Vet. Res. (2008) 39:18
DOI: 10.1051/vetres:2007057

Escherichia coli, but not Staphylococcus aureus triggers an early increased expression of factors contributing to the innate immune defense in the udder of the cow

Wolfram Petzl¹, Holm Zerbe¹, Juliane Günther², Wei Yang^{2, 3}, Hans-Martin Seyfert², Gerd Nürnberg² and Hans-Joachim Schuberth<sup>4

1</sup>  Clinic for Ruminants, Ludwig-Maximilians-University, Munich, Germany
²  Research Institute for the Biology of Farm Animals, Dummerstorf, Germany
³  Present address: Duke University, Durham, North Carolina, USA
⁴  Institute of Immunology, University of Veterinary Medicine, Hannover, Germany

(Received 3 March 2007; accepted 7 November 2007 ; published online 29 January 2008)

Abstract - The outcome of an udder infection is influenced by the pathogen species. We established a strictly defined infection model to better analyze the unknown molecular causes for these pathogen-specific effects, using Escherichia coli and Staphylococcus aureus strains previously asseverated from field cases of mastitis. Inoculation of quarters with 500 CFU of E. coli (n = 4) was performed 6 h, 12 h, and 24 h before culling. All animals showed signs of acute clinical mastitis 12 h after challenge: increased somatic cell count (SCC), decreased milk yield, leukopenia, fever, and udder swelling. Animals inoculated with 10 000 CFU of S. aureus for 24 h (n = 4) showed no or only modest clinical signs of mastitis. However, S. aureus caused clinical signs in animals, inoculated for 72 h-84 h. Real-time PCR proved that E. coli inoculation strongly and significantly upregulated the expression of -defensins, TLR2 and TLR4 in the pathogen inoculated udder quarters as well as in mammary lymph nodes. TLR3 and TLR6 were not significantly regulated by the infections. Immuno-histochemistry identified mammary epithelial cells as sites for the upregulated TLR2 and -defensin expression. S. aureus, in contrast, did not significantly regulate the expression of any of these genes during the first 24 h after pathogen inoculation. Only 84 h after inoculation, the expression of -defensins, but not of TLRs was significantly (> 20 fold) upregulated in five out of six pathogen inoculated quarters. Using the established mastitis model, the data clearly demonstrate a pathogen-dependent difference in the time kinetics of induced pathogen receptors and defense molecules.

Key words: toll-like receptor / mastitis / beta-defensin / mammary epithelial cell

Corresponding author: hans-joachim.schuberth@tiho-hannover.de

© INRA, EDP Sciences 2008