Neutralization of toxic shock syndrome toxin-1 by monoclonal antibodies in vitro and in vivo

Abstract

Sixteen monoclonal antibodies (MAbs) directed against toxic shock syndrome toxin-1 (TSST-1) were generated by immunization of mice with purified TSST-1 and subsequent fusion of spleen cells with myeloma cells. Antibody-producing clones, identified by an enzyme-linked immunosorbent assay, were maintained as ascites tumors, and MAbs were purified by protein A chromatography. High-titered clones were further characterized and tested for the ability to neutralize several biological activities of TSST-1. The MAbs, which are of several immunoglobulin subtypes, reacted specifically with purified TSST-1 and TSST-1 present in Staphylococcus aureus culture supernatants. Three MAbs neutralized TSST-1-induced mitogenesis in a dose-dependent manner. Three of eight MAbs tested were able to neutralize induction by TSST-1 of interleukin-1 production by human monocytes. One neutralizing MAb, 8-5-7, was tested for the ability to protect rabbits from a constant infusion of TSST-1. Rabbits given the MAb had an attenuated clinical illness and were protected from the hypocalcemia, lipemia, and hepatic and renal insufficiency seen in control rabbits. Six of seven control rabbits died, compared with only one of seven rabbits treated with MAb 8-5-7. These experiments suggest that MAb 8-5-7 is directed against an antigenic determinant critical to the toxicity of TSST-1 and that the MAbs should be useful as probes in structure-function analyses of the TSST-1 molecule.