Burny A, Cleuter Y, Kettmann R, Mammerickx M, Marbaix G, Portetelle D, Van den Broeke A, Willems L, Thomas R
Faculty of Agronomy, Gembloux, Belgium.
Cancer Surv. 1987;6(1):139-59.
Bovine leukaemia virus (BLV) is the aetiological agent of a chronic lymphatic leukaemia/lymphoma in cows, sheep and goats. Infection without neoplastic transformation has also been demonstrated in pigs, rhesus monkeys, chimpanzees and rabbits and observed in capybaras and water buffaloes. Structurally and functionally, BLV is a relative of human T lymphotropic viruses 1 and 2 (HTLV-I and HTLV-II) since all three viruses show clear-cut sequence homologies. The pathology of the BLV-induced disease, most notably the absence of chronic viraemia, a long latency period and lack of preferred proviral integration sites in tumours, is similar to that of adult T-cell leukaemia/lymphoma induced by HTLV-I. The most striking feature of the three naturally transmitted leukaemia viruses is the X region located between the env gene and the long terminal repeat (LTR) sequence. The X region contains several overlapping long open reading frames, one of which, designated XBL-1, encodes a trans-activator function capable of increasing the level of gene expression directed by BLV-LTR and is most probably involved in genetic instability of BLV-infected cells of the B-cell lineage. The 'genetic instability' may put the cell into a state of fragility, ready to move along a number of stages towards full malignancy. Little is known about these events and their causes and we present some theoretical possibilities. BLV infection has a worldwide distribution. In temperate climates the virus spreads mostly through iatrogenic transfer of infected lymphocytes. In warm climates and in areas heavily populated by haematophagous insects, there are indications of insect-borne propagation of the virus.
牛白血病病毒（BLV）是牛、绵羊和山羊慢性淋巴细胞白血病/淋巴瘤的病原体。在猪、恒河猴、黑猩猩和兔子中也证实了无肿瘤转化的感染，并在水豚和水牛中观察到。在结构和功能上，BLV是人类嗜T淋巴细胞病毒1型和2型（HTLV - I和HTLV - II）的亲属，因为这三种病毒都显示出明显的序列同源性。BLV诱导疾病的病理学，最显著的是缺乏慢性病毒血症、潜伏期长以及肿瘤中缺乏优先的前病毒整合位点，与HTLV - I诱导的成人T细胞白血病/淋巴瘤相似。这三种自然传播的白血病病毒最显著的特征是位于env基因和长末端重复序列（LTR）之间的X区域。X区域包含几个重叠的长开放阅读框，其中一个称为XBL - 1，编码一种反式激活功能，能够增加由BLV - LTR指导的基因表达水平，并且很可能参与B细胞系BLV感染细胞的遗传不稳定性。这种“遗传不稳定性”可能使细胞处于脆弱状态，准备沿着多个阶段发展为完全恶性肿瘤。关于这些事件及其原因知之甚少，我们提出了一些理论可能性。BLV感染在全球范围内分布。在温带气候地区，病毒主要通过感染淋巴细胞的医源性转移传播。在温暖气候地区和吸血昆虫大量繁殖的地区，有迹象表明病毒通过昆虫传播。
