VIRAL HEMORRHAGIC SEPTICEMIA VIRUS MULTIPLICATION AND INTERFERON-PRODUCTION IN RAINBOW-TROUT AND IN RAINBOW-TROUT X BROOK TROUT HYBRIDS

Rainbow trout (Oncorhynchus mykiss) susceptible to Viral Haemorrhagic Septicaemia (VHS) Virus type 1 and rainbow trout x brook trout (Salvel inus fontinalis) triploid hybrids were challenged with VHSV by either immersion or i.p. injection of the virus. In both cases susceptible ra inbow trout displayed an increasing viraemia which was paralleled by h igh interferon titres in the serum. In contrast virus multiplication a s well as serum interferon production remained low in resistant hybrid s. When blood leucocytes were infected in vitro the adsorption of viru s appeared low and there was no obvious multiplication of the virus an d trout and hybrid leucocytes released similar levels of interferon in the culture medium. When leucocytes were stimulated by monolayers of VHSV infected cells fixed with glutaraldehyde at the time virus was bu dding at their surface, interferon production was the same in kidney l eucocytes but was much lower in hybrid than in trout blood leucocyte c ultures.