Detection and antigenic characterization of salmonid alphavirus isolates from sera obtained from farmed Atlantic salmon, Salmo salar L., and farmed rainbow trout, Oncorhynchus mykiss (Walbaum)

Abstract

A simple method of detecting the presence of the salmonid alphaviruses (SAVs), salmon pancreas disease virus (SPDV) and sleeping disease virus (SDV), from serum samples is described. Using a 96‐well tissue‐culture plate format, test sera are diluted in medium and added to chinook salmon embryo (CHSE‐214) cells. After incubation for 3 days at 15 °C, plates are fixed and stained using a monoclonal antibody (mAb)‐based immunoperoxidase (IPX) detection system, and virus‐infected cells are observed microscopically by white light. Application of this screening test, which is now used routinely in our laboratory in conjunction with an IPX‐based virus neutralization (IPX‐VN) test for detecting antibodies to SAVs, has resulted in the recovery of 12 additional isolates from salmon sera and four additional isolates from trout sera. A low level of antigenic variation was detected when these SAV isolates were investigated by indirect immunofluorescence using a panel of mAbs raised to reference SPDV and SDV isolates.

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