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Title: Development and characterization of a Rift Valley fever virus cell-cell fusion assay using alphavirus replicon vectors

Abstract

Rift Valley fever virus (RVFV), a member of the Phlebovirus genus in the Bunyaviridae family, is transmitted by mosquitoes and infects both humans and domestic animals, particularly cattle and sheep. Since primary RVFV strains must be handled in BSL-3+ or BSL-4 facilities, a RVFV cell-cell fusion assay will facilitate the investigation of RVFV glycoprotein function under BSL-2 conditions. As for other members of the Bunyaviridae family, RVFV glycoproteins are targeted to the Golgi, where the virus buds, and are not efficiently delivered to the cell surface. However, overexpression of RVFV glycoproteins using an alphavirus replicon vector resulted in the expression of the glycoproteins on the surface of multiple cell types. Brief treatment of RVFV glycoprotein expressing cells with mildly acidic media (pH 6.2 and below) resulted in rapid and efficient syncytia formation, which we quantified by {beta}-galactosidase {alpha}-complementation. Fusion was observed with several cell types, suggesting that the receptor(s) for RVFV is widely expressed or that this acid-dependent virus does not require a specific receptor to mediate cell-cell fusion. Fusion occurred over a broad temperature range, as expected for a virus with both mosquito and mammalian hosts. In contrast to cell fusion mediated by the VSV-G glycoprotein, RVFV glycoprotein-dependent cellmore » fusion could be prevented by treating target cells with trypsin, indicating that one or more proteins (or protein-associated carbohydrate) on the host cell surface are needed to support membrane fusion. The cell-cell fusion assay reported here will make it possible to study the membrane fusion activity of RVFV glycoproteins in a high-throughput format and to screen small molecule inhibitors for the ability to block virus-specific membrane fusion.« less

Authors:
 [1];  [2];  [3];  [4]
  1. Department of Microbiology, University of Pennsylvania, 301 Johnson Pavilion, 3610 Hamilton Walk, Philadelphia, PA 19104 (United States)
  2. Departments of Genetics and Microbiology and Immunology, The Carolina Vaccine Institute, University of North Carolina, Chapel Hill, NC 27599 (United States)
  3. Department of Microbiology, University of Pennsylvania, 301 Johnson Pavilion, 3610 Hamilton Walk, Philadelphia, PA 19104 (United States). E-mail: doms@mail.med.upenn.edu
  4. Department of Microbiology, University of Pennsylvania, 301 Johnson Pavilion, 3610 Hamilton Walk, Philadelphia, PA 19104 (United States). E-mail: aciarlet@mail.med.upenn.edu
Publication Date:
OSTI Identifier:
20850582
Resource Type:
Journal Article
Resource Relation:
Journal Name: Virology; Journal Volume: 356; Journal Issue: 1-2; Other Information: DOI: 10.1016/j.virol.2006.07.035; PII: S0042-6822(06)00512-5; Copyright (c) 2006 Elsevier Science B.V., Amsterdam, Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; CATTLE; FEVER; GALACTOSIDASE; GLYCOPROTEINS; MOSQUITOES; RECEPTORS; SHEEP; TRYPSIN; VIRUSES

