Abstract

The bovine teat canal provides the first-line of defence against pathogenic bacteria infecting the mammary gland, yet the protein composition and host-defence functionality of the teat canal lining (TCL) are not well characterised. In this study, TCL collected from six healthy lactating dairy cows was subjected to two-dimensional electrophoresis (2-DE) and mass spectrometry. The abundance and location of selected identified proteins were determined by western blotting and fluorescence immunohistochemistry. The variability of abundance among individual cows was also investigated. Two dominant clusters of proteins were detected in the TCL, comprising members of the keratin and S100 families of proteins. The S100 proteins were localised to the teat canal keratinocytes and were particularly predominant in the cornified outermost layer of the teat canal epithelium. Significant between-animal variation in the abundance of the S100 proteins in the TCL was demonstrated. Four of the six identified S100 proteins have been reported to have antimicrobial activity, suggesting that the TCL has additional functionality beyond being a physical barrier to invading microorganisms. These findings provide new insights into understanding host-defence of the teat canal and resistance of cows to mastitis.

Highlights

  • Mastitis is a significant economic and welfare issue facing the dairy industry worldwide [1]

  • The teat canal is lined with a sebum-like material and a number of studies [8,9,10] have demonstrated growth inhibitory activity against mastitis-causing bacteria by lipids derived from this teat canal lining (TCL)

  • Some of the complexity observed among the keratins is likely due to variable phosphorylation as has been previously reported to be the case for keratins in other epithelial tissues [23]

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Summary

Introduction

Mastitis is a significant economic and welfare issue facing the dairy industry worldwide [1]. The teat canal is the first host tissue that bacteria encounter on the way to colonising the mammary gland. Inoculation of pathogens directly into the teat sinus, bypassing the teat canal, significantly increases the likelihood of developing a clinical infection compared to inoculation within the teat canal [3]. One interpretation of this finding is that the teat canal has a host-defence capacity and conceivably, this could influence susceptibility to mastitis. The teat canal is lined with a sebum-like material and a number of studies [8,9,10] have demonstrated growth inhibitory activity against mastitis-causing bacteria by lipids derived from this teat canal lining (TCL). To date the identity of these cationic proteins is still to be established, and the detailed protein composition of the TCL has not been characterised

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