Activation Potential of Enteric Bacteriophages on the Intestinal Epithelium

Allison Hedin

Program: M.S. in Cell and Molecular Biology
Date: Friday, May 1, 2026
Time: 10:30am
Location: Donald P. Shiley BioScience Center (BSCI)
Zoom: https://SDSU.zoom.us/j/87845410205

Abstract

Enteric pathogens such as enteropathogenic and enterohemorrhagic Escherichia coli remain major causes of diarrheal mortality in children under five years of age, highlighting the need for novel therapeutics. Bacteriophages (phages) are being increasingly explored as alternative antimicrobials and could potentially be used for enteric infections due to their host specificity. Although lytic phages are promising candidates, important safety considerations remain. Much like conventional drug development, to ensure the safety of phage therapy we need to understand the interactions between phages and host cells. This includes whether viral particles elicit host responses, whether phages are sufficiently purified to remove toxic bacterial contaminants, and the potential for phage-microbe interactions to produce detrimental effects on the human host.

In this work, I developed alternative phage purification strategies to improve endotoxin removal and investigated how therapeutic phages influence the intestinal epithelium independent of bacterial killing. Two phages, CrRp3 and CrRp10, were purified and characterized for experimental and translational applications. These phages infect Citrobacter rodentiun, a murine model for enteropathogenic and enterohemorrhagic E. coli. Human intestinal epithelial cells were exposed to a high concentration of purified phages to assess uptake, transcriptional responses, and barrier integrity. Although phage-cell association occurred at low levels, phage exposure induced measurable transcriptional changes, including enrichment of pathways associated with barrier reinforcement and immune activation. These findings demonstrate that phages can directly modulate epithelial gene expression even in the absence of cytotoxicity.

To address concerns regarding phage resistance-associated virulence, C. rodentium strains resistant to CrRp3 were evaluated and did not exhibit enhanced virulence phenotypes. Collectively, this work demonstrates that therapeutic phages influence the intestinal environment beyond bacterial lysis. This observation underscores the importance of evaluating purification strategies and host epithelial responses, to ensure safe and effective phage therapy development.