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The flavivirus NS1 protein: molecular and structural biology, immunology, role in pathogenesis and application as a diagnostic biomarker.

David A. Muller, +1 more
- 01 May 2013 - 
- Vol. 98, Iss: 2, pp 192-208
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TLDR
An overview of these somewhat disparate areas of research is provided, drawing together the wealth of data generated over more than 40 years of study of this fascinating protein, which plays an essential cofactor role in replication.
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This article is published in Antiviral Research.The article was published on 2013-05-01 and is currently open access. It has received 433 citations till now. The article focuses on the topics: Viral replication complex & Glycoprotein.

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The continued threat of emerging flaviviruses

TL;DR: The basic biology of these viruses, their life cycles, the diseases they cause and available therapeutic options are reviewed, and the global distribution of flaviviruses is discussed, with a focus on lesser-known species that have the potential to emerge more broadly in human populations.
Journal ArticleDOI

Dengue virus NS1 triggers endothelial permeability and vascular leak that is prevented by NS1 vaccination

TL;DR: The results of in vitro and in vivo experiments point to circulating dengue virus non-structural protein 1 (NS1) and the innate immune Toll-like receptor 4 (TLR4) as a focus for basic scientists as well as vaccine and drug developers.
Journal ArticleDOI

Dengue virus NS1 protein activates cells via Toll-like receptor 4 and disrupts endothelial cell monolayer integrity

TL;DR: It is shown that the secreted form of the dengue virus nonstructural protein 1 (NS1) is a pathogen-associated molecular pattern (PAMP) that activates mouse macrophages and human peripheral blood mononuclear cells (PBMCs) in culture via Toll-like receptor 4 (TLR4), resulting in release of inflammatory cytokines—an effect that was blocked by either a TLR4 antagonist or an anti-TLR 4 antibody.
Journal ArticleDOI

Flavivirus NS1 structures reveal surfaces for associations with membranes and the immune system.

TL;DR: In this article, crystal structures for full-length, glycosylated nonstructural protein 1 (NS1) from West Nile and dengue viruses were reported, which reveal distinct domains for membrane association of the dimer and interactions with the immune system and are a basis for elucidating the molecular mechanism of NS1 function.
References
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Journal ArticleDOI

Functional rafts in cell membranes

Kai Simons, +1 more
- 05 Jun 1997 - 
TL;DR: A new aspect of cell membrane structure is presented, based on the dynamic clustering of sphingolipids and cholesterol to form rafts that move within the fluid bilayer that function as platforms for the attachment of proteins when membranes are moved around inside the cell and during signal transduction.
Journal ArticleDOI

How Cells Handle Cholesterol

TL;DR: The regulation of cholesterol homeostasis is now receiving a new focus, and this changed perspective may throw light on diseases caused by cholesterol excess, the prime example being atherosclerosis.
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Nucleotide sequence of yellow fever virus: implications for flavivirus gene expression and evolution

TL;DR: The sequence of the entire RNA genome of the type flavivirus, yellow fever virus, has been obtained and implies that mature viral proteins are produced by posttranslational cleavage of a polyprotein precursor and has implications for flaviv virus RNA replication and for the evolutionary relation of this virus family to other RNA viruses.
Journal ArticleDOI

Composition and three-dimensional architecture of the dengue virus replication and assembly sites.

TL;DR: Dengue virus (DENV) modifies ER membrane structure to promote replication and efficient encapsidation of the genome into progeny virus, which could explain the coordination of distinct steps of the flavivirus replication cycle.
Related Papers (5)
Frequently Asked Questions (15)
Q1. What are the contributions in this paper?

A review of the current state of knowledge of the structure and trafficking of this protein within and from the infected cell, its potential as a vaccine candidate, value in diagnostic applications and its role in pathogenesis in vivo through the interaction of the protein itself or the antibodies it elicits is presented in this paper. 

The presence of both NS1 and the antibodies it induces during the acute phase of disease is unusual and further studies are required to determine the modulating effect each has on the other, and of course the contribution of their interaction, immune complexes, to the overall disease process. Their hope is that it will provide insights into further research directions that may answer some of the many outstanding questions posed above. Perhaps one of the most intriguing aspects of this viral gene product can be found in a comparison with the genome coding strategy of the two related members of the Flaviviridae family, the hepaciviruses and pestiviruses. Studies that directly compare the replication of these separate members of the Flaviviradae may be quite revealing. 

Intracellular NS1 plays an essential cofactor role in virus replication and has been shown to co-localize with dsRNA and other components of viral replication complexes (Mackenzie et al., 1996; Westaway et al., 1997). 

In a recombinant vaccinia virus expression system it was found that 70% of NS2A was required to mediate effective cleavage (Hori and Lai, 1990; Leblois and Young, 1995). 

At a time of rising anti-NS1 antibody levels and the presence of NS1 in immune complexes (IC), IC deposition and complement activation is more likely to contribute to severe disease outcome, at least for dengue, than is free NS1 binding to complement regulating proteins. 

However a complicating factor for NS1 detection in secondary dengue infections is the rapid anamnestic rise of serotype cross-reactive anti-NS1 antibodies. 

In addition to complement-dependent and independent antibody mediated protection, NS1 has also been identified as a target of cell-mediated immunity, indicating that both arms of the immune response are likely to play a role (Gao et al., 2008; Green and Rothman, 2006; MuraliKrishna et al., 1995). 

One of the major concerns for any vaccine strategy against the dengue viruses is the potential priming of antibody dependent enhancement (ADE), an important and accepted risk factor for the development of the more severe disease outcomes of dengue infection, dengue haemorrhagic fever (DHF) and dengue shock syndrome (DSS). 

NS1 induction of autoantibodies and a potential role in pathogenesisDespite the fact that most antibodies directed against NS1 have been found to provide some level of passive protection to mice from a lethal flavivirus challenge (Henchal et al., 1988 Schlesinger, 1985 #233; Schlesinger et al., 1986), a small number have been shown to increase morbidity (Falconar,1997, 2008; Henchal et al., 1988). 

deposition of the sNS1-C4BP complex on to the cell surface could lead to inactivation of cell surface bound C4b thereby protecting infected cells from complement mediated lysis (Avirutnan et al., 2011) (Figure 4, step 14). 

The importance of correct NS1 glycosylation for virus replicative capacity and the potential of this post-translational modification as a target for antiviral drug design was recently demonstrated in a study of the effects of the α-glucosidase inhibitor, Celgosivir (Rathore et al., 2011). 

In Kunjin virus and MVE, a single amino acid substitution at residue 250 from proline to leucine has been shown to result in a loss of detectable dimers, suggesting a role for this C-terminal region of the protein in the dimerization process (Figure 3A). 

Further evidence for NS1 involvement in the generation of soluble membrane attack complexes was suggested when NS1 was found to bind directly to the complement inhibitory factor clusterin, which inhibits the formation of the membrane attack complex (Kurosu et al., 2007). 

This immune-mediated liver injury in mice provides supporting evidence that anti-NS1 antibody responses may also play a role in the liver damage characteristically seen in human dengue virus disease. 

Although overtaken to some degree by live attenuated chimeric virus vaccine candidates, there is renewed interest in NS1 as a component of second generation sub-unit vaccines for dengue as well as other flaviviruses (Krishna et al., 2009; Miller, 2010).