感染冠状病毒的大鼠胸腺组织超微结构观察

Ultrastructural observation of rat thymus tissue with coronavirus infection

目的通过对感染大鼠冠状病毒(rat coronavirus,RCV)的大鼠胸腺组织进行超微结构的研究,阐明RCV在细胞内形成的形态学机制.方法用在进行自噬性形态学研究中的Wistar大鼠做模型,常规电镜取材、固定、包埋、切片和观察.结果胸腺上皮细胞的胞质内出现大小不等的内质网池,并相互融合形成巨大的内质网湖,湖内充满RCV颗粒,称为病毒包涵体.病毒在内质网囊壁上通过出芽方式进入内质网湖基质,发育为成熟的RCV,最终排出于细胞外.病毒颗粒呈圆形,直径约100～130 nm.病毒胞浆成均质状,病毒的膜蛋白有二层,外层为包膜,内层为核衣壳.包膜与核衣壳之间为低电子密度的中间层,其内有时可见1～2层较薄的膜样结构.钉突成放射状贯穿包膜,其内侧端连于核衣壳,外侧端膨大,由一层絮状的糖蛋白包绕,形成日冕状.病毒颗粒分布在胸腺上皮细胞的内质网湖、胞浆、内吞体/溶酶体以及胸腺上皮细胞间,溶酶体内的病毒无包膜和核衣壳.结论内质网湖参与RCV包膜的形成,从细胞外侵入的RCV均在内吞体/溶酶体内脱去包膜和核衣壳,脱下的包膜和核衣壳被其降解,而RCV在胸腺上皮细胞基质中进行复制.在胸腺细胞内未见有RCV.

Objectiv e To investigate the ultrastructure of rat thymus tissues with rat coronavirus (RC V) infection for clarifying the mechanism responsible for the morphologica l changes of the cells infected by RCV. Method Routine electron micros copy was performed for observing RCV-infected rat thymus tissues. Results Follow ing RCV infection, endoplasmic reticulum (ER) pools of different dimensions wer e observed in the cytoplasm of the thymic epithelial reticular cells, merging s ubsequently with each other into larger ER lakes filled with particles of mature RCV, or viral inclusion bodies. After germination on the ER membrane, the viru ses entered the matrix of the ER lake to mature and were eventually excreted to the extracellular space. The RCV particles were spherical in shape with a diame ter of 100-130 nm and two distinct membranes, the outer one being the envelope and the inner one the nuclear capsid to enclose the viroplasm. Between the envel op and nuclear capsid was a electron-lucent middle layer comprising one to two thin membranous structures. Large quantity of short spike-like projections star ting from the nucleus capsid penetrated the middle layer and the envelop to reac h the glycoprotein coat and formed a corona-like structure. Mature RCV particle s were distributed around the ER pools, cytoplasm, and intercellular space, and the RCVs in the endosome/lysosome were devoid of the envelop and nuclear capsid . Conclusions The ER lakes are involved in the maturation of the viruses, and t he envelop and nuclear capsid of the virus entering the cells from extracellular space are removed and degraded in the endosome/lysosome. Replications of virus occurs in plasma of the thymic epithelial reticular cells, and no RCV can be d etected in the thymocytes.