Largemouth bass virus (LMBV) is the causative agent of a disease causing high mortality rates in largemouth bass during summer. However, there is little information available about the development of vaccines for LMBV disease. Hence, a DNA vaccine, named pCDNA3.1(+)-MCP-Flag, was constructed by inserting the cloned LMBV major capsid protein (MCP) gene into the pCDNA3.1(+)-Flag plasmid. The expression of the recombinant plasmid was confirmed by Western blot (WB) and RT-PCR. The WB result revealed that the MCP protein produced a band of approximately 53 kDa, consistent with the expected result. The RT-PCR results also confirmed that MCP was transcribed in the EPC cells transfected with the recombinant plasmid. The largemouth bass in the DNA vaccine group were immunized with the pCDNA3.1(+)-MCP-Flag plasmid by pectoral fin base injection, and the relative percent survival (RPS) of fish challenged with LMBV was 63%. The relative immunological analyses were as follows. Compared with the PBS and pCDNA3.1(+) groups, the DNA vaccine group showed significantly upregulated expression of IL-1β, IL-8, TNF-α and Mx in the spleen, head kidney and liver. All largemouth bass immunized with the DNA vaccine produced a high titre of LMBV-specific neutralizing antibody during the immunization period. The titre was 1:375 ± 40 and peaked at 14 days post-vaccination. The expression of the recombinant plasmid was analysed in the tissues of the DNA vaccine group by RT-PCR. The recombinant plasmid was expressed in the spleen, head kidney and liver, and MCP protein was successfully expressed after vaccination. In conclusion, the recombinant plasmid expressing LMBV MCP induced significant immune responses in largemouth bass, and might represent a potential LMBV vaccine candidate for largemouth bass.

大嘴鲈鱼病毒（LMBV）是导致夏季大嘴鲈死亡率高的疾病的病原体。但是，关于LMBV疾病疫苗开发的信息很少。因此，通过将克隆的LMBV主要衣壳蛋白（MCP）基因插入pCDNA3.1（+）-Flag质粒中，构建了一种名为pCDNA3.1（+）-MCP-Flag的DNA疫苗。通过Western印迹（WB）和RT-PCR确认重组质粒的表达。WB结果表明，MCP蛋白产生的条带约为53 kDa，与预期结果一致。RT-PCR结果也证实了MCP在用重组质粒转染的EPC细胞中转录。DNA疫苗组中的大嘴鲈鱼通过胸鳍碱基注射用pCDNA3.1（+）-MCP-Flag质粒免疫，LMBV攻击的鱼类的相对存活率（RPS）为63％。相对免疫分析如下。与PBS和pCDNA3.1（+）组相比，DNA疫苗组在脾脏，头部肾脏和肝脏中IL-1β，IL-8，TNF-α和Mx的表达明显上调。用DNA疫苗免疫的所有大嘴鲈在免疫期间均产生高滴度的LMBV特异性中和抗体。滴度为1：375±40，在接种后14天达到峰值。通过RT-PCR分析重组质粒在DNA疫苗组组织中的表达。重组质粒在脾，头肾和肝中表达，接种疫苗后成功表达MCP蛋白。结论，