Design, synthesis and determination of physical and chemical characteristics of glycoconjugates as model for oligosaccharide vaccines against vibrio cholerae

Abstract

Cholera is toxin-mediated enteroinfection, with epidemic character and there are approximately 120000 death cases per year worldwide. Protection against cholera has not been accomplished due to deficiencies in the licensed vaccines. Serum vibriocidal activity mediated by LPS antibodies is the only immune segment correlated with the resistance of cholera. On the basis of literature data (Robbins JB, 1990; Ogawa Y, 1996) we synthesized glucoconjugates, composed of detoxified LPS from Vibrio cholerae and protein carriers. Conjugate vaccines were prepared by binding acetic acid and hydrazine-treated lipopolysaccharide (LPS) from Vibrio cholerae O1, serotype Inaba, to cholera toxin B-subunit (CT-B) and bovine serum albumin (cBSA). Adipic acid dihydrazide was used for derivatization of oligosaccharides and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) as conjugating agent. SDS-PAGE, glycoprotein detection and TLC dot-blot were used for physical and chemical analysis of the prepared four types of conjugates. Safe level of endotoxins, measured by LAL assay was detected in all conjugates. The synthesized conjugates can be used for monitoring immunization schemes on experimental animals. It is to be expected that conjugated vaccines are safe and efficient and that will have high immunogenic and T-dependant characteristics with long immune protection against cholera.