Modulation of the intracellular calcium content by NNV infection and the effect of cytoplasmic calcium availability on ROS production and NNV replication. A Intracellular calcium measurement with the fluorescent probe FLUO-4 AM in SSN-1 cells during infection with NNV. Values are the fold change of the fluorescence value obtained for the infected cells compared to the uninfected ones. B Calcium content measurement with FLUO-4 AM in brain cells isolated from in vivo NNV-infected sea bass and represented as the fold change value compared to the uninfected fish. C ROS production detection in head kidney leukocytes after in vitro pretreatment with the calcium chelators BAPTA-AM and EGTA and with or without NNV infection for 1 h. The data are represented as the fold change compared to untreated and uninfected cells. D Replication of NNV in SSN-1 cells after pretreatment with calcium channel blockers and chelators and infection with NNV for 48 h. Viral replication was detected by qPCR amplification of the gene encoding the NNV capsid.