Induction of protective immunity against malaria by MSP1/hsc70 fusion protein vaccine

我们开发了一种方法，通过用一种特定抗原作为小鼠热休克同源蛋白70 （hsc70）的融合伴侣免疫小鼠来诱导CD4和CDS特异性免疫反应。我们使用这种策略诱导针对疟疾孢子虫感染的保护性免疫。我们制备了MSP1与hsc70融合的重组蛋白（MSP1/hsc70），并研究其是否能诱导对肝期约氏P. yoelii的保护性免疫，因为我们发现MSP1在约氏P. yoelii生命周期的肝期表达。MSP1/hsc70在不添加任何佐剂的情况下免疫小鼠可诱导强烈的特异性抗体反应和IFN-y的产生。当免疫小鼠接受约氏疟原虫孢子虫攻击时，寄生虫病的发病时间比单纯接种hsc70的小鼠或未接种hsc70的小鼠晚几天，这表明免疫小鼠可诱导对肝期疟疾的保护性免疫反应。为了证实msp1对红细胞外型疟疾感染的特异性保护性免疫反应，我们对感染肝脏中约氏疟原虫特异性rRNA进行了RT-PCR分析。用该融合蛋白免疫小鼠的约氏疟原虫水平降低，而单独用hsc70免疫小鼠的约氏疟原虫水平没有降低，这表明msp1特异性保护性免疫对肝期疟疾有效。这种保护性免疫是通过免疫小鼠的脾细胞或肝淋巴细胞转移到小鼠体内，而不是通过抗血清转移到小鼠体内，表明这种保护是通过细胞机制介导的。最后，在C57BL/6、A/J、BALB/c和C3H小鼠中观察到疫苗诱导的保护作用，这表明在各种遗传背景的动物中都可以在红细胞外期诱导msp1特异性保护性免疫。

We have developed a method to induce CD4 and CDS specific immune responses by immunizing mice with a particular antigen as a fusion partner of mouse heat-shock cognate protein 70 (hsc70). We used this strategy to induce protective immunity against malaria sporozoite infection. We generated a recombinant protein of MSP1 fused to hsc70 (MSP1/hsc70) and studied whether it could induce protective immunity against liver stage P. yoelii, since we found that MSP1 is expressed during liver stage of P. yoelii life cycle. The immunization of mice with MSP1/hsc70 without any additional adjuvant induced strong specific antibody responses and IFN-y production. When the immunized mice were challenged with P. yoelii sporozoites, the onset of parasitemia delayed a few days when compared with naive mice or mice immunized with hsc70 alone, suggesting the induction of protective immune responses against liver stage malaria. To confirm the MSP1-specific protective immune responses against exoerythrocytic forms of malaria infection, we performed RT-PCR analysis of P. yoelii-specific rRNA in the infected liver. The level of P. yoelii was reduced in mice immunized with this fusion protein, but not in mice immunized with hsc70 alone, suggesting that MSP1-specific protective immunity is effective at liver stage malaria. This protective immunity was transferred into naive mice by spleen cells or liver lymphocytes of immune mice but not by antiserum, indicating that the protection is mediated by cellular mechanisms. Finally, the vaccine-induced protection was observed in C57BL/6, A/J, BALB/c and C3H mice suggesting that MSP1-specific protective immunity at the exoerythrocytic stage can be induced in animals over a wide range of genetic backgrounds.