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Legionella pneumophila Outer Membrane Vesicles: Isolation and Analysis of Their Pro-inflammatory Potential on Macrophages
Published on: February 22, 2017
Outer Membrane Vesicles Attenuate Klebsiella pneumoniae Infection Injury by Affecting Macrophage Polarisation and
Wei Fan1, Wei Wang1, Lin Kong1
1Department of Veterinary Medicine, College of Agricultural, Yanbian University, Yanji 133002, China.
Abstract:
Klebsiella pneumoniae (K. pneumoniae) is an opportunistic bacteria that can result in severe liver abscesses, pulmonary damage, and potentially fatal outcomes. Research has demonstrated that the outer membrane vesicles (OMVs) released by it can provide significant protection to infected animals and may serve as a promising candidate antigen for the development of a novel vaccine. Nevertheless, the specific mechanisms through which OMVs mitigate the detrimental effects of K. pneumoniae infection by promoting the polarization pathways of macrophages and T helper cells (Th cells) remain poorly understood. In this study, we first confirmed that Klebsiella pneumoniae outer membrane vesicles (K. pneumoniae_OMVs) were protective in K. pneumoniae-infected mice, and then we investigated the protective mechanisms by transcriptome data analysis. Then, we constructed a model of in vitro macrophage polarization, an in vivo model for Th differentiation, and a K. pneumoniae infection model in K. pneumoniae_OMVs-immunized mice. qRT-PCR, IHC, Western blotting, and ELISA were used to confirm the polarization indicators. The results showed that K. pneumoniae_OMVs were able to provide specific protection for mice with a maximum protection rate of 80%. In addition, the results of a transcriptome analysis suggested that the protective mechanism might be related to Th cells and macrophage polarization. Mice immunized with K. pneumoniae_OMVs were able to achieve rapid bacterial clearance after K. pneumoniae infection through an M1/Th1 immune response. Subsequently, tissue repair was accomplished through Th2/M2 immune response in the late stage of K. pneumoniae infection to avoid causing inflammatory damage. This study offers a theoretical foundation for the K. pneumoniae_OMVs vaccine's actual application.
Insights
Outer membrane vesicles (OMVs) from Klebsiella pneumoniae protect mice against infection by modulating macrophage and T helper cell responses. This study reveals OMVs promote early bacterial clearance and later tissue repair, supporting their vaccine potential.
Area of Science:
- Immunology
- Microbiology
- Vaccinology
Background:
- Klebsiella pneumoniae causes severe infections, and its outer membrane vesicles (OMVs) show protective potential.
- The precise mechanisms by which K. pneumoniae OMVs confer protection, particularly regarding immune cell polarization, are not fully understood.
Purpose of the Study:
- To investigate the protective mechanisms of K. pneumoniae OMVs in mice.
- To elucidate how K. pneumoniae OMVs influence macrophage and T helper cell polarization during infection.
Main Methods:
- Transcriptome analysis, in vitro macrophage polarization models, in vivo Th differentiation models, and K. pneumoniae infection models in OMV-immunized mice.
- Quantitative reverse transcription PCR (qRT-PCR), immunohistochemistry (IHC), Western blotting, and ELISA were employed to assess immune responses.
Main Results:
- K. pneumoniae OMVs provided up to 80% protection in infected mice.
- Transcriptome data indicated a role for T helper (Th) cells and macrophage polarization in the protective effects.
- OMV immunization led to rapid bacterial clearance via M1/Th1 responses and subsequent tissue repair through Th2/M2 responses, mitigating inflammation.
Conclusions:
- K. pneumoniae OMVs induce a biphasic immune response, crucial for combating infection and promoting recovery.
- This study provides a theoretical basis for developing K. pneumoniae OMVs as a vaccine candidate.
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