FBS components in viral culture fluid interfere with the detection of specific antibody in immunized fish. In the present study, we developed a method to eliminate the interference of FBS using a model of red sea bream iridovirus (RSIV) vaccine. In an experiment using yellowtail antiserum against BSA, which is a major component of FBS in cell culture media, antibodies against BSA were completely absorbed via incubation of antiserum in 50% FBS at 25 degrees C for 1 h. In antibody detection, ELISA with the sera of yellowtail surviving RSIV-challenge, antibodies against RSIV were detected, but those against FBS disappeared via the pre-treatment of the sera. Therefore, antibodies against RSIV are effectively detected using ELISA with the pre-treatment of fish sera. RSIV培養液を接種したブリからの抗RSIV抗体検出ELISA法について検討した。培養液に含まれるFBSの主要成分であるBSAに対する抗ブリ血清を用いた場合、血清に終濃度50％（v／v）となるようFBSを添加し25℃で1時間処理することで、血清中の抗BSA抗体が完全に吸収された。培養RSIV液で攻撃した生残ブリから得た血清を同様に処理することで、抗体検出ELISAにより抗RSIV抗体が検出できることが明らかになった。