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Immunochemical properties of streptococcal M protein purified by isoelectric focusing
Abstract:
Electrofucusing of an alkaline extract of type 24 streptococcal M protein yielded an antigenic fraction that was type specific and apparently homogeneous. The haptenic nature of this fraction was suggested by its inability to precipitate type-specific antiserum or to induce opsonic antibodies in rabbits, despite its ability to strongly inhibit opsonization of homologous-type streptococci by M antibody. The fraction migrated as a single band upon electrophoresis in sodium dodecyl sulfate (SDS) acrylamide gel. The mobility of the protein band was consistent with a molecular weight of 36,500 daltons. In some experiments using larger quantities of protein, a second faint protein band with an average molecular weight of 70,000 was observed, suggesting the presence of dimers of the 36,500-dalton protein. Amino acid analysis showed the predominant amino acid to be glycine followed by aspartic acid and glutamic acid. Moreover, this M protein fraction was free of non-type-specific immunotoxic properties in guinea pigs and in man. Although apparently not immunogenic, this nontoxic fraction may provide a useful tool to study the relationship of the type-specific protective moiety to potentially harmful "impurities" in M protein vaccines.
Insights
Researchers isolated a type-specific, nontoxic fraction of streptococcal M protein. This purified protein may help understand vaccine impurities and improve safety.
Area of Science:
- Microbiology
- Immunology
- Biochemistry
Background:
- Streptococcal M protein is crucial for virulence and vaccine development.
- Understanding M protein's antigenic and toxic properties is vital for safe and effective vaccines.
Purpose of the Study:
- To isolate and characterize a type-specific antigenic fraction of M protein.
- To assess the haptenic, immunogenic, and toxic properties of the isolated fraction.
- To evaluate its potential as a tool for vaccine research.
Main Methods:
- Electrofucusing of alkaline extract of type 24 streptococcal M protein.
- Sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis for molecular weight determination.
- Amino acid analysis.
- Inhibition assays for opsonization and precipitation tests.
Main Results:
- An apparently homogeneous, type-specific antigenic fraction was isolated.
- The fraction exhibited haptenic properties, inhibiting opsonization but not precipitating antiserum.
- Electrophoresis indicated a primary molecular weight of 36,500 daltons, with potential dimers observed.
- Amino acid analysis revealed glycine as the predominant amino acid.
- The fraction was found to be nontoxic and free of non-type-specific immunotoxic properties.
Conclusions:
- A purified, nontoxic, type-specific M protein fraction was obtained.
- This fraction may serve as a valuable tool for investigating the protective components of M protein vaccines and identifying harmful impurities.
- Further research can utilize this fraction to enhance the safety and efficacy of streptococcal vaccines.