Pre-treatment with 100-200 μg/mL GRFT, followed by PRRSV inoculation at a multiplicity of infection of 1 or 10, reduced viral replication in MARC145 cells in a dose-dependent manner, achieving almost 100% inhibition of ORF5 and ORF7 RNA compared with untreated controls (<i>p</i> < 0.0001). This evidence concerns the gene CWC15 and infection.