Poster Presentation 14th Lorne Infection and Immunity 2024

The Helicobacter pylori autotransporter ImaA associates with extracellular vesicles to modulate host immune responses (#125)

Angus Cramond 1 2 , Jack Emery 1 2 , Nina Colon 2 , Dongmei Tong 2 , Caroline Skene 2 , Richard Ferrero 1 2 3
  1. Department of Molecular and Translational Science, Monash University, Clayton, Vic, Australia
  2. Centre for Innate Immunity and Infectious Diseases, Hudson Institute of Medical Research, Clayton, VIC, Australia
  3. Department of Microbiology, Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia

Helicobacter pylori produces four autotransporter proteins, which use a conserved beta barrel to transport passenger domains through the bacterial membrane. Each H. pylori autotransporter protein has a distinct passenger domain, but with the exception of the vacuolating cytotoxin, VacA, these autotransporters remain largely unstudied. Previous work on the H. pylori autotransporter ImaA found that imaA knockout bacteria induce stronger IL-8 responses in gastric epithelial cells (AGS), suggesting ImaA may be an immunomodulatory protein. Proteomic studies showed that H. pylori ImaA associates with extracellular vesicles (EVs) which are known to induce inflammatory responses in host cells. Thus, we hypothesised that EVs containing ImaA may be able to modulate host responses. To address this hypothesis, we generated H. pylori imaA mutant bacteria then isolated EVs from these and the corresponding WT bacteria. Nanoparticle tracking analysis showed that these imaA and WT EVs have similar particle sizes (median sizes 95 and 100 nm, respectively). Next, we stimulated AGS cells with WT and imaA EVs. We found imaA EVs induced weaker IL-8 responses than WT EVs (3.4- and 2.6-fold change from unstimulated for WT and imaA EVs, respectively). To investigate the immunomodulatory effects of ImaA in vivo, mice were vaccinated on days 0 and 28 with H. pylori WT or imaA EVs, or PBS, then euthanised on day 56. Splenocytes from mice that were vaccinated with either H. pylori WT or imaA EVs ex vivo showed reduced IFN‑γ and IL-17 responses to ConA stimulation ex vivo relative to splenocytes from unvaccinated mice, suggesting both EVs suppress Th1 and Th17 responses. Taken together, we propose that H. pylori ImaA contributes to the pro-inflammatory effects of EVs on epithelial cells. Further work is, however, required to understand the role of EV-associated ImaA in vivo.