Poster X18 - Developing probiotic bacterial extracellular vesicles for oral delivery of biologics to treat inflammatory bowel disease

Introduction: Probiotic bacterial extracellular vesicles (BEVs) have emerged as a promising alternative to live microbiome therapeutics for treatment of inflammatory diseases. Probiotic BEVs are cell-secreted membrane nanovesicles that contain abundant protein and RNA cargo and can be administered in a “drug-like” fashion with more reliable PK/PD compared to live therapies. After administration, probiotic BEVs offer cargo protection from degradation in harsh environments and delivery across biologic barriers to reach target cells. Furthermore, probiotic BEVs can potentially be loaded with designer therapeutic cargo for delivery to a variety of tissues. Thus, probiotic BEVs hold potential as both standalone therapeutics and as engineered drug delivery vehicles.

Materials and

Methods: Our lab has found probiotic BEVs derived from several species of lactic acid bacteria (LAB; historically, Lactobacillus) are particularly effective treatments in the dextran sodium sulfate (DSS) mouse model of colitis. In our model, oral gavage of LAB BEVs produced superior therapeutic efficacy compared to both BEV-depleted probiotic conditioned media and BEVs secreted by a probiotic strain of Escherichia coli (Nissle 1917). Additionally, qPCR and flow cytometry analysis reveal probiotic BEVs (i) increase regulatory T cells and limit inflammatory responses (e.g., IFNy, IL-1β, TNF-α), and (ii) increase genes related to epithelial barrier integrity (E-cadherin, IL-22). Finally, we conducted a screen of LAB BEVs using an in vitro human macrophage cytokine release assay and the DSS colitis mouse model and found specific species of LAB BEVs with more potent therapeutic efficacy.

Results, Conclusions, and Discussions: Our current hypothesis surrounding LAB BEV’s therapeutic effects is that orally-administered LAB BEVs deliver their constituent cargo to GI tissues, with primary recipient cells being mucosal immune cells and epithelial cells. Establishing this mechanism would have significant implications for oral delivery of biologics, especially since BEVs can potentially be loaded with designer recombinant therapeutic cargo. To test this hypothesis, we have demonstrated LAB BEVs (i) accumulate in GI tissues after oral administration, (ii) protect biologic cargo in simulated GI fluids and (iii) cross a model human GI barrier comprised of co-culture of Caco-2 epithelial cells and mucus-producing HT29-MTX cells. Our current work is focused on further investigating mucosal delivery of biologics after oral administration and engineering probiotic BEVs for designer cargo loading to ultimately develop a therapeutic for inflammatory bowel disease.

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