Staphylococci are the most common cause of nosocomial infections worldwide. The exotoxin staphylococcal enterotoxin B (SEB) generated by Staphylococcus aureus is a significant source of pathology. M0313, an anti-SEB human monoclonal antibody, was previously identified. This antibody is further characterised in vitro and in vivo in this paper. M0313 was correctly identified and bound to SEB according to immunoblotting and ELISA findings. Its affinity for natural SEB was tested at the nM level.

M0313 significantly prevented SEB from promoting proliferation and cytokine release in mouse splenic lymphocytes and human peripheral blood mononuclear cells in cell culture. M0313 also inhibited SEB toxicity in female BALB/c mice. Most significantly, M0313 increased the survival of mice exposed to SEB-expressing bacteria. M0313 therapy dramatically decreased the multiplication of SEB-expressing bacteria in mice, according to in-vivo imaging. M0313’s neutralising capability was connected to its ability to prevent SEB from binding to major histocompatibility complex II and T-cell receptors by binding to SEB residues 85–102 and 90–92, respectively. As a result, the monoclonal antibody M0313 might be turned into a therapeutic agent.