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Updated: Aug 15, 2026

Size Exclusion Chromatography to Analyze Bacterial Outer Membrane Vesicle Heterogeneity
Published on: March 31, 2021
Free-soluble and outer membrane vesicle-associated VacA from Helicobacter pylori: Two forms of release, a different
Vittorio Ricci1, Valentina Chiozzi, Vittorio Necchi
1Department of Experimental Medicine, Human Physiology Section, Pavia University, Pavia, Italy. vricci@unipv.it
Abstract:
Helicobacter pylori releases VacA both as free-soluble and as outer membrane vesicle (OMV)-associated toxin. In this study, we investigated the amount of VacA released in each of the two forms and the role of each form in VacA-induced cell vacuolation in vitro. We found that: (1) free-soluble toxin accounted for about 75% of released VacA, while the remaining 25% was OMV-associated; (2) although OMV-associated VacA caused a statistically significant vacuolation, virtually all the vacuolating activity of a H. pylori broth culture filtrate was due to free-soluble VacA. While it is widely accepted that OMVs may represent an important vehicle for delivering virulence factors to the gastric mucosa, our results suggest that OMV-associated VacA could play a pathobiological role different from that of free-soluble toxin. This conclusion fits with mounting evidence that VacA exerts a large pattern of pathobiological effects among which cell vacuolation might not be the main one.
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