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Title: ELEVATED MILK SOLUBLE CD14 IN BOVINE MAMMARY GLANDS CHALLENGED WITH ESCHERICHIA COLI LIPOPOLYSACCHARIDE

Author
item LEE, JAI-WEI - MCGILL UNIV, CANADA
item Paape, Max
item ELSASSER, THEODORE - USDA ARS BELTSVILLE MD
item ZHAO, XIN - MCGILL UNIV, CANADA

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/4/2003
Publication Date: 7/1/2003
Citation: LEE, J., PAAPE, M.J., ELSASSER, T.H., ZHAO, X. ELEVATED MILK SOLUBLE CD14 IN BOVINE MAMMARY GLANDS CHALLENGED WITH ESCHERICHIA COLI LIPOPOLYSACCHARIDE. JOURNAL OF DAIRY SCIENCE. vol. 86, pp. 2382-9, 2003.

Interpretive Summary: Soluble CD14 plays a crucial role in protecting the host from LPS challenge, or infection caused by Gram-negative bacteria. Mastitis caused by E. coli is a common management-related problem in dairy cattle, and causes a great deal of economic loss in the dairy industry. However, pathogenesis of E. coli and the response of the host immune system to this pathogen in the mammary gland are not well understood. There is general agreement that LPS, a cell wall component of Gram-negative bacteria, is the main pathogenic factor involved in infections by E. coli. Use of LPS to simulate E. coli intramammary infection is commonly used. The mammary gland is a unique organ in terms of its biological function and structure. The existence of sCD14 in milk may protect dairy calves from gastrointestinal infections, and cows from mastitis. Scientists at the USDA-Beltsville identified factors affecting concentration of sCD14 in milk, as well as the change in sCD14 in milk after intramammary challenge with LPS. These discoveries are now being used to develop strategies for preventing mastitis in dairy cows caused by Gram-negative bacteria.

Technical Abstract: The purpose of this study was to determine whether soluble CD14 in milk was affected by stage of lactation, milk somatic cell count (SCC), presence of bacteria or lipopolysaccharide (LPS)-induced inflammation. Milk samples from 100 lactating cows were assayed for sCD14 in milk to determine effects of stage of lactation, SCC and intramammary infection. Soluble CD14 was highest in transitional milk (0-4 days postpartum) and in milk with high SCC (> 750,000 cells/ml). No difference was found between non-infected and infected quarters. Left front quarters of 6 healthy lactating cows were challenged with 100 ug lipopolysaccharide (LPS) in order to study the kinetics of sCD14 during an LPS-induced inflammation. Rectal temperature, milk tumor necrosis factor (TNF)-a, and interleukin-8 (IL-8) increased immediately after challenge. The increase in sCD14 paralleled the increase in SCC and peaked at 12 h. Serum leakage, as characterized by the level of bovine serum albumin (BSA) in milk, peaked at 4 h and then gradually decreased. In vitro experiments indicated that neutrophils released sCD14 in response to LPS, in a dose-dependent manner. The results indicate that the concentration of sCD14 is significantly increased in milk after LPS challenge, and was not likely due to serum leakage. Instead, infiltrated neutrophils appear to be the main source of sCD14 in milk.