Olive flounder were vaccinated with
polyinosinic:polycytidylic acid [
Poly (I:C)] to prevent
viral hemorrhagic septicemia (VHS).
Vaccine efficacy was verified by detection of anti- VHS virus (VHSV)
antibodies using
enzyme-linked
immunosorbent assay (ELISA). In the study, ELISA absorbance values of the negative control group [
Poly (I:C)-MEM10] were saturated when an ELISA protocol, that includes pretreatment of the fish sera with 5% skim milk, was used. However, the saturated OD values in the negative control did not correlate with a specific immune response against VHSV, because the group showed low survival rate (only 10%) following the VHSV challenge. Also, OD values of
Poly (I:C)- VHSV group were high, and the group showed high survival rate (97.5%) against VHSV challenge test. It was suggested that the high OD values were possibly due to the presence of anti-
fetal bovine serum (FBS) cross-reactivity. To compensate this, we subtracted the absorbance of infectious hematopoietic
necrosis (IHNV)-Ag plates from those of the VHSV-Ag plates. However, the average value for the
Poly (I:C)-VHSV group (0.167) was lower than expected even though high survival rate. We used an advanced ELISA system to pre-treat fish sera with 5% skim milk and two novirhabdoviruses as capture
antigens as well as 50% FBS. The corrected absorbance values for pre-treated fish sera from the negative control
Poly (I:C)-MEM10 and experimental
Poly (I:C)-VHSV groups averaged 0.033 and 0.579, respectively. The specific VHSV antibody response of the vaccinated group was assessed using fish sera pretreated with skim milk and FBS and by calculating the corrected absorbance values from ELISA with two novirhabdovirus capture
antigens.