Submitted to: Infection and Immunity
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/26/2008
Publication Date: 11/20/2008
Citation: Stamm, I., Mohr, M., Bridger, P., Schropfer, E., Konig, M., Stoffregen, W.C., Nystrom, E.A., Baljer, G., Menge, C. 2008. Epithelial and Mesenchymal Cells in the Bovine Colonic Mucosa Differ in Their Responsiveness to Escherichia coli Shiga Toxin 1. Infection and Immunity. 76(11):5381-5391. Interpretive Summary: Cattle are an important source of Shiga toxin-producing Escherichia coli (STEC) O157:H7 bacteria, foodborne pathogens that cause severe diarrhea and sometimes kidney failure and death in humans. Reduction of the levels of O157:H7 in the cattle population would have a positive impact on the frequency of human exposure to this pathogen. Shiga toxins (Stx) promote STEC infections and persistence in cattle. Cells in the depth of large intestinal crypts in the large intestines of cattle have Stx receptors (molecules that bind Stx). To determine if Stx receptor-positive cells in the bovine intestine are responsive to Stx, we identified and characterized Stx receptor-positive cells in bovine colonic crypt cultures. We found that only a small subset of primary epithelial cells harbored Stx receptors and these cells were not responsive to Stx. In contrast, we found some novel Stx receptor-positive non-epithelial cells which were responsive to Stx. We preliminarily identified these latter cells, which were located next to the crypts in bovine intestinal tissues, as mucosal macrophages. These results will facilitate identification of STEC and host factors involved in STEC colonization of cattle and identification of strategies for reducing STEC levels in cattle.
Technical Abstract: Cells in the depth of the crypts in the bovine colon express CD77 molecules that potentially act as receptors for Shiga toxins (Stx). The implication of this finding for the intestinal colonization 25 of cattle with human pathogenic Stx-producing Escherichia coli (STEC) remains undefined. We used flow cytometric and real-time PCR analyses of primary cultures of colonic crypt cells to evaluate cell viability, CD77 expression, and gene transcription in the presence and absence of purified Stx1. A subset of epithelial cells harbored Stx receptors but receptors were mainly detected intracellularly with 30 a perinuclear distribution. Cultured epithelial cells resisted Stx1 induced apoptosis. Stx1 also did not influence the cells' chemokine expression pattern. On the contrary, high numbers of Stx receptors were detected on the surface of a population of vimentin-positive, i.e. mesenchymal/non-epithelial cells, and this cell population was depleted from the cultures by Stx1. In situ, CD77**+ cells were located in the lamina propria of the bovine colon by immunofluorescence staining. A newly established 35 vimentin-positive crypt cell line with high CD77 expression resisted the cytolethal effect of Stx1 but responded to Stx1 with a significant increase in il-8, gro-alpha, mcp-1 and rantes mRNA. Combined stimulation with LPS and Stx1 increased il-10 mRNA. Our results show that bovine colonic crypt cells of epithelial origin are resistant to both cytotoxic and modulatory effects of Stx1. In contrast, some mucosal mesenchymal cells, preliminarily characterized as mucosal macrophages, are Stx1-responsive 40 cells that may participate in the interaction of STEC with the bovine intestinal mucosa.