为了分析番鸭细小病毒(muscovy duck parvovirus,MDPV) YL08株NS1蛋白(氨基酸序列全长627 aa)抗原表位,本研究设计了一套覆盖整个NS1蛋白的短肽,短肽长为30个氨基酸左右,有10个氨基酸重叠.为了表达这些短肽,共设计合成了31对互补的寡核苷酸片段.每对寡核苷酸片段5'端磷酸化.上述寡核苷酸片段退火后,插入至原核表达载体pET-32a(+)中,经IPTG诱导获得了相应重组蛋白的表达.利用切胶纯化的方法对表达蛋白进行了纯化.应用MDPV YL08株人工感染番鸭血清对表达的31个重组蛋白的抗原性进行了检测,Western blot结果表明,表达的7个融合蛋白NS(481-510)、NS (501-530)、NS (521-550)、NS (541-570)、NS(561-590)、NS (581-610)和NS (601-627)能被MDPV感染血清所识别,而其他融合蛋白不能被MDPV感染血清所识别.同时,上述7个表达的融合蛋白不与灭活MDPV免疫番鸭血清反应.综合上述试验结果,MDPV YL08株NS1蛋白的B细胞线性抗原表位区位于NS1蛋白的羧基末端481 aa~627aa.Dot-ELISA试验表明,重组蛋白NS(501-530)的抗原性相对更强.本研究为建立基于抗原表位的MDPV自然感染和人工免疫番鸭的鉴别诊断方法提供了理论依据.
To analyze the antigenic epitopes of muscovy duck parvovirus (MDPV) YL08 strain NS1 protein, a set of 10 aa partially overlapping fragments of 30 aa spanning NS1 protein were designed. A total of 31 pairs of primers were synthesized. Each pair of primers were annealed and cloned into expression vector, pET-32a (+). The inserted DNA fragments were confirmed by sequencing. Each fragment was expressed in Escherichia coli Rosetta (DE3) and purified by elution from sodium dodecyl sulphate (SDS) polyacrylamide gels. Western blotting analysis showed that linear immunodominant B-cell epitopes were primarily found in seven fragments: NS (481-510), NS (501- 530), NS (521-550), NS (541-570), NS (561-590), NS (581-610) and NS (601-627). Meanwhile, the seven fragments showed negative reactivity to sera induced by inactivated MDPV. Thus, the non-structural protein linear B-cell epitopes are located on the C-terminal (481-627 ). Fragments NS (501-530) showed stronger positive reaction than the other fragments in Dot-ELISA assays. This study pro-vides a basis for differentiation of infected muscovy ducks from those vaccinated with inactivated virus.