Diseases of aquatic organisms, 2007, vol. 74, n. 2
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 septicaemia 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.
