Lee S P, Thomas W A, Murray R J, Khanim F, Kaur S, Young L S, Rowe M, Kurilla M, Rickinson A B
Department of Cancer Studies, University of Birmingham, United Kingdom.
J Virol. 1993 Dec;67(12):7428-35. doi: 10.1128/JVI.67.12.7428-7435.1993.
Cytotoxic T-lymphocyte (CTL) responses induced by persistent Epstein-Barr virus (EBV) infection in normal B-lymphoid tissues could potentially be directed against EBV-positive malignancies if expression of the relevant viral target proteins is maintained in tumor cells. For malignancies such as nasopharyngeal carcinoma and Hodgkin's disease, this will require CTL targeting against the nuclear antigen EBNA1 or the latent membrane proteins LMP1 and LMP2. Here we analyze in detail a B95.8 EBV-reactivated CTL response which is specific for LMP2 and restricted through a common HLA allele, A2.1. We found that in vitro-reactivated CTL preparations from several A2.1-positive virus-immune donors contained detectable reactivity against A2.1-bearing target cells expressing either LMP2A or the smaller LMP2B protein from recombinant vaccinia virus vectors. Peptide sensitization experiments then mapped the A2.1-restricted response to a single epitope, the nonamer CLGGLLTMV (LMP2A residues 426 to 434), whose sequence accords well with the proposed peptide binding motif for A2.1. Most Caucasian and African virus isolates (whether of type 1 or type 2) were identical in sequence to B95.8 across this LMP2 epitope region, although 2 of 12 such isolates encoded a Leu-->Ile change at epitope position 6. In contrast, most Southeast Asian and New Guinean isolates (whether of type 1 or type 2) constituted a different virus group with a Cys-->Ser mutation at epitope position 1. CTLs raised against the B95.8-encoded epitope were nevertheless able to recognize these variant epitope sequences in the context of A2.1 whether they were provided exogenously as synthetic peptides or generated endogenously in B cells transformed with the variant viruses. A CTL response of this kind could have therapeutic potential in that it is directed against a protein expressed in many EBV-positive malignancies, is reactive across a range of virus isolates, and is restricted through a relatively common HLA allele.
在正常B淋巴细胞组织中，由持续性EB病毒（EBV）感染诱导产生的细胞毒性T淋巴细胞（CTL）反应，如果相关病毒靶蛋白在肿瘤细胞中持续表达，那么这种反应就有可能针对EBV阳性恶性肿瘤。对于鼻咽癌和霍奇金病等恶性肿瘤来说，这就需要CTL靶向核抗原EBNA1或潜伏膜蛋白LMP1和LMP2。在此，我们详细分析了一种B95.8 EBV激活的CTL反应，该反应对LMP2具有特异性，并通过常见的HLA等位基因A2.1进行限制。我们发现，来自几个A2.1阳性病毒免疫供体的体外激活的CTL制剂，对表达LMP2A或来自重组痘苗病毒载体的较小LMP2B蛋白的携带A2.1的靶细胞具有可检测到的反应性。肽致敏实验随后将A2.1限制的反应定位到一个单一表位，即九聚体CLGGLLTMV（LMP2A的426至434位残基），其序列与所提出的A2.1肽结合基序非常吻合。大多数白种人和非洲病毒分离株（无论是1型还是2型）在这个LMP2表位区域的序列与B95.8相同，尽管12个这样的分离株中有2个在表位位置6处编码了Leu→Ile的变化。相比之下，大多数东南亚和新几内亚分离株（无论是1型还是2型）构成了一个不同的病毒组，在表位位置1处有Cys→Ser突变。然而，针对B95.8编码表位产生的CTL能够在A2.1的背景下识别这些变异表位序列，无论它们是作为合成肽外源提供的，还是在用变异病毒转化的B细胞中内源性产生的。这种CTL反应可能具有治疗潜力，因为它针对许多EBV阳性恶性肿瘤中表达的一种蛋白，对一系列病毒分离株具有反应性，并且通过一个相对常见的HLA等位基因进行限制。
