Limits...
The Vi capsular polysaccharide enables Salmonella enterica serovar typhi to evade microbe-guided neutrophil chemotaxis.

Wangdi T, Lee CY, Spees AM, Yu C, Kingsbury DD, Winter SE, Hastey CJ, Wilson RP, Heinrich V, Bäumler AJ - PLoS Pathog. (2014)

Bottom Line: Typhimurium) is associated with a localized gastroenteritis in humans.Typhi.Collectively, these data suggest that expression of the virulence-associated (Vi) capsular polysaccharide of S.

View Article: PubMed Central - PubMed

Affiliation: Department of Medical Microbiology and Immunology, School of Medicine, University of California, Davis, Davis, California, United States of America.

ABSTRACT
Salmonella enterica serovar Typhi (S. Typhi) causes typhoid fever, a disseminated infection, while the closely related pathogen S. enterica serovar Typhimurium (S. Typhimurium) is associated with a localized gastroenteritis in humans. Here we investigated whether both pathogens differ in the chemotactic response they induce in neutrophils using a single-cell experimental approach. Surprisingly, neutrophils extended chemotactic pseudopodia toward Escherichia coli and S. Typhimurium, but not toward S. Typhi. Bacterial-guided chemotaxis was dependent on the presence of complement component 5a (C5a) and C5a receptor (C5aR). Deletion of S. Typhi capsule biosynthesis genes markedly enhanced the chemotactic response of neutrophils in vitro. Furthermore, deletion of capsule biosynthesis genes heightened the association of S. Typhi with neutrophils in vivo through a C5aR-dependent mechanism. Collectively, these data suggest that expression of the virulence-associated (Vi) capsular polysaccharide of S. Typhi obstructs bacterial-guided neutrophil chemotaxis.

Show MeSH

Related in: MedlinePlus

The Vi capsular polysaccharide inhibits chemotactic responses of murine neutrophils in vitro and in vivo.(A–E) Video micrographs of single-cell experiments with an agglutinated non-capsulated ΔtviB-vexE mutant and pipette-held murine neutrophils from the mouse strains indicated on the right. The assay was performed in buffer containing serum from the mouse strains indicated on the left. Blood from 4 animals was pooled for isolation of serum and neutrophils for an experiment. Each experiment was repeated at least four times and one representative example is shown. (F) Migration of human neutrophils into the bottom compartment of a Boyden chamber containing the indicated attractants was measured in the presence or absence of anti-C5a antibody. Bars represent averages ± standard error from three experiments. (G) Generation of C5a was detected by ELISA 15 minutes after incubation of the indicated S. Typhi strains in human serum. Bars represent averages ± standard error from experiments. (H and I) Mice were infected intraperitoneally with the indicated GFP-labeled bacterial strains and cells were collected one hour later by intraperitoneal lavage. Representative images of bacterial association (Y-axis) with neutrophils from wild type mice or congenic C5aR-deficient mice (H) and quantitative analysis of the data (averages ± standard error) from groups of six animals (I) are shown. ns, not significantly different.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4125291&req=5

ppat-1004306-g003: The Vi capsular polysaccharide inhibits chemotactic responses of murine neutrophils in vitro and in vivo.(A–E) Video micrographs of single-cell experiments with an agglutinated non-capsulated ΔtviB-vexE mutant and pipette-held murine neutrophils from the mouse strains indicated on the right. The assay was performed in buffer containing serum from the mouse strains indicated on the left. Blood from 4 animals was pooled for isolation of serum and neutrophils for an experiment. Each experiment was repeated at least four times and one representative example is shown. (F) Migration of human neutrophils into the bottom compartment of a Boyden chamber containing the indicated attractants was measured in the presence or absence of anti-C5a antibody. Bars represent averages ± standard error from three experiments. (G) Generation of C5a was detected by ELISA 15 minutes after incubation of the indicated S. Typhi strains in human serum. Bars represent averages ± standard error from experiments. (H and I) Mice were infected intraperitoneally with the indicated GFP-labeled bacterial strains and cells were collected one hour later by intraperitoneal lavage. Representative images of bacterial association (Y-axis) with neutrophils from wild type mice or congenic C5aR-deficient mice (H) and quantitative analysis of the data (averages ± standard error) from groups of six animals (I) are shown. ns, not significantly different.

Mentions: Expression of the Vi capsular polysaccharide reduces complement activation by the alternative pathway [12], [16], as indicated by diminished fixation of complement fragment C3b on the surface of the capsulated S. Typhi wild-type strain compared to a non-capsulated S. Typhi mutant (ΔtviB-vexE mutant) (Fig. 2E and 2F). To further investigate whether chemotactic responses were dependent on C3, we performed single-cell experiments with serum and/or neutrophils from mice with C3-deficiency [39]. In serum from C3-deficient mice (bred on a C57BL/6 background), neutrophils from C3-deficient mice did not exhibit a chemotactic response toward the non-capsulated S. Typhi ΔtviB-vexE mutant (Fig. 3A, Video S9). In contrast, neutrophils from C3-deficient mice extended chemotactic pseudopodia toward the non-capsulated S. Typhi ΔtviB-vexE mutant when the experiment was performed in serum from wild type (C57BL/6) mice, which contains functional C3 protein (Fig. 3B, Video S10). As expected, chemotactic responses were also observed when both serum and neutrophils were derived from wild type (C57BL/6) mice (Fig. 3C, Video S11).


