Zebrafish were used to investigate the expression levels of several antiviral and inflammatory genes (IL-1β, iNOS, TNF-α, TLR3, IFN-I, IFNγ, IRF3, MDA-5, Mx) constitutively and after viral stimulation during early development. We also determined how their expression was affected by changes in the temperature. The antiviral genes were almost completely inhibited at 15°C with the exception of TLR3. In contrast, IL-1β, iNOS and TNF-α expression was not obviously different between the two temperatures. At 15°C, most of the genes examined did not differ following stimulation with poly I:C or viral hemorrhagic septicemia virus (VHSV). However, at 28°C, all of the genes showed significant differences in at least some of the sampling points after poly I:C treatment with the largest differences observed for Mx. Mx expression in adult zebrafish was not significantly altered by temperature and poly I:C treatment led to a smaller increase in gene expression when compared to larval Mx levels. Thus, Mx seems to play an important role in viral immunity in larvae, when the adaptive immune response is not fully functional.
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