Defra - Department for Environment, Food and Rural Affairs.

Science Search

Science and Research Projects

Return to Science Search homepage   Return to Project List

Structural analysis and diagnostic assays for bluetongue virus and related orbiviruses - SE2609

Description

The primary aim of this research project is to provide additional basic information concerning the structure and function of the orbivirus particles, proteins and RNAs, as well as reagents and data for the development of improved detection and identification assay systems.
British breeds of sheep, horses and other livestock species are among the most susceptible to the orbiviruses, including particularly bluetongue (BTV) and African horse sickness (AHSV), with mortality levels that may exceed 70% (BTV in sheep) to 99% (AHSV in horses). In the absence of any immunity in the serologically naive animal populations, any outbreak of these diseases in the UK would cause catastrophic mortality levels in Summer and with climate change may be less reliably curtailed by our colder Winters. The recent outbreak of BTV in Greece, Turkey and Cyprus which has spread as far North as Bulgaria may simply be a sign of things to come. The most abundant species of Culicoides in Bulgaria (Culicoides obsoletus, and C. pulicaris), which in the absence of C. imicola are thought to be acting as vectors, are widely distributed throughout northern Europe including the UK.
The work described underpins MAFF's policy on the control of orbivirus-caused diseases through maintenance of a diagnostic capability and the development of appropriate test systems. MAFF's primary strategy for control of these diseases is to prevent their entry into the UK. However, increasing international trade in animals and animal products, including trade with areas of the world where Orbivirus diseases are endemic or cause periodic epizootics, continues to elevate the threat to the UK agriculture. A fundamental part of MAFF's control strategy, is the design and use of reliable assay systems that can detect and identify not only antibodies to these viruses in infected animals, but also the viruses themselves.
The project will seek to further define the relationships between different Orbivirus species, particularly by extending the available RNA sequence data for specific conserved genome segments. In this way phylogenetic trees and data bases will be constructed that may be used to place new sequences and rapidly identify the virus species, without a need to compare the virus serologically to each of the 19 existing virus serogroups. The project will also generate high quality virus antigens and virus specific antibodies that can be used to identify Orbivirus serogroups (species) in ELISA. Each of the orbivirus species contains several distinct serotypes that do not cross react in serum neutralisation assays. It is important for epidemiological reasons and for the design of vaccination strategies, to identify the virus serotype. The high quality antigens produced by these purification methods will also allow generation of high titre antisera that will improve our current capability to identify virus serotype in neutralisation assays. Recently an RT PCR based serotyping assay has been developed for the nine serotypes of AHSV, which is much faster than conventional serological assays, although similar assays may be more difficult to develop with BTV because twenty four serotypes are currently recognised.
This work meets the policy of safeguarding the health of UK animal populations. The Group responsible for the work is the UK's only source of expertise.
Objective

01) Further development of purification procedures and characterisation of EEV particles

02)Develop a serogroup (species) specific diagnostic ELISA for detection and identification of Equine encephalosis virus (EEV), using the purified particles now available.

03) Further analysis of the structure and enzyme functions of the purified orbivirus particles.

04) Provide additional sequence data for conserved genome segments (1 and 3) of unassigned or uncharacterised orbiviruses, as an resource to establish the relationships between Orbivirus species and for the identification of new virus isolates.

05) Develop purification methods for use with other Orbivirus species (eg Palyam virus)

06)Purify AHSV, EHDV and different BTV serotypes to raise serogroup specific antisera for maintenance of existing species specific diagnostic assays and high titre neutralising antisera for improved serotyping assays.

07) Develop diagnostic ELISA for additional Orbivirus species (eg Palyam virus).

08) Develop RT PCR based assays for genome segment 2 of BTV and assess their ability to detect different serotypes.
Project Documents
• Final Report : Structural Analysis and Diagnosis for Bluetongue Virus and Related Orbviruses   (175k)
Time-Scale and Cost
From: 2000

To: 2003

Cost: £510,247
Contractor / Funded Organisations
Institute for Animal Health (BBSRC)
Keywords
Animal Diseases              
Animal Health              
Biotechnology              
Bluetongue              
Control              
Diagnosis              
Plants and Animals              
Fields of Study
Animal Health