Control of highly virulent pathogenic European porcine reproductive and respiratory syndrome viruses – KILLeuPRRSV

Porcine reproductive and respiratory syndrome (PRRS) is the most important viral disease
in pigs worldwide. Failure of vaccination and the emergence of highly virulent strains, the
so-called High Fever Disease (HFD) PRRSV strains, cause huge economical losses to pig
industry and is a big issue in animal welfare. HFD PRRSV strains of genotype II (American)
emerged in 2006 in Asia. At present, the situation is there out of hand. These HFD PRRSV II
strains pose a long distance threat to Europe. However, at the same time HFD PRRSV
strains of type I (European, subtype 3 (Lena-like)) were also discovered in Eastern Europe
(Belarus). This year, more virulent/pathogenic PRRSV I subtype 1 strains emerged in
Western Europe, causing fever for one week and respiratory problems. Type I HFD PRRSV
strains replicate to higher levels (x10-100) than the traditional PRRSV strains by infecting
more subtypes of monocytic cells (use of new receptors), suppress heavily the
antimicrobial defence and immune responses and cause respiratory problems and
mortality. Vaccination against these strains with commercial attenuated and inactivated
vaccines sometimes lead to an aggravation of the disease instead of protection. Type I
HFD strains are menacing now the whole European pig industry. This brings HFD PRRS in
the group of viral diseases that cannot be fully controlled by the available vaccines.
Therefore, HFD PRRS should be prioritized in surveillance (diagnosis) and search for safe
and efficacious vaccines.
In the present project proposal, a group of five European PRRS experts that are already
cooperating in a EU PRRS project (2009-2014) will join forces again to control HFD PRRS in
Europe. By studying the pathogenesis, it will be examined what the mechanisms are of (i)
the higher replication power of HFD PRRSV (target cells, new receptors), (ii) the
immunosuppression and (iii) the immunity-dependent enhancement of virus replication.
Based on the results new vaccines (inactivated/vector/attenuated) will be designed,
developed and tested. In parallel, PRRS surveillance will be launched, in order to trace HFD
PRRSV and to take the correct actions, whenever this virus causes a catastrophic epidemic
in Western Europe.