Fatty Acid Composition and Thermotropic Behavior of Glycolipids and Other Membrane Lipids of Ulva lactuca (Chlorophyta) Inhabiting Different Climatic Zones

Increasing global temperatures are expected to increase the risk of extinction of various species due to acceleration in the pace of shifting climate zones. Nevertheless, there is no information on the physicochemical properties of membrane lipids that enable the adaptation of the algae to different climatic zones. The present work aimed to compare fatty acid composition and thermal transitions of membrane lipids from green macroalgae Ulva lactuca harvested in the Sea of Japan and the Adriatic Sea in summer. U. lactuca inhabiting the Adriatic Sea had bleached parts of thalli which were completely devoid of chloroplast glycolipids. The adaptation to a warmer climatic zone was also accompanied by a significant decrease in the ratio between unsaturated and saturated fatty acids (UFA/SFA) of membrane lipids, especially in bleached thalli. Hence, bleaching of algae is probably associated with the significant decrease of the UFA/SFA ratio in glycolipids. The decreasing ratio of n-3/n-6 polyunsaturated fatty acids (PUFAs) was observed in extra-plastidial lipids and only in the major glycolipid, non-lamellar monogalactosyldiacylglycerol. The opposite thermotropic behavior of non-lamellar and lamellar glycolipids can contribute to maintenance of the highly dynamic structure of thylakoid membranes of algae in response to the increasing temperatures of climatic zones.

Recombinant Fusion Protein Joining E Protein Domain III of Tick-Borne Encephalitis Virus and HSP70 of Yersinia pseudotuberculosis as an Antigen for the TI-Complexes

Domain III (DIII) of the tick-borne encephalitis virus (TBEV) protein E contains epitopes, which induce antibodies capable of neutralizing the virus. To enhance the immunogenicity of this protein, which has a low molecular weight, the aim of the present work was to express, isolate, and characterize a chimeric protein based on the fusion of the bacterial chaperone HSP70 of Yersinia pseudotuberculosis and EIII (DIII + stem) as a prospective antigen for an adjuvanted delivery system, the tubular immunostimulating complex (TI-complex). The chimeric construction was obtained using pET-40b(+) vector by ligating the respective genes. The resulting plasmid was transformed into DE3 cells for the heterologous expression of the chimeric protein, which was purified by immobilized metal affinity chromatography (IMAC). ELISA, differential scanning calorimetry, intrinsic fluorescence, and computational analysis were applied for the characterization of the immunogenicity and conformation of the chimeric protein. Mice immunization showed that the chimeric protein induced twice the number of anti-EIII antibodies in comparison with EIII alone. In turn, the incorporation of the HSP70/EIII chimeric protein in the TI-complex resulted in a twofold increase in its immunogenicity. The formation of this vaccine construction was accompanied by significant conformational changes in the chimeric protein. Using HSP70 in the content of the chimeric protein represents an efficient means for presenting the main antigenic domain of the TBEV envelope protein to the immune system, whereas the incorporation of this chimeric protein into the TI-complex further contributes to the development of a stronger immune response against the TBEV infection.

Modulation of Immunogenicity and Conformation of HA1 Subunit of Influenza A Virus H1/N1 Hemagglutinin in Tubular Immunostimulating Complexes

The HA1 subunit of the influenza virus hemagglutinin (HA) is a valuable antigen for the development of vaccines against flu due to the availability of most antigenic sites which are conformational. Therefore, a novel adjuvanted antigen delivery system, tubular immunostimulating complexes (TI-complexes) comprising monogalactosyldiacylglycerol (MGDG) from different marine macrophytes as a lipid matrix for an antigen, was applied to enhance the immunogenicity of recombinant HA1 of influenza A H1N1 and to study the relation between its immunogenicity and conformation. The content of anti-HA1 antibodies and cytokines was estimated by ELISA after the immunization of mice with HA1 alone, and HA1 was incorporated in TI-complexes based on different MGDGs isolated from green algae Ulva lactuca, brown algae Sargassum pallidum, and seagrass Zostera marina. Conformational changes of HA1 were estimated by differential scanning calorimetry and intrinsic fluorescence. It was shown that the adjuvant activity of TI-complexes depends on the microviscosity of MGDGs, which differently influence the conformation of HA1. The highest production of anti-HA1 antibodies (compared with the control) was induced by HA1 incorporated in a TI-complex based on MGDG from S. pallidum, which provided the relaxation of the spatial structure and, likely, the proper presentation of the antigen to immunocompetent cells.

On the possibility of lipid-induced regulation of conformation and immunogenicity of influenza a virus H1/N1 hemagglutinin as antigen of TI-complexes

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 (HA0S) of influenza A virus H1/N1. Differential scanning calorimetry, fluorescence spectroscopy and circular dichroism showed a dependence of the conformational changes of HA0S on the microviscosity of MGDG. The most viscous MGDG from Zostera marina induced the strongest rearrangements in protein conformation. Immunization of mice with HA0S within TI-complexes comprising different MGDGs resulted in an approximately 2-fold increase of the levels of anti-HA0S antibodies and granulocyte-macrophage colony-stimulating factor (GM-CSF) compared with those induced by HA0S alone. TI-complexes based on MGDG from Z. marina stimulated the maximal production of GM-CSF. However, humoral immune response (anti-HA0S 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 HA0S regions, which are responsible for these types of immune responses.

Cryopreservation of primary cell cultures of marine invertebrates

Primary cell cultures obtained from somatic and larval tissues of bivalve molluscs and from embryos of sea urchins were frozen to -196 degrees C by two-step freezing using 10% dimethyl sulfoxide (DMSO) or/and trehalose (3-30 mg/ml) as cryoprotectants. We estimated both cell viability and the RNA synthetic activity after freeze-thaw. Total lipid extracts from the tissues of echinoderms examined as possible cryoprotective agents demonstrated a weak cryoprotective capacity. Mussel lipid extract was found to possess a considerable cryoprotective activity. Cryoprotective capacity of tested lipids correlated with their thermotropic behaviour. DMSO + trehalose combination was shown to be a favourable cryoprotectant and sea urchin blastula cells the most freezing-tolerant cells.