toxin CNF1. Consistently, this innate immune response is abrogated in caspase-1/11-impaired mice or following the treatment of infected mice with an IL-1β antagonist. In vitro experiments further revealed the synergistic effects of CNF1 and LPS in promoting the maturation/secretion of IL-1β and establishing the roles of Rac, ASC and caspase-1 in this pathway. Furthermore, we found that the α-hemolysin toxin inhibits IL-1β secretion without affecting the recruitment of Gr1+ cells. Here, we report the first example of anti-virulence-triggered immunity counteracted by a pore-forming toxin during bacteremia.

Show MeSH
Related in: MedlinePlus