不活化虹彩病毒雙價疫苗對龍膽石斑魚保護效力評估

Abstract

嘉鱲虹彩病毒 (Red sea bream iridovirus, RSIV) 及石斑魚虹彩病毒 (Grouper iridovirus, GIV) 感染常造成台灣養殖漁業的經濟損失，本研究以福馬林不活化RSIV及GIV製備成雙價疫苗，並以龍膽石斑魚苗評估其保護效果。疫苗以腹腔接種石斑魚，全程施打兩劑，兩劑間隔14天，於第二次施打後4週進行RSIV及GIV的攻毒試驗，實驗結果顯示施打兩劑疫苗2週後，魚隻皆存活無異常狀況，且各臟器組織切片結果皆正常無病變，顯示此對龍膽石斑魚是安全的，此雙價疫苗對RSIV及GIV攻毒後的相對存活率皆達60%以上。此外，雙價疫苗免疫後，於第6週分析血清中和抗體力價，RSIV中和抗體力價是131，而GIV中和抗體力價是128。頭腎與脾臟之免疫基因表現方面，IgM、IgT顯著高於對照組別，證實雙價疫苗誘發體液免疫反應，而MHC-I、CD8基因的上調，亦證實雙價疫能發誘發細胞免疫作用，並協同體液免應反應以較全面性之免疫力抵抗虹彩病毒感染，此結果顯示不活化虹彩病毒雙價疫苗可誘發龍膽石斑魚的專一性免疫力來抵抗病毒感染。

Infections with red sea bream iridovirus (RSIV) and grouper iridovirus (GIV) often cause economic losses in aquaculture in Taiwan. In this study, formalin-inactivated RSIV and GIV were used to develop a bivalent vaccine, and its protective effect on giant grouper juveniles was evaluated. Groupers were intraperitoneally immunized with this bivalent vaccine twice. The interval between the two vaccinations was 14 days. RSIV and GIV challenge was conducted at 2 weeks post booster. The results showed that all the fish survived without abnormality after immunization and the tissue sections of organs were all normal and showed no histological change, revealing this vaccine is safe for groupers. After challenge with RSIV and GIV, the relative percent survival (RPS) in the immunized fish were >60%. In addition, the neutralizing antibody titers in serum were analyzed at 6 weeks post vaccination. The neutralizing antibody titer against RSIV was 131, while that against GIV was 128. In the analysis of immune gene expression in the head kidney and spleen, IgM and IgT gene expression were significantly higher than those in the control group, confirming that the bivalent vaccine induces humoral immunity. The upregulation of MHC-I and CD8 gene expression may induce cellular immunity, which could be cooperated with the humoral immune response to resist iridovirus infection with more comprehensive immunity. These results revealed that this inactivated iridovirus bivalent vaccine can induce the specific immunity of giant groupers against virus infection.