Dmitry V. Yashunsky

The Effect of a BSA Conjugate of a Synthetic Hexasaccharide Related to the Fragment of Capsular Polysaccharide of Streptococcus pneumoniae Type 14 on the Activation of Innate and Adaptive Immune Responses

We report the effect of a bovine serum albumin (BSA) conjugate of a synthetic hexasaccharide (HS) related to the fragment of the capsular polysaccharide (PS) of Streptococcus pneumoniae type 14 on the stimulation of innate immune system and the subsequent development of a PS-specific antibody response. Glycoconjugate (GC) in the presence (GC + AL) or absence of aluminum hydroxide was administered to mice twice. GC increased the number of TLR2-expressing cells and induced the maturation of dendritic cells (CD11c+, CD80+ and, MHCII+), which secreted IL-1β, IL-6, and TNFα into the culture medium. The level of IL-1β, IL-10, IFNγ, and TNFα in the blood increased within 24 h after the single GC administration to mice. On day 7, the numbers of splenic CD4+ and CD8+ T lymphocytes and B lymphocytes increased. After the second immunization, the levels of CD4+ and CD8+ T lymphocytes were lower than in the control, whereas the B cell, NK cell, and MHC class II-expressing cell numbers remained enhanced. However, of the presence of anti-PS, IgG antibodies were not detected. The addition of aluminum hydroxide to GC stimulated the production of GM-CSF, IL-1β, IL-5, IL-6, IL-10, IL-17, IFNγ, and TNFα. Anti-PS IgG1 antibody titers 7 days after the second immunization were high. During that period, normal levels of splenic CD4+ T lymphocytes were maintained, whereas reduced CD8+ T lymphocyte numbers and increased levels of B lymphocytes, NK cells, and MHC class II-expressing cell numbers were observed. Anti-PS IgG levels diminished until day 92. A booster immunization with GC + AL stimulated the production of anti-PS IgG memory antibodies, which were determined within 97 days. The elucidation of specific features of the effect of the synthetic HS conjugate on the stimulation of innate, cell-mediated immunity, and antibody response can favor the optimization of GC vaccine design.

Neural cell activation by phenolic compounds from the Siberian larch (Larix sibirica).

Small organic phenolic compounds from natural sources have attracted increasing attention due to their potential to ameliorate the serious consequences of acute and chronic traumata of the mammalian nervous system. In this contribution, it is reported that phenols from the knot zones of Siberian larch (Larix sibirica) wood, namely, the antioxidant flavonoid (+)-dihydroquercetin (1) and the lignans (-)-secoisolariciresinol (2) and (+)-isolariciresinol (3), affect migration and outgrowth of neurites/processes from cultured neurons and glial cells of embryonic and early postnatal mice. Compounds 1-3, which were available in preparative amounts, enhanced neurite outgrowth from cerebellar granule neurons, dorsal root ganglion neurons, and motoneurons, as well as process formation of Schwann cells in a dose-dependent manner in the low nanomolar range. Migration of cultured astrocytes was inhibited by 1-3, and migration of neurons out of cerebellar explants was enhanced by 1. These observations provide evidence for the neuroactive features of these phenolic compounds in enhancing the beneficial properties of neurons and reducing the inhibitory properties of activated astrocytes in an in vitro setting and encourage the further investigation of these effects in vivo, in animal models of acute and chronic neurological diseases.

Development of approaches to creation of experimental test system for evaluation of antigenic activity of synthetic oligosaccharide ligands related to fragments of the Streptococcus pneumoniae type 14 capsular polysaccharide

A conjugate of a synthetic hexasaccharide fragment of the Streptococcus pneumoniae type 14 capsular polysaccharide with bovine serum albumin (BSA) has been prepared. The antigenic activity and specificity of this conjugate are comparable with those of natural antigens of S. pneumoniae type 14. The data suggest that the resulting synthetic conjugate can be used as a coating antigen in an experimental test system (based on enzyme immunoassay) for evaluating the antigenic activity and specificity of synthetic oligosaccharide ligands and for testing specimens of natural capsular polysaccharides and immune sera.

The evaluation of β-(1 → 3)-nonaglucoside as an anti-Candida albicans immune response inducer.

Synthetically prepared bovine serum albumin (BSA) conjugate of linear β‐(1 → 3)‐nonaglucoside ligand (G9) has been applied as a biological response immunomodulator in vivo and ex vivo. Active immunization of Balb/c mice revealed effective induction of specific humoral responses in comparison with Candida β‐D‐glucan and Candida whole cells. Induced post‐vaccination serum exhibited a growth‐inhibition effect on the multi‐azole‐resistant clinical strain Candida albicans CCY 29‐3‐164 in experimental mucocutaneous infection ex vivo. Evaluation of immune cell proliferation and the cytotoxic potential of the G9‐ligand has revealed its bioavailability and an immunostimulative effect in vaccination‐sensitized Balb/c mice splenocytes and RAW 264.7 macrophages.

Theoretical and Experimental Conformational Studies of Oligoglucosides Structurally Related to Fragments of Fungal Cell Wall β-(1→3)-D-Glucan

The conformational behavior of linear oligo-β-(1→3)-D-glucosides was studied using NMR experiments and molecular modeling. The explicit solvent model in calculations yielded the best coincidence between experimental and theoretical values of NOE and spin-spin coupling constants to evidence the strong influence of solvation upon the conformations of the oligoglucosides. Long-range coupling constants calculated for di- and trimeric clusters of the studied glucosides fit the experimental data much better than the single-molecule approach. It was shown that conformational properties of disaccharide fragments in studied oligoglucosides depended on neither their position in the chain nor the length of the chain.

