PRRS continues to be a threat for the pig industry. In 2006, a highly pathogenic PRRSV variant emerged in China. Current vaccines are ineffective because of the genetic variation and the immune evasion strategies of the virus in the field. This PhD study aims to provide information on (i) a new adaptable candidate vaccine to protect pigs from highly pathogenic PRRSV and (ii) the cell-mediated immune response evoked by the highly pathogenic Chinese PRRSV variant.