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Updated: Aug 2, 2026
An In vitro Model to Study Immune Responses of Human Peripheral Blood Mononuclear Cells to Human Respiratory Syncytial Virus Infection
Published on: December 10, 2013
Yields and Immunomodulatory Effects of Pneumococcal Membrane Vesicles Differ with the Bacterial Growth Phase
Mina Mehanny1,2,3, Tobias Kroniger4, Marcus Koch5
1Helmholtz Institute for Pharmaceutical Research Saarland, Biogenic Nanotherapeutics Group, Campus E8.1, Saarbrücken, 66123, Germany.
Abstract:
Streptococcus pneumoniae infections are a leading cause of death worldwide. Bacterial membrane vesicles (MVs) are promising vaccine candidates because of the antigenic components of their parent microorganisms. Pneumococcal MVs exhibit low toxicity towards several cell lines, but their clinical translation requires a high yield and strong immunogenic effects without compromising immune cell viability. MVs are isolated during either the stationary phase (24 h) or death phase (48 h), and their yields, immunogenicity and cytotoxicity in human primary macrophages and dendritic cells have been investigated. Death-phase vesicles showed higher yields than stationary-phase vesicles. Both vesicle types displayed acceptable compatibility with primary immune cells and several cell lines. Both vesicle types showed comparable uptake and enhanced release of the inflammatory cytokines, tumor necrosis factor and interleukin-6, from human primary immune cells. Proteomic analysis revealed similarities in vesicular immunogenic proteins such as pneumolysin, pneumococcal surface protein A, and IgA1 protease in both vesicle types, but stationary-phase MVs showed significantly lower autolysin levels than death-phase MVs. Although death-phase vesicles produced higher yields, they lacked superiority to stationary-phase vesicles as vaccine candidates owing to their similar antigenic protein cargo and comparable uptake into primary human immune cells.
Insights
Bacterial membrane vesicles (MVs) from Streptococcus pneumoniae show potential as vaccine candidates. While death-phase MVs offer higher yields, stationary-phase MVs are equally effective due to similar immunogenic proteins and uptake.
Area of Science:
- Microbiology
- Immunology
- Vaccine Development
Background:
- Streptococcus pneumoniae infections cause significant global mortality.
- Bacterial membrane vesicles (MVs) are explored as vaccine candidates due to their antigenic properties.
- Pneumococcal MVs require high yield and immunogenicity without compromising immune cell viability for clinical use.
Purpose of the Study:
- To compare the yield, immunogenicity, and cytotoxicity of MVs isolated from stationary-phase (24h) and death-phase (48h) cultures of Streptococcus pneumoniae.
- To evaluate the potential of these MVs as vaccine candidates.
Main Methods:
- Isolation of MVs from stationary and death phases of bacterial growth.
- Assessment of MV yield, cytotoxicity in cell lines and primary human macrophages/dendritic cells.
- Analysis of cytokine release (TNF-α, IL-6) from immune cells upon MV exposure.
- Proteomic analysis of MVs to identify key immunogenic proteins.
Main Results:
- Death-phase MVs exhibited higher yields than stationary-phase MVs.
- Both MV types demonstrated acceptable compatibility with immune cells and cell lines.
- Comparable uptake and enhanced inflammatory cytokine release (TNF-α, IL-6) were observed for both MV types.
- Proteomic analysis revealed similar key antigenic proteins (e.g., pneumolysin, PspA) but lower autolysin levels in stationary-phase MVs.
Conclusions:
- Despite higher yields, death-phase MVs did not show superiority over stationary-phase MVs as vaccine candidates.
- Similar antigenic protein composition and immune cell uptake contribute to comparable efficacy.
- Stationary-phase MVs may be preferable due to lower autolysin levels, warranting further investigation.
