High permissivity of the fish cell line SSN-1 for piscine nodaviruses.
Seventeen isolates of piscine nodavirus from larvae or juveniles of 13 marine fish species affected with viral nervous necrosis (VNN) were examined for their infectivity to a fish cell line SSN-1. Based on cytopathic effects (CPE) and virus antigen detection by fluorescent antibody technique (FAT) after incubation at 25 degrees C, the infectivity of these virus isolates was divided into 4 groups. Group 1, including 9 virus isolates from 4 species of grouper, 2 species of sea bass, barramundi, rock porgy, and Japanese flounder showed CPE characterized by rounded, granular cells with heavy cytoplasmic vacuoles within 3 d post-incubation (p.i.), and the monolayer partially or completely disintegrated over 3 to 6 d p.i. Scattered FAT-positive cells appeared at 3 h p.i. and spread through the cell sheet with an increasing fluorescence signal over 24 h p.i. Group 2, consisting of 3 virus isolates from striped jack, induced CPE with thin or rounded, granular, refractile cells without conspicuous vacuole formation, and extensive FAT-positive reaction was observed in a time course similar to that of Group 1. Cells inoculated with Group 3 (1 isolate from tiger puffer) developed no distinct CPE but viral infection was evidenced by localized FAT-positive cells. There were no FAT-positive cells in Group 4, which included 4 isolates from Japanese flounder, Pacific cod and Atlantic halibut. However, when incubation was performed at 20 degrees C, the SSN-1 cells inoculated with the Group 3 isolate showed CPE similar to that of Group 1 and extensive FAT-positive reaction. Evidence of virus proliferation at 20 degrees C was also obtained in Group 4 isolates. The virus titers in the infected fish varied from 10(11) to 10(16) tissue culture infectious dose (TCID50) g(-1) of fish. There is a good correlation between these infectivities to the SSN-1 cells and the coat protein gene genotypes of the isolates. The present results indicate that SSN-1 cells are useful for propagating and differentiating genotypic variants of piscine nodavirus.
Iwamoto
T
T
Fish Pathology Laboratory, Faculty of Applied Biological Science, Hiroshima University, Higashihiroshima, Japan.
Mori
K
K
Arimoto
M
M
Nakai
T
T
D000818:Animals; D000956:Antigens, Viral / Q000302:isolation & purification; D002213:Capsid / Q000235:genetics; D002460:Cell Line; D003588:Cytopathogenic Effect, Viral; D005393:Fish Diseases / Q000821:virology*; D005399:Fishes; D005455:Fluorescent Antibody Technique / Q000662:veterinary; D007814:Larva; D008854:Microscopy, Electron / Q000662:veterinary; D012150:Polymorphism, Restriction Fragment Length; D012327:RNA Virus Infections / Q000662:veterinary*; D012328:RNA Viruses / Q000235:genetics / Q000254:growth & development* / Q000276:immunology; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000662:veterinary
D000956:Antigens, Viral