Dowd Kimberly A, DeMaso Christina R, Pierson Theodore C
Viral Pathogenesis Section, Laboratory of Viral Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA.
Viral Pathogenesis Section, Laboratory of Viral Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
mBio. 2015 Nov 3;6(6):e01559-15. doi: 10.1128/mBio.01559-15.
Flaviviruses sample an ensemble of virion conformations resulting from the conformational flexibility of their structural proteins. To investigate how sequence variation among strains impacts virus breathing, we performed studies with the monoclonal antibody (MAb) E111, which binds an inaccessible domain III envelope (E) protein epitope of dengue virus serotype 1 (DENV1). Prior studies indicated that an observed ~200-fold difference in neutralization between the DENV1 strains Western Pacific-74 (West Pac-74) and 16007 could not be explained by differences in the affinity of MAb E111 for each strain. Through neutralization studies with wild-type and variant viruses carrying genes encoding reciprocal mutations at all 13 amino acid differences between the E proteins of West Pac-74 and 16007, we found that E111 neutralization susceptibility mapped solely to the presence of a lysine or arginine at E domain II residue 204, located distally from the E111 epitope. This same residue correlated with neutralization differences observed for MAbs specific for epitopes distinct from E111, suggesting that this amino acid dictates changes in the conformational ensembles sampled by the virus. Furthermore, an observed twofold difference in the stability of infectious West Pac-74 versus 16007 in solution also mapped to E residue 204. Our results demonstrate that neutralization susceptibility can be altered in an epitope-independent manner by natural strain variation that influences the structures sampled by DENV. That different conformational ensembles of flaviviruses may affect the landscape available for antibody binding, as well as virus stability, has important implications for functional studies of antibody potency, a critical aspect of vaccine development.
The global burden of dengue virus (DENV) is growing, with recent estimates of ~390 million human infections each year. Antibodies play a crucial role in protection from DENV infection, and vaccines that elicit a robust antibody response are being actively pursued. We report here the identification of a single amino acid residue in the envelope protein of DENV serotype 1 that results in global changes to virus structure and stability when it is changed. Our results indicate that naturally occurring variation at this particular site among virus strains impacts the ensemble of structures sampled by the virus, a process referred to as virus breathing. The finding that such limited and conservative sequence changes can modulate the landscape available for antibody binding has important implications for both vaccine development and the study of DENV-reactive antibodies.
黄病毒会呈现出由其结构蛋白的构象灵活性所导致的一系列病毒粒子构象。为了研究毒株之间的序列变异如何影响病毒的“呼吸”作用，我们使用单克隆抗体（MAb）E111进行了研究，该抗体可结合登革热病毒1型（DENV1）包膜（E）蛋白结构域III中一个无法接近的表位。先前的研究表明，DENV1毒株西太平洋-74（西太平洋-74）和16007之间观察到的中和作用约200倍的差异，无法用MAb E111对各毒株的亲和力差异来解释。通过对野生型和携带在西太平洋-74和16007的E蛋白之间所有13个氨基酸差异处编码相互突变基因的变异病毒进行中和研究，我们发现E111中和敏感性仅取决于E结构域II残基204处赖氨酸或精氨酸的存在，该残基位于远离E111表位的位置。这个相同的残基与针对不同于E111表位的表位的单克隆抗体所观察到的中和差异相关，这表明该氨基酸决定了病毒所呈现的构象集合的变化。此外，在溶液中观察到的有感染性的西太平洋-74与16007稳定性上的两倍差异也映射到E残基204。我们的结果表明，中和敏感性可以通过影响DENV所呈现结构的自然毒株变异以不依赖表位的方式改变。黄病毒不同的构象集合可能会影响抗体结合的可用格局以及病毒稳定性，这对于抗体效力的功能研究具有重要意义，而抗体效力是疫苗开发的一个关键方面。
登革热病毒（DENV）的全球负担正在增加，最近估计每年约有3.9亿人感染。抗体在预防DENV感染中起着关键作用，目前正在积极研发能引发强烈抗体反应的疫苗。我们在此报告，在DENV 1型包膜蛋白中鉴定出一个单一氨基酸残基，当它发生变化时会导致病毒结构和稳定性的整体变化。我们的结果表明，病毒毒株之间在这个特定位点的自然变异会影响病毒所呈现的结构集合，这一过程称为病毒“呼吸”。这一发现表明，如此有限且保守的序列变化能够调节抗体结合的可用格局，这对于疫苗开发和DENV反应性抗体的研究都具有重要意义。
