Localization of biologic functions of toxic shock syndrome toxin-1 by use of monoclonal antibodies and cyanogen bromide-generated toxin fragments.

Monoclonal antibodies (mAb) against toxic shock syndrome toxin-1 (TSST-1) were generated that block two of the most important biologic activities of TSST-1, nonspecific T lymphocyte mitogenicity and the suppression of immunoglobulin synthesis. Fourteen hybridomas producing antibody against TSST-1 were isolated independently. The culture supernatant and ascitic fluids from each were analyzed to determine the mAb isotypes. Seven of the mAb were IgG1, and the remaining seven were IgM; all the mAb had kappa light chains. Immunoglobulin was partially purified from hybridoma-generated ascitic fluid by ammonium sulfate precipitation and tested for the ability to block TSST-1-induced mitogenicity and immunosuppression. Three mAb (all IgG1) were shown to block both the toxin-induced mitogenicity and the suppression. None of the mAb tested inhibited just one of the two toxin activities. The neutralizing mAb were then used in Western analysis with previously mapped cyanogen bromide (CNBr)-generated toxin fragments to localize the aforementioned biologic functions. The Western blot analysis showed that the mitogenic and the suppressive functions of TSST-1 were located on a 14,000 dalton internal CNBr fragment.