Identifying Potential Therapeutic Targets of Methicillin-resistant Staphylococcus aureus Through in Vivo Proteomic Analysis

Background. Detailed knowledge on protein repertoire of a pathogen during host infection is needed for both developing a better understanding of the pathogenesis and defining potential therapeutic targets. Such data, however, have been missing for Staphylococcus aureus, a major human pathogen. Methods. We determined the surface proteome of methicillin-resistant S. aureus (MRSA) clone USA300 derived directly from murine systemic infection. Results. The majority of the in vivo-expressed surface-associated proteins were lipoproteins involved in nutrient acquisition, especially uptake of metal ions. Enzyme-linked immunosorbent assay (ELISA) of convalescent human serum samples revealed that proteins that were highly produced during murine experimental infection were also produced during natural human infection. We found that among the 7 highly abundant lipoproteins only MntC, which is the manganese-binding protein of the MntABC system, was essential for MRSA virulence during murine systemic infection. Moreover, we show that MntA and MntB are equally important for MRSA virulence. Conclusions. Besides providing experimental evidence that MntABC might be a potential therapeutic target for the development of antibiotics, our in vivo proteomics data will serve as a valuable basis for defining potential antigen combinations for multicomponent vaccines.