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Yersinia pseudotuberculosis Blocks Neutrophil Degranulation
Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR). Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). (Anna Fahlgren)
Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR). Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR). Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS). Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
2016 (English)In: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 84, no 12, p. 3369-3378Article in journal (Refereed) Published
Abstract [en]

Neutrophils are essential components of immunity and are rapidly recruited to infected or injured tissue. Upon their activation, neutrophils release granules to the cell's exterior, through a process called degranulation. These granules contain proteins with antimicrobial properties that help combat infection. The enteropathogenic bacterium Yersinia pseudotuberculosis successfully persists as an extracellular bacterium during infection by virtue of its translocation of virulence effectors (Yersinia outer proteins [Yops]) that act in the cytosol of host immune cells to subvert phagocytosis and proinflammatory responses. Here, we investigated the effect of Y. pseudotuberculosis on neutrophil degranulation upon cell contact. We found that virulent Y. pseudotuberculosis was able to prevent secondary granule release. The blocking effect was general, as the release of primary and tertiary granules was also reduced. Degranulation of secondary granules was also blocked in primed neutrophils, suggesting that this mechanism could be an important element of immune evasion. Further, wild-type bacteria conferred a transient block on neutrophils that prevented their degranulation upon contact with plasmid-cured, avirulent Y. pseudotuberculosis and Escherichia coli Detailed analyses showed that the block was strictly dependent on the cooperative actions of the two antiphagocytic effectors, YopE and YopH, suggesting that the neutrophil target structures constituting signaling molecules needed to initiate both phagocytosis and general degranulation. Thus, via these virulence effectors, Yersinia can impair several mechanisms of the neutrophil's antimicrobial arsenal, which underscores the power of its virulence effector machinery.

Place, publisher, year, edition, pages
2016. Vol. 84, no 12, p. 3369-3378
Keywords [en]
Yersinia, neutrophil, degranulation
National Category
Immunology Microbiology Other Biological Topics
Identifiers
URN: urn:nbn:se:umu:diva-128892DOI: 10.1128/IAI.00760-16ISI: 000390128700011PubMedID: 27620724OAI: oai:DiVA.org:umu-128892DiVA, id: diva2:1057550
Available from: 2016-12-19 Created: 2016-12-19 Last updated: 2019-01-18Bibliographically approved
In thesis
1. Host-pathogen interactions during Campylobacter and Yersinia infections
Open this publication in new window or tab >>Host-pathogen interactions during Campylobacter and Yersinia infections
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The innate immune system is known for protecting the host against invading pathogens, for instance enteropathogens infecting the gastrointestinal tract. The production of e.g. antimicrobial peptides, cytokines, and chemokines by innate immune cells and intestinal epithelial cells contribute to bacterial clearance. Given the significance of this system in overall defense, pathogens affect and/or manipulate immune cells and responses in favor of their own survival. This thesis focuses on how the Gram-negative enteropathogenic bacteria Yersinia pseudotuberculosis and Campylobacter jejuni affect the host, either directly via type 3 secretion system (T3SS) effector proteins or via outer membrane vesicles (OMVs), and how host factors potentially affect their virulence.

Yersinia pseudotuberculosis uses its T3SS to translocate virulence factors that disable various immune responses and subvert phagocytosis. Neutrophils are main target cells during Yersinia infection. They release granules that contain proteins with antimicrobial properties to the cell's exterior upon activation through a process called degranulation. We found that extracellular Y. pseudotuberculosis could prevent neutrophil degranulation upon cell contact. Prevention of degranulation was shown to be mediated via co-operative actions of the two anti-phagocytic Yersinia outer proteins YopH and YopE. Bacterial contact with neutrophils resulted in a transient inhibition of degranulation and further prevented degranulation upon subsequent contact with avirulent Y. pseudotuberculosis (lacking YopE and YopH) as well as Escherichia coli. Thus, Y. pseudotuberculosis impairs several neutrophil defense mechanisms to remain in the extracellular environment and to increase its survival during infection.

Campylobacter jejuni lacks a T3SS and appears to use OMVs and flagella as its main secretion apparatus. During passage through the intestine C. jejuni is exposed to bile, an important physiological component and part of the natural barrier of the intestine, and ability to resist bile is advantageous for C. jejuni survival. We investigated how C. jejuni OMV production and protein content is affected by bile. The main invasion and colonization of C. jejuni occurs in the lower part of the intestine where the concentration of bile is low compared with the proximal intestine. The OMV proteomic profiles were radically altered when bacteria were grown in low concentration of bile corresponding to cecal concentrations. Twenty-five present of the detected proteins of OMVs showed an altered abundance in the presence of low concentration of bile. In contrast, the overall proteome of the bacteria was unaffected. Moreover, OMVs frombile-exposed bacteria could enhance adhesion as well as invasion of bacteria into intestinal epithelial cells, suggesting a role of OMVs to the virulence of C. jejuni in the gut. The body temperature differs between the asymptomatic avian carriers of C. jejuni and humans, which develop symptomatic disease. We investigated whether the bacterial growth temperature affects the OMV proteome and found that 59 proteins were differentially expressed at 37°C. Among the higher abundant proteins, significantly more proteins were predicted to be related to virulence. Thus, temperature has an impact on the property of the OMVs, and this might affect the outcome of infection by C. jejuni in different hosts.

C. jejuni OMV interactions with innate immune cells were studied by analyses of OMV-mediated inflammasome activation. OMVs were found to induce ASC- and caspase-1-dependent inflammasome activation in murine and human macrophages and dendritic cells as well as in human neutrophils. While C. jejuni infection induced a low level of inflammasome-dependent cell death, OMV-induced inflammasome activation did not result in cell death. Thus, OMVs disseminate into tissue without bacteria can be a vehicle for virulence factors without inducing inflammatory cell death.

Place, publisher, year, edition, pages
Umeå: Umeå University, 2019. p. 79
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 2005
Keywords
Campylobacter jejuni, Yersinia pseudotuberculosis, OMV, bile, temperature, proteomic
National Category
Biochemistry and Molecular Biology Microbiology Immunology
Identifiers
urn:nbn:se:umu:diva-155504 (URN)978-91-7855-003-6 (ISBN)
Public defence
2019-02-15, Hörsal D Unod T9, NUS, Umeå, 09:00 (English)
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Available from: 2019-01-25 Created: 2019-01-18 Last updated: 2019-01-29Bibliographically approved

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Taheri, NayyerFahlgren, AnnaFällman, Maria

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