Multiple Passages of Grunt Fin Cells Persistently Infected with Red Seabream Iridovirus (RSIV) at 15ºC or 30ºC to Yield Uninfected Cells

Red seabream iridovirus (RSIV), a member within genus Megalocytivirus ( Iridoviridae ), causes serious economic losses to marine fish aquaculture industry in East Asia. In this study, we established a Blue Striped Grunt Haemulon sciurus fin (grunt fin; GF) cell line persistently infected with RSIV (PI‐GF RSIV ) by subculturing GF cells that survived RSIV inoculation. PI‐GF RSIV cells were morphologically indistinguishable from naive GF cells. They could stably produce RSIV at approximately 10 4.9 ± 0.5 genomes per microliter after 24 passages over 18 months. The optimum temperature to produce RSIV in PI‐GF RSIV cells was 25°C. These cells also produced RSIV at 15, 20, and 30°C with multiple subcultures. The amount of RSIV yielded from PI‐GF RSIV cells decreased gradually by multiple subculturing at 15°C or 30°C. Red seabream iridovirus was no longer detected from PI‐GF RSIV cells after subcultures at these temperatures. These PI‐GF RSIV cells freed from RSIV infection exhibited a level of RSIV productivity similar to those of naive GF cells after inoculation with RSIV. Therefore, we consider that these PI‐GF RSIV cells were no longer infected with RSIV after multiple subculturing at 15°C or 30°C. Received October 15, 2015; accepted June 27, 2016Published online October 13, 2016