This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Cryz, S. J. Articles by Holmes, R. K. Search for Related Content PubMed PubMed Citation Articles by Cryz, S. J., Jr. Articles by Holmes, R. K.

 Previous Article  |  Next Article 

Infect Immun. 1980 December; 30(3): 835-846

Immunochemical Studies of Diphtherial Toxin and Related Nontoxic Mutant Proteins

Stanley J. Cryz Jr., Susan L. Welkos and Randall K. Holmes

Uniformed Services University of the Health Sciences, Bethesda, Maryland 20014

ABSTRACT

Competitive binding radioimmunoassays were used to analyze the immunochemistry of diphtherial toxin. Rabbit antisera obtained by immunization with formolized toxoid or fragment A were used to characterize purified toxin, toxoid, fragment A, and related nontoxic mutant proteins. Antitoxoid serum had a high titer of neutralizing activity. Most of the antibodies in antitoxoid bound to toxin but not to fragment A. The anti-fragment A antibodies that were present in antitoxoid recognized determinants of fragment A that were exposed on unnicked toxin. Formaldehyde treatment partially destroyed antibody-binding sites associated with the A and B domains of toxin. Anti-fragment A serum had a low titer of neutralizing activity. The specificities of the anti-fragment A antibodies in antitoxoid and anti-fragment A sera were different. Approximately half of the anti-fragment A antibodies in anti-fragment A serum recognized determinants of fragment A that were masked in toxin. Per unit of fragment A-binding activity, anti-fragment A serum was significantly more potent than antitoxoid serum as an inhibitor of the enzymatic activity of fragment A. By analyzing the antigenic structure of several nontoxic mutant proteins (cross-reacting materials) that cross-react with toxin, we distinguished three different subgroups of antigenic determinants associated with the B domain of toxin. Furthermore, the exposed antigenic determinants of the A domain of toxin were separated into two subgroups, both of which were distinct from the masked determinants of the A domain. The radioimmunoassays described here provide rapid, sensitive, quantitative, and versatile methods for immunochemical characterization of toxin or related cross-reacting proteins encoded by corynebacteriophages.

Present address: Department of Microbiology and Immunology, University of Oregon Health Science Center, Portland, OR 97205.

Present address: Department of Microbiology and Immunology, Eastern Virginia Medical School, Norfolk, VA 23501.

This article has been cited by other articles:

• Neill, R., Ivins, B., Holmes, R. (1983). Synthesis and secretion of the plasmid-coded heat-labile enterotoxin of Escherichia coli in Vibrio cholerae. Science 221: 289-291 [Abstract]