PURIFICATION AND CHARACTERIZATION OF 2 FISH ENCEPHALITIS VIRUSES (FEV) INFECTING LATES-CALCARIFER AND DICENTRARCHUS-LABRAX

Two viruses causing fish encephalitis (D1EV and LcEV) were isolated from larvae of Dicentrarchius labrax and Lates calcarifer collected from hatcheries in France and in Tahiti, respectively. In both cases, viral particles were icosahedral, and measured 27-28 nm in negatively stained preparations. Complete particles exhibited a buoyant density of 1.351. 36 g/ml in CsCl. The genome of each virus consisted of two pieces of ssRNA with molecular weights of 1.056 x 10(6) and 0.495 x 10(6) Da. Characterization of the virions' structural polypeptides on SDS-PAGE resolved two polypeptides with molecular weights of 42 and 40 kDa in D1EV or 42 and 36 kDa in LcEV. From their characteristics, these viruses are very similar and closely related to the members of the Nodaviridae family. To distinguish them from the insect nodaviruses, we named provisionally these agents, fish encephalitis viruses (FEV).