Center for Molecular Parasitology, Department of Microbiology and Immunology, Drexel University College of Medicine, Philadelphia, Pennsylvania, USA.
Infect Immun. 2012 Jul;80(7):2473-84. doi: 10.1128/IAI.00211-12. Epub 2012 May 14.
The C-terminal 19-kDa domain of merozoite surface protein 1 (MSP1₁₉) is the target of protective antibodies but alone is poorly immunogenic. Previously, using the Plasmodium yoelii murine model, we fused P. yoelii MSP1₁₉ (PyMSP1₁₉) with full-length P. yoelii merozoite surface protein 8 (MSP8). Upon immunization, the MSP8-restricted T cell response provided help for the production of high and sustained levels of protective PyMSP1₁₉- and PyMSP8-specific antibodies. Here, we assessed the vaccine potential of MSP8 of the human malaria parasite, Plasmodium falciparum. Distinct from PyMSP8, P. falciparum MSP8 (PfMSP8) contains an N-terminal asparagine and aspartic acid (Asn/Asp)-rich domain whose function is unknown. Comparative analysis of recombinant full-length PfMSP8 and a truncated version devoid of the Asn/Asp-rich domain, PfMSP8(ΔAsn/Asp), showed that both proteins were immunogenic for T cells and B cells. All T cell epitopes utilized mapped within rPfMSP8(ΔAsn/Asp). The dominant B cell epitopes were conformational and common to both rPfMSP8 and rPfMSP8(ΔAsn/Asp). Analysis of native PfMSP8 expression revealed that PfMSP8 is present intracellularly in late schizonts and merozoites. Following invasion, PfMSP8 is found distributed on the surface of ring- and trophozoite-stage parasites. Consistent with a low and/or transient expression of PfMSP8 on the surface of merozoites, PfMSP8-specific rabbit IgG did not inhibit the in vitro growth of P. falciparum blood-stage parasites. These studies suggest that the further development of PfMSP8 as a malaria vaccine component should focus on the use of PfMSP8(ΔAsn/Asp) and its conserved, immunogenic T cell epitopes as a fusion partner for protective domains of poor immunogens, including PfMSP1₁₉.
裂殖子表面蛋白 1（MSP1₁₉）的 C 端 19kDa 结构域是保护性抗体的靶标，但单独使用时免疫原性较差。以前，我们使用约氏疟原鼠模型，将约氏疟原虫 MSP1₁₉（PyMSP1₁₉）与全长约氏疟原虫裂殖子表面蛋白 8（MSP8）融合。在免疫时，MSP8 限制性 T 细胞反应为产生高水平和持续的 PyMSP1₁₉和 PyMSP8 特异性抗体提供了帮助。在这里，我们评估了人类疟原虫，恶性疟原虫 MSP8 的疫苗潜力。与 PyMSP8 不同，恶性疟原虫 MSP8（PfMSP8）含有一个 N 端天冬酰胺和天冬氨酸（Asn/Asp）丰富的结构域，其功能尚不清楚。对重组全长 PfMSP8 和缺乏 Asn/Asp 丰富结构域的截短版本 PfMSP8（ΔAsn/Asp）的比较分析表明，这两种蛋白都能刺激 T 细胞和 B 细胞产生免疫反应。所有 T 细胞表位都位于 rPfMSP8（ΔAsn/Asp）内。主要的 B 细胞表位是构象性的，与 rPfMSP8 和 rPfMSP8（ΔAsn/Asp）都相同。对天然 PfMSP8 表达的分析表明，PfMSP8 在内含子晚期裂殖体和裂殖子中存在于细胞内。入侵后，PfMSP8 分布在环和滋养体阶段寄生虫的表面。与 PfMSP8 在裂殖子表面的低表达或瞬时表达一致，PfMSP8 特异性兔 IgG 不能抑制恶性疟原虫血期寄生虫的体外生长。这些研究表明，PfMSP8 作为疟疾疫苗成分的进一步开发应集中在使用 PfMSP8（ΔAsn/Asp）及其保守的、免疫原性 T 细胞表位作为包括 PfMSP1₁₉在内的免疫原性差的保护性结构域的融合伴侣上。
