INFECTIOUS PANCREATIC NECROSIS VIRUS (IPNV) IN NORMAL RAINBOW TROUT SERUM (RTS) AND ITS EFFECTS ON THE VIRUS

Abstract approved: The characteristics of an inhibitor of infectious pancreatic necrosis virus (IPNV) found in normal rainbow trout serum (RTS) were studied. The serum inhibitor had a molecular weight of approximately 150 kDa and was dependent on divalent cations, either Ca2 or Mg2. It was stable at temperatures up to 50°C and at a pH range between 4-10. The inhibitor directly inactivated the virus and the inhibition level was dependent on cell densities and on the time at which virus was exposed to RTS. The level of virus inhibition by RTS was altered by the cell line in which virus was produced. IPNV was more efficiently inhibited by RTS in salmonid cell lines than in non-salmonid cell lines. Most of the salmonid sera tested showed inhibition, while non-salmonid sera did not inhibit IPNV replication. Rainbow trout continuously showed a significant level of inhibition in their serum after 23 weeks post hatch. Three isolates of IPNV were passaged five times in RTG-2 cells with either MEM- 10 or MEM- 10 with 1 % rainbow trout serum and virus from each passage were tested for RTS sensitivity in vitro and virulence in vivo. The mortality level in brook trou