Abstract：
Largemouth bass ranavirus (LMBV) is highly contagious and lethal to largemouth bass, causing significant economic losses to the aquaculture industry. Oral vaccination is generally considered the most ideal strategy for protecting fish from viral infection. In this study, the fusion protein MCP-FlaC, consisting of the main capsid protein (MCP) as the antigen and flagellin C (FlaC) as the adjuvant, was intracellularly expressed in Pichia pastoris. Subsequently, the recombinant P. pastoris was freeze-dried to prepare the oral vaccine P-MCP-FlaC. Transmission electron microscopy and scanning electron microscopy analysis showed that the morphology and structure of the freeze-dried recombinant P. pastoris vaccine remained intact. The experiment fish (n = 100) was divided into five groups (P-MCP-FlaC, P-MCP, P-FlaC, P-pPIC3.5K, control) to evaluate the protective efficacy of the recombinant vaccine. Oral P-MCP-FlaC vaccine effectively up-regulated the serum enzymes activity (total superoxide dismutase, lysozyme, total antioxidant capacity, and complement component 3). The survival rate of P-MCP-FlaC group was significantly higher than that of the other groups. The mRNA expression of crucial immune genes (IL-1β, TNF-α, MHC-II, IFN-γ, Mx, IgM, IgT) was also signally elevated in P-MCP-FlaC group. Vaccine P-MCP-FlaC markedly inhibited the replication of LMBV in the spleen, head kidney, and intestine, while reducing the degree of lesion in the spleen. These results suggest that the oral P-MCP-FlaC vaccine could effectively control LMBV infection, proving an effective strategy for viral diseases prevention in aquaculture.
摘要：
大嘴鲈鱼病毒（LMBV）对大嘴鲈鱼具有高度传染性和致命性，给养殖业造成重大的经济损失。口服疫苗通常被认为是保护鱼类免受病毒感染的最理想策略。在这项研究中,融合蛋白MCP-FlaC,由主要衣壳蛋白（MCP）作为抗原和鞭毛蛋白C（FlaC）作为佐剂组成，在巴斯德毕赤酵母细胞内表达。随后，将重组巴斯德毕赤酵母冻干以制备口服疫苗P-MCP-FlaC。透射电镜和扫描电镜分析显示冻干重组巴斯德毕赤酵母疫苗的形态和结构保持完整。实验鱼（n=100）分为五组（P-MCP-FlaC，P-MCP,P-FlaC,P-pPIC3.5K,对照），以评估重组疫苗的保护效力。口服P-MCP-FlaC疫苗有效上调血清酶活性(总超氧化物歧化酶，溶菌酶,总抗氧化能力，和补体成分3)。P-MCP-FlaC组的存活率明显高于其他组。关键免疫基因(IL-1β，TNF-α,MHC-II，IFN-γ，Mx,IgM,P-MCP-FlaC组IgT）也显著升高。疫苗P-MCP-FlaC显著抑制LMBV在脾脏中的复制,头肾,和肠，同时减少脾脏的病变程度。提示口服P-MCP-FlaC疫苗能有效控制LMBV感染,证明了水产养殖中预防病毒性疾病的有效策略。
