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Updated: Nov 14, 2025
Legionella pneumophila Outer Membrane Vesicles: Isolation and Analysis of Their Pro-inflammatory Potential on Macrophages
Published on: February 22, 2017
Outer membrane vesicles derived from hypervirulent Klebsiella pneumoniae stimulate the inflammatory response
Jing Zhang1, Jinxin Zhao1, Jiaxi Li1
1Department of Laboratory Medicine, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China.
Abstract:
Hypervirulent Klebsiella pneumoniae (hvKP), an increasing important pathotype, was initially recognized as a cause of severe liver abscesses and subsequently as a cause of other complications posing a clinical threat. Outer membrane vesicles (OMVs) secreted from abundant gram-negative bacteria are considered an important vehicle for delivery of effector molecules to target cells. However, the products and role in bacterial pathogenesis of OMVs secreted from hvKP, have not yet been determined. In order to examine the production of OMVs from hvKP and to determine their effects on the stimulation of the host innate immune response, we used ultracentrifugation to obtain homogeneous OMVs from hvKP ATCC 1706 cultured in vitro. Proteomic analysis was performed and hvKP OMVs were found to contain diverse proteins. Furthermore, hvKP OMVs exhibited discrepant cytotoxic effects on different cell types, in vitro. The vesicles induced the expression of proinflammatory cytokines including interleukin (IL)-6 and IL-8 in host cells. In addition, transtracheal injection of hvKP OMVs in wild-type mice led to an inflammatory response manifested by elevated levels of pro-inflammatory mediators including IL-6, IL-8 and TNF-α in bronchoalveolar lavage fluid (BAL), in accord with in vitro experiments. However, hvKP OMVs were insufficient to kill mice. In summary, OMVs originating from hvKP may serve to provoke the inflammatory response.
Insights
Outer membrane vesicles (OMVs) from hypervirulent Klebsiella pneumoniae (hvKP) provoke inflammation by inducing cytokines like IL-6 and IL-8. These bacterial OMVs contribute to pathogenesis but are not directly lethal.
Area of Science:
- Microbiology
- Immunology
- Pathogenesis
Background:
- Hypervirulent Klebsiella pneumoniae (hvKP) is a significant pathogen causing severe infections.
- Outer membrane vesicles (OMVs) are key mediators of bacterial communication and pathogenesis.
- The specific role and composition of OMVs from hvKP remain largely unknown.
Purpose of the Study:
- To investigate the production and protein content of OMVs from hvKP.
- To determine the effects of hvKP OMVs on host innate immune responses in vitro and in vivo.
- To elucidate the contribution of hvKP OMVs to bacterial pathogenesis.
Main Methods:
- Isolation of homogeneous OMVs from hvKP ATCC 1706 using ultracentrifugation.
- Proteomic analysis to identify proteins within hvKP OMVs.
- In vitro cell culture assays to assess cytotoxicity and cytokine induction.
- In vivo transtracheal injection in wild-type mice to evaluate inflammatory responses.
Main Results:
- Proteomic analysis revealed diverse proteins within hvKP OMVs.
- hvKP OMVs demonstrated differential cytotoxic effects on various cell types.
- OMVs induced the expression of pro-inflammatory cytokines (IL-6, IL-8) in host cells.
- In vivo, hvKP OMVs triggered an inflammatory response with elevated mediators (IL-6, IL-8, TNF-α) in mouse lungs.
- hvKP OMVs alone were not sufficient to cause mortality in mice.
Conclusions:
- hvKP-derived OMVs contain a variety of proteins.
- These OMVs play a role in stimulating host inflammatory responses.
- hvKP OMVs contribute to the pathogenesis of hvKP infections by modulating the innate immune system.
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