Fingeroth J D, Diamond M E, Sage D R, Hayman J, Yates J L
Divisions of Infectious Disease and Experimental Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts 02215, USA.
J Virol. 1999 Mar;73(3):2115-25. doi: 10.1128/JVI.73.3.2115-2125.1999.
Epstein-Barr virus (EBV) is invariably present in undifferentiated nasopharyngeal carcinomas, is found sporadically in other carcinomas, and replicates in the differentiated layer of the tongue epithelium in lesions of oral hairy leukoplakia. However, it is not clear how frequently or by what mechanism EBV infects epithelial cells normally. Here, we report that a human epithelial cell line, 293, can be stably infected by EBV that has been genetically marked with a selectable gene. We show that 293 cells express a relatively low level of CD21, that binding of fluorescein-labeled EBV to 293 cells can be detected, and that both the binding of virus to cells and infection can be blocked with antibodies specific for CD21. Two proteins known to form complexes with CD21 on the surface of lymphoid cells, CD35 and CD19, could not be detected at the surface of 293 cells. All infected clones of 293 cells exhibited tight latency with a pattern of gene expression similar to that of type II latency, but productive EBV replication and release of infectious virus could be induced inefficiently by forced expression of the lytic transactivators, R and Z. Low levels of mRNA specific for the transforming membrane protein of EBV, LMP-1, as well as for LMP-2, were detected; however, LMP-1 protein was either undetectable or near the limit of detection at less than 5% of the level typical of EBV-transformed B cells. A slight increase in expression of the receptor for epidermal growth factor, which can be induced in epithelial cells by LMP-1, was detected at the cell surface with two EBV-infected 293 cell clones. These results show that low levels of surface CD21 can support infection of an epithelial cell line by EBV. The results also raise the possibility that in a normal infection of epithelial cells by EBV, the LMP-1 protein is not expressed at levels that are high enough to be oncogenic and that there might be differences in the cells of EBV-associated epithelial cancers that have arisen to allow for elevated expression of LMP-1.
爱泼斯坦-巴尔病毒（EBV）始终存在于未分化鼻咽癌中，偶尔见于其他癌症，并在口腔毛状白斑病变的舌上皮分化层中复制。然而，尚不清楚EBV正常感染上皮细胞的频率或机制。在此，我们报告一种人类上皮细胞系293可被携带可选择基因进行基因标记的EBV稳定感染。我们发现293细胞表达相对较低水平的CD21，可检测到荧光素标记的EBV与293细胞的结合，并且病毒与细胞的结合及感染均可被CD21特异性抗体阻断。在293细胞表面未检测到已知在淋巴细胞表面与CD21形成复合物的两种蛋白CD35和CD19。293细胞的所有感染克隆均表现出紧密潜伏期，基因表达模式类似于II型潜伏期，但通过强制表达裂解反式激活因子R和Z可低效诱导EBV的 productive复制及感染性病毒释放。检测到EBV转化膜蛋白LMP-1以及LMP-2的低水平特异性mRNA；然而，LMP-1蛋白要么无法检测到，要么接近检测极限，其水平低于EBV转化B细胞典型水平的5%。在两个EBV感染的293细胞克隆的细胞表面检测到表皮生长因子受体表达略有增加，该受体可由LMP-1在上皮细胞中诱导产生。这些结果表明低水平的表面CD21可支持EBV感染上皮细胞系。结果还提出了一种可能性，即在EBV对上皮细胞的正常感染中，LMP-1蛋白的表达水平不足以致癌，并且EBV相关上皮癌的细胞可能存在差异，从而允许LMP-1表达升高。