Citation Formats

Filone, Claire Marie, Heise, Mark, Doms, Robert W., and Bertolotti-Ciarlet, Andrea. Development and characterization of a Rift Valley fever virus cell-cell fusion assay using alphavirus replicon vectors. United States: N. p., 2006. Web. doi:10.1016/j.virol.2006.07.035.
Filone, Claire Marie, Heise, Mark, Doms, Robert W., & Bertolotti-Ciarlet, Andrea. Development and characterization of a Rift Valley fever virus cell-cell fusion assay using alphavirus replicon vectors. United States. doi:10.1016/j.virol.2006.07.035.
Filone, Claire Marie, Heise, Mark, Doms, Robert W., and Bertolotti-Ciarlet, Andrea. Wed . "Development and characterization of a Rift Valley fever virus cell-cell fusion assay using alphavirus replicon vectors". United States. doi:10.1016/j.virol.2006.07.035.
@article{osti_20850582,
title = {Development and characterization of a Rift Valley fever virus cell-cell fusion assay using alphavirus replicon vectors},
author = {Filone, Claire Marie and Heise, Mark and Doms, Robert W. and Bertolotti-Ciarlet, Andrea},
abstractNote = {Rift Valley fever virus (RVFV), a member of the Phlebovirus genus in the Bunyaviridae family, is transmitted by mosquitoes and infects both humans and domestic animals, particularly cattle and sheep. Since primary RVFV strains must be handled in BSL-3+ or BSL-4 facilities, a RVFV cell-cell fusion assay will facilitate the investigation of RVFV glycoprotein function under BSL-2 conditions. As for other members of the Bunyaviridae family, RVFV glycoproteins are targeted to the Golgi, where the virus buds, and are not efficiently delivered to the cell surface. However, overexpression of RVFV glycoproteins using an alphavirus replicon vector resulted in the expression of the glycoproteins on the surface of multiple cell types. Brief treatment of RVFV glycoprotein expressing cells with mildly acidic media (pH 6.2 and below) resulted in rapid and efficient syncytia formation, which we quantified by {beta}-galactosidase {alpha}-complementation. Fusion was observed with several cell types, suggesting that the receptor(s) for RVFV is widely expressed or that this acid-dependent virus does not require a specific receptor to mediate cell-cell fusion. Fusion occurred over a broad temperature range, as expected for a virus with both mosquito and mammalian hosts. In contrast to cell fusion mediated by the VSV-G glycoprotein, RVFV glycoprotein-dependent cell fusion could be prevented by treating target cells with trypsin, indicating that one or more proteins (or protein-associated carbohydrate) on the host cell surface are needed to support membrane fusion. The cell-cell fusion assay reported here will make it possible to study the membrane fusion activity of RVFV glycoproteins in a high-throughput format and to screen small molecule inhibitors for the ability to block virus-specific membrane fusion.},
doi = {10.1016/j.virol.2006.07.035},
journal = {Virology},
number = 1-2,
volume = 356,
place = {United States},
year = {Wed Dec 20 00:00:00 EST 2006},
month = {Wed Dec 20 00:00:00 EST 2006}
}
  • Rift Valley fever virus (RVFV) is a negative-sense RNA virus (genus Phlebovirus, family Bunyaviridae) that infects livestock and humans and is endemic to sub-Saharan Africa. Like all negative-sense viruses, the segmented RNA genome of RVFV is encapsidated by a nucleocapsid protein (N). The 1.93-{angstrom} crystal structure of RVFV N and electron micrographs of ribonucleoprotein (RNP) reveal an encapsidated genome of substantially different organization than in other negative-sense RNA virus families. The RNP polymer, viewed in electron micrographs of both virus RNP and RNP reconstituted from purified N with a defined RNA, has an extended structure without helical symmetry. N-RNA speciesmore » of {approx}100-kDa apparent molecular weight and heterogeneous composition were obtained by exhaustive ribonuclease treatment of virus RNP, by recombinant expression of N, and by reconstitution from purified N and an RNA oligomer. RNA-free N, obtained by denaturation and refolding, has a novel all-helical fold that is compact and well ordered at both the N and C termini. Unlike N of other negative-sense RNA viruses, RVFV N has no positively charged surface cleft for RNA binding and no protruding termini or loops to stabilize a defined N-RNA oligomer or RNP helix. A potential protein interaction site was identified in a conserved hydrophobic pocket. The nonhelical appearance of phlebovirus RNP, the heterogeneous {approx}100-kDa N-RNA multimer, and the N fold differ substantially from the RNP and N of other negative-sense RNA virus families and provide valuable insights into the structure of the encapsidated phlebovirus genome.« less
  • Rift Valley fever virus (RVFV; Bunyaviridae; Phlebovirus) is an emerging human and veterinary pathogen causing acute hepatitis in ruminants and has the potential to cause hemorrhagic fever in humans. We report a three-dimensional reconstruction of RVFV vaccine strain MP-12 (RVFV MP-12) by cryo-electron microcopy using icosahedral symmetry of individual virions. Although the genomic core of RVFV MP-12 is apparently poorly ordered, the glycoproteins on the virus surface are highly symmetric and arranged on a T = 12 icosahedral lattice. Our RVFV MP-12 structure allowed clear identification of inter-capsomer contacts and definition of possible glycoprotein arrangements within capsomers. This structure providesmore » a detailed model for phleboviruses, opens new avenues for high-resolution structural studies of the bunyavirus family, and aids the design of antiviral diagnostics and effective subunit vaccines.« less