Formation of cationic cage-like complexes composed of DC-cholesterol, Quil-A and Phospholipid

摘要

This study describes the formation of cationic, cage-likecomplexes which have a structure similar to classicanionic immuno-stimulating complexes (ISCOMs). Inorder to prepare these complexes cholesterol, a majorcomponent of ISCOM formulations, was substituted withthe cationic derivative DC-CHOL. Colloidal dispersionswith varying compositions of DC-CHOL, phosphatidylcholineand Quil-A, which is a semi-purified fraction ofimmuno-stimulatory triterpene saponins, were preparedby lipid-film hydration and characterised by transmissionelectron microscopy and laser Doppler electrophoresis.The colloidal structures obtained were described inpseudo-ternary phase diagrams with TRIS buffered salinepH 7.4 (TBS) as the pseudo-component. Using TBS,cage-like particles formed at compositions with highproportions of DC-CHOL and had a strongly positivezeta-potential. The formation of these particles was evenobserved in binary mixtures of DC-CHOL and Quil-A. Itwas found that the formation of cationic, cage-likeparticles highly depended on the formulation buffer. Theuse of phosphate buffered saline and low concentrationsof TRIS in the formulation buffer did not result information of those particles. The cage-like particles couldbe purified by differential centrifugation.