Solution Structure and Structural Dynamics of Envelope Protein Domain III of Mosquito- and Tick-Borne Flaviviruses

Abstract

The mosquito-borne West Nile (WNV) and dengue 2 (DEN2V) viruses and tick-borne Langat (LGTV) and Omsk hemorrhagic fever (OHFV) viruses are arthropod-borne flaviviruses (family Flaviviridae, genus Flavivirus). These viruses are quite similar at both the nucleotide and amino acid level, yet they are very divergent in their biological properties and in the diseases they cause. The objective of this study was to examine the putative receptor-binding domains of the flaviviruses, the envelope (E) protein domain III (D3), which assume very similar structures either as part of the whole envelope protein or as individual entities, and to define the biophysical properties that distinguish among these viruses. Circular dichroism and Fourier transform infrared spectroscopy were employed to monitor the solution structure of these proteins. While the spectroscopic results found that the D3 from each of these viruses is composed of either beta-sheets or beta-turns, which is consistent with X-ray crystal data for tick-borne encephalitis and dengue viruses, these results reveal that recombinant D3s (rED3s) derived from tick-borne flaviviruses (LGT-rED3 and OHF-rED3) were similar to each other, while those from mosquito-borne flaviviruses (WN-rED3 and DEN-rED3) were similar to each other yet distinct from rED3 of the tick-borne viruses. Protein dynamic studies probed by fluorescence quenching and hydrogen/deuterium exchange found that the rED3s are dynamic entities. The tick-borne proteins again exhibit very similar dynamic properties, which are different from the mosquito-borne proteins. The WN-rED3 is significantly less stable than the other three rED3s. Overall, these differences in biophysical properties correlate with biological properties of these viruses that tick-borne flaviviruses are more stable than mosquito-borne flaviviruses.

Genome-Wide Patterns of Intrahuman Dengue Virus Diversity Reveal Associations with Viral Phylogenetic Clade and Interhost Diversity

“…Domains I, II, and III (which form the ectodomain) and the C-terminal hydrophobic domain (C-term) of the E protein not only have distinct structural functionalities in the folding and assembly of the protein on the surface of the virion but also elicit substantially different antibody responses in humans (49,50,59). Domain II (EDII) contains the fusion loop responsible for low-pH-mediated fusion with endosomal compartments, while EDIII is a putative receptor-binding domain with an immunoglobulin-like fold, as predicted from E structures in other flaviviruses (8,60,71,78). Murine monoclonal antibody studies have determined that epitopes in EDI and EDII generally elicit serotype cross-reactive antibodies that are poorly to moderately neutralizing (12,55), while antibodies targeting EDIII are, on the whole, more serotype specific and potently neutralizing (14,21,42,44,65), although some cross-reactive and nonneutralizing monoclonal antibodies binding to EDIII epitopes have been recently identified (62,64,65).…”

Functional Analysis of Antibodies against Dengue Virus Type 4 Reveals Strain-Dependent Epitope Exposure That Impacts Neutralization and Protection

“…Domain II (DII) is a long, fingerlike protrusion from DI with the highly conserved fusion peptide at its distal end and an N-linked glycan that recognizes DC-SIGN (21)(22)(23)(24). Domain III (DIII), which adopts an immunoglobulinlike fold, has been suggested to contain cell surface receptor recognition sites (25)(26)(27).…”

Structure and Function Analysis of Therapeutic Monoclonal Antibodies against Dengue Virus Type 2

“…DII is a long, finger-like protrusion from DI, with the highly conserved fusion peptide at its distal end and a second N-linked glycan that recognizes DC-SIGN (37,38,46,59). DIII, which adopts an immunoglobulin-like fold, has been suggested to contain cell surface receptor recognition sites (5,64,71). Several groups have recently defined contact residues for type-specific, subcomplex-specific, and cross-reactive monoclonal antibodies (MAbs) that recognize DIII of DENV-2 (16,17,31,47,57,61).…”