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Immunity to intracellular Salmonella depends on surface-associated antigens.

Barat S, Willer Y, Rizos K, Claudi B, Mazé A, Schemmer AK, Kirchhoff D, Schmidt A, Burton N, Bumann D - PLoS Pathog. (2012)

Bottom Line: Surprisingly, this was not due to superior immunogenicity of surface antigens compared to internal antigens as had been suggested by previous studies and novel findings for CD4 T cell responses to model antigens.In the absence of accessible internal antigens, detection of these infected cells might require CD4 T cell recognition of Salmonella surface-associated antigens that could be processed and presented even from intact Salmonella.In conclusion, our findings might pave the way for development of an efficacious Salmonella vaccine with broad serovar coverage, and suggest a similar crucial role of surface antigens for immunity to both extracellular and intracellular pathogens.

View Article: PubMed Central - PubMed

Affiliation: Focal Area Infection Biology, Biozentrum, University of Basel, Basel, Switzerland.

ABSTRACT
Invasive Salmonella infection is an important health problem that is worsening because of rising antimicrobial resistance and changing Salmonella serovar spectrum. Novel vaccines with broad serovar coverage are needed, but suitable protective antigens remain largely unknown. Here, we tested 37 broadly conserved Salmonella antigens in a mouse typhoid fever model, and identified antigen candidates that conferred partial protection against lethal disease. Antigen properties such as high in vivo abundance or immunodominance in convalescent individuals were not required for protectivity, but all promising antigen candidates were associated with the Salmonella surface. Surprisingly, this was not due to superior immunogenicity of surface antigens compared to internal antigens as had been suggested by previous studies and novel findings for CD4 T cell responses to model antigens. Confocal microscopy of infected tissues revealed that many live Salmonella resided alone in infected host macrophages with no damaged Salmonella releasing internal antigens in their vicinity. In the absence of accessible internal antigens, detection of these infected cells might require CD4 T cell recognition of Salmonella surface-associated antigens that could be processed and presented even from intact Salmonella. In conclusion, our findings might pave the way for development of an efficacious Salmonella vaccine with broad serovar coverage, and suggest a similar crucial role of surface antigens for immunity to both extracellular and intracellular pathogens.

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Related in: MedlinePlus

Detection of intact and damaged Salmonella cells in infected mouse tissues.A) Flow cytometry of a spleen homogenate infected with Salmonella sifB::gfp using 488 nm excitation. Gate 1 contains GFP-positive Salmonella. The inset shows the relationship between flow cytometry data and plate counts for individual mice, the dashed line represents a 1∶1 ratio. B) Confocal micrographs of liver cryosections infected with Salmonella sifB::gfp that were stained with antibodies to Salmonella lipopolysaccharide (red) and macrophage marker CD68 (blue). Individual color channels are shown with inverted grey scale for better visualization of weak staining. Micrographs represent typical observations for four independently infected mice. C) Confocal micrographs of lipopolysaccharide-positive particles that lack detectable GFP (even when contrast was increased compared to B). Such particles were absent in non-infected control sections.
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ppat-1002966-g007: Detection of intact and damaged Salmonella cells in infected mouse tissues.A) Flow cytometry of a spleen homogenate infected with Salmonella sifB::gfp using 488 nm excitation. Gate 1 contains GFP-positive Salmonella. The inset shows the relationship between flow cytometry data and plate counts for individual mice, the dashed line represents a 1∶1 ratio. B) Confocal micrographs of liver cryosections infected with Salmonella sifB::gfp that were stained with antibodies to Salmonella lipopolysaccharide (red) and macrophage marker CD68 (blue). Individual color channels are shown with inverted grey scale for better visualization of weak staining. Micrographs represent typical observations for four independently infected mice. C) Confocal micrographs of lipopolysaccharide-positive particles that lack detectable GFP (even when contrast was increased compared to B). Such particles were absent in non-infected control sections.

Mentions: Salmonella expressing GFP from the chromosomal in vivo induced locus sifB were readily detected in infected tissue homogenates using flow cytometry [12] (Fig. 7A). Flow cytometric counts for GFP+Salmonella closely correlated with viable counts as determined by plating (Fig. 7A, inset) suggesting that detectable GFP levels were present in all live Salmonella.


