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Title: INCREASED LEVELS OF LPS-BINDING PROTEIN IN BOVINE BLOOD AND MILK FOLLOWING BACTERIAL LIPOPOLYSACCHARIDE CHALLENGE

Author
item Bannerman, Douglas
item Paape, Max
item Hare Jr, William
item SOHN, EUN JUNG - UNIVERSITY OF MARYLAND

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/14/2003
Publication Date: 10/1/2003
Citation: BANNERMAN, D.D., PAAPE, M.J., HARE JR, W.R., SOHN, E. INCREASED LEVELS OF LPS-BINDING PROTEIN IN BOVINE BLOOD AND MILK FOLLOWING BACTERIAL LIPOPOLYSACCHARIDE CHALLENGE. JOURNAL OF DAIRY SCIENCE. vol. 86, pp. 3128-37, 2003.

Interpretive Summary: In well-managed herds, almost half of all clinical cases of mastitis are caused by Gram-negative bacteria. All of these bacteria contain a highly pro-inflammatory molecule called endotoxin or lipopolysaccharide (LPS), which is shed from the bacterial surface during replication or death. Host recognition of LPS is a key step in the activation of innate immune defense mechanisms that are required for optimal response to the infection. Two host proteins involved in LPS recognition are CD14 and LPS-binding protein (LBP). Previous studies have demonstrated an increase in CD14 in milk following intramammary challenge with LPS. Injection of CD14 into the mammary gland has been shown to enhance bacterial clearance and to increase recovery from experimentally-induced mastitis. In the present study, we demonstrate an increase in milk LBP following intramammary LPS exposure. To our knowledge, this is the first report to quantify changes in LBP in bovine milk. Future studies will be needed to assess whether recombinant LBP, similar to CD14, may serve as a novel therapeutic that can be used in the treatment of Gram-negative mastitis.

Technical Abstract: Several species of Gram-negative bacteria, including Escherichia coli, Klebsiella pneumoniae, and various species of Enterobacter, are common mastitis pathogens. All of these bacteria are characterized by the presence of endotoxin or lipopolysaccharide (LPS) in their outer membrane. The bovine mammary gland is highly sensitive to LPS, and LPS has been implicated, in part, in the pathogenesis of Gram-negative mastitis. Recognition of LPS is a key event in the innate immune response to Gram-negative infection and is mediated by the accessory molecules CD14 and LPS-binding protein (LBP). The objective of the current study was to determine whether LBP levels increased in the blood and mammary gland following LPS challenge. The left and right quarters of five mid-lactating Holstein cows were challenged with either saline or LPS (100 mg), respectively, and milk and blood samples collected. Basal levels of plasma and milk LBP were 38 and 6 mg/ml, respectively. Plasma LBP levels increased as early as 8 h post-LPS challenge and reached maximal levels of 138 mg/ml by 24 h. Analysis of whey samples derived from LPS-treated quarters revealed an increase in milk LBP by 12 h. Similar to plasma, maximal levels of milk LBP (34 mg/ml) were detected 24 h following the initial LPS challenge. Increments in milk LBP levels paralleled a rise in soluble CD14 (sCD14) levels and initial rises in the levels of these proteins were temporally coincident with maximal neutrophil recruitment to the inflamed gland. Since LBP and sCD14 are known to enhance LPS-induced host cell activation and to facilitate detoxification of LPS, these data are consistent with a role for these molecules in mediating mammary gland responses to LPS.