Mycobacterial Membrane Vesicles in Immunomodulation

Abstract

Release of extracellular vesicles is an evolutionarily conserved trait present among all life forms. Bacterial extracellular vesicles are released in the extracellular space to interact with the surrounding environment. The vesicles are known to be involved in cell-cell, intra species communication and produced in response to stress. Recently, emerging evidence of virulence factors present in vesicles blebbed out of pathogenic mycobacterial strain were reported.
In this study, isolation of mycobacterial extracellular vesicles (MEVs) released by Mycobacterium bovis bacillus Calmette Guerin (BCG) in a chemically defined minimal medium (n-MEVs) was performed. Additionally, vesicles released in response to sub-inhibitory concentration of first-line TB antibiotics (Isoniazid (i-MEVs) and Ethambutol (e-MEVs)), treated on BCG in the minimal medium were isolated and quantified. The n-MEVs were highly immunogenic whereas, the later induced mild inflammation, recorded from a monocyte derived cell line containing NF-κB reporter. Furthermore, NZX, an antimicrobial peptide (AMP) that showed bactericidal effect against clinical isolates of various mycobacteria, was used in combination with MEVs to assess the effect of the peptide against immunogenic MEVs. Although a trend showed decrease in inflammation, the effect was not significant against n-MEVs. In case of antibiotic-induced vesicles, the effect of NZX on highest dilution of i-MEVs and e-MEVs appears to have a mild impact. Although, the effect of NZX was not significant and couldn’t be distinguished as the MEVs inflammatory response was low.
Overall, further studies need to be done to assess the content and immunogenicity of MEVs released under different conditions to aid in definition of potential immunomodulatory effects.

Popular Abstract

Extracellular Vesicles – A key in Tuberculosis?


Is the age-old foe, Tuberculosis (TB) still in prevalence? Indeed, the TB has efficiently maneuvered interactions with host to ensure survival and humans are its only known reservoir. WHO reports TB as the deadliest disease, that affects around one-fourth of the word population whose causative agent is Mycobacterium tuberculosis (MTB).

WHO strategized to eradicate TB by 2035 however, the pandemic COVID-19 led to the disruption in the progress made all over the world. Despite years of vaccination and antibiotic therapy, TB accounts for higher mortality rate than HIV/AIDS. However, majority of the infected individual contain the infection in the latent form where the disease progression is contained and only 5-10% of affected population gets active infection. Besides, the TB therapy lasts for six months and incorporates four drugs that are prominently administered. In spite of efficient host mechanism and potent therapeutics, what contributes to the unending burden of TB on incidence and mortality rate? One of the potential factors is the ability of the bacteria to communicate with the surrounding. Signaling molecules and bacterial extracellular vesicles (BEVs) released by bacteria in the extracellular space could play a role to aid in survival. BEVs are lipid vesicles released by living bacteria that encloses cargo component which includes lipids, protein, metabolites and toxin and has potent to mediate cell-cell communication.

In this project, we investigated BEVs released by Mycobacterium bovis bacillus Calmette-Guérin (BCG), an organism belonging to MTB complex. Two different stress inducing environment were employed to isolate mycobacterium released extracellular vesicles (MEVs) and were characterized based on the size, concentration and visualized in electron microscopy to confirm its presence. Further, we assessed the immunogenic potentials of MEVs in human derived monocyte cell lines to understand if the MEVs could cause effect on immune response. Previously, our group has proved the effectiveness of an antimicrobial peptide NZX against broad spectrum of mycobacterial strains, including clinical isolates. Out of curiosity, we employed the treatment of NZX on potent immunogenic vesicles to assess for therapeutic effect. Further studies need to be conducted to understand the impact of MEVs in the host environment.

From the thesis entitled Mycobacterial Membrane Vesicles in Immunomodulation performed at the department of Medical Microbiology under the supervision of Gabriela Godaly.

• author: Santhana Krishnan, Niviyah
• supervisor: Gabriela Godaly
• organization: Degree Projects in Molecular Biology
• course: MOBN03 20212
• year: 2022
• type: H2 - Master's Degree (Two Years)
• subject: Biology and Life Sciences
• language: English
• id: 9085341
• date added to LUP: 2022-06-08 11:31:54
• date last changed: 2022-06-08 11:31:54