Attenuation of Bluetongue Virus (BTV) in an in ovo Model Is Related to the Changes of Viral Genetic Diversity of Cell-Culture Passaged BTV.

Fabian Z X Lean,John R White,Vittoria Stevens,David T Williams,Kelly R Davies,Matthew J Neave,Teresa Eastwood,Joanne Devlin,John Bingham,Antonio Di Rubbo,Jemma Bergfeld,Jean Payne

doi:10.3390/v11050481

Abstract

The embryonated chicken egg (ECE) is routinely used for the laboratory isolation and adaptation of Bluetongue virus (BTV) in vitro. However, its utility as an alternate animal model has not been fully explored. In this paper, we evaluated the pathogenesis of BTV in ovo using a pathogenic isolate of South African BTV serotype 3 (BTV-3) derived from the blood of an infected sheep. Endothelio- and neurotropism of BTV-3 were observed by immunohistochemistry of non-structural protein 1 (NS1), NS3, NS3/3a, and viral protein 7 (VP7) antigens. In comparing the pathogenicity of BTV from infectious sheep blood with cell-culture-passaged BTV, including virus propagated through a Culicoides-derived cell line (KC) or ECE, we found virus attenuation in ECE following cell-culture passage. Genomic analysis of the consensus sequences of segments (Seg)-2, -5, -6, -7, -8, -9, and -10 identified several nucleotide and amino-acid mutations among the cell-culture-propagated BTV-3. Deep sequencing analysis revealed changes in BTV-3 genetic diversity in various genome segments, notably a reduction of Seg-7 diversity following passage in cell culture. Using this novel approach to investigate BTV pathogenicity in ovo, our findings support the notion that pathogenic BTV becomes attenuated in cell culture and that this change is associated with virus quasispecies evolution.

Highlights

Bluetongue virus (BTV) is an arthropod-borne virus that is primarily transmitted by Culicoides midges
Sheep Blood Containing BTV serotype 3 (BTV-3) is Pathogenic in the embryonated chicken egg (ECE) Model
In order to characterize the pathogenesis of BTV in ECE, we performed a time-course study using sheep blood containing BTV-3 (Sh virus; Figure 1)

Summary

Introduction

Bluetongue virus (BTV) is an arthropod-borne (arbo-) virus that is primarily transmitted by Culicoides midges. It is a non-enveloped virus, with a 10-segmented double-stranded RNA (dsRNA). The infection of susceptible ruminant species can result in viral hemorrhagic disease [1], as with other important human and animal arboviruses, for example, dengue and Rift valley fever [2,3]. Other features of arbovirus infection of vertebrate hosts include the development of in utero congenital neurological diseases, as seen with. BTV may serve as a model arbovirus to better understand the pathogenesis of viral hemorrhagic disease and congenital neurological diseases arising from arboviral infection

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Conclusion