Mutational effects on protein folding stability and antigenicity: The case of streptococcal pyrogenic exotoxin A

John H. Carra, Brent C. Welcher, Rowena D. Schokman, Chella S. David, Sina Bavari

Research output: Contribution to journalArticle

8 Scopus citations


The influence of mutationally induced changes in protein folding on development of effective neutralizing antibodies during vaccination remains largely unexplored. In this study, we probed how mutational substitutions of streptococcal pyrogenic exotoxin A (SPEA), a model bacterial superantigen, affect native conformational stability and antigenicity. Stability changes for the toxin variants were determined using circular dichroism and fluorescence measurements, and scanning calorimetry. Self-association was assayed by dynamic light scattering. Inactivated SPEA proteins containing particular combinations of mutations elicited antibodies in HLA-DQ8 transgenic mice that neutralized SPEA superantigenicity in vitro, and protected animals from lethal toxin challenge. However, a highly destabilized cysteine-free mutant of SPEA did not provide effective immunity, nor did an irreversibly denatured version of an otherwise effective mutant protein. These results suggest that protein conformation plays a significant role in generating effective neutralizing antibodies to this toxin, and may be an important factor to consider in vaccine design.

Original languageEnglish (US)
Pages (from-to)60-68
Number of pages9
JournalClinical Immunology
Issue number1
StatePublished - Jul 1 2003



  • Circular dichroism
  • DSC
  • Exotoxin
  • Protein folding
  • SPEA
  • Superantigen
  • Vaccine

ASJC Scopus subject areas

  • Immunology
  • Immunology and Allergy

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