Establishment of a New Endothelial Cell Line of Japanese Eel and Its Application to the Investigation of Temperature Preference of Japanese Eel Endothelial Cells‐Infecting Virus

Japanese eel endothelial cells-infecting virus (JEECV) is the causative agent of viral endothelial cell necrosis of eel (VECNE), which adversely affects eel aquaculture in East Asian countries. The virus primarily infects vascular endothelial cells and causes the enlargement of cell nuclei. Notably, high water temperatures (approximately 35°C) reduce the mortality from VECNE, but the temperature preference of this virus is not known. In this study, we established a cell line, designated JEE-2, from the bulbus arteriosus of the Japanese eel (Anguilla japonica). JEE-2 was considered endothelial because of its morphology and cholesterol uptake activity. JEECV was successfully cultured in the cells. In vitro-cultured JEECV caused cytopathic effects, such as enlarged nuclei in JEE-2 and VECNE symptoms in vivo. We examined the temperature preferences of the cells and the virus in vitro. JEE-2 cells showed the highest growth at 25°C-30°C, relatively slower growth at 35°C, and slight growth at 37°C. JEECV grew at 25°C-32.5°C, but the growth was considerably limited at 35°C. These results explain the lower mortality of Japanese eels with VECNE at high temperatures. This study will help further understand the infection mechanism of JEECV and develop control measures against it.