Studies On The DNA Probe Detection Of Turbot Reddish Body Iridovirus And Experimental Infection Of Flouder Gill Cell Line With The Virus

A novel infectious disease affecting farmed turbot, (Scophthalmus maximus), was described. This disease named as'Viral reddish body syndrome'(VRBS) has caused severe mortalities of farmed turbot and led to serious economic losses in China. Affected fish generally lacked external lesions. The only consistent abnormalities were pale gills with local haemorrhages, petechial haemorrhages in fins and fin bases, especially haemorrhages in muscle and skin. Anaemia, pallor and enlarged kidneys were usually observed in severe affected fish. Numerous viral particles 125 nm in diameter with icosahedral in symmetry were detected by transmission electron microscopic examination in the cytoplasm of diseased turbot. The virus is subsequently identified as Turbot reddish body iridovirus (TRBIV).The TRBIV DNA probe labeled with digonigenin was generated by PCR amplification. A DNA probe detection method of TRBIV was developed subsequently. The sensitivity and specificity was tested by dot blot hybridization with TRBIV recombined plasmid(pGAPZαA-MCP) and TRBIV DNA, DNA extracted from TRBIV-infected turbot, DNA extracted from TRBIV-free Turbot, healthy turbot tissues and Lymphocystis disease virus (LCDV) DNA. The sensitivity was 2.095pg, corresponding to 4.561×105 copies of TRBIV recombined plasmid (pGAPZαA-MCP) and was able to hybridize with TRBIV DNA from 48ng tissues homogenate of TRBIV-infected turbot. No hybridization signals were observed using healthy tissue DNA, supernatant of TRBIV–free turbot and LCDV DNA.In this study, Flouder Gill cell line was infected with TRBIV. Cytopathic effect (CPE) occurs in 30h post-infection.Typical iridovirus viron in FG cells was detected by transmission electron microscopic examination in 20℃, and the diameter of high electron-dense nucleoid was about 60nm-80n. But all the virons are half-baked.