Respiratory burst of turbot (Scophthalmus maximus) macrophages in response to experimental infection with viral haemorrhagic septicaemia virus (VHSV)

Synthetic oligodeoxynucleotides (ODNs) containing unmethylated CpG motifs are known to stimulate immune responses and are potent adjuvants in higher vertebrates, but so far the effects in fish are poorly described. We here report that CpG ODNs induce IL-1β expression and production of interferon-like cytokines in rainbow trout head-kidney macrophages, whereas ODNs with an inverted motif (GpC) have a much less stimulatory effect. We further demonstrate that endosomal maturation is essential for CpG signalling, as chloroquine, a compound known to block endosomal acidification, inhibits cytokine expression in the macrophages.