Preparation,Safety and Immunogenicity of S.paratyphoid A-Tetanus Toxoid Conjugate Vaccine

Objective To prepare S.paratyphoid A-tetanus toxoid(TT) conjugate vaccine and study its safety and immunogenicity.Methods The polysaccharide O-SP of S.paratyphoid A was activated with CDAP,derived with ADH,then coupled to TT using EDAC as condensing agent and purified by column chromatography to prepare S.paratyphoid A-tetanus toxoid(TT) conjugate.After control tests,the conjugate was further tested for safety and immunogenicity in animals.Results The ratio of polysaccharide to protein of the prepared conjugate was as stable as 0.6-0.8.The recovery rate of conjugate,determined by Sepharose Cl-4B chromatography,was more than 75% when Kd value was not more than 0.2.The content of high molecular conjugate was not less than 90%.Double immunodiffusion test showed visual precipitation lines of the conjugate with hyperimmune rabbit serum against S.paratyphoid A and TT antiserum.The conjugate showed good safety in animal test.The antibody titer against S.paratyphoid A of mice immunized with the conjugate increased significantly,and the antibody positive conversion rate reached 100%.Conclusion The S.paratyphoid A-tetanus toxoid(TT) conjugate vaccine prepared by activating polysaccharide O-SP with CDAP showed good stability,safety and immunogenicity.