The effects of Mannheimia haemolytica products on bovine inflammatory mononuclear cells in vitro

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Dan, Tonima

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University of Guelph


Bovine pneumonic pasteurellosis is an economically important disease to the North American cattle industry. 'Mannheimia haemolytica' is an opportunistic bacterium that causes this pneumonia. It produces virulence factors including a heat-labile leukotoxin and O-sialoglycoprotease and a heat-stable endotoxin. Heat-labile components of 'M. haemolytica' culture supernatant (CS) were found to decrease the metabolic activity of bovine mononuclear cells in vitro. Microarray analysis of the gene expression of monocyte-derived macrophages exposed to CS resulted in the up-regulation of chemokine genes and the down-regulation of thrombospondin-1 and genes involved in cell adhesion, phagocytosis and antigen presentation. This study demonstrates that heat labile components of CS inhibit thrombospondin-2 protein expression in bovine monocytes. As well, protease activated receptor-3 mRNA expression is established in bovine macrophages and monocytes. These results indicate that 'M. haemolytica' products affect bovine mononuclear cells in vitro and suggest that these genes and proteins may be involved in the disease process in vivo.



bovine pneumonic pasteurellosis, Mannheimia haemolytica, virulence factor, heat-labile leukotoxin, O-sialoglycoprotease, heat-stable endotoxin, culture supernatant, bovine mononuclear cells, gene expression, thrombospondin-1, thrombospondin-2