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Saliva proteins of vector Culicoides modify structure and infectivity of bluetongue virus particles.

Darpel, KE, Langner, KF, Nimtz, M, Anthony, SJ, Brownlie, J, Takamatsu, HH, Mellor, PS and Mertens, PP (2011) Saliva proteins of vector Culicoides modify structure and infectivity of bluetongue virus particles. PLoS One, 6 (3).

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Abstract

Bluetongue virus (BTV) and epizootic haemorrhagic disease virus (EHDV) are related orbiviruses, transmitted between their ruminant hosts primarily by certain haematophagous midge vectors (Culicoides spp.). The larger of the BTV outer-capsid proteins, 'VP2', can be cleaved by proteases (including trypsin or chymotrypsin), forming infectious subviral particles (ISVP) which have enhanced infectivity for adult Culicoides, or KC cells (a cell-line derived from C. sonorensis). We demonstrate that VP2 present on purified virus particles from 3 different BTV strains can also be cleaved by treatment with saliva from adult Culicoides. The saliva proteins from C. sonorensis (a competent BTV vector), cleaved BTV-VP2 more efficiently than those from C. nubeculosus (a less competent/non-vector species). Electrophoresis and mass spectrometry identified a trypsin-like protease in C. sonorensis saliva, which was significantly reduced or absent from C. nubeculosus saliva. Incubating purified BTV-1 with C. sonorensis saliva proteins also increased their infectivity for KC cells ∼10 fold, while infectivity for BHK cells was reduced by 2-6 fold. Treatment of an 'eastern' strain of EHDV-2 with saliva proteins of either C. sonorensis or C. nubeculosus cleaved VP2, but a 'western' strain of EHDV-2 remained unmodified. These results indicate that temperature, strain of virus and protein composition of Culicoides saliva (particularly its protease content which is dependent upon vector species), can all play a significant role in the efficiency of VP2 cleavage, influencing virus infectivity. Saliva of several other arthropod species has previously been shown to increase transmission, infectivity and virulence of certain arboviruses, by modulating and/or suppressing the mammalian immune response. The findings presented here, however, demonstrate a novel mechanism by which proteases in Culicoides saliva can also directly modify the orbivirus particle structure, leading to increased infectivity specifically for Culicoides cells and, in turn, efficiency of transmission to the insect vector.

Item Type: Article
Divisions : Faculty of Health and Medical Sciences > School of Veterinary Medicine
Authors :
AuthorsEmailORCID
Darpel, KEUNSPECIFIEDUNSPECIFIED
Langner, KFUNSPECIFIEDUNSPECIFIED
Nimtz, MUNSPECIFIEDUNSPECIFIED
Anthony, SJUNSPECIFIEDUNSPECIFIED
Brownlie, JUNSPECIFIEDUNSPECIFIED
Takamatsu, HHUNSPECIFIEDUNSPECIFIED
Mellor, PSUNSPECIFIEDUNSPECIFIED
Mertens, PPUNSPECIFIEDUNSPECIFIED
Date : 14 March 2011
Identification Number : 10.1371/journal.pone.0017545
Uncontrolled Keywords : Animals, Bluetongue, Bluetongue virus, Cell Line, Ceratopogonidae, Chymotrypsin, Electrophoresis, Polyacrylamide Gel, Insect Vectors, Molecular Weight, Protease Inhibitors, Saliva, Salivary Proteins and Peptides, Sheep, Temperature, Trypsin, Viral Proteins, Virion
Additional Information : Copyright 2011 Darpel et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Depositing User : Symplectic Elements
Date Deposited : 18 Nov 2015 18:30
Last Modified : 18 Nov 2015 18:30
URI: http://epubs.surrey.ac.uk/id/eprint/809071

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