疟疾疫苗

Malaria vaccine

疟疾是世界上分布和流行最广的寄生虫性疾病之一 ,世界上有 2 0亿人口生活在疫区。每年全球大约有 5亿人口患病 ,其中 5 0 %是由恶性疟原虫引起的 ,每年死于疟疾的人口约 10 0万～ 30 0万。尽管疟原虫的生物学研究仍不甚明晰 ,疟疾疫苗的研究在最近的 30年中仍取得了明显的成果。针对疟原虫的生活各周期的主要保护性抗原 ,科研人员已研制了一系列的疟疾侯选疫苗 ,如CSP疟疾疫苗、MSP1疟疾疫苗、pfs2 5疟疾疫苗和SPf6 6多期多抗原合成疟疾疫苗等。目前疟疾疫苗主要历经减毒疫苗、亚单位疫苗和DNA疫苗三种形式。因为在疟原虫生活周期不同阶段存在着不同的侯选抗原 ,依此又可将疟疾侯选疫苗按其起作用时期分为红细胞前期疫苗、红细胞内期疫苗、配子期疫苗和多期多抗原疫苗。但到目前为止 ,仍未开发出十分理想的疟疾疫苗。由于疟原虫生活史复杂、抗原多且免疫原性弱 ,单独应用疟疾疫苗难以取得很好的预防效果 ,所以必须配合以佐剂来增强其免疫效果。然而不同的佐剂对不同疟疾侯选疫苗的免疫增强效果有着明显差异 ,因此佐剂的选择是疫苗成功与否的关键因素之一。另外 ,宿主的遗传性限制也影响着疫苗的保护效果。

Malaria is one of the most widespread parasite diseases in the world. About two billion people live in malaria epidemic areas. 500 million clinical cases of malaria per year occur all over the world, 50 percent of which are caused by Plasmodium falciparum. And the 1～3 million patients die of malaria every year. Although the knowledge of the parasite's biological behaviors is indefinite, significant progress has been made in the development of malaria vaccine during the last 30 years. According to the stages of the parasite's life cycle and some main conserved antigens,which play an important role in multiple or alternative steps during the invasion process, researchers have developed a series of vaccine against malaria, such as CSP vaccine, MSP1 vaccine, pfs25 vaccine, SPf66 synthetic vaccine and so on. At present, there have been three types of malaria vaccine: attenuated vaccine, subunit vaccine and DNA vaccine. Because different antigens are expressed during different stages of the parasite's life cycle, we can also divide malaria vaccines into pre-erythrocytic vaccine, erythrocytic vaccine, sexual vaccine and multiantigenic synthetic vaccine of multistage. Successful malaria vaccine is not developed by this time. Owing to the complexity of the parasite's life cycle, the variety of antigens, low immunogenicity and limited protection induced by single candidate malaria vaccine, adjuvants must be applied with these candidate vaccines in order to improve their immunogenicity. It lies the definite difference in protection induced by uniting the different adjuvants and the different candidate vaccine, so it is important for ideal malaria vaccine to select suitable adjuvant. Furthermore, genetic restriction of the immune response to malaria has also an effect on vaccine protection.