Abstract
Bovine mastitis remains a primary focus of dairy cattle disease research due to its considerable negative economic impact on the dairy industry. Subclinical mastitis (SCM), commonly caused by Staphylococcus aureus, lacks overt clinical signs and the diagnosis is based on bacteriological culture and somatic cell counts of milk, both of which have limitations. The main objective of this study was to identify, characterize and quantify the differential abundance of milk whey proteins from cows with S. aureus SCM compared to whey from healthy cows. Using two-dimensional differential gel electrophoresis (2D-DIGE) coupled with liquid chromatography and tandem mass spectrometry, 28 high-abundant proteins were detected in whey from mastitic milk, 9 of which had host defense functions. These included acute phase proteins involved in innate immunity and antimicrobial functions (e.g., serotransferrin, complement C3, fibrinogen gamma-B chain and cathepsin B), and proteins associated with the immune response to pathogens (e.g., polymeric immunoglobulin receptor-like protein, MHC class I antigen and beta-2-microglobulin). These results provide a unique 2D map of the modulated milk proteome during S. aureus mastitis. The broader importance is that the identified proteins, particularly those with host-defense biological functions, represent potential candidate biomarkers of subclinical mastitis in dairy cows.
Highlights
Bovine mastitis is one of the most prevalent and costly diseases currently affecting dairy herds
This study highlights the differential abundance of the proteomic signatures of S. aureus-positive whey fractions compared to the non-infected fractions and provides an insight into understanding the role of milk proteins in host-pathogen interaction during S. aureus intramammary infection
Dominated by the six major milk proteins, accumulated evidence has shown that milk contains a range of low-abundance proteins which are associated with host defense functions that form a significant first line of defense against the invading pathogens
Summary
Bovine mastitis is one of the most prevalent and costly diseases currently affecting dairy herds. The inflammatory response during establishment of the infection is characterized by a number of changes in milk composition due to infiltration of cellular components such as neutrophils, macrophages and soluble immune factors such as complement proteins and acute phase proteins which together synchronize to clear the infection and the pathogen [6,7]. Because these innate immune mediators are usually pathogen-dependent and play an important role in early stages of infection their identification can offer insights into the host inflammatory and immune responses during mastitis
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