Monoclonal antibodies to staphylococcal enterotoxins B and C: cross-reactivity and localization of epitopes on tryptic fragments.

Murine monoclonal antibodies reactive with staphylococcal enterotoxins B (SEB) and C1 (SEC1) were isolated by hybridoma techniques. Of the nine antibodies, three reacted only with SEB, two reacted with SEB and SEC1, three reacted with all subtypes of SEC, and one reacted only with SEC2 and SEC3. All of the antibodies reacted with protein blotted onto nitrocellulose from electrophoresis gels which corresponded to the enterotoxin band. Fragments of SEB and SEC1 were generated by limited digestion of the toxin with trypsin. With the immunoblot technique, four of the five antibodies reactive with SEB reacted with the tryptic fragment of molecular weight 17,000, and the five antibodies reactive with SEC1 reacted with the tryptic fragment of molecular weight 14,000.

Isolation and some properties of an enterotoxin produced by Bacillus cereus.

Extracellular proteins produced by Bacillus cereus B-4ac were separated by chromatography on Amberlite CG-400, QAE-Sephadex, Sephadex G-75, and hydroxylapatite. A fraction, containing three detectable antigens, obtained from chromatography on hydroxylapatite caused fluid accumulation in ligated rabbit ileal loops, was dermonecrotic to rabbit skin, was cytotoxic to cultured cells, and was lethal to mice after intravenous injection. Two other fractions obtained from chromatography on hydroxylapatite showed essentially no toxic activity when tested individually. Each nontoxic fraction contained two of the three proteins present in the toxic material. When the two nontoxic fractions were combined, activity in all of the biological assays was observed. Antiserum against either of the nontoxic fractions neutralized the dermonecrotic response of the combined material. These results suggest that all of these biological activities probably are due to a single entity and that more than one component probably comprise the toxic entity.