The Vi capsular polysaccharide enables Salmonella enterica serovar typhi to evade microbe-guided neutrophil chemotaxis.

Wangdi T, Lee CY, Spees AM, Yu C, Kingsbury DD, Winter SE, Hastey CJ, Wilson RP, Heinrich V, Bäumler AJ - PLoS Pathog. (2014)

The Vi capsular polysaccharide inhibits chemotactic responses of murine neutrophils in vitro and in vivo.(A–E) Video micrographs of single-cell experiments with an agglutinated non-capsulated ΔtviB-vexE mutant and pipette-held murine neutrophils from the mouse strains indicated on the right. The assay was performed in buffer containing serum from the mouse strains indicated on the left. Blood from 4 animals was pooled for isolation of serum and neutrophils for an experiment. Each experiment was repeated at least four times and one representative example is shown. (F) Migration of human neutrophils into the bottom compartment of a Boyden chamber containing the indicated attractants was measured in the presence or absence of anti-C5a antibody. Bars represent averages ± standard error from three experiments. (G) Generation of C5a was detected by ELISA 15 minutes after incubation of the indicated S. Typhi strains in human serum. Bars represent averages ± standard error from experiments. (H and I) Mice were infected intraperitoneally with the indicated GFP-labeled bacterial strains and cells were collected one hour later by intraperitoneal lavage. Representative images of bacterial association (Y-axis) with neutrophils from wild type mice or congenic C5aR-deficient mice (H) and quantitative analysis of the data (averages ± standard error) from groups of six animals (I) are shown. ns, not significantly different.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4125291&req=5

ppat-1004306-g003: The Vi capsular polysaccharide inhibits chemotactic responses of murine neutrophils in vitro and in vivo.(A–E) Video micrographs of single-cell experiments with an agglutinated non-capsulated ΔtviB-vexE mutant and pipette-held murine neutrophils from the mouse strains indicated on the right. The assay was performed in buffer containing serum from the mouse strains indicated on the left. Blood from 4 animals was pooled for isolation of serum and neutrophils for an experiment. Each experiment was repeated at least four times and one representative example is shown. (F) Migration of human neutrophils into the bottom compartment of a Boyden chamber containing the indicated attractants was measured in the presence or absence of anti-C5a antibody. Bars represent averages ± standard error from three experiments. (G) Generation of C5a was detected by ELISA 15 minutes after incubation of the indicated S. Typhi strains in human serum. Bars represent averages ± standard error from experiments. (H and I) Mice were infected intraperitoneally with the indicated GFP-labeled bacterial strains and cells were collected one hour later by intraperitoneal lavage. Representative images of bacterial association (Y-axis) with neutrophils from wild type mice or congenic C5aR-deficient mice (H) and quantitative analysis of the data (averages ± standard error) from groups of six animals (I) are shown. ns, not significantly different.
Mentions: Expression of the Vi capsular polysaccharide reduces complement activation by the alternative pathway [12], [16], as indicated by diminished fixation of complement fragment C3b on the surface of the capsulated S. Typhi wild-type strain compared to a non-capsulated S. Typhi mutant (ΔtviB-vexE mutant) (Fig. 2E and 2F). To further investigate whether chemotactic responses were dependent on C3, we performed single-cell experiments with serum and/or neutrophils from mice with C3-deficiency [39]. In serum from C3-deficient mice (bred on a C57BL/6 background), neutrophils from C3-deficient mice did not exhibit a chemotactic response toward the non-capsulated S. Typhi ΔtviB-vexE mutant (Fig. 3A, Video S9). In contrast, neutrophils from C3-deficient mice extended chemotactic pseudopodia toward the non-capsulated S. Typhi ΔtviB-vexE mutant when the experiment was performed in serum from wild type (C57BL/6) mice, which contains functional C3 protein (Fig. 3B, Video S10). As expected, chemotactic responses were also observed when both serum and neutrophils were derived from wild type (C57BL/6) mice (Fig. 3C, Video S11).

Bottom Line: Typhimurium) is associated with a localized gastroenteritis in humans.Typhi.Collectively, these data suggest that expression of the virulence-associated (Vi) capsular polysaccharide of S.

View Article: PubMed Central - PubMed

Affiliation: Department of Medical Microbiology and Immunology, School of Medicine, University of California, Davis, Davis, California, United States of America.

ABSTRACT
Salmonella enterica serovar Typhi (S. Typhi) causes typhoid fever, a disseminated infection, while the closely related pathogen S. enterica serovar Typhimurium (S. Typhimurium) is associated with a localized gastroenteritis in humans. Here we investigated whether both pathogens differ in the chemotactic response they induce in neutrophils using a single-cell experimental approach. Surprisingly, neutrophils extended chemotactic pseudopodia toward Escherichia coli and S. Typhimurium, but not toward S. Typhi. Bacterial-guided chemotaxis was dependent on the presence of complement component 5a (C5a) and C5a receptor (C5aR). Deletion of S. Typhi capsule biosynthesis genes markedly enhanced the chemotactic response of neutrophils in vitro. Furthermore, deletion of capsule biosynthesis genes heightened the association of S. Typhi with neutrophils in vivo through a C5aR-dependent mechanism. Collectively, these data suggest that expression of the virulence-associated (Vi) capsular polysaccharide of S. Typhi obstructs bacterial-guided neutrophil chemotaxis.

Show MeSH
Related in: MedlinePlus