METHODS
Cell line. GF cells (Clem et al., 1961) were purchased from ATCC.
Cell lines were maintained in basal medium Eagle (BME; MP
Biomedicals) supplemented with 10% FBS (Equitech-Bio) and
antibiotics (100 U penicillin ml21 and 100 mg streptomycin ml21),
and were cultivated at 25 uC.
Virus. The virus used for the present study, RSIV KagYT-96, was
isolated in 2010 using GF cells from a diseased Japanese amberjack
frozen at 280 uC originally sampled in Kagoshima Prefecture in 1996.
Homogenate of the spleen was prepared with approximately 50 times
volume of BME and passed through a 0.45 mm filter after
centrifugation (400 g, 4 uC, 10 min). Then, 500 ml of the inoculum
was added into a 25 cm2 flask containing suspended GF cells just after
dispersion and the GF cells were incubated at 25 uC for isolation of
the virus.