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A Yersinia pestis tat mutant is attenuated in bubonic and small-aerosol pneumonic challenge models of infection but not as attenuated by intranasal challenge.

Bozue J, Cote CK, Chance T, Kugelman J, Kern SJ, Kijek TK, Jenkins A, Mou S, Moody K, Fritz D, Robinson CG, Bell T, Worsham P - PLoS ONE (2014)

Bottom Line: Deletion of the tatA gene resulted in several consequences for the mutant as compared to wild-type.In contrast, when mice were challenged intranasally with the mutant, very little difference in the LD50 was observed between wild-type and mutant strains.Collectively, these findings demonstrate an essential role for the Tat pathway in the virulence of Y. pestis in bubonic and small-aerosol pneumonic infection but less important role for intranasal challenge.

View Article: PubMed Central - PubMed

Affiliation: Bacteriology Division, The United States Army of Medical Research Institute of Infectious Diseases, Fort Detrick, Maryland, United States of America.

ABSTRACT
Bacterial proteins destined for the Tat pathway are folded before crossing the inner membrane and are typically identified by an N-terminal signal peptide containing a twin arginine motif. Translocation by the Tat pathway is dependent on the products of genes which encode proteins possessing the binding site of the signal peptide and mediating the actual translocation event. In the fully virulent CO92 strain of Yersinia pestis, the tatA gene was deleted. The mutant was assayed for loss of virulence through various in vitro and in vivo assays. Deletion of the tatA gene resulted in several consequences for the mutant as compared to wild-type. Cell morphology of the mutant bacteria was altered and demonstrated a more elongated form. In addition, while cultures of the mutant strain were able to produce a biofilm, we observed a loss of adhesion of the mutant biofilm structure compared to the biofilm produced by the wild-type strain. Immuno-electron microscopy revealed a partial disruption of the F1 antigen on the surface of the mutant. The virulence of the ΔtatA mutant was assessed in various murine models of plague. The mutant was severely attenuated in the bubonic model with full virulence restored by complementation with the native gene. After small-particle aerosol challenge in a pneumonic model of infection, the mutant was also shown to be attenuated. In contrast, when mice were challenged intranasally with the mutant, very little difference in the LD50 was observed between wild-type and mutant strains. However, an increased time-to-death and delay in bacterial dissemination was observed in mice infected with the ΔtatA mutant as compared to the parent strain. Collectively, these findings demonstrate an essential role for the Tat pathway in the virulence of Y. pestis in bubonic and small-aerosol pneumonic infection but less important role for intranasal challenge.

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Pathology of mice challenged intranasally with Y. pestis.A and B) Skull sections (4×) of a mouse challenged with the ΔtatA mutant (2,800 CFU). The mouse was moribund and euthanized on day 8 postchallenge. Note inflammation (indicated by *) that extends into the cranial vault and meninges. Panel A shows HE staining, and Panel B shows IHC staining with antibody to the F1 capsule. C) HE stained section from a mouse (2×) challenged with wild-type Y. pestis (5,500 CFU) that succumbed to infection on day 3 post challenge. In contrast to panel A, the inflammation for mice challenged with the wild-type strain, is contained in the inner ear area and did not extend into the brain (arrow). D and E) Lung sections of mice challenged intranasally with Y. pestis. Overall, lung lesion development and character are the same between strains with necrosuppurative inflammation surrounding large colonies of bacteria. Panel D is of a lung section stained with HE (20×) from a mouse challenged with the ΔtatA mutant. Panel E is of a lung section stained with HE (20×) challenged with wild-type Y. pestis. IE = inner ear; CRB = cerebrum.
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pone-0104524-g007: Pathology of mice challenged intranasally with Y. pestis.A and B) Skull sections (4×) of a mouse challenged with the ΔtatA mutant (2,800 CFU). The mouse was moribund and euthanized on day 8 postchallenge. Note inflammation (indicated by *) that extends into the cranial vault and meninges. Panel A shows HE staining, and Panel B shows IHC staining with antibody to the F1 capsule. C) HE stained section from a mouse (2×) challenged with wild-type Y. pestis (5,500 CFU) that succumbed to infection on day 3 post challenge. In contrast to panel A, the inflammation for mice challenged with the wild-type strain, is contained in the inner ear area and did not extend into the brain (arrow). D and E) Lung sections of mice challenged intranasally with Y. pestis. Overall, lung lesion development and character are the same between strains with necrosuppurative inflammation surrounding large colonies of bacteria. Panel D is of a lung section stained with HE (20×) from a mouse challenged with the ΔtatA mutant. Panel E is of a lung section stained with HE (20×) challenged with wild-type Y. pestis. IE = inner ear; CRB = cerebrum.

Mentions: Histologic examination of cranial sections of mice infected intranasally with the ΔtatA mutant (Fig. 7A) or the wild-type CO92 strain (Fig. 7C) showed severe middle ear involvement, which was usually bilaterally present. The high incidence of infection/inflammation of the inner and external ear canal was most likely related to the intranasal route of exposure. Lesions were characterized by necrosuppurative inflammation with marked bacterial colonization in the associated bone marrow within the tympanic bulla, inner ear, and/or external ear (Fig. 7A–C). Bacteria were confirmed to be Y. pestis through immuno-histochemical (IHC) staining with antibody to the F1 capsule which is specific for Y. pestis[56], [57] (Fig. 7B).


