Interaction of monoclonal antibodies with pertussis toxin and its subunits.

The binding of two monoclonal antibodies to crude and pure preparations of pertussis toxin was examined. Antibody P11B10 reacted with an epitope present on the S2 subunit of pertussis toxin by immunoblot techniques. Radioimmunoprecipitation analysis and immunoaffinity chromatography with P11B10 indicated that subunits S2 and S3 were closely associated. Antibody P7B10 was unreactive in immunoblots and radioimmunoprecipitation but was able to bind and retain toxin subunits during affinity chromatography. The P7B10 epitope may thus be labile to detergent treatment or radioiodination; or the epitope may form as a result of subunit association. Neither antibody alone nor both in combination neutralized the histamine-sensitizing activity of pertussis toxin in passive-transfer experiments. However, toxin isolated by immunoaffinity chromatography with either monoclonal antibody was able to sensitize mice to histamine challenge.