10.6084/m9.figshare.5368549.v1 Koymans K.J. Koymans K.J. Goldmann O. Goldmann O. Karlsson C.A.Q. Karlsson C.A.Q. Sital W. Sital W. Thänert R. Thänert R. Bisschop A. Bisschop A. Vrieling M. Vrieling M. Malmström J. Malmström J. van Kessel K.P.M. van Kessel K.P.M. de Haas C.J.C. de Haas C.J.C. van Strijp J.A.G. van Strijp J.A.G. Medina E. Medina E. Supplementary Material for: The TLR2 Antagonist Staphylococcal Superantigen-Like Protein 3 Acts as a Virulence Factor to Promote Bacterial Pathogenicity in vivo Karger Publishers 2017 Staphylococcus aureus Immune evasion Innate immunity Toll-like receptor 2 TLR2 antagonist Staphylococcal superantigen-like protein 3 2017-09-01 12:27:04 Figure https://karger.figshare.com/articles/figure/Supplementary_Material_for_The_TLR2_Antagonist_Staphylococcal_Superantigen-Like_Protein_3_Acts_as_a_Virulence_Factor_to_Promote_Bacterial_Pathogenicity_in_vivo/5368549 Toll-like receptor (TLR) signaling is important in the initiation of immune responses and subsequent instigation of adaptive immunity. TLR2 recognizes bacterial lipoproteins and plays a central role in the host defense against bacterial infections, including those caused by <i>Staphylococcus aureus</i>. Many studies have demonstrated the importance of TLR2 in murine <i>S. aureus</i> infection. <i>S. aureus</i> evades TLR2 activation by secreting two proteins, staphylococcal superantigen-like protein 3 (SSL3) and 4 (SSL4). In this study, we demonstrate that antibodies against SSL3 and SSL4 are found in healthy individuals, indicating that humans are exposed to these proteins during <i>S. aureus</i> colonization or infection. To investigate the TLR2-antagonistic properties of SSL3 and SSL4, we compared the infection with wild-type and SSL3/4 knockout <i>S. aureus</i> strains in an intravenous murine infection model. Direct evaluation of the contribution of SSL3/4 to infection pathogenesis was hindered by the fact that the SSLs were not expressed in the murine system. To circumvent this limitation, an SSL3-overproducing strain (pLukM-SSL3) was generated, resulting in constitutive expression of SSL3. pLukM-SSL3 exhibited increased virulence compared to the parental strain in a murine model that was found to be TLR2 dependent. Altogether, these data indicate that SSL3 contributes to <i>S. aureus</i> virulence in vivo.