Young L S, Yao Q Y, Rooney C M, Sculley T B, Moss D J, Rupani H, Laux G, Bornkamm G W, Rickinson A B
Department of Cancer Studies, University of Birmingham, U.K.
J Gen Virol. 1987 Nov;68 ( Pt 11):2853-62. doi: 10.1099/0022-1317-68-11-2853.
All Epstein-Barr virus (EBV) isolates can be classified as type A or type B depending upon the identity of their EBV nuclear antigen (EBNA) 2 protein. The great majority of isolates examined to date encode an EBNA 2A protein like that of the reference type A strain B95-8. Type B virus strains, encoding an antigenically distinct EBNA 2B protein, have as yet only been rescued from rare Burkitt's lymphoma (BL) cell lines of African origin (Jijoye, AG876). Our recent finding that type B isolates are less efficient than type A in in vitro transformation assays prompted us to determine (i) the relative contribution the two types of virus make to the incidence of BL in endemic areas of Africa (Kenya) and New Guinea and (ii) the relative incidence of infection with these two types in the normal population in these same areas. On the first point, EBNA 2 gene typing using specific DNA probes showed that four of ten recently established Kenyan BL cell lines and two of four BL cell lines from New Guinea carried type B virus isolates. To address the second point, spontaneous lymphoblastoid cell lines were established from the blood of normal virus carriers and typed for EBNA 2 at the protein level; a significant proportion (greater than 20%) of the normal population in both the above BL-endemic areas were infected with type B isolates. This is the first indication of the widespread nature of type B virus infection in any community and the first isolation of such viruses from a non-BL source. The reproducible size of the EBNA 2B protein encoded by all type B isolates irrespective of their geographical origin, and of the EBNA 1 protein encoded by all type B isolates from one area, contrasted markedly with the extreme variability in the size both of EBNA 2A and of EBNA 1 seen generally among type A isolates. This suggests that the number of type B virus strains in existence worldwide could be quite limited. Most importantly, the data suggest that type B viruses, despite their relatively poor performance in in vitro transformation assays, can contribute at least as efficiently as can type A viruses to the pathogenesis of BL.
根据爱泼斯坦-巴尔病毒（EBV）核抗原（EBNA）2蛋白的特性，所有EBV分离株可分为A或B型。迄今为止，绝大多数检测的分离株编码的EBNA 2A蛋白与参考A型毒株B95-8的相似。编码抗原性不同的EBNA 2B蛋白的B型病毒株，目前仅从少数非洲来源的罕见伯基特淋巴瘤（BL）细胞系（Jijoye、AG876）中分离得到。我们最近发现，在体外转化试验中，B型分离株的效率低于A型，这促使我们确定：（i）这两种病毒对非洲（肯尼亚）和新几内亚流行地区BL发病率的相对贡献；（ii）这两种病毒在这些相同地区正常人群中的相对感染率。关于第一点，使用特异性DNA探针进行EBNA 2基因分型显示，最近建立的10个肯尼亚BL细胞系中有4个以及来自新几内亚的4个BL细胞系中有2个携带B型病毒分离株。为了解决第二点，从正常病毒携带者的血液中建立自发淋巴母细胞系，并在蛋白质水平对EBNA 2进行分型；上述两个BL流行地区的正常人群中，相当大比例（超过20%）感染了B型分离株。这是B型病毒感染在任何社区广泛存在的首个迹象，也是首次从非BL来源分离出此类病毒。所有B型分离株（无论其地理来源）编码的EBNA 2B蛋白大小可重复，以及来自一个地区的所有B型分离株编码的EBNA 1蛋白大小可重复，这与A型分离株中普遍观察到的EBNA 2A和EBNA 1大小的极端变异性形成鲜明对比。这表明全球现存的B型病毒株数量可能相当有限。最重要的是，数据表明，B型病毒尽管在体外转化试验中的表现相对较差，但在BL发病机制中的作用至少与A型病毒一样有效。
