Nanoparticulate Tubular Immunostimulating Complexes: Novel Formulation of Effective Adjuvants and Antigen Delivery Systems.

New generation vaccines, based on isolated antigens, are safer than traditional ones, comprising the whole pathogen. However, major part of purified antigens has weak immunogenicity. Therefore, elaboration of new adjuvants, more effective and safe, is an urgent problem of vaccinology. Tubular immunostimulating complexes (TI-complexes) are a new type of nanoparticulate antigen delivery systems with adjuvant activity. TI-complexes consist of cholesterol and compounds isolated from marine hydrobionts: cucumarioside A2-2 (CDA) from Cucumaria japonica and monogalactosyldiacylglycerol (MGDG) from marine algae or seagrass. These components were selected due to immunomodulatory and other biological activities. Glycolipid MGDG from marine macrophytes comprises a high level of polyunsaturated fatty acids (PUFAs), which demonstrate immunomodulatory properties. CDA is a well-characterized individual compound capable of forming stable complex with cholesterol. Such complexes do not possess hemolytic activity. Ultralow doses of cucumariosides stimulate cell as well as humoral immunity. Therefore, TI-complexes comprising biologically active components turned out to be more effective than the strongest adjuvants: immunostimulating complexes (ISCOMs) and complete Freund's adjuvant. In the present review, we discuss results published in series of our articles on elaboration, qualitative and quantitative composition, ultrastructure, and immunostimulating activity of TI-complexes. The review allows immersion in the history of creating TI-complexes.

Interaction of holothurian triterpene glycoside with biomembranes of mouse immune cells.

The in vitro interactions between triterpene glycoside, cucumarioside A(2)-2, isolated from the Far-Eastern holothurian Cucumaria japonica, and mouse splenocyte and peritoneal macrophage biomembranes were studied. Multiple experimental approaches were employed, including determination of biomembrane microviscosity, membrane potential and Ca(2+) signaling, and radioligand binding assays. Cucumarioside A(2)-2 exhibited strong cytotoxic effect in the micromolar range of concentrations and showed pronounced immunomodulatory activity in the nanomolar concentration range. It was established that the cucumarioside A(2)-2 effectively interacted with immune cells and increased the cellular biomembrane microviscosity. This interaction led to a dose-dependent reversible shift in cellular membrane potential and temporary biomembrane depolarization; and an increase in [Ca(2+)](i) in the cytoplasm. It is suggested that there are at least two binding sites for [(3)H]-cucumarioside A(2)-2 on cellular membranes corresponding to different biomembrane components: a low affinity site match to membrane cholesterol that is responsible for the cytotoxic properties, and a high affinity site corresponding to a hypothetical receptor that is responsible for immunostimulation.

[Immunostimulatory characteristics of a novel carrier on the basis of cucumarioside A2-2 and monogalactosyldiacylgycerol].

A novel antigen carrier has been formulated on the basis of a cucumarioside-A2-2 triterpene glycoside (CD) complex with cholesterol and monogalactosyldiacylglycerol from Ahnfeltia tobuchiensis (MGDG(At)) and Ulva fenestrate (MGDG(Uf)). Morphological and immunostimulative characteristics of the carrier were studied. Electron microscopy experiments demonstrated the formation of homogeneous tubular structures in a mixture of CD, cholesterol, and MGDG in molar ratio of 1:2:3. In animals immunized by the carrier bearing pore forming protein monomer of pseudotuberculosis agent CD and MGDG synergically affected synthesis of specific antibodies, interleukin-2, and gamma-interferon and delayed hypersensitivity reaction when compared to Freund's complete adjuvant or to immunostimulatory complexes between Quillaja saponaria saponins and phosphatidylcholine from egg yolk. The immunostimulatory effect depends upon the composition of polyunsaturated fatty acids of MGDG. The new tubular adjuvant carrier is a competitive adjuvant, as it includes CD obtained from far-eastern sea cucumber commercial species Cucumaria japonica, and MGDG from seaweed.