基于钉螺血蓝蛋白与日本血吸虫共有碳水化合物表位的新型疫苗和诊断抗原研究

Schistosomiasis is a severe parasitic disease, infecting 200 million people mainly in developing countries and resulting in more than 250,000 deaths per year. So far, vaccines against schistosome are not yet available for schistosomiasis.A major problem that has hindered schistosomiasis vaccine research and development lies in the identification and selection of potential protective antigens. During schistosome 's life cycle, the parasite generates a large array of carbohydrates which have been shown to be major targets of the host immune system, raising the possibility that such carbohydrate antigens might be useful targets for the development of new vaccines. Our previous research indicates that the hemocyanin from Oncomelania hupensis shared carbohydrate epitopes with different developmental stages of Schistosoma japonicum including cercaria, schistosomulum, adult worm and egg, which have a potential for use in diagnostic and therapeutic studies of schistosomiasis. However the development of carbohydrate-based vaccines and diagnostic antigens are hampered by the technical difficulty of chemically synthesizing complex carbohydrate structures. Use of carbohydrate mimetic peptides can circumvents this difficulty, as short peptide can be easily synthesized and modified.In this project application, we will be screening mimetic peptides of the shared carbohydrate epitopes between Oncomelania hupensis hemocyanin and different developmental stages of Schistosoma japonicum with phage random twelve peptide library. These carbohydrate-mimetic peptides will be used as immunogens to raise anti-carbohydrate antibodies against schistosomiasis or as diagnostic antigens for the serodiagnosis of Schistosomiasis.

血吸虫病为世界第二大寄生虫病,但迄今为止还没有找到一种可用于阻断血吸虫病传播的高效疫苗，为此有必要继续探索寻找新的疫苗候选分子。血吸虫发育的各阶段均合成大量的碳水化合物，它们是宿主免疫系统攻击的重要靶点，但当前基于碳水化合物表位的血吸虫疫苗研究还很少有见报道,为此研究基于碳水化合物表位的疫苗可为血吸虫疫苗的发展提供新的策略。申请者前期研究表明血吸虫中间宿主钉螺血淋巴中的血蓝蛋白与日本血吸虫不同发育阶段均共有碳水化合物表位，这些共有表位在血吸虫病诊断和疫苗研究中展示了非常好的应用效果。但由于碳水化合物表位不能像多肽表位进行克隆表达，限制了其发展。为此本项目申请旨在采用噬菌体随机十二肽库获得钉螺血蓝蛋白与日本血吸虫不同发育阶段共有碳水化合物表位的模拟肽表位，通过表型模拟获得碳水化合物表位的抗原性和保护力。随后进一步，考察模拟肽表位在日本血吸虫病诊断和疫苗研究中的价值。

我们开展了采用噬菌体随机十二肽库筛选钉螺血蓝蛋白与日本血吸虫不同发育阶段共有碳水化合物表位的模拟肽表位工作，随后考察模拟肽表位在日本血吸虫病诊断和疫苗研究中的价值。以最后一轮洗脱并扩增的混合噬菌体及经 ELISA鉴定筛选的2个噬菌体模拟肽单克隆为免疫原,分别免疫小鼠进行抗日本血吸虫免疫保护力研究。结果与对照组相比，混合噬菌体免疫小鼠导致了48.6％的减虫率和61.4％的减卵率；2个噬菌体模拟肽单克隆免疫小鼠分别导致了28.3％ 和 37.5％的减虫率，及43.7％ 和 50.4％的减卵率。最后我们评估了2个噬菌体模拟肽单克隆作为日本血吸虫病诊断抗原的效果， 结果展示具有较好的特异性。