Qian Feng, Wu Yimin, Muratova Olga, Zhou Hong, Dobrescu Gelu, Duggan Peter, Lynn Lambert, Song Guanhong, Zhang Yanling, Reiter Karine, MacDonald Nicholas, Narum David L, Long Carole A, Miller Louis H, Saul Allan, Mullen Gregory E D
Malaria Vaccine Development Branch, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 5640 Fishers Lane, Rockville, MD 20852, USA.
Vaccine. 2007 May 16;25(20):3923-33. doi: 10.1016/j.vaccine.2007.02.073. Epub 2007 Mar 13.
Conjugation of polysaccharides to carrier proteins has been a successful approach for producing safe and effective vaccines. In an attempt to increase the immunogenicity of two malarial vaccine candidate proteins of Plasmodium falciparum, apical membrane antigen 1 (AMA1) to a blood stage vaccine candidate and surface protein 25 (Pfs25) a mosquito stage vaccine candidate, were each independently chemically conjugated to the mutant, nontoxic Pseudomonas aeruginosa ExoProtein A (rEPA). AMA1 is a large (66kD) relatively good immunogen in mice; Pfs25 is a poorly immunogenic protein when presented on alum to mice. Mice were immunized on days 0 and 28 with AMA1- or Pfs25-rEPA conjugates or unconjugated AMA1 or Pfs25, all formulated on Alhydrogel. Remarkably, sera from mice 14 days after the second immunization with Pfs25-rEPA conjugates displayed over a 1000-fold higher antibody titers as compared to unconjugated Pfs25. In contrast, AMA1 conjugated under the same conditions induced only a three-fold increase in antibody titers. When tested for functional activity, antibodies elicited by the AMA1-rEPA inhibited invasion of erythrocytes by blood-stage parasites and antibodies elicited by the Pfs25-rEPA conjugates blocked the development of the sexual stage parasites in the mosquito midgut. These results demonstrate that conjugation to rEPA induces a marked improvement in the antibody titer in mice for the poor immunogen (Pfs25) and for the larger protein (AMA1). These conjugates now need to be tested in humans to determine if mice are predictive of the response in humans.
将多糖与载体蛋白结合是生产安全有效疫苗的一种成功方法。为了提高恶性疟原虫两种疟疾疫苗候选蛋白的免疫原性，即作为血液阶段疫苗候选物的顶端膜抗原1（AMA1）和作为蚊子阶段疫苗候选物的表面蛋白25（Pfs25），分别独立地将它们化学偶联到突变的无毒铜绿假单胞菌外蛋白A（rEPA）上。AMA1是一种较大的（66kD）在小鼠中免疫原性相对较好的蛋白；Pfs25在明矾上呈递给小鼠时是一种免疫原性较差的蛋白。在第0天和第28天用AMA1-或Pfs25-rEPA偶联物或未偶联的AMA1或Pfs25对小鼠进行免疫，所有这些都用氢氧化铝佐剂配制。值得注意的是，与未偶联的Pfs25相比，用Pfs25-rEPA偶联物进行第二次免疫14天后小鼠血清中的抗体滴度高出1000倍以上。相比之下，在相同条件下偶联的AMA1仅诱导抗体滴度增加了三倍。当测试功能活性时，AMA1-rEPA引发的抗体抑制血液阶段寄生虫对红细胞的侵袭，而Pfs25-rEPA偶联物引发的抗体阻断蚊子中肠中性阶段寄生虫的发育。这些结果表明，与rEPA偶联可显著提高小鼠中免疫原性较差的蛋白（Pfs25）和较大蛋白（AMA1）的抗体滴度。现在需要在人体中测试这些偶联物，以确定小鼠是否能预测人体的反应。
