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The tubular immunostimulating complex (TI-complex) consisting of cucumarioside A₂-2, cholesterol and monogalactosyldiacylglycerol (MGDG) from marine macrophytes is the perspective antigen delivery system for subunit vaccines. MGDG is a lipid matrix for the protein antigen incorporated in the TI-complex. The aim of the present work was to study the influence of MGDGs from different macrophytes on conformation and immunogenicity of the secreted recombinant uncleaved hemagglutinin monomer (HA0_S) of influenza A virus H1/N1. Differential scanning calorimetry, fluorescence spectroscopy and circular dichroism showed a dependence of the conformational changes of HA0_S on the microviscosity of MGDG. The most viscous MGDG from Zostera marina induced the strongest rearrangements in protein conformation. Immunization of mice with HA0_S within TI-complexes comprising different MGDGs resulted in an approximately 2-fold increase of the levels of anti-HA0_S antibodies and granulocyte-macrophage colony-stimulating factor (GM-CSF) compared with those induced by HA0_S alone. TI-complexes based on MGDG from Z. marina stimulated the maximal production of GM-CSF. However, humoral immune response (anti-HA0_S antibodies), unlike cell-mediated immune response (GM-CSF), did not depend on the physicochemical properties of MGDGs. It is assumed that this is due to the different localization and conformational lipid sensitivity of the HA0_S regions, which are responsible for these types of immune responses.

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New minor triterpene glycoside, cucumarioside E (1) has been isolated from the Far Eastern sea cucumber Cucumaria japonica. The structure of the glycoside was elucidated by 2D-NMR specroscopy and mass-spectrometry. The glycoside has glucose instead of quinovose as the second monosaccharide residue and xylose as third monosaccharide residue that is unique structural feature for triterpene glycosides carbohydrate chains from sea cucumbers belonging to the genus Cucumaria.

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