A Yersinia pestis tat mutant is attenuated in bubonic and small-aerosol pneumonic challenge models of infection but not as attenuated by intranasal challenge.

Bozue J, Cote CK, Chance T, Kugelman J, Kern SJ, Kijek TK, Jenkins A, Mou S, Moody K, Fritz D, Robinson CG, Bell T, Worsham P - PLoS ONE (2014)

Pathology of mice challenged intranasally with Y. pestis.A and B) Skull sections (4×) of a mouse challenged with the ΔtatA mutant (2,800 CFU). The mouse was moribund and euthanized on day 8 postchallenge. Note inflammation (indicated by *) that extends into the cranial vault and meninges. Panel A shows HE staining, and Panel B shows IHC staining with antibody to the F1 capsule. C) HE stained section from a mouse (2×) challenged with wild-type Y. pestis (5,500 CFU) that succumbed to infection on day 3 post challenge. In contrast to panel A, the inflammation for mice challenged with the wild-type strain, is contained in the inner ear area and did not extend into the brain (arrow). D and E) Lung sections of mice challenged intranasally with Y. pestis. Overall, lung lesion development and character are the same between strains with necrosuppurative inflammation surrounding large colonies of bacteria. Panel D is of a lung section stained with HE (20×) from a mouse challenged with the ΔtatA mutant. Panel E is of a lung section stained with HE (20×) challenged with wild-type Y. pestis. IE = inner ear; CRB = cerebrum.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4125294&req=5

pone-0104524-g007: Pathology of mice challenged intranasally with Y. pestis.A and B) Skull sections (4×) of a mouse challenged with the ΔtatA mutant (2,800 CFU). The mouse was moribund and euthanized on day 8 postchallenge. Note inflammation (indicated by *) that extends into the cranial vault and meninges. Panel A shows HE staining, and Panel B shows IHC staining with antibody to the F1 capsule. C) HE stained section from a mouse (2×) challenged with wild-type Y. pestis (5,500 CFU) that succumbed to infection on day 3 post challenge. In contrast to panel A, the inflammation for mice challenged with the wild-type strain, is contained in the inner ear area and did not extend into the brain (arrow). D and E) Lung sections of mice challenged intranasally with Y. pestis. Overall, lung lesion development and character are the same between strains with necrosuppurative inflammation surrounding large colonies of bacteria. Panel D is of a lung section stained with HE (20×) from a mouse challenged with the ΔtatA mutant. Panel E is of a lung section stained with HE (20×) challenged with wild-type Y. pestis. IE = inner ear; CRB = cerebrum.
Mentions: Histologic examination of cranial sections of mice infected intranasally with the ΔtatA mutant (Fig. 7A) or the wild-type CO92 strain (Fig. 7C) showed severe middle ear involvement, which was usually bilaterally present. The high incidence of infection/inflammation of the inner and external ear canal was most likely related to the intranasal route of exposure. Lesions were characterized by necrosuppurative inflammation with marked bacterial colonization in the associated bone marrow within the tympanic bulla, inner ear, and/or external ear (Fig. 7A–C). Bacteria were confirmed to be Y. pestis through immuno-histochemical (IHC) staining with antibody to the F1 capsule which is specific for Y. pestis[56], [57] (Fig. 7B).

Bottom Line: Deletion of the tatA gene resulted in several consequences for the mutant as compared to wild-type.In contrast, when mice were challenged intranasally with the mutant, very little difference in the LD50 was observed between wild-type and mutant strains.Collectively, these findings demonstrate an essential role for the Tat pathway in the virulence of Y. pestis in bubonic and small-aerosol pneumonic infection but less important role for intranasal challenge.

View Article: PubMed Central - PubMed

Affiliation: Bacteriology Division, The United States Army of Medical Research Institute of Infectious Diseases, Fort Detrick, Maryland, United States of America.

ABSTRACT
Bacterial proteins destined for the Tat pathway are folded before crossing the inner membrane and are typically identified by an N-terminal signal peptide containing a twin arginine motif. Translocation by the Tat pathway is dependent on the products of genes which encode proteins possessing the binding site of the signal peptide and mediating the actual translocation event. In the fully virulent CO92 strain of Yersinia pestis, the tatA gene was deleted. The mutant was assayed for loss of virulence through various in vitro and in vivo assays. Deletion of the tatA gene resulted in several consequences for the mutant as compared to wild-type. Cell morphology of the mutant bacteria was altered and demonstrated a more elongated form. In addition, while cultures of the mutant strain were able to produce a biofilm, we observed a loss of adhesion of the mutant biofilm structure compared to the biofilm produced by the wild-type strain. Immuno-electron microscopy revealed a partial disruption of the F1 antigen on the surface of the mutant. The virulence of the ΔtatA mutant was assessed in various murine models of plague. The mutant was severely attenuated in the bubonic model with full virulence restored by complementation with the native gene. After small-particle aerosol challenge in a pneumonic model of infection, the mutant was also shown to be attenuated. In contrast, when mice were challenged intranasally with the mutant, very little difference in the LD50 was observed between wild-type and mutant strains. However, an increased time-to-death and delay in bacterial dissemination was observed in mice infected with the ΔtatA mutant as compared to the parent strain. Collectively, these findings demonstrate an essential role for the Tat pathway in the virulence of Y. pestis in bubonic and small-aerosol pneumonic infection but less important role for intranasal challenge.

Show MeSH
Related in: MedlinePlus