Workpackage 1
Workpackage
1 - Virological and serological surveillance for
influenza in pigs
Virologic
surveillance: Three antigenically and
genetically distinct swine influenza virus subtypes
co-circulate in the swine population in Europe. For
the better understanding of the complex
epidemiology of SI, the virologic surveillance aims
to collect as many SIV isolates as possible over
the three year period of the project. All SIVs will
be subtyped and a number of these isolates will be
selected for further use in WP2 and WP3 (antigenic
and genetic characterisation) and will be later
added to the virus bank (WP6). Any change in the
epidemiology of SIVs in Europe, i.e. significant
genetic changes in SIVs, will be taken into
consideration in WP4 (updating of classical
techniques for SIV subtyping and serology).
Serological
surveillance: During ESNIP 1, a
limited seroprevalence study for different SIV
subtypes was undertaken in different countries. The
approach of the serological surveillance in ESNIP 2
has changed. Our current aim is to better
understand the dynamics of the (co-)circulation of
different SIV subtypes at the farm level. To this
purpose each partner involved in the serological
surveillance (P1, 4, 5, 8 and 9) will collect sera
from 20 farms twice a year, over a 3-year period.
This will allow us to determine whether the same
SIV subtype(s) continue to (re)circulate on a given
farm, or whether the predominant subtypes change
over the years. The presence of antibodies against
SIV subtypes will indicate the course of SIV
infections and the possible emergence and
re-emergence of SIVs.
Workpackage 2
The aim of this WP is to determine the extent of antigenic evolution and variation in the haemagglutinin (HA) of influenza virus subtypes circulating in European pigs. Though it is known that swine influenza viruses evolve at a much slower rate than their human counterparts, some extent of antigenic drift may occur. Close monitoring of antigenic drift and antigenic heterogeneity in SIVs is particularly important for optimization of serodiagnostic methods as explained under WP4. Furthermore, the strains included in the commercial inactivated SIV vaccines must show serologic cross-reactivity with circulating strains in order to provide cross-protection.
Workpackage 3
The aim of this WP is to determine the extent of genetic evolution within and between SIV subtypes. By partial or full gene sequencing and subsequent phylogenetic analysis the exact genotype/phenotype of viruses can be determined and offers an insight for the emergence of new influenza re-assortments in the European pig population and their potential origin. To this end recent isolates detailed in WP2 will be studied in detail by genetic analysis and each partner involved in this WP has agreed to share their genetic data. In addition the receptor binding site of these SIVs will be sequenced. Viruses from different host species usually display binding preference for either Neu5Ac2-3Gal (avian) or Neu5Ac2-6Gal (human) disaccharide epitopes. Pigs are thought to contain both epitopes in their tracheal tissues and so have the potential to become infected with both avian and human viruses which could lead to a re-assortment virus being generated and the potential of interspecies transmission. This will be investigated.
Workpackage 4
The haemagglutination inhibition (HI) test is currently the best option for the serological diagnosis of SI, for serological surveillance and for subtyping and antigenic characterisation of SIVs. To standardize and harmonize HI test results between laboratories, we have prepared a standard HI test protocol and we have organized ring trials among consortium participants during ESNIP 1.
However, the sensitivity of the HI test is greatly influenced by the antigenic characteristics of the strains used, with recent strains that closely match with field strains giving higher numbers of seropositives and higher antibody titres than strains from the 1980s. The primary aim of WP 4, therefore, is to make recommendations regarding SIV strains for use in the HI test in Europe. For this purpose, we will perform comparative HI tests with different strains of each SIV subtype.
All partners involved in WP1 have agreed to conduct comparative serology: when a new SIV is isolated from a farm, the partner will return to the farm 3 to 4 weeks later and collect blood from the same pigs for examination in the HI test. The HI titres against the homologous virus and the strains used routinely in the HI test by that partner will be compared. This will allow us to judge upon the need to update the strains used in the HI test.
Workpackage 5
Workpackage
5 - Development and validation of a novel, rapid test
for the detection and/or subtyping of
SIVs
Present classic
techniques for the detection and subtyping of SIV,
though very sensitive and reliable, are slow. The
aim of this WP is to develop a validated test that
enables rapid detection of influenza A virus in
clinical specimens collected from pigs, with the
potential to extend to virus subtyping of both the
haemagglutinin (HA) and neuraminidase (NA) of SIVs.
The preferred method for this test is RT-PRC. For
this reason the WP manager (P2) is organizing a PCR
ring trial among the project participants who
already use the technique for the subtyping of
SIVs.
Workpackage 6
The objective of this WP is to maintain a virus bank of influenza viruses from pigs ensuring traceability. Furthermore, information relating to all aspects of ESNIP2 will be available in the public domain through a website.
The current virus bank is based in the lab of P1. It will be expanded with virus strains obtained in WP1. Information on the virus strains will be collected and stored in the electronic database.
Workpackage 7
The objective of this WP is to develop and validate a sensitive and specific assay for detection of avian influenza (AI) virus antibodies in swine, after which these tests are applied in a limited surveillance to determine whether AI viruses (particularly H4, H5, H7 and H9 subtypes) are circulating in swine in Europe.
Workpackage 8
The objective of this work package is to provide an interface between laboratories working with swine, avian and human influenza to ensure the exchange of information to gain an insight into the relationship and epidemiology of influenza viruses in pigs, humans and avian hosts.
As OIE/FAO/EU Reference laboratory for avian influenza (AI), VLA has established close links with many laboratories and Institutes from across the world dealing with AI, but also links with WHO Reference Laboratories. Through formal agreements with these laboratories it allows for the exchange of data but also viruses as well. VLA is also a member of a number of Influenza networks and EU funded projects, where through annual meetings, data is exchanged and discussed.