On the Possibility of Lipid-Induced Regulation of Conformation and Immunogenicity of Influenza A Virus H1/N1 Hemagglutinin as Antigen of TI-Complexes

Abstract

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.

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

“…We used the same MGDG samples that were applied earlier in the study of secreted uncleaved HA (HA0s) of influenza A virus H1/N1 A/California/04/2009 [ 11 ]. MGDGs isolated from green algae U. lactuca , brown algae S. pallidum , and seagrass Z. marina differ in their fatty acid composition [ 13 ] and, therefore, microviscosity [ 10 ].…”

“…The same MGDG samples as those employed in Reference [ 11 ] were applied. To prepare them, three species of marine macrophytes from three divisions: S. pallidum (Phaeophyta), U. lactuca (Chlorophyta), and Z. marina (Embryophyta) were harvested in the Sea of Japan in summer at a seawater temperature of 20–23 °C.…”

“…Samples for DSC and spectroscopic studies were prepared as described in Reference [ 11 ]. MGDG dissolved in chloroform was introduced into standard aluminum pans.…”

“…The content of anti-HA1 antibodies was estimated in mouse blood serum by ELISA, applying anti-mouse IgG labeled with peroxidase (Research Institute of Epidemiology and Microbiology, RAMS) as described in Reference [ 11 ]. The sera of the PBS-injected animals served as negative controls.…”

“…Our previous studies have shown that TI-complexes can not only significantly enhance the immune response against porin of enterobacteria Yersinia pseudotuberculosis , but also allow for the optimization of vaccine construction by changing the physicochemical properties of the lipid surrounding the protein and, consequently, affecting its conformation and immunogenicity [ 10 ]. TI-complexes incorporating HA0 of Influenza A H1N1 hemagglutin (A/California/04/2009(H1N1) also stimulated the production of anti-HA0 antibodies [ 11 ]. However, the level of anti-HA0 antibodies did not depend on the physicochemical properties of MGDGs despite changes in the spatial structure of HA0.…”