Immunoproteomic analysis of surface proteins in bovine-adapted lineages of Staphylococcus aureus

In Ireland, Staphylococcus aureus is the most frequent cause of bovine intramammary infection (IMI) with the bovine-adapted lineages CC151 and CC97 most commonly found. While bovine mastitis vaccines are available that target S. aureus, this pathogen is still a significant source of infection in dairy cows. Therefore, there’s a clear need for a more effective vaccine against S. aureus. However, S. aureus is considered a clonal organism, therefore identifying new potential protein targets common to all major lineages is an important step for vaccine design.

Two S. aureus strains, one belonging to ST151 and another to ST3170 (CC97), were used to infect two groups of dairy cows. Antibodies raised by individual cows were used to identify immunodominantsurface proteins for each strain. One-dimensional serum blotting determined that the antibody response to S. aureus infection was largely strain specific, and to a lesser extent, animal specific.

Two-dimensional serum blotting followed by mass spectrometry of immunoreactive spots was used to identify potential vaccine candidates that were immunodominant for both strains. These blots showed that proteins to which an antibody response was generated in the ST151 infected cows were generally different to those generated in the ST3170 infected cows. However, mass spectrometry also identified immunoreactive proteins common to both strains including Clumping factor B and Iron-regulated surface determinant protein A. Common immunoreactive secreted proteins are also currently being identified.

This study will identify immunodominant proteins expressed by the bovine-adapted strains ST3170 and ST151 that could potentially be used as candidates in vaccine research.