生物法合成伤寒O-糖蛋白结合疫苗及其免疫原性评估

摘要

Typhoid fever caused bySalmonella Typhi is still a major public health problem in developing coun-tries. In this study, we constructed a genetically modifiedSalmonella Typhi strain expressing O-specific polysaccha-rides (OPS) antigen conjugated to a carrier, recombinant Pseudomonas aeruginosa exotoxin A(rEPA N29). The conju-gates (OPS-rEPA N29) were further purified and evaluated for their immunogenicity. The results of ELISA showed that the conjugates evoked higher titers of IgG than OPS, suggesting that rEPAN29 increased immunogenicity of OPS significantly as a carrier. Moreover, three injections with 3-week interval evoked slightly higher titers of IgG than three injections with 2-week interval. However, injection of excess conjugates could not evoke higher titers of IgG against lipid polysaccharide (LPS). In summary, our study provides a new strategy for preparing polysaccha-rides-protein conjugate vaccines as well as similar bio-conjugate vaccines of other Gram-negative pathogens.%伤寒由伤寒沙门氏菌(Salmonella Typhi)引发,至今在发展中国家仍是备受关注的重要公共卫生问题.文章通过敲除伤寒菌脂多糖合成途径中O-抗原连接酶基因,转入含脑膜炎奈瑟球菌(Neisseria meningitidis)蛋白糖基化途径中糖基转移酶的表达载体,以及改构的重组铜绿假单胞菌(Pseudomonas Aeruginosa)外毒素A(rEPAN29)的表达载体,使细胞内能够诱导合成以伤寒O特异性多糖(O-specific polysaccharides, OPS)为目标抗原、以rEPAN29为载体蛋白的伤寒OPS-rEPAN29糖蛋白复合物,并对纯化所得复合物进行了免疫原性评价.ELISA测定血清抗体滴度表明,rEPA N29作为载体蛋白能有效增加糖链的免疫原性,糖蛋白比单独的多糖能诱导产生更好的免疫应答;3次免疫、间隔3周比间隔2周IgG滴度稍有提高;而免疫过量的糖蛋白,抗O-多糖的血清抗体效价并无提升.文章为生物法制备多糖-蛋白结合疫苗提供了新思路,理论上也适用于其他革兰氏阴性菌的疫苗研发.