Department of Biological Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai, India.
Department of Genetics and Complex Diseases, Harvard T. H. Chan School of Public Health, Graduate School of Arts and Sciences, Harvard University, Boston, USA.
Malar J. 2018 Aug 20;17(1):304. doi: 10.1186/s12936-018-2455-6.
Plasmodium enolase is a target for the growth neutralizing antibodies. Interestingly, the three invasive stages i.e. sporozoites, merozoites, and ookinetes express this protein on their cell surface. Polyclonal anti-Plasmodium falciparum enolase (Pfeno) antibodies disrupt traversal of ookinete through mosquito mid-gut wall as well as have inhibitory effect on parasite growth at erythrocytic stage. In a recent study, it was observed that immunization with a unique epitope of parasite enolase (EWGWS) could confer partial protection against mouse malaria. Further validation is needed for the protective potential of this unique epitope in otherwise highly conserved enolase.
In order to investigate the efficacy of growth inhibitory potential of the epitope of P falciparum enolase, a monoclonal antibody specific to EWGWS is generated. In vitro parasite growth inhibition assays and passive immunization of Plasmodium yoelii (or Plasmodium berghei) infected mice were used to assess the parasite growth neutralizing activity of the antibody.
Screening a panel of monoclonal antibodies raised against recombinant Pfeno that were specific to EWGWS resulted in isolation of H12E1. This antibody recognized only EWGWS epitope containing enolases. H12E1 strongly inhibited parasite growth in culture. This inhibition was strain transcending. Passive infusion of this antibody in P. yoelii or P. berghei infected mice showed significant reduction in parasitemia as compared to controls (p < 0.001). Surface Plasmon Resonance measurements indicated high affinity binding of H12E1 to P. falciparum enolase (K ~ 7.6 × 10M).
A monoclonal antibody directed against EWGWS epitope of Pfeno was shown to inhibit the growth of blood stage malarial parasites. This inhibition was species/strain transcending and is likely to arise due to blockade of enolase on the surface of merozoites, functionally implicating Pfeno in invasion related events. Presence of enolase on the cell surface of merozoites and ookinetes could potentially result in inhibition of host cell invasions at erythrocytic and transmission stages in the parasite life cycle. It is suggested that antibodies against EWGWS epitope have the potential to confer dual stage, species and strain transcending protection against malaria.
疟原虫烯醇化酶是生长中和抗体的靶标。有趣的是，三个侵袭阶段，即孢子、裂殖体和动合子，在其细胞表面表达这种蛋白。多克隆抗恶性疟原虫烯醇化酶（Pfeno）抗体可破坏动合子穿过蚊中肠壁的过程，对红细胞阶段的寄生虫生长具有抑制作用。在最近的一项研究中，观察到用寄生虫烯醇化酶的独特表位（EWGWS）免疫可部分保护小鼠疟疾。需要进一步验证这种在高度保守的烯醇酶中独特表位的保护潜力。
为了研究 Pfeno 表位的生长抑制潜力，生成了针对 EWGWS 的单克隆抗体。体外寄生虫生长抑制试验和感染 Plasmodium yoelii（或 Plasmodium berghei）的小鼠被动免疫用于评估该抗体对寄生虫生长的中和活性。
筛选针对重组 Pfeno 的一组针对 EWGWS 的单克隆抗体，分离出 H12E1。该抗体仅识别含有 EWGWS 表位的烯醇化酶。H12E1 强烈抑制培养中的寄生虫生长。这种抑制是跨株的。在 P. yoelii 或 P. berghei 感染的小鼠中输注这种抗体可显著降低寄生虫血症与对照组相比（p<0.001）。表面等离子体共振测量表明 H12E1 与恶性疟原虫烯醇化酶具有高亲和力结合（K~7.6×10M）。
针对 Pfeno EWGWS 表位的单克隆抗体被证明可抑制血期疟原虫寄生虫的生长。这种抑制是跨物种/株的，可能是由于裂殖体表面烯醇化酶的阻断，在功能上表明 Pfeno 参与了入侵相关事件。裂殖体和动合子细胞表面的烯醇化酶可能导致寄生虫生命周期中红细胞期和传播期宿主细胞入侵的抑制。建议针对 EWGWS 表位的抗体具有赋予针对疟疾的双重阶段、物种和株的跨免疫保护潜力。
