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

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, affe...

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Bibliographic Details
Published in:Clinical immunology (Orlando, Fla.) Fla.), 2003-07, Vol.108 (1), p.60-68
Main Authors: Carra, John H, Welcher, Brent C, Schokman, Rowena D, David, Chella S, Bavari, Sina
Format: Article
Language:English
Subjects:
Animals
Bacterial Proteins
Biological and medical sciences
Circular dichroism
Dimerization
DSC
Epidemiology. Vaccinations
Exotoxin
Exotoxins - genetics
Exotoxins - immunology
Exotoxins - metabolism
General aspects
Hot Temperature
Infectious diseases
Medical sciences
Membrane Proteins
Mice
Mice, Transgenic
Protein Folding
SPEA
Structure-Activity Relationship
Superantigen
Thermodynamics
Vaccine
Vaccines - immunology
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Summary: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.
ISSN:1521-6616
1521-7035
DOI:10.1016/S1521-6616(03)00058-5