核衣壳(nucleocapsid，N)蛋白有稳定病毒基因组、调控病毒复制及细胞状态的特殊作用。鼠肝炎病毒(murine hepatitis virus，MHV)为乙型冠状病毒属的原型病毒，是研究冠状病毒N蛋白功能的经典模型。本研究用去污剂处理鼠冠状病毒粒子暴露N蛋白，另用原核表达纯化的重组N蛋白分别免疫小鼠，制备多克隆及单克隆抗体。酶联免疫吸附试验(enzyme-linked immunosorbent assay，ELISA)和蛋白免疫印迹分析结果显示两类抗体均具有高灵敏度和特异度，与甲型冠状病毒猪传染性胃肠炎病毒(porcine transmissible gastroenteritis virus，TGEV)的N蛋白无交叉反应。原核表达缺失突变的N蛋白分析结果显示，多克隆抗体与单克隆抗体2E6识别的鼠冠状病毒N蛋白抗原决定簇完全一致，位于N端结构域(N-terminal domain，NTD)C端与SR之间的58个氨基酸残基内。此外，基于单克隆抗体2E6的ELISA及免疫荧光法能检测到感染细胞中和培养上清液中的N蛋白组分，且其含量与病毒复制的滴度一致。这些结果表明，鼠冠状病毒复制过程中粒子与细胞中的N蛋白可能维持相似的结构，使NTD与SR之间的部分氨基酸残基一直暴露在表面，从而形成了优势抗原决定簇。

Nucleocapsid (N) protein of virus plays special roles in stabilization of viral genome, regulation of viral replication and adapting cellular circumstance. Murine hepatitis virus (MHV), the prototype of Betacoronavirus, is a classic model for the exploration of coronavirus N protein functions. Viral N proteins from detergent-treated virions and recombinant N proteins expressed in prokaryotic cells were prepared and used to immunize BALB/c mice for the preparation of polyclonal and monoclonal antibodies respectively. Antibodies with high sensitivity and specificity against the antigens were selected and subjected an assay for antigenic determinants. The results indicated that both polyclonal antiserum and mAb 2E6 recognized a region covering 58 residues motif. An enzyme-linked immunosorbent assay (ELISA) with mAb 2E6 was established for N proteins in medium supernatants and cellular lysates. The signal could be detected at 4 h after infection and the readings were consistent to viral titers.