In the brain, the target tissue for NNV, an up-regulation of genes coding for csf1r, mx, cxcl9, and hsp70 was registered upon infection in all NP-exposed fish while the transcription of il8 and nrf2 was only induced in PS-COOH-exposed and NNV-infected specimens (Figure 4C). This evidence concerns the gene CXCL8 and infection.