Variable Surface Epitopes in the Crystal Structure of Dengue Virus Type 3 Envelope Glycoprotein

Children's Hospital, Enders 673, 320 Longwood Ave., Boston, MA 02115, USA.
Journal of Virology (Impact Factor: 4.44). 02/2005; 79(2):1223-31. DOI: 10.1128/JVI.79.2.1223-1231.2005
Source: PubMed


Dengue virus is an emerging global health threat. The major envelope glycoprotein, E, mediates viral attachment and entry
by membrane fusion. Antibodies that bind but fail to neutralize noncognate serotypes enhance infection. We have determined
the crystal structure of a soluble fragment of the envelope glycoprotein E from dengue virus type 3. The structure closely
resembles those of E proteins from dengue type 2 and tick-borne encephalitis viruses. Serotype-specific neutralization escape
mutants in dengue virus E proteins are all located on a surface of domain III, which has been implicated in receptor binding.
While antibodies against epitopes in domain I are nonneutralizing in dengue virus, there are neutralizing antibodies that
recognize serotype-conserved epitopes in domain II. The mechanism of neutralization for these antibodies is probably inhibition
of membrane fusion. Our structure shows that neighboring glycans on the viral surface are spaced widely enough (at least 32
Å) that they can interact with multiple carbohydrate recognition domains on oligomeric lectins such as DC-SIGN, ensuring maximum
affinity for these putative receptors.

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Available from: Yorgo Modis
    • "The structural proteins include capsid protein (C), membrane protein (M) and envelope protein (E), while the non-structural (NS) proteins are NS1, NS2A, NS2B, NS3, NS4A, NS4B and NS5 (Welsch et al., 2009). Encapsulation of the RNA genome is mediated by multiple copies of C protein (11 kDa) and results in a viral nucleocapsid, surrounded by a lipid bi-layer in which, remarkably, 180 copies of anchored M and E proteins are present (Modis et al., 2005; Nybakken et al., 2006). The processing of a precursor protein (prM) results in a mature (M) protein of approximately 8 kDa, which plays a regulatory role in virus fusion, virus entry and E protein folding (Heinz et al., 2003; Hsieh et al., 2011). "
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    ABSTRACT: Every year, millions of individuals throughout the world are seriously affected by dengue virus. The unavailability of a vaccine and of anti-viral drugs has made this mosquito-borne disease a serious health concern. Not only does dengue cause fatalities but it also has a profoundly negative economic impact. In recent decades, extensive research has been performed on epidemiology, vector biology, life cycle, pathogenesis, vaccine development and prevention. Although dengue research is still not at a stage to suggest definite hopes of a cure, encouraging significant advances have provided remarkable progress in the fight against infection. Recent developments indicate that both anti-viral drug and vaccine research should be pursued, in parallel with vector control programs.
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    • "While DIII is encoded in a single genomic sequence within the viral genome, DI and DII (DI/DII) are discontinuous with respect to the protein and encoded in intercalated genomic segments (three for DI, two for DII) (Modis, 2014). DI folds into a b-barrel structure with an axis parallel to the viral membrane and occupies a central position in the mature monomer (Modis et al., 2005; Rey et al., 1995). DII forms an elongated finger-like structure with a stable core that expands distally in two loops (Rey et al., 1995; Zhang et al., 2004); the most distal one carries a hydrophobic glycine-rich sequence that serves as the internal fusion loop during fusion to host cell membranes "
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    ABSTRACT: Dengue virus (DENV) is currently among the most important human pathogens and affects millions of people throughout the tropical and subtropical regions of the world. Although it has been a World Health Organization priority for several years, there's still no efficient vaccine available to prevent infection. The envelope glycoprotein (E), exposed on the surface on infective viral particles, is the main target of neutralizing antibodies. For this reason it has been used as the antigen of choice for vaccine development efforts. Here we show a detailed analysis of factors involved in the expression, secretion and folding of E ectodomain from all four DENV serotypes in mammalian cells, and how this affects their ability to induce neutralising antibody responses in DNA-vaccinated mice. Proper folding of DII is essential for efficient E ectodomain secretion, with DIII playing a significant role in stabilising soluble dimers. We also show that the level of protein secreted from transfected cells determines the strength and efficiency of antibody responses in the context of DNA vaccination, and should be considered a pivotal feature for the development of E-based DNA vaccines against DENV.
    Full-text · Article · Sep 2015 · Journal of General Virology
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    • "Two alpha helices anchored in the viral membrane attach to E through a 53-residue C-terminal stem [6]. Domain III, at E's C-terminus, helps the virus target cell receptors, leading to endocytosis [7] [8] [9] [10] [11] [12] [13] [14]. Once inside the endosome, a low pH-driven conformational change of E results in exposure of hydrophobic residues at the tip of the beta-structured Domain II that attach E to the host endosomal membrane and promote virus–membrane fusion (Fig. 1) [15] [16]. "
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    ABSTRACT: Dengue virus is coated by an icosahedral shell of 90 envelope protein dimers that convert to trimers at low pH and promote fusion of its membrane with the membrane of the host endosome. We provide the first estimates for the free energy barrier and minimum for two key steps in this process: host membrane bending and protein-membrane binding. Both are studied using complementary membrane elastic, continuum electrostatics and all-atom molecular dynamics simulations. The predicted host membrane bending required to form an initial fusion stalk presents a 22-30 kcal/mol free energy barrier according to a constrained membrane elastic model. Combined continuum and molecular dynamics results predict a 15 kcal/mol free energy decrease on binding of each trimer of Dengue envelope protein to a membrane with 30% anionic phosphatidylglycerol lipid. The bending cost depends on the preferred curvature of the lipids composing the host membrane leaflets, while the free energy gained for protein binding depends on the surface charge density of the host membrane. The fusion loop of the envelope protein inserts exactly at the level of the interface between the membrane's hydrophobic and head-group regions. The methods used in this work provide a means for further characterization of the structures and free energies of protein-assisted membrane fusion. Copyright © 2014 The Authors. Published by Elsevier B.V. All rights reserved.
    Full-text · Article · Jan 2015 · Biochimica et Biophysica Acta (BBA) - Biomembranes
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