The Proliferation Of Flounder Lymphocystis Disease Virus In Flounder Gill Cell Line (FG) And The Tissue Tropism Of The Virus In Flounder

Flounder (Paralichthys olivaceus), also named as Olive flounder, Bastard halibut, Japanese flounder and brown flounder for its body color, is a famous marine fish species and one of the most important marine cultured fishes. Lymphocystis disease, caused by lymphocystis disease virus, LCDV, is one severe fish viral disease to coastal fishery of China recent years. In 1990s, the breakout of lymphocystis disease has led to great economic loss in the flounder culture.In this study, the flounder gill (FG) cell line was used for virus culture. Cytopathic effect (CPE) of virus-infected cells was obviously shown under a light microscope. Virus-infected cells were collected and ultra-thin sliced for the electron microscopic observation. Virus particles with typical pentagonal or hexagonal outlines were discovered. The mean diameter of the virus, capsid and core are 220~290 nm, 190~240 nm and 130~140 nm, respectively. The inclusion body of LCDV was found in cytoplasm of virus-infected cells. Virus-infected cells were collected and their DNA was extracted through the classic phenol/chloroform method. Then the DNA template was amplified by PCR using a primer set designed based on the conserve sequence of the gene encoding major capsid protein of LCDV. A specific band of 454 bp was yielded, which proved that FG cell line could be the susceptible cell line of LCDV.The replication cycle of LCDV in cultured cells in vitro was also studied. It is found by electron microscopy that LCDV could finish one replication cycle in 8 hours after its adsorption. At 2 h post-infection (h.p.i), virus-infected cells had a normal structure without any CPE signs of cell organs. Virus was not observed inside cells but many virions were adsorbing and invading cells, which were typical in shape and...