A RECOMBINANT VIRAL HEMORRHAGIC SEPTICEMIA VIRUS GLYCOPROTEIN EXPRESSED IN INSECT CELLS INDUCES PROTECTIVE IMMUNITY IN RAINBOW-TROUT

Viral haemorrhagic septicaemia (VHS) is a fish rhabdovirus infection o f world-wide importance. Control policies have been established but th e disease still causes heavy losses in fish farming. The development o f a recombinant subunit vaccine was initiated to produce a safe and ef fective vaccine to protect fish against VHS. The VHS virus (VHSV) glyc oprotein, which induces neutralizing antibodies in rainbow trout, was chosen for expression in insect cells using a baculovirus vector. The M(r) of the recombinant protein estimated by SDS-PAGE was slightly low er than that of the native viral protein. The recombinant protein disp layed different degrees of glycosylation and was recognized in ELISA b y neutralizing antibodies. It was transported to the plasma membrane o f insect cells where its ability to induce membrane fusion was preserv ed. The efficacy of the recombinant protein as a vaccine was compared with those of an inactivated and an attenuated vaccine. When injected intraperitoneally into rainbow trout, the baculovirus-encoded protein was shown (i) to induce the synthesis of VHSV-neutralizing antibodies and (ii) to confer protection against virus challenge. Immunization pe rformed by immersion failed. This is the first report of a recombinant vaccine that protects fish against VHSV.