Three serological tests, enzyme linked immunosorbent assay (ELISA), 50 % plaque neutralisation test (50%PNT) and Western blotting (WB), were used to detect antibodies against viral haemorrhagic septicaerma virus (VHSV) in 50 rainbow trout broodstock from a rainbow trout farm endemically infected with VHS but with no clinical signs of infection. When the sera were examined by 50%PNT using the VHSV reference isolate DK-F1 or the heat attenuated DK-F25 mutant strain, no neutralizing antibodies were found. In contrast, when one of the virus isolates from the farm (homologous virus) was used in the 50 %PNT, 90 % of the fish were found to be positive. By examining a panel of different VHSV isolates in 50 %PNT, it was demonstrated that the virus isolate used as test antigen could significantly affect the sensitivity and titre determination in 50 %PNT for detection of rainbow trout antibodies against VHSV. When the sera were examined for the presence of VHSV antibodies by ELISA or WB, 61 % were found to be positive. When conducting WB analysis, the viral glycoprotein was the protein most frequently recognized, followed by the viral nucleoprotein.
- trout antibody
- plaque neutralisation