Theoretical and NMR-based Conformational Analysis of Phosphodiester-linked Disaccharides

The conformational behaviour of three phosphate-bridged dimannosides was studied by means of NMR and computational molecular modelling. First, the conformations of the phosphodiester linker were determined by quantum chemistry methods using dimethyl phosphate as a model. Then, a series of conformations was constructed for each of the studied molecules. Preliminary molecular dynamics (MD) simulations revealed that the inclusion of a cation had a drastic influence on the obtained results. Additionally, triethylammonium had the same effect as sodium as the counter-ion. After that, another series of MD simulations was run. The resulting MD trajectories were used to define the conformations responsible for the observed nuclear Overhauser effects and inter-nuclear coupling.

Antioxidant activity of polyphenols from larch wood: an amperometric study

Purpose The purpose of this paper is to determine the antioxidant activity of natural polyphenols from larch wood by the amperometric method. Design/methodology/approach Direct measurements of antioxidant activity were carried out by the amperometric method in an oxidizing mode with glassy carbon as a working electrode, set potential +1.3V and using a flow-injection system with 2.2 mM phosphoric acid as the mobile phase with a flow rate of 1.2 ml/min. Findings The reported results show the following values of antioxidant activity for the tested compounds: (−)-secoisolariciresinol – 0.199 ± 0.002 mg/L (p < 0.05); isolariciresinol – 0.196 ± 0.002 mg/L (p < 0.05); lariciresinol - 0.222 ± 0.001 mg/L (p < 0.05); O-isopropylidene derivative of (−)-secoisolariciresinol - 0.143 ± 0.002 mg/L (p < 0.05); (+)-dihydroquercetin – 0.153 ± 0.002 mg/L (p < 0.05); and quercetin – 0.521 ± 0.001 mg/L (p < 0.05). The last product was tested as the reference of a widely used current antioxidant. General tendencies of determined values of antioxidant activity for studied compounds are in good correlation with published data as determined by the t-BuOOH-initiated lipid peroxidation method. Practical implications Described results show practical applicability of the amperometric method as being faster and cheaper in comparison to other methods, including oxygen radical absorbance capacity (ORAC) assay or 2,2′diphenyl-1-picrylhydrazyl (DPPH) reagent based assay. Originality/value The described results show the first-time application of the amperometric method for the evaluation of the antioxidant activity of phenolic compounds from larch wood.

Synthesis and effects of flavonoid structure variation on amyloid-β aggregation

Abstract Dietary flavonoids and synthetic derivatives have a well-known potential for biomedical applications. In this perspective, we report herein new methodologies to access chrysin and 5,7-dihydroxychromone, and these structures were combined with those of naturally occurring quercetin, luteolin, (+)-dihydroquercetin and apigenin to assemble a set of polyphenols with structure variations for in vitro testing over the aggregation of Alzheimer’s disease (AD) amyloid peptide Aβ1−42. Using thioflavin-T (ThT) monitored kinetics and subsequent mechanistic analysis by curve fitting, we show that catechol-type flavonoids reduce Aβ1−42 fibril content by 30% at molar ratios over 10. Without affecting secondary nucleation, these compounds accelerate primary nucleation events responsible for early primary oligomer formation, putatively redirecting the latter into off-pathway aggregates. Atomic force microscopy (AFM) imaging of reaction end-points allowed a comprehensive topographical analysis of amyloid aggregate populations formed in the presence of each compound. Formation of Aβ1−42 small oligomers, regarded as the most toxic amyloid structures, seems to be limited by flavonoids with a C2 phenyl group, while flavonol 3-OH is not a beneficial structural feature. Overall, the diversity of structural variations within flavonoids opens avenues for their development as chemical tools in the treatment of AD by tackling the formation and distribution of neurotoxic oligomers species.

The synthesis of the phosphate-bridged tetrasaccharide representing the repeating unit of the capsular polysaccharide of Streptococcus pneumoniae serotype 6B

GRAPHICAL ABSTRACT ABSTRACT Phosphate-bridged tetrasaccharide 1 corresponding to the repeating unit of the capsular polysaccharide of Streptococcus pneumoniae serotype 6B has been synthesized using the hydrogen phosphonate procedure.

Synthesis of a pseudotetrasaccharide corresponding to a repeating unit of the Streptococcus pneumoniae type 6B capsular polysaccharide

GRAPHICAL ABSTRACT ABSTRACT 2-Aminoethyl glycoside of the pseudotetrasaccharide α-d-Glcp-(1→3)-α-l-Rhap-(1→4)-d-Rib-ol-(5-P-2)-α-d-Galp structurally related to a repeating unit of the Streptococcus pneumoniae type 6B capsular polysaccharide has been synthesized. At the key step, suitably protected pseudotrisaccharide α-d-Glcp-(1→3)-α-l-Rhap-(1→4)-d-Rib-ol with a free 5-OH group in the ribitol moiety and 2-OH α-galactoside were connected via a phosphate bridge using the hydrogen phosphonate procedure.