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Adjuvant activity of QS-21 isomers
S Soltysik1, D A Bedore, C R Kensil
1Cambridge Biotech Corporation, Worcester, Massachusetts 01605.
Annals of the New York Academy of Sciences
|August 12, 1993
Summary
Two structural isomers of QS-21, a saponin adjuvant, were identified. Structural variations did not affect the adjuvant activity in mice, indicating this part of QS-21 is not critical for its function.
Area of Science:
- Biochemistry
- Immunology
- Natural Products Chemistry
Background:
- QS-21 is a purified triterpene glycoside from Quillaja saponaria.
- QS-21 functions as an adjuvant, enhancing immune responses.
Purpose of the Study:
- To investigate the structural heterogeneity of QS-21.
- To determine if structural variations impact QS-21's adjuvant activity.
Main Methods:
- High-performance hydrophilic interaction chromatography (HILIC) for separation.
- Fast atom bombardment-mass spectrometry (FAB-MS) for structural analysis.
- Monosaccharide composition and linkage analysis for carbohydrate structure.
- Dose-response studies in mice to assess adjuvant activity.
Main Results:
- QS-21 resolved into two distinct peaks via HILIC, identified as structural isomers.
- FAB-MS confirmed identical pseudomolecular ion weights and fragmentation patterns.
- Carbohydrate analysis revealed a difference in terminal pentose residues between the isomers.
- Both isomers and purified QS-21 showed similar dose-response curves with a minimum effective dose of 5 µg/mouse.
Conclusions:
- The structural variation observed in QS-21 does not affect its adjuvant activity.
- The specific structural difference identified is not critical for the adjuvant function of QS-21.