Shiga Toxin 1 fromEscherichia coliBlocks Activation and Proliferation of Bovine Lymphocyte Subpopulations In Vitro

Abstract

Shiga toxin-producing Escherichia coli (STEC) is widespread in the cattle population, but the clinical significance of Shiga toxins (Stx’s) for the bovine species remains obscure. Since Stx’s exert immunomodulating effects in other species, we examined the effect of purified Stx1 on a bovine B lymphoma cell line (BL-3) and peripheral blood mononuclear cells (PBMC) isolated from adult bovine blood by viability assays and flow cytometry analysis. Stx1 markedly induced apoptosis in stimulated BL-3 cells. The susceptibility of this B-cell-derived cell line was induced only by either lipopolysaccharide (LPS) or pokeweed mitogen, while cultures stimulated with T-cell mitogens were unaffected by the toxin. In contrast, Stx1 did not induce cellular death—neither apoptosis nor necrosis—in primary cultures of PBMC but hindered the mitogen-induced increase in metabolic activity. The influence of Stx1 on single PBMC subpopulations varied with the type of mitogenic stimulus applied. Stimulation with phytohemagglutinin P particularly induced the proliferation of bovine CD8-expressing (BoCD8+) cells, and this proliferative response was blocked by Stx1. On the other hand, Stx1 reduced the portion of viable B cells in the presence of LPS. Modulation of activation marker expression (BoCD25 and BoCD71) by Stx1 indicated that the toxin hindered the proliferation of cells by blocking their activation. In conclusion, we assume that Stx1 contributes to the pathogenesis of STEC-associated diarrhea in calves by suppressing the mucosa-associated immune response. The usefulness of cattle as a model in which to study Stx-induced immunomodulation is discussed.

A systematic review and meta-analysis of the epidemiology of pathogenic Escherichia coli of calves and the role of calves as reservoirs for human pathogenic E. coli

“…The high prevalence of STEC, EPEC, and EHEC in healthy and diarrheic animals shows, that these animals can be considered as reservoirs for human pathogenic E. coli. The role of STEC, EPEC, and EHEC as causative agents of diarrhea in calves have been widely investigated (Dean-Nystrom et al, 1998;Menge et al, 1999;Pruimboom-Brees et al, 2000;Hoey et al, 2002). Lack of Stx receptor in vascular endothelium makes cattle a perfect candidate as a reservoir of STEC/EHEC as it is not possible for them to develop systemic disease.…”

“…Lack of Stx receptor in vascular endothelium makes cattle a perfect candidate as a reservoir of STEC/EHEC as it is not possible for them to develop systemic disease. Other actions of STEC/EHEC like immunomodulation (Menge et al, 1999) and intestinal colonization (Etcheverría and Padola, 2013) help them to survive and propagate in the host intestine. Major questions remain to be answered as to whether these processes contribute to pathogenesis of diarrhea.…”

Non‐O157 Shiga Toxin‐producing Escherichia coli Isolated from Diarrhoeic Calves in Argentina

“…Similarly to previous studies in which stx 1 -positive STEC has been more frequently associated with diarrhoeic calves than stx 2 -positive STEC (Wieler et al, 1996), we have found that the majority (80.0%) of the STEC strains recovered harboured the stx 1 gene. Recently, Menge et al (1999) have reported that Stx1 seems to contribute to the pathogenesis of STEC-associated diarrhoea in calves by suppressing the mucosa-associated immune response. Otherwise, epidemiological studies suggested that patients with the most severe forms of the disease, including renal and extra-renal symptoms, were generally infected with Stx1-Stx2-producing or Stx2-producing E. coli (Scotland et al, 1987;Lo´pez et al, 1998).…”

Telithromycin inhibits the production of proinflammatory mediators and the activation of NF-κB inin vitro-stimulated murine cells

“…3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide by mitochondrial enzymes in viable cells (Menge et al, 1999). The cellular metabolic activity was not affected by telithromycin in a concentration range from 2.5 to 10 mg mL À1 even when the cells were incubated with the ketolide for 24 h (data not shown).…”