Synthesis of glycinated glycoconjugates based on 1-thioglycosides and their preliminary studies as potential immunomodulatory factor.

The biological importance of lipopolysaccharides (LPS), components of bacterial cell wall has not been explained sufficiently. The glycine present in these structures could play an important role in the immunological response after bacterial infections and during sepsis. In our studies we obtained synthetic and stable substituted glycinated 1-thioglycosides derivatives of monosaccharides, e.g., D-glucose or D-galactose as well as disaccharides, e.g., melibiose and lactose. The conditions of acylation reactions were validated and specific products were separated by using chromatography methods. Their structures were confirmed by NMR. These compounds were conjugated with carrier proteins e.g., bovine serum albumin and horse myoglobin. Prior to conjugation proteins were modified with glycidol to create the protein-diol intermediates and subsequent periodate oxidation of the glycol moieties to generate the reactive aldehyde functionalities. Modified and formylated carrier proteins were conjugated with acylated thioglycosides in the presence of sodium cyanoborohydride. Subsequently, the products obtained were analyzed in SDS-PAGE and separated by using HW-55S gel-filtration chromatography. The immunoreactivity of selected glycinated glycoconjugates were studied in ELISA assays with specific anti-aminoacylated glyconjugate antibodies obtained after rabbit immunization with Escherichia coli K12 C600 core oligosaccharide glycine-containing glycoconjugate. The differences in the immunoreactivity of different glycinated 1-thioglycosides were observed. The received glycine-acylated glycoconjugates could mimic the non-sugar substituents localized in various bacterial LPS. These synthetic compounds could be candidates for their use as glycoconjugate vaccines in protection against serious bacterial infections, e.g.. sepsis.