Mmapping the neutralizing epitope on the coat protein of fish nodavirus.

斑纹杰克神经坏死病毒（SJNNV）是引起海鱼病毒性神经坏死的病原体，是鱼类诺达病毒的一个成员。鱼诺达病毒是一种由单一外壳蛋白和两个正义RNA分子组成的等长病毒，根据外壳蛋白基因（RNA2）的核苷酸序列可分为四种不同的基因型（SJ型、TP型、BF型和RG型）。本研究将SJNNV和其他基因型鱼诺达病毒外壳蛋白基因的两个不同区域克隆到表达载体质粒中，分析了SJNNV的血清学关系，并定位了SJNNV的中和表位。用DIG标记的DNA探针进行杂交，证实了四种不同基因型的诺达病毒可以很容易地相互区分。此外，用A/S SJNNV和对SJNNV具有中和活性的单克隆抗体进行western blot分析，发现SJNNV和其他鱼类诺达病毒与其他基因型病毒共享大量抗原决定因子，尽管SJNNV在血清学上与它们区分。结果表明，SJNNV抗体的抗原决定因子是一个内衬表位，由外壳蛋白上的重复氨基酸序列组成。人们认为，SJNNV的中和性表位之一是PAN （aa 254-256）。TP、BF和RG基因型的诺达病毒在与SJNNV外壳蛋白相同的氨基酸位置上都有一个PPG、PEG和/或PDG，因此可以认为这四种不同基因型的诺达病毒在血清学上也存在差异。

The striped jack nervous necrosis virus (SJNNV), the causative agent of viral nervous necrosis in marine fish, is a members of fish nodaviruses. The fish nodavirus is an isometric virus consisting of a single type of coat protein and two positive-sense RNA molecules, and is divided into four different genotypes (SJ, TP, BF and RG types) based on the nucleotide sequence of the coat protein gene (RNA2). In this study, two different regions of the coat protein gene of SJNNV and other genotypes of fish nodaviruses were cloned into expression vector plasmids for analysis of the serological relationships and mapping the neutralizing epitope on SJNNV.The four different genotypes of nodaviruses were confirmed to be distinguishable from each other easily by the hybridization with DIG labeled DNA probes. Furthermore, by western blot analysis with A/S SJNNV and MAbs having neutralizing activities against SJNNV, it was revealed that SJNNV and other fish nodaviruses shared a significant number of antigenic determinants with other genotype viruses, although SJNNV was serologically distinguishable from them. And it was suggested that the antigenic determinant of SJNNV for the neutralizing MAbs was a liner epitope, which consisted of a repeated amino acid sequence at the coat protein. It was considered that one of the neutralizing epitopes of SJNNV was PAN (aa 254-256). The other genotypes of fishnodaviruses, TP, BF and RG types, have a PPG, PEG and/or PDG at the same amino acid position as SJNNV coat protein, thus it was considered that the four different genotypes of fish nodaviruses were also serologically different from each other.