Structural and biophysical analysis of sero-specific immune responses using epitope grafted Dengue ED3 mutants
Structural and biophysical analysis of sero-specific immune responses using epitope grafted Dengue ED3 mutants
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DOI：
10.1016/j.bbapap.2015.07.004
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发表时间：
2015-10-01
影响因子：
3.2
通讯作者：
Kuroda, Yutaka
中科院分区：
文献类型：
--
作者：
Kulkarni, Manjiri R.;Islam, Monirul M.;Kuroda, Yutaka
登革热是一种重新出现的热带疾病，其严重形式是由其四种血清型(DEN1、DEN2、DEN3和DEN4)之间的交叉反应引起的。病毒包膜蛋白(ED3)的第三个结构域包含两个主要的表位，是一种非常适合于检测病毒血清特异性的分子决定因素的模型蛋白。在这里，我们检验了针对DEN3和DEN4ED3的免疫反应的血清特异性和交叉反应性，使用六个表位嫁接的ED3变异体，其中来自DEN3ED3的表面暴露的表位残基被切换为DEN4ED3的表位残基，反之亦然。我们用瑞士白化小鼠免疫制备了抗DEN3和抗DEN4ED3血清，并测定了它们对所有6个接枝突变株的反应性。正如预期的那样，这两种血清都表现出与其自身血清型的ED3的强烈反应性，而与其对应的血清型的ED35的交叉反应很少。E_2在抗DEN_3血清的特异性中起主要作用，而E_1对DEN_4ED3‘S的血清特异性起重要作用。接下来，反应模式证实了我们的工作假设，即通过将表面暴露的表位残基从一种血清型移植到另一种血清型，可以转移血清特异性。为了从结构的角度分析上述结果，我们确定了一个DEN4 ED3变体的晶体结构，其中E2是从DEN3 ED3嫁接而来的，分辨率为2.78埃，并假设总的主链保持不变，对剩余的五个嫁接变体的结构进行了建模。对变异体的静电和分子表面的检查为免疫反应的血清特异性提供了一些进一步的理论基础。(C)2015爱思唯尔B.V.保留所有权利。
Dengue fever is a re-emerging tropical disease and its severe form is caused by cross-reactivity between its four serotypes (DEN1, DEN2, DEN3 and DEN4). The third domain of the viral envelope protein (ED3) contains the two major putative epitopes and is a highly suitable model protein for examining the molecular determinants of a virus' sero-specificity. Here we examine d the sero-specificity and cross-reactivity of the immune response against DEN3 and DEN4 ED3 using six epitope grafted ED3 variants where the surface-exposed epitope residues from DEN3 ED3 were switched to those of DEN4 ED3 and vice versa. We prepared anti-DEN3 and anti-DEN4 ED3 serum by immunizing Swiss albino mice and measured their reactivities against all six grafted mutants. As expected, both sera exhibited strong reactivity against its own serotype's ED3, and little cross-reactivity against their counterpart serotype's ED35. E2 played a major role in the sero-specificity of anti-DEN3 serum, whereas El was important for DEN4 ED3's sero-specificity. Next, the reactivity patterns corroborated our working hypothesis that sero-specificity could be transferred by grafting the surface exposed epitope residues from one serotype to the other. To analyze the above results from a structural viewpoint, we determined the crystal structure of a DEN4 ED3 variant, where E2 was grafted from DEN3 ED3, at 2.78 angstrom resolution and modeled the structures of the five remaining grafted variants by assuming that the overall backbone remained unchanged. The examination of the electrostatic and molecular surfaces of the variants suggested some further rationale for the serospecificity of the immune responses. (C) 2015 Elsevier B.V. All rights reserved.