synthesis, characterization and immunological properties of escherichia coli 0157:h7 lipopolysaccharide- diphtheria toxoid conjugate vaccine

background and objective: escherichia coli o157:h7, an emerging pathogen, causes severe enteritis and the extraintestinal complication of hemolytic-uremic syndrome. the goal of this study was to evaluate the conjugate of e. coli o157: h7 lipopolysaccharide (lps) with diphtheria toxoid (dt) as a candidate vaccine in mice model. material and methods: lps from e. coli o157:h7 was extracted by hot phenol method and then detoxified. purified lps was coupled to dt with adipic acid dihydrazide (adh) as a spacer and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (edac) as a linker. the coupling molar ratio of lps to dt was 3:1. clinical evaluation of e. coli o157:h7 lps-dt conjugate was also performed. results: the conjugate was devoid of endotoxin activity and indicated 0.125 u/ml of d-lps. mice immunization with d-lps dt conjugate elicited fourfold higher igg antibody in comparison to d-lps. also, in vivo protection of mice with conjugate provided high protection against the ld50 of e. coli o157:h7, which indicated a good correlation with the igg titer. conclusion: our results showed that the suggested vaccine composed of e. coli o157:h7 lps and dt had a significant potential to protect against e. coli infections.