Exploring The Potential Adjuvant Role Of Bacterial Extracellular Vesicles Derived From Bifidobacterium Pseudocatenulatum Strains

Jordan, Anne (2025) Exploring The Potential Adjuvant Role Of Bacterial Extracellular Vesicles Derived From Bifidobacterium Pseudocatenulatum Strains. Doctoral thesis, University of East Anglia.

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Abstract

Bifidobacterium is a known microbiota determinant of early-life immune function and overall health. Many studies have reported the multifaceted immune stimulatory and regulatory properties of different Bifidobacterium strains. However, little research has investigated the potential for immune modulation by bacterial extracellular vesicles (BEVs) derived from Bifidobacterium. In this project, I focused on understanding BEV production and potential immune stimulation of BEVs derived from two strains belonging to a key but understudied early-life microbiota species – Bifidobacterium pseudocatenulatum.

I determined bacterial growth conditions for optimal BEV harvesting time points via CFU and OD growth assays. Following optimisation of bifidobacterial BEV purification, I evaluated several biophysiological properties and proteomic load of BEV batches, showing abundance of different potentially immunostimulatory proteins in a BEV preparation-dependent manner. Moreover, I confirmed uptake of BEVs into the epithelial barrier and potential underlying endocytosis pathways in Caco-2 cells using confocal microscopy. In vitro studies, using different cell lines, indicated potential modulation of the intestinal barrier via TJ gene induction, stimulation of the NF-κB pathway, production of TNF-α, IL-1β, IL-10, IL-6, IL-8, and TSLP in human monocytes and macrophages. Additionally, I performed ex vivo characterisations, including stimulation of murine splenocytes, resulting in production of IL-6, KC, and TNF-α, confirming potential immunostimulation by bifidobacterial BEVs. Further investigations, using additional in vitro and ex vivo studies, resulted in induced production of TNF-α in human PBMCs, and IgA production in murine Peyer’s patch fragments in a strain- and time point-dependent manner. Simulation of an infection, using LPS, showed evidence for protective properties of bifidobacterial BEVs in cultured epithelial cells and macrophages. To date, there are limited studies on bifidobacterial BEVs, and no studies on BEVs derived from B. pseudocatenulatum strains have been undertaken. These data may provide insights into the potential immunostimulatory and protective properties of products from health-promoting B. pseudocatenulatum, which could facilitate development of novel immune adjuvants.

Item Type:	Thesis (Doctoral)
Faculty \ School:	Faculty of Science > School of Biological Sciences
Depositing User:	Chris White
Date Deposited:	23 Feb 2026 12:02
Last Modified:	23 Feb 2026 12:02
URI:	https://ueaeprints.uea.ac.uk/id/eprint/102008
DOI:

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