A protective interferon response is induced upon CHIKV infection.

<p>(A–C) Expression of zebrafish type I IFNs <i>ifnφ1</i> (A) and <i>ifnφ3</i> (B) and the IFN-stimulated gene <i>viperin</i> (C), upon CHIKV-GFP infection. qRT-PCR, mean ± s.e.m of 3 pools of 10 larvae from 3 independent experiments. (D–F) Effect of morpholino-mediated knockdown of IFN receptor subunits (<i>CRFB1+2</i> MO) and of MAVS (<i>MAVS</i> MO) on CHIKV-GFP infection. No MO, not injected with a morpholino; No V, uninfected controls; Control MO, injected with a unspecific morpholino oligonucleotide. (D) Disease score at 3 days post-infection; (E) survival of infected zebrafish; (F) quantification of viral <i>E1</i> transcripts over time. qRT-PCR, mean ± s.e.m of 3 pools of 3–5 larvae, except for the CRFB morphants at 72 hpi (one single pool of 5 larvae). Hatched bars represent groups where a fraction of the fish had already died, implying selection of survivors for the analysis. ND, not determined. (G) Pattern of <i>ifnφ1</i> expression, whole-mount <i>in situ</i> hybridization in uninfected larva (top) or CHIKV-GFP infected larva (bottom) at 24 hpi, representative out of 7 fish. Arrows indicate some <i>ifnφ1⁺</i> leukocytes, arrowhead point to an <i>ifnφ1⁺</i> hepatocyte; L = liver. (***<i>P</i> &lt; 0.001; **<i>P</i> &lt; 0.01; *<i>P</i> &lt; 0.05; ns - not significant).