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Background:
Swine
Vesicular Disease (SVD) is a disease of increased prevalence and
economic significance in EU Member States. An OIE Category list
A disease, SVD is highly contagious and rapidly spread by direct
contact with infected pigs and by contamination of the environment.
Its eradication within the EU is a priority objective of the Member
States.
Current
diagnosis of SVD, based on conventional serological methods, does
not allow enough confidence in screening of animals and needs
to be improved. The proposed study directly complies with a priority
objective of the Agricultural and Fisheries work programme (4.
4 Animal and Plant Health, Animal Welfare), as one of the research
tasks of this programme is the development of improved diagnostic
tests, including application of bio-technology, and systems for
zoonoses and diseases of economic significance (4.4.2).
Objectives:
The
goals of this project are to investigate and develop re-agents
and methods which will improve the diagnosis of swine vesicular
disease (SVD). In particular, the `singleton reactor' phenomenon
will be specifically addressed. We will also investigate those
aspects of viral pathogenesis which affect the effectiveness of
control programs for the disease, such as the persistence of SVD
virus in pigs and the cells involved in early infection.
Description:
The
specific objectives are:
1)
To improve virus detection. Accurate and versatile ELISA and
PCR techniques for the detection of small traces of SVD virus
in nasal swabs, faeces and tissues will be developed. In
situ hybridisation and in-situ PCR will be optimised
to detect virus in post-mortem organs. SVD virus isolates will
be characterised to identify the origin of new outbreaks, patterns
of spread and viral evolution.
2)
To improve serology. Novel and simple ELISA based on recombinant
and synthetic antigens will be developed and validated. We will
also develop novel techniques to detect SVD virus-specific cellular
immune response and serological methods, including isotype (igg/igm)
analysis of the sera to study the evolution of the disease.
3)
To study viral pathogenesis.
The application of the above techniques will be applied to study
the duration of SVDV infection as well as the identification of
cells and organs involved in viral persistence. The use of biotechnology
to develop more specific, sensitive and cost-effective diagnostics
will result in quicker diagnosis of SVD infections and hopefully
the resolution of the singleton reactor phenomenon. Rapid and
accurate diagnosis of SVD will limit the potential spread of disease
to other animals, thus maintaining animal well-being. In addition,
the use of recombinant or synthetic antigens will eliminate the
need for mass production of susceptible cell cultures for production
and purification of SVD antigens.
A
range of established technological expertise necessary for completion
of the project is spread out throughout the network of participating
partners. In addition, excellent training opportunities for scientists
in these new disciplines will be provided.
Current
situation/results:
Different
panels of Mabs have been selected to detect and classify all antigenic
variants of SVDV, and one Mab has been proven to be useful as
an universal detector for the identification of SVDV in pathological
samples.
An
overall view the work carried out on the PCR methods suggest that
in field conditions the standard PCR assay is more suitable than
the immuno-PCR to perform multiple assays. However, newly developed
improved protocols of PCR-ELISA seem to be promising because it
is faster and more sensitive than both standard PCR and virus
isolation.
The
virus bank contains all the isolates from the new and old outbreaks,
and most of them are molecularly and antigenically characterised.
The results indicate that all Italian isolates from 1993 to 1998
belong to the same group (Group IV). The same group of viruses
were isolated in Italy during the period 1988 to 1992 and were
responsible for the outbreaks of SVD in the Netherlands, Portugal
and Spain during the early 1990's. The isolates from the outbreaks
of Taiwan 97, Taiwan 98, Hong Kong 80's and 90's, belong to a
subgroup within Group IV. Finally, the recent European SVDV probably
have a common origin with viruses from the Far East.
The
development of a method for the detection of cytokines by T-cells
in response to SVDV has been difficult due to technical problems.
However, the protocol is set up for several cytokines. This method
could be very useful as an alternative for the diagnosis of SVD,
as it is for other animal infections, and it could be possible
to perform the assay using recombinant or synthetic SVDV antigens.
All
the results derived from the work with recombinant SVDV antigens
indicate that these polypeptides are not suitable for use in diagnosis.
The majority of antibodies induced by infection with SVDV are
to conformational, discontinuous epitopes. However, the recombinant
P1 protein is recognised by, and induces antibody almost exclusively
to the linear, sequential epitopes of capsid. Therefore, it is
not recognised by the majority of antibodies induced during SVDV
infection.
Accordingly,
although the capsid precursor polyprotein P1 is highly immunogenic,
it does not induce neutralising, protective immunity in pigs.
If synthetic antigens and immunogens are to be produced they must
therefore mimic conformational rather than linear determinants.
Finally,
the study of the singleton reactor phenomenon has provide interesting
results. The data obtained during this year indicate that it is
possible to find the conditions to reduce the detection of SR
by at least 50%.
Website:
http://www.iah.bbsrc.ac.uk/svd_project/
The
common username is: "singleton" and the password is
"pigswill"
Coordinator
Victoria
LEY
I.N.I.A.
Carretera
Coruña Km 7.5
E-28040
Madrid
Tel:
+34 91 620 23 00
Fax:
+34 91 620 22 47
E-mail:
ley@inia.es
Partners
- Alastair DOUGLAS
The Queen's University of Belfast
Stoney road
UK-BT4 3SD Stormond - Belfast
Tel: +44 1232 52 56 39
Fax: +44 1232 52 57 73
E-mail: a.douglas@qub.ac.uk
- Emiliana BROCCHI
Istituto Zooprofilattico Sperimentale della Lombardia e Dell'Emilia
Via Antonio Bianchi 7
I-25124 Brescia
Tel: +39 030 229 03 10
Fax: +39 030 22 56 13
E-mail: ebrocchi@bs.izs.it
- Kris DE CLERCQ
Veterinary and Agrochemical Reseach Centre (VAR)
Groeselenberg 99
B-1180 Bruxelles
Tel: +32 2 375 44 55
Fax: +32 2 375 09 79
E-mail: krdec@var.fgov.be
- Aldo DEKKER
ID-DLO - Institute for Animal Science and Health
Houtribweg 39
P.O. Box 65
NL-8200 AB Lelystad
Tel: +31 320 23 82 38
Fax: +31 320 23 86 68
E-mail: a.dekker@id.dlo.nl
- Nick Knowles
The Institute for Animal Health
ASH Road - Pirbright
UK-GU24 0NF Pirbright - Woking
Tel: +44 1483 23 24 41
Fax: +44 1483 23 26 21
E-mail: nick.knowles@bbsrc.ac.uk
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