Fine mapping of an epitope recognized by an invasion-inhibitory monoclonal antibody on the malaria vaccine candidate apical membrane antigen 1
Fine mapping of an epitope recognized by an invasion-inhibitory monoclonal antibody on the malaria vaccine candidate apical membrane antigen 1
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DOI：
10.1074/jbc.m610562200
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发表时间：
2007-03-09
影响因子：
4.8
通讯作者：
Blackman, Michael J.
中科院分区：
文献类型：
--
作者：
Collins, Christine R.;Withers-Martinez, Chrislaine;Blackman, Michael J.
抑制疟原虫裂殖子侵入红细胞的抗体阻断引起临床疟疾的红细胞周期。侵袭抑制性单克隆抗体（mAb）4G 2识别恶性疟原虫必需微线体蛋白和疫苗候选物顶端膜抗原1（PfAMA 1）胞外域中的保守表位。在这里，我们证明，纯化的Fab片段的4G 2抑制入侵显着更有效地比完整的mAb，这表明该mAb的侵袭抑制活性不仅是由于空间效应和表位位于分子的功能关键区域内。我们已经利用合成基因编码的PfAMA 1的修饰形式，和现有的X-射线晶体结构数据，充分表征该表位。我们首先通过证明它完全补充了恶性疟原虫中真实基因的功能来验证该基因。然后，我们用它来确定一组残基在前面描述的结构域11环的PfAMA 1的识别mAb 4G 2的关键，并证明，表位只位于这个环与分子的其他结构域中的残基没有贡献。这是PfAMA 1上保守的侵袭抑制表位的第一个完整表征。我们的研究结果将有助于亚单位疫苗的设计，旨在产生广泛有效的，集中的抗PfAMA 1保护性免疫反应，并可能有助于阐明PfAMA 1的功能。
Antibodies that inhibit red blood cell invasion by the Plasmodium merozoite block the erythrocytic cycle responsible for clinical malaria. The invasion-inhibitory monoclonal antibody (mAb) 4G2 recognizes a conserved epitope in the ectodomain of the essential Plasmodium falciparum microneme protein and vaccine candidate, apical membrane antigen 1 (PfAMA1). Here we demonstrate that purified Fab fragments of 4G2 inhibit invasion markedly more efficiently than the intact mAb, suggesting that the invasion-inhibitory activity of this mAb is not due solely to steric effects and that the epitope lies within a functionally critical region of the molecule. We have taken advantage of a synthetic gene encoding a modified form of PfAMA1, and existing x-ray crystal structure data, to fully characterize this epitope. We first validate the gene by demonstrating that it fully complements the function of the authentic gene in P. falciparum. We then use it to identify a group of residues within the previously described domain 11 loop of PfAMA1 that are critical for recognition by mAb 4G2 and demonstrate that the epitope lies exclusively within this loop with no contributions from residues in other domains of the molecule. This is the first complete characterization of a conserved invasion-inhibitory epitope on PfAMA1. Our results will aid in the design of subunit vaccines designed to generate a broadly effective, focused anti-PfAMA1 protective immune response and may help elucidate the function of PfAMA1.