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Counter inhibition between leukotoxins attenuates Staphylococcus aureus virulence.

Yoong P, Torres VJ - Nat Commun (2015)

Bottom Line: Despite extensive sequence conservation, each leukotoxin has unique properties, including disparate cellular receptors and species specificities.Using in vivo murine models of infection, we show that LukSF-PV negatively influences S. aureus virulence and colonization by inhibiting LukED.Thus, while S. aureus leukotoxins can certainly injure immune cells, the discovery of leukotoxin antagonism suggests that they may also play a role in reducing S. aureus virulence and maintaining infection without killing the host.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology, New York University School of Medicine, New York, New York 10016, USA.

ABSTRACT
Staphylococcus aureus subverts host defences by producing a collection of virulence factors including bi-component pore-forming leukotoxins. Despite extensive sequence conservation, each leukotoxin has unique properties, including disparate cellular receptors and species specificities. How these toxins collectively influence S. aureus pathogenesis is unknown. Here we demonstrate that the leukotoxins LukSF-PV and LukED antagonize each other's cytolytic activities on leukocytes and erythrocytes by forming inactive hybrid complexes. Remarkably, LukSF-PV inhibition of LukED haemolytic activity on both human and murine erythrocytes prevents the release of nutrients required for in vitro bacterial growth. Using in vivo murine models of infection, we show that LukSF-PV negatively influences S. aureus virulence and colonization by inhibiting LukED. Thus, while S. aureus leukotoxins can certainly injure immune cells, the discovery of leukotoxin antagonism suggests that they may also play a role in reducing S. aureus virulence and maintaining infection without killing the host.

No MeSH data available.


Related in: MedlinePlus

LukSF-PV inhibition of LukED-mediated haemolysis prevents the release of nutrients necessary for S. aureus growth.Iron-starved USA400-MW2 (a) and USA300-LAC (b) were subcultured into iron-restricted medium supplemented with increasing concentrations (v/v) of cell-free lysates of human RBCs treated with PBS, LukED (1 μg ml−1), LukSF-PV (10 μg ml−1), and a mixture of LukED (1 μg ml−1) and LukSF-PV (10 μg ml−1). Bacterial growth was monitored by measuring optical density, which was normalized to 100% of the maximal growth. Results represent the average from three or more independent replicates±s.e.m. **P<0.01, ***P<0.001 and ****P<0.0001 by two-way analysis of variance.
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f3: LukSF-PV inhibition of LukED-mediated haemolysis prevents the release of nutrients necessary for S. aureus growth.Iron-starved USA400-MW2 (a) and USA300-LAC (b) were subcultured into iron-restricted medium supplemented with increasing concentrations (v/v) of cell-free lysates of human RBCs treated with PBS, LukED (1 μg ml−1), LukSF-PV (10 μg ml−1), and a mixture of LukED (1 μg ml−1) and LukSF-PV (10 μg ml−1). Bacterial growth was monitored by measuring optical density, which was normalized to 100% of the maximal growth. Results represent the average from three or more independent replicates±s.e.m. **P<0.01, ***P<0.001 and ****P<0.0001 by two-way analysis of variance.

Mentions: Iron is necessary for bacterial growth, but as there is little to no free iron in vertebrates. Bacterial pathogens have evolved sophisticated mechanisms to scavenge iron bound to host proteins30. S. aureus primarily scavenges iron from human haemoglobin thought to be released upon lysis of RBCs3132333435. Thus, we reasoned that LukED-mediated lysis of RBCs could promote S. aureus growth, but not if haemolysis is inhibited by LukSF-PV. To directly test this possibility, cell-free supernatants were generated by treating human RBCs with LukED and/or LukSF-PV and used as nutrient sources. We observed impaired growth when two CA-MRSA strains, MW2 (Fig. 3a) and LAC (Fig. 3b), were inoculated into iron-starved medium supplemented with cell-free supernatants from RBCs treated with buffer or with LukSF-PV. In contrast, the strains were able to grow when inoculated into cell-free supernatants from the LukED treated human RBCs. Notably, bacterial growth was impaired in cell-free supernatants from RBCs treated with a mixture of LukED and LukSF-PV (Fig. 3a,b).


