EFFECT OF A NOVEL SAPONIN ADJUVANT DERIVED FROM QUILLAJA-SAPONARIA ONTHE IMMUNE-RESPONSE TO RECOMBINANT HEPATITIS-B SURFACE-ANTIGEN

Adjuvant activity of saponins extracted from the South American tree Q uillaja saponaria has been demonstrated with many antigens. Recently, four saponin fractions (designated as QS-7, QS-17, QS-18, and QS-21) w ith adjuvant activity were purified by reverse phase chromatography. I n particular, efficacy of the less toxic QS-21 fraction has been demon strated with several recombinant viral antigens including HIV gp120. H ere, we report a novel saponin fraction (designated as QS-L1) derived from Quillaja saponaria. Unlike previously identified saponins, QS-L1 had a different chemical structure and showed adjuvant activity only w hen administered in the presence of alum-precipitated antigen. Interes tingly, the QS-L1 greatly increased not only a humoral immune response but also cellular immune response to recombinant hepatitis B virus su rface antigen (HBsAg), Furthermore, QS-L1 showed lower toxicity in viv o and in vitro than the previously identified saponin fraction, QS-21. Finally, we examined the chemical structure of the QS-L1 using mass s pectroscopic analysis, carbohydrate composition analysis and NMR spect roscopic analysis. Thus, our results indicated that this novel QS-L1 s aponin fraction had several desirable properties required for an effec tive adjuvant.