Porcine Respiratory and Reproductive Syndrome Virus (PRRSV) is a major concern for porcine sector vin Europe. Despite a rapid availability of commercial vaccines and their intensive use by farmers, the PRRSV still circulates in a large proportion of herds. This can be partially explained by suboptimal management and vaccination practices and by the incomplete protection of the available vaccines, but also other unknown factors are probably involved.

This project will provide a new approach of the problem of suboptimal efficacy of the vaccines by focusing on the immune status of sows and piglets and their response to vaccination.

First the general management and vaccination practices will be evaluated by a field survey, and connected to the presence and frequency of seronegative sows in vaccinating herds. Next, the impact of the maternal immune status on the immune status of the offspring and the response of piglets to vaccination will be investigated.

In experimental studies, the potential of alternative vaccination protocols will be evaluated to determine if non-response to vaccination at weaning can be avoided and protection against PRRS increased.

Finally, the cellular mechanisms of the immune response will be evaluated by characterisation of the activated cells and detection of messenger RNA of factors involved in the pathways.

Based on the results, recommendations for vaccination practices will be formulated for farmers.