Counter inhibition between leukotoxins attenuates Staphylococcus aureus virulence.

Yoong P, Torres VJ - Nat Commun (2015)

LukSF-PV inhibition of LukED-mediated haemolysis prevents the release of nutrients necessary for S. aureus growth.Iron-starved USA400-MW2 (a) and USA300-LAC (b) were subcultured into iron-restricted medium supplemented with increasing concentrations (v/v) of cell-free lysates of human RBCs treated with PBS, LukED (1 μg ml−1), LukSF-PV (10 μg ml−1), and a mixture of LukED (1 μg ml−1) and LukSF-PV (10 μg ml−1). Bacterial growth was monitored by measuring optical density, which was normalized to 100% of the maximal growth. Results represent the average from three or more independent replicates±s.e.m. **P<0.01, ***P<0.001 and ****P<0.0001 by two-way analysis of variance.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4562310&req=5

f3: LukSF-PV inhibition of LukED-mediated haemolysis prevents the release of nutrients necessary for S. aureus growth.Iron-starved USA400-MW2 (a) and USA300-LAC (b) were subcultured into iron-restricted medium supplemented with increasing concentrations (v/v) of cell-free lysates of human RBCs treated with PBS, LukED (1 μg ml−1), LukSF-PV (10 μg ml−1), and a mixture of LukED (1 μg ml−1) and LukSF-PV (10 μg ml−1). Bacterial growth was monitored by measuring optical density, which was normalized to 100% of the maximal growth. Results represent the average from three or more independent replicates±s.e.m. **P<0.01, ***P<0.001 and ****P<0.0001 by two-way analysis of variance.
Mentions: Iron is necessary for bacterial growth, but as there is little to no free iron in vertebrates. Bacterial pathogens have evolved sophisticated mechanisms to scavenge iron bound to host proteins30. S. aureus primarily scavenges iron from human haemoglobin thought to be released upon lysis of RBCs3132333435. Thus, we reasoned that LukED-mediated lysis of RBCs could promote S. aureus growth, but not if haemolysis is inhibited by LukSF-PV. To directly test this possibility, cell-free supernatants were generated by treating human RBCs with LukED and/or LukSF-PV and used as nutrient sources. We observed impaired growth when two CA-MRSA strains, MW2 (Fig. 3a) and LAC (Fig. 3b), were inoculated into iron-starved medium supplemented with cell-free supernatants from RBCs treated with buffer or with LukSF-PV. In contrast, the strains were able to grow when inoculated into cell-free supernatants from the LukED treated human RBCs. Notably, bacterial growth was impaired in cell-free supernatants from RBCs treated with a mixture of LukED and LukSF-PV (Fig. 3a,b).

Bottom Line: Despite extensive sequence conservation, each leukotoxin has unique properties, including disparate cellular receptors and species specificities.Using in vivo murine models of infection, we show that LukSF-PV negatively influences S. aureus virulence and colonization by inhibiting LukED.Thus, while S. aureus leukotoxins can certainly injure immune cells, the discovery of leukotoxin antagonism suggests that they may also play a role in reducing S. aureus virulence and maintaining infection without killing the host.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology, New York University School of Medicine, New York, New York 10016, USA.

ABSTRACT
Staphylococcus aureus subverts host defences by producing a collection of virulence factors including bi-component pore-forming leukotoxins. Despite extensive sequence conservation, each leukotoxin has unique properties, including disparate cellular receptors and species specificities. How these toxins collectively influence S. aureus pathogenesis is unknown. Here we demonstrate that the leukotoxins LukSF-PV and LukED antagonize each other's cytolytic activities on leukocytes and erythrocytes by forming inactive hybrid complexes. Remarkably, LukSF-PV inhibition of LukED haemolytic activity on both human and murine erythrocytes prevents the release of nutrients required for in vitro bacterial growth. Using in vivo murine models of infection, we show that LukSF-PV negatively influences S. aureus virulence and colonization by inhibiting LukED. Thus, while S. aureus leukotoxins can certainly injure immune cells, the discovery of leukotoxin antagonism suggests that they may also play a role in reducing S. aureus virulence and maintaining infection without killing the host.

No MeSH data available.


Related in: MedlinePlus