Immunoproteomic analysis of the serum IgG response to cell wall-associated proteins of Staphylococcus aureus strains belonging to CC97 and CC151

CC97 and CC151 are two of the most common Staphylococcus aureus lineages associated with bovine intramammary infection. The genotype of the infecting S. aureus strain influences virulence and the progression of intramammary disease. Strains from CC97 and CC151 encode a distinct array of virulence factors. Identification of proteins elaborated in vivo will provide insights into the molecular mechanism of pathogenesis of these lineages, as well as facilitating the development of tailored treatments and pan-lineage vaccines and diagnostics. The repertoire of genes encoding cell wall-anchored (CWA) proteins was identified for S. aureus strains MOK023 (CC97) and MOK124 (CC151); MOK023 encoded more CWA proteins than MOK124. Serum collected during an in vivo challenge trial was used to investigate whether the humoral response to cell wall proteins was strain-specific. Immunoproteomic analysis demonstrated that the humoral response in MOK023-infected cows predominantly targeted high molecular weight proteins while the response in MOK124-infected cows targeted medium or low molecular weight proteins. Antigenic proteins were identified by two-dimensional serum blotting followed by mass spectometry-based identification of immunoreactive spots, with putative antigens subsequently validated. The CWA proteins ClfB, SdrE/Bbp and IsdA were identified as immunogenic regardless of the infecting strain. In addition, a number of putative strain-specific imunogens were identified. The variation in antigens produced by different strains may indicate that these strains have different strategies for exploiting the intramammary niche. Such variation should be considered when developing novel control strategies including vaccines, therapeutics and diagnostics.

Automated summary

CC97 and CC151 are common lineages of Staphylococcus aureus associated with bovine intramammary infection. The genotype of the infecting strain affects virulence and disease progression. Proteins produced by these strains can provide insights into their pathogenesis and contribute to the development of targeted treatments, vaccines, and diagnostics. The identification and evaluation of cell wall-anchored (CWA) proteins in strains MOK023 (CC97) and MOK124 (CC151) showed differences in protein repertoire. Variations in the humoral response to these proteins were observed among infected cows. Immunogenic proteins were identified, including ClfB, SdrE/Bbp, and IsdA, suggesting their potential as vaccine targets. The strain-specific antigens detected indicate the need to consider strain variation when designing control strategies.