Immunity to intracellular Salmonella depends on surface-associated antigens.

Barat S, Willer Y, Rizos K, Claudi B, Mazé A, Schemmer AK, Kirchhoff D, Schmidt A, Burton N, Bumann D - PLoS Pathog. (2012)

Detection of intact and damaged Salmonella cells in infected mouse tissues.A) Flow cytometry of a spleen homogenate infected with Salmonella sifB::gfp using 488 nm excitation. Gate 1 contains GFP-positive Salmonella. The inset shows the relationship between flow cytometry data and plate counts for individual mice, the dashed line represents a 1∶1 ratio. B) Confocal micrographs of liver cryosections infected with Salmonella sifB::gfp that were stained with antibodies to Salmonella lipopolysaccharide (red) and macrophage marker CD68 (blue). Individual color channels are shown with inverted grey scale for better visualization of weak staining. Micrographs represent typical observations for four independently infected mice. C) Confocal micrographs of lipopolysaccharide-positive particles that lack detectable GFP (even when contrast was increased compared to B). Such particles were absent in non-infected control sections.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3475680&req=5

ppat-1002966-g007: Detection of intact and damaged Salmonella cells in infected mouse tissues.A) Flow cytometry of a spleen homogenate infected with Salmonella sifB::gfp using 488 nm excitation. Gate 1 contains GFP-positive Salmonella. The inset shows the relationship between flow cytometry data and plate counts for individual mice, the dashed line represents a 1∶1 ratio. B) Confocal micrographs of liver cryosections infected with Salmonella sifB::gfp that were stained with antibodies to Salmonella lipopolysaccharide (red) and macrophage marker CD68 (blue). Individual color channels are shown with inverted grey scale for better visualization of weak staining. Micrographs represent typical observations for four independently infected mice. C) Confocal micrographs of lipopolysaccharide-positive particles that lack detectable GFP (even when contrast was increased compared to B). Such particles were absent in non-infected control sections.
Mentions: Salmonella expressing GFP from the chromosomal in vivo induced locus sifB were readily detected in infected tissue homogenates using flow cytometry [12] (Fig. 7A). Flow cytometric counts for GFP+Salmonella closely correlated with viable counts as determined by plating (Fig. 7A, inset) suggesting that detectable GFP levels were present in all live Salmonella.

Bottom Line: Surprisingly, this was not due to superior immunogenicity of surface antigens compared to internal antigens as had been suggested by previous studies and novel findings for CD4 T cell responses to model antigens.In the absence of accessible internal antigens, detection of these infected cells might require CD4 T cell recognition of Salmonella surface-associated antigens that could be processed and presented even from intact Salmonella.In conclusion, our findings might pave the way for development of an efficacious Salmonella vaccine with broad serovar coverage, and suggest a similar crucial role of surface antigens for immunity to both extracellular and intracellular pathogens.

View Article: PubMed Central - PubMed

Affiliation: Focal Area Infection Biology, Biozentrum, University of Basel, Basel, Switzerland.

ABSTRACT
Invasive Salmonella infection is an important health problem that is worsening because of rising antimicrobial resistance and changing Salmonella serovar spectrum. Novel vaccines with broad serovar coverage are needed, but suitable protective antigens remain largely unknown. Here, we tested 37 broadly conserved Salmonella antigens in a mouse typhoid fever model, and identified antigen candidates that conferred partial protection against lethal disease. Antigen properties such as high in vivo abundance or immunodominance in convalescent individuals were not required for protectivity, but all promising antigen candidates were associated with the Salmonella surface. Surprisingly, this was not due to superior immunogenicity of surface antigens compared to internal antigens as had been suggested by previous studies and novel findings for CD4 T cell responses to model antigens. Confocal microscopy of infected tissues revealed that many live Salmonella resided alone in infected host macrophages with no damaged Salmonella releasing internal antigens in their vicinity. In the absence of accessible internal antigens, detection of these infected cells might require CD4 T cell recognition of Salmonella surface-associated antigens that could be processed and presented even from intact Salmonella. In conclusion, our findings might pave the way for development of an efficacious Salmonella vaccine with broad serovar coverage, and suggest a similar crucial role of surface antigens for immunity to both extracellular and intracellular pathogens.

Show MeSH
Related in: MedlinePlus