Temperature-dependency of Betanodavirus infection in SSN-1 cell line

This study examined the in vitro effects of temperature on Betanodavirus infection in the SSN-1 cell line. A Betanodavirus isolated from moribund sea bass fry Dicentrarchus labrax farmed in the Adriatic Sea and characterised as a RGNNV (Redspotted Grouper Nervous Necrosis Virus) genotype was used. Virus-infected SSN-1 cells were incubated at temperatures between 10 and 30 degrees C and observed for cytopathic effects daily for 15 d. Cell-free and cell-associated viral growth were evaluated by 50% tissue culture infectious dose (TCID50) titration at 0, 24, 48, 72, 96, 144, 192, 240, 312 and 360 h post-infection. Virus replication was observed at all temperatures from 15 to 30 degrees C. The optimal temperature for virus growth was 25 degrees C. A temperature of 10 degrees C was detrimental to the growth of the SSN-1 cells and cell death interfered with interpretations of viral growth. The isolate of Betanodavirus from Italian sea bass in this study demonstrates a different temperature range for growth compared to previous reports for related Betanodavirus strains, most likely due to an adaptation to the normal environmental temperatures of the host fish species of origin.