High permissivity of the fish cell line SSN-1 for piscine nodaviruses.

Iwamoto Tokinori

Mori Koh-ichiro

Arimoto Misao

Nakai Toshihiro

Diseases of Aquatic Organisms

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°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°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°C was also obtained in Group 4 isolates. The virus titers in the infected fish varied from 1011 to 1016 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.

Nodavirus

Viral nervous necrosis

Viral encephalopathy and retinopathy

SSN-1 cell line

FAT

RFLP

RT-PCR

Zoology [ 480 ]

eng

Inter-Research

Copyright (c) 1999 Inter-Research.

[ISSN] 0177-5103

[ISSN] 1616-1580

[DOI] 10.3354/dao039037

[NCID] AA10443976

[DOI] http://dx.doi.org/10.3354/dao039037