Lasky R D, Troy F A
Proc Natl Acad Sci U S A. 1984 Jan;81(1):33-7. doi: 10.1073/pnas.81.1.33.
Epstein-Barr virus (EBV)-genome-negative human lymphoma lines, Ramos and BJAB, can be converted by EBV in vitro into EBV-genome-positive virus nonproducer lines. These cell lines have been used to identify surface antigens unique to EBV, with the expectation that such determinants might be related to the antigenic target responsible for EBV-specific immunosurveillance. Antisera prepared in rabbits immunized with either whole cells or purified plasma membranes were used in immunoblot experiments to analyze antigenic differences resulting from expression of the resident EBV genome. Unexpectedly, an increase in polypeptides of 32 and 70 kilodaltons was consistently observed in the EBV-converted Ramos lines. In contrast, these antigens were not expressed in BJAB or in its EBV-converted lines. These data suggested that p32 and gp70 might be murine leukemia virus (MuLV)-coded antigens because Ramos, but not BJAB, had been passaged in athymic nude mice during establishment of this cell line. This conclusion was confirmed by using antisera specific for MuLV p30 and gp70. Retroviral antigens were expressed constitutively at low levels in Ramos. Quantitative immunoblotting showed that EBV conversion of Ramos amplified the expression of MuLV proteins 3- to 5-fold. The molecular mechanism responsible for the enhanced expression is unknown. The biological relevance of this phenomenon is also not clear, but the interaction between a DNA and a RNA tumor virus in a Burkitt lymphoma line that carries both viruses may have important biological consequences in relation to retrovirus latency and tumor induction. These results also show that caution must be used when ascribing "uniqueness" to EBV-determined antigens, particularly in the Ramos lines. This warning extends also to the use of Ramos cell lines as immunogens, because immunization of rabbits elicited antibodies that recognized proteins of the same size as the retroviral antigens.
爱泼斯坦-巴尔病毒（EBV）基因组阴性的人淋巴瘤细胞系Ramos和BJAB，可在体外被EBV转化为EBV基因组阳性的病毒非产生细胞系。这些细胞系已被用于鉴定EBV特有的表面抗原，期望此类决定簇可能与负责EBV特异性免疫监视的抗原靶点相关。用全细胞或纯化的质膜免疫的兔制备的抗血清用于免疫印迹实验，以分析由常驻EBV基因组表达导致的抗原差异。出乎意料的是，在EBV转化的Ramos细胞系中持续观察到32和70千道尔顿多肽的增加。相比之下，这些抗原在BJAB或其EBV转化的细胞系中不表达。这些数据表明p32和gp70可能是鼠白血病病毒（MuLV）编码的抗原，因为在建立该细胞系过程中，Ramos（而非BJAB）曾在无胸腺裸鼠中传代。使用针对MuLV p30和gp70的特异性抗血清证实了这一结论。逆转录病毒抗原在Ramos中以低水平组成性表达。定量免疫印迹显示，Ramos的EBV转化使MuLV蛋白的表达增加了3至5倍。导致表达增强的分子机制尚不清楚。这种现象的生物学相关性也不明确，但在携带两种病毒的伯基特淋巴瘤细胞系中，一种DNA肿瘤病毒和一种RNA肿瘤病毒之间的相互作用可能对逆转录病毒潜伏期和肿瘤诱导具有重要的生物学意义。这些结果还表明，在将“独特性”归因于EBV决定的抗原时必须谨慎，特别是在Ramos细胞系中。这一警告也适用于将Ramos细胞系用作免疫原，因为用其免疫兔会引发能识别与逆转录病毒抗原大小相同的蛋白质的抗体。
