Specific antibody responses (IgM) against Piscine orthoreovirus (PRV) in Atlantic salmon (Salmo salar), measured in a multiplexed magnetic bead-based system

Abstract

Piscine orthoreovirus (PRV) causes heart- and skeletal muscle inflammation (HSMI) in farmed Atlantic salmon (Salmo salar). HSMI causes significant economic losses to the salmon aquaculture industry, and there is currently no vaccine available. In the trial this master thesis is based on, Atlantic salmon were injected with PRV-1, PRV-2, PRV-3 and inactivated PRV-1 to explore cross immunity and protection. In this thesis work, the focus was on detecting PRV specific antibodies (i.e., an IgM response). For the detection of PRV specific antibodies a multiplexed bead-based immunoassay was used to detect antibodies targeting the antigens PRV-1 σ1, PRV-μ1C, PRV-3 σ1 and PRV-3 μNS. PRV specific antibodies targeting PRV-1 σ1 were detected in Atlantic salmon immunized with PRV-2 and PRV-3, and PRV specific antibodies targeting PRV-1 σ1 and PRV-μ1C were detected in Atlantic salmon infected with PRV-1. There was also detected an increase in unspecific antibodies binding to controls after PRV-1 infection. No specific antibodies were detected in fish injected with InPRV-1. The PRV-3 µNS and PRV-3 σ1 antigens did not bind antibodies in this assay and could not be used as a reliable detection method. Immunization with PRV-3 induced anti-PRV antibodies and completely blocked a secondary PRV-1 infection and protected against HSMI. PRV-2 produced low levels of anti-PRV antibodies, but did not block PRV-1 infection or efficiently protected against HSMI. No antibodies were detected after immunization with inactivated PRV-1, but an intermediate protection was still obtained. Multiplexed bead-based immunoassay is a sensitive and fast method that can be used as a reliable diagnostic tool for immunity.