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African swine fever virus: Improvement of diagnostic tests and vaccine development - SE1514

Description
African swine fever (ASF) is a highly contagious, fatal, acute haemorrhagic viral disease of pigs which causes major economic losses. ASF is currently endemic in many sub-Saharan African countries, Sardinia and the Caucasus region. The virus (ASFV) was introduced to the Iberian peninsula in the 1960’s, to South America the Caribbean and other European countries during the 1970's. In 2007 further transcontinental spread of ASF occurred with the introduction of the virus to Georgia in the Caucasus. Subsequent spread to neighbouring countries and virus isolation from wild boar in the region, indicates erradication will be difficult. The virus persists for long periods in pigs which recover from infection, its natural hosts, warthogs and bushpigs and in Ornithodoros species of soft ticks. These can act as reservoirs for infecting healthy pigs. The virus can also persist in pork products and pigs may become infected by eating contaminated pork. Since no vaccine is available, options for disease control are limited. In addition ASFV causes similar disease signs to CSFV and some other pig diseases. This, combined with the fact that some ASFV isolates may cause atypical disase signs, means there is a possibility that diagnosis of ASF disease may be delayed leading to further spread.

In this project we will improve the methods available for diagnosis of ASFV by further validation of a test which detects the ASFV and CSFV genomes at the same time. This will increase confidence in the use of this test which will help to ensure that outbreaks of ASF are diagnosed quickly. In addition we will improve tests which can detect the virus particles in samples from infected animals. These tests provide a useful confirmatory diagnostic test in the event of a suspected outbreak and can be adpated to use in penside tests. Similar penside tests have already proved effective for control of other virus diseases.
To date, an effective vaccine against ASFV has not been produced, partly due to the complexity of the virus, the acute fatal nature of the disease and a poor understanding of the what types of immune response and which of the virus proteins is important for protection. In this project we will screen libraries of expressed ASFV proteins for their ability to induce both antibody and cell-mediated immune responses in immunised pigs. This will allow us to measure and rank the potential of each of the approximatley 200 proteins encoded to induce a protective immune response. This screen will be carried out in two ways. First we will screen antibodies and lymphocytes from pigs immunised with an attenuated live ASFV virus against the individual expressed ASFV proteins, to identify those that are recognised by the antibody and cell-mediated immune response. Secondly, we will immunise pigs with pools of the ASFV genes such that they are expressed as proteins in pigs. We will then measure the antibody and cell-mediated response to each protein. By comparing the response to the library group’s with that of live virus, immunogenic proteins normally hidden during viral infection will be identified.
These experiments will allow us to rank each ASFV protein according to the type and strength of immune response generated and to select a subset for further analysis. We will next assemble pools of the most immunogenic proteins and immunise pigs with library pools which express these proteins. Immune responses will be profiled as described before. Immunised pigs will be challenged with a lethal dose of ASFV and the level of protection measured by timing the appearance of any clinical signs of ASFV and measuring the level of virus replication. We will optimise the composition of these pools to deliver those that are most effective in induction of protection.The identification of ASFV proteins which can induce a protective immune response in pigs is an extremely important step for the development of effective and safe ASFV vaccines.
This project will benefit DEFRA and the UK by developing more rapid methods for detecting ASF should it be introduced to the UK and by significantly advancing the development of safe and effective vaccines. Application of vaccines and better diagnostic tests in other countries will aid control and reduce risks for introduction of ASF to the UK. Control of ASF globally will aid developing countries and improve food security.






Objective
Objective 1: To improve diagnostic tests for ASFV

(a) Further validation of novel PCR assays.
(b) Optimising sample preparation and further validation of virus antigen detection methods.

Objective 2: To identify ASFV antigens important for generating protective immunity

(a) Identification of ASFV antigens which are recognised by sera and immune lymphocytes from pigs immunized with an attenuated ASFV strain.

b) Induction of immune responses in pigs immunized with pools of genes expressing ASFV antigens.

(c) Effect of vaccination with pools of ASFV genes on induction of protection against challenge with a lethal dose of ASFV
Project Documents
• EVID4 - Final project report : final report – SE1514   (271k)
Time-Scale and Cost
From: 2010

To: 2013

Cost: £978,521
Contractor / Funded Organisations
Institute for Animal Health (BBSRC)
Keywords
African Swine Fever              
Animal Diseases              
Animal Health              
Plants and Animals              
Vaccines              
Fields of Study
Animal Health