Generation of a Monoclonal Antibody Against Staphylococcal Superantigen-Like Protein 5 (SSL5) That Discriminates SSL5 from Other SSL Proteins.

Staphylococcus aureus secretes a family of exoproteins structurally homologous to bacterial superantigens, such as toxic shock syndrome toxin-1 (TSST-1), and those exoproteins are thus called staphylococcal superantigen-like proteins (SSLs). Recent studies have revealed that SSLs play roles in evasion of the host defense by disturbing host immune responses. We previously reported that staphylococcal superantigen-like protein 5 (SSL5; a member of the SSL family) inhibited matrix metalloproteinase-9 (MMP-9), which is crucial for leukocyte recruitment to sites of infection. In this study, we established a mouse hybridoma clone (30G5C) producing a monoclonal antibody specific for SSL5. In immunoblotting analysis using recombinant His-tagged SSL1 to SSL14 (His-SSLs), the antibody was found to specifically recognize SSL5 without crossreactivity with other His-SSLs. The antibody bound to the C-terminal region of SSL5 (β-grasp domain), but did not interfere with the binding of SSL5 to MMP-9, suggesting that this antibody is useful for identification of SSL5-producing S. aureus and screening for inhibitors of the SSL5/MMP-9 complex formation.