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Yersinia pestis endowed with increased cytotoxicity is avirulent in a bubonic plague model and induces rapid protection against pneumonic plague.

Zauberman A, Tidhar A, Levy Y, Bar-Haim E, Halperin G, Flashner Y, Cohen S, Shafferman A, Mamroud E - PLoS ONE (2009)

Bottom Line: Following subcutaneous infection, this strain had reduced ability to colonize internal organs, was unable to induce septicemia and exhibited at least a 10(7)-fold reduction in virulence.Yet, upon intravenous or intranasal infection, it was still as virulent as the wild-type strain.These observations have novel implications for the development of vaccines/therapies against Y. pestis and shed new light on the virulence strategies of Y. pestis in nature.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry and Molecular Genetics, Israel Institute for Biological Research, Ness-Ziona, Israel.

ABSTRACT
An important virulence strategy evolved by bacterial pathogens to overcome host defenses is the modulation of host cell death. Previous observations have indicated that Yersinia pestis, the causative agent of plague disease, exhibits restricted capacity to induce cell death in macrophages due to ineffective translocation of the type III secretion effector YopJ, as opposed to the readily translocated YopP, the YopJ homologue of the enteropathogen Yersinia enterocolitica Oratio8. This led us to suggest that reduced cytotoxic potency may allow pathogen propagation within a shielded niche, leading to increased virulence. To test the relationship between cytotoxic potential and virulence, we replaced Y. pestis YopJ with YopP. The YopP-expressing Y. pestis strain exhibited high cytotoxic activity against macrophages in vitro. Following subcutaneous infection, this strain had reduced ability to colonize internal organs, was unable to induce septicemia and exhibited at least a 10(7)-fold reduction in virulence. Yet, upon intravenous or intranasal infection, it was still as virulent as the wild-type strain. The subcutaneous administration of the cytotoxic Y. pestis strain appears to activate a rapid and potent systemic, CTL-independent, immunoprotective response, allowing the organism to overcome simultaneous coinfection with 10,000 LD(50) of virulent Y. pestis. Moreover, three days after subcutaneous administration of this strain, animals were also protected against septicemic or primary pneumonic plague. Our findings indicate that an inverse relationship exists between the cytotoxic potential of Y. pestis and its virulence following subcutaneous infection. This appears to be associated with the ability of the engineered cytotoxic Y. pestis strain to induce very rapid, effective and long-lasting protection against bubonic and pneumonic plague. These observations have novel implications for the development of vaccines/therapies against Y. pestis and shed new light on the virulence strategies of Y. pestis in nature.

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Kim53ΔJ+P is deficient in dissemination to target organs and to the blood following subcutaneous infection.Mice were infected subcutaneously with 1×104 cfu of either Kim53pGFP (black symbols) or Kim53ΔJ+P (white symbols). Animals (4–5 per group) were sacrificed at 60 hours post-infection. Blood was collected, and the draining inguinal lymph nodes (ILN) and spleens were harvested, homogenized in 1 ml PBS and cultured on brain heart infusion agar plates at 28°C for 48 hrs. Values in Figure represent total bacterial loads in infected organs (cfu/organ), or bacterial concentration in blood (cfu/ml). LOD, limit of detection. Horizontal bars represent the average value of bacterial load in each case. Differences in bacterial concentrations in blood and internal organs were analyzed by the non-parametric Mann-Whitney test.
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pone-0005938-g002: Kim53ΔJ+P is deficient in dissemination to target organs and to the blood following subcutaneous infection.Mice were infected subcutaneously with 1×104 cfu of either Kim53pGFP (black symbols) or Kim53ΔJ+P (white symbols). Animals (4–5 per group) were sacrificed at 60 hours post-infection. Blood was collected, and the draining inguinal lymph nodes (ILN) and spleens were harvested, homogenized in 1 ml PBS and cultured on brain heart infusion agar plates at 28°C for 48 hrs. Values in Figure represent total bacterial loads in infected organs (cfu/organ), or bacterial concentration in blood (cfu/ml). LOD, limit of detection. Horizontal bars represent the average value of bacterial load in each case. Differences in bacterial concentrations in blood and internal organs were analyzed by the non-parametric Mann-Whitney test.

Mentions: Host immune cells may serve in vivo as a favorable intracellular niche and a shielding vehicle for plague bacilli [31], [32], [33]. It was therefore interesting to determine whether the avirulent phenotype of Kim53ΔJ+P is associated with the cytotoxic effect of YopP through interference with bacterial propagation and delivery to internal tissues. Accordingly, we monitored the colonization of internal organs by Kim53ΔJ+P compared to the Y. pestis Kim53pGFP control strain. Mice were subcutaneously infected with 1×104 cfu of each strain. Dissemination to draining inguinal lymph nodes (ILNs), the spleen and blood was examined 60 hours post-infection, a time point representing terminal stages of disease in Kim53pGFP-infected mice that served as controls. The number of colony forming units in the ILNs and the spleen of mice infected with Kim53ΔJ+P was about 100-fold lower than with the control Y. pestis strain (Figure 2). An even more pronounced disparity was observed in blood. Kim53ΔJ+P could not be detected in blood whereas the Y. pestis control strain reached an average concentration of 1×106 cfu/ml. Interestingly, despite the fact that colonization of the spleen in Kim53ΔJ+P-infected mice reaches substantial bacterial count (1×105 bacteria per spleen), the infection with high dose of Kim53ΔJ+P is not lethal (Figure 1D).


