Anti-clumping factor A and anti-staphylococcal protein A antibodies suppress adhesion of Staphylococcus aureus to bovine mammary epithelial cells.

Abstract

Staphylococcus aureus causes mastitis, which results in large economic losses in the dairy industry. The adhesion of S. aureus to the mammary epithelium is a critical first step in the pathogenesis of mastitis. S. aureus expresses several adhesins, including clumping factor A (ClfA) and staphylococcal protein A (SpA). An understanding of the adhesion of S. aureus to bovine mammary epithelial cells (BMECs) is necessary for developing effective mastitis vaccines. In this study, we investigated the relationship between S. aureus adhesins and adhesion to the bovine mammary epithelium using cultured BMECs and S. aureus strains, including those isolated from bovine mastitis. In addition, the inhibitory effects of two adhesin-specific antibodies on adhesion were examined. The amount of adhesin and adhesion ratio differed among S. aureus strains. A very strong positive correlation was observed between the ratio of adhesion to BMECs and the levels of ClfA and SpA. Anti-ClfA and anti-SpA antibodies suppressed the adhesion ratio, and a stronger adhesion-inhibitory effect was obtained with simultaneous binding of these antibodies. These findings could contribute to deciphering the mechanism of S. aureus adhesion to the bovine mammary epithelium and developing effective vaccines for S. aureus mastitis.