Multivalent Nanobodies for Potent and Broad Neutralization of <i>Staphylococcus aureus</i> Toxins

<i>S. aureus</i> is among the most common, antibiotic-resistant, and deadly causes of bacterial infections. We developed nanobodies against clinically significant virulence factors in <i>S. aureus</i> sepsis and pneumonia, including superantigens (SAgs) SEB, SEC, and TSST-1 as well as pore forming toxin Hla. These nanobodies displayed complete and potent neutralization of each toxin, exploiting a wide variety neutralizing mechanisms. Structural investigation of these diverse neutralizing nanobodies, which were elicited in llamas using clinically investigated cocktail vaccines, highlighted the importance of disrupting SAg interaction with TCR or MHCII and potential flaws in targeting poorly neutralizing conserved SAg epitopes using vaccine cocktails. Nb leads against each toxin were combined in different multivalent configurations, including an aerosolizable trimeric Nb and a half-life extended decameric Nb IgG Fc fusion construct. This work highlights multivalent nanobodies as a comprehensive yet therapeutically precise drug platform that addresses the complex virulence profiles of bacterial infectious diseases.