Yersinia pestis endowed with increased cytotoxicity is avirulent in a bubonic plague model and induces rapid protection against pneumonic plague.

Zauberman A, Tidhar A, Levy Y, Bar-Haim E, Halperin G, Flashner Y, Cohen S, Shafferman A, Mamroud E - PLoS ONE (2009)

Kim53ΔJ+P is deficient in dissemination to target organs and to the blood following subcutaneous infection.Mice were infected subcutaneously with 1×104 cfu of either Kim53pGFP (black symbols) or Kim53ΔJ+P (white symbols). Animals (4–5 per group) were sacrificed at 60 hours post-infection. Blood was collected, and the draining inguinal lymph nodes (ILN) and spleens were harvested, homogenized in 1 ml PBS and cultured on brain heart infusion agar plates at 28°C for 48 hrs. Values in Figure represent total bacterial loads in infected organs (cfu/organ), or bacterial concentration in blood (cfu/ml). LOD, limit of detection. Horizontal bars represent the average value of bacterial load in each case. Differences in bacterial concentrations in blood and internal organs were analyzed by the non-parametric Mann-Whitney test.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2691952&req=5

pone-0005938-g002: Kim53ΔJ+P is deficient in dissemination to target organs and to the blood following subcutaneous infection.Mice were infected subcutaneously with 1×104 cfu of either Kim53pGFP (black symbols) or Kim53ΔJ+P (white symbols). Animals (4–5 per group) were sacrificed at 60 hours post-infection. Blood was collected, and the draining inguinal lymph nodes (ILN) and spleens were harvested, homogenized in 1 ml PBS and cultured on brain heart infusion agar plates at 28°C for 48 hrs. Values in Figure represent total bacterial loads in infected organs (cfu/organ), or bacterial concentration in blood (cfu/ml). LOD, limit of detection. Horizontal bars represent the average value of bacterial load in each case. Differences in bacterial concentrations in blood and internal organs were analyzed by the non-parametric Mann-Whitney test.
Mentions: Host immune cells may serve in vivo as a favorable intracellular niche and a shielding vehicle for plague bacilli [31], [32], [33]. It was therefore interesting to determine whether the avirulent phenotype of Kim53ΔJ+P is associated with the cytotoxic effect of YopP through interference with bacterial propagation and delivery to internal tissues. Accordingly, we monitored the colonization of internal organs by Kim53ΔJ+P compared to the Y. pestis Kim53pGFP control strain. Mice were subcutaneously infected with 1×104 cfu of each strain. Dissemination to draining inguinal lymph nodes (ILNs), the spleen and blood was examined 60 hours post-infection, a time point representing terminal stages of disease in Kim53pGFP-infected mice that served as controls. The number of colony forming units in the ILNs and the spleen of mice infected with Kim53ΔJ+P was about 100-fold lower than with the control Y. pestis strain (Figure 2). An even more pronounced disparity was observed in blood. Kim53ΔJ+P could not be detected in blood whereas the Y. pestis control strain reached an average concentration of 1×106 cfu/ml. Interestingly, despite the fact that colonization of the spleen in Kim53ΔJ+P-infected mice reaches substantial bacterial count (1×105 bacteria per spleen), the infection with high dose of Kim53ΔJ+P is not lethal (Figure 1D).

Bottom Line: Following subcutaneous infection, this strain had reduced ability to colonize internal organs, was unable to induce septicemia and exhibited at least a 10(7)-fold reduction in virulence.Yet, upon intravenous or intranasal infection, it was still as virulent as the wild-type strain.These observations have novel implications for the development of vaccines/therapies against Y. pestis and shed new light on the virulence strategies of Y. pestis in nature.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry and Molecular Genetics, Israel Institute for Biological Research, Ness-Ziona, Israel.

ABSTRACT
An important virulence strategy evolved by bacterial pathogens to overcome host defenses is the modulation of host cell death. Previous observations have indicated that Yersinia pestis, the causative agent of plague disease, exhibits restricted capacity to induce cell death in macrophages due to ineffective translocation of the type III secretion effector YopJ, as opposed to the readily translocated YopP, the YopJ homologue of the enteropathogen Yersinia enterocolitica Oratio8. This led us to suggest that reduced cytotoxic potency may allow pathogen propagation within a shielded niche, leading to increased virulence. To test the relationship between cytotoxic potential and virulence, we replaced Y. pestis YopJ with YopP. The YopP-expressing Y. pestis strain exhibited high cytotoxic activity against macrophages in vitro. Following subcutaneous infection, this strain had reduced ability to colonize internal organs, was unable to induce septicemia and exhibited at least a 10(7)-fold reduction in virulence. Yet, upon intravenous or intranasal infection, it was still as virulent as the wild-type strain. The subcutaneous administration of the cytotoxic Y. pestis strain appears to activate a rapid and potent systemic, CTL-independent, immunoprotective response, allowing the organism to overcome simultaneous coinfection with 10,000 LD(50) of virulent Y. pestis. Moreover, three days after subcutaneous administration of this strain, animals were also protected against septicemic or primary pneumonic plague. Our findings indicate that an inverse relationship exists between the cytotoxic potential of Y. pestis and its virulence following subcutaneous infection. This appears to be associated with the ability of the engineered cytotoxic Y. pestis strain to induce very rapid, effective and long-lasting protection against bubonic and pneumonic plague. These observations have novel implications for the development of vaccines/therapies against Y. pestis and shed new light on the virulence strategies of Y. pestis in nature.

Show MeSH
Related in: MedlinePlus