Submitted to: Interscience Conference on Antimicrobial Agents & Chemotherapy Proceedings
Publication Type: Abstract only
Publication Acceptance Date: 7/18/2008
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: Background: Shiga toxin (Stx) binding to polymorphonuclear leukocytes (PMN) is hypothesized to play a role in the pathogenesis of Shiga toxin-producing Escherichia coli (STEC) disease in humans. Pigs are an excellent model for studying the role of PMN in STEC disease because, like humans, they are susceptible to Stx-mediated disease and Stx binds to porcine PMN in vitro. The objective of this study was to evaluate effects of Stx2 on the viability and oxidative burst of isolated porcine granulocytes. Methods: Binding and internalization of Stx2 or the non-toxic binding subunit of Stx2 (Stx2B) to granulocytes isolated from 4 healthy pigs, and the effects on granulocyte viability and oxidative burst were monitored by flow cytometry. Effects on granulocytes incubated with Stx2 were compared to effects on granulocytes incubated with Stx2B, with Stx2 or Stx2B pre-incubated with a monoclonal antibody against the B subunit, or with cell culture medium alone. Results: Granulocyte preparations contained PMN and eosinophils (EOS) that bound and internalized both Stx2 and Stx2B. Incubation with Stx2, but not with Stx2B , increased the mean percentage of apoptotic cells when compared to the medium control (PMN 82% vs. 37% and EOS 65% vs. 33%, respectively; p<0.001) and reduced the mean percentage of cells capable of an oxidative burst when compared to the medium control (PMN 32% vs. 82% and EOS 30% vs. 63%, respectively; p<0.001). Pre-incubation of Stx2 with monoclonal antibodies against the Stx2B prevented Stx2 binding and effects on apoptosis and oxidative burst. Conclusion:This study showing that Stx interacts with both porcine PMN and EOS extends the evidence that PMN may contribute to STEC pathogenesis. The porcine Stx-mediated disease model will facilitate further investigations on what role granulocytes play in STEC disease.