Development of new vaccine strategies against Marek's disease virus with increased virulence

本研究旨在对马立克氏病病毒（Marek ′ s disease virus，MDV）新分离株进行分子生物学特性鉴定，以开发利用L-meq基因修饰的MDV疫苗来对抗这些极强毒MDV（very ventricular MDV，vvMDV）的新策略。并将它们的核苷酸序列与已知的vvMDV的核苷酸序列进行比较。最近在日本分离的MDV的meq基因（MDV的候选癌基因）的核苷酸序列与已知的vvMDV的核苷酸序列具有很高的同源性，但在这些分离株中也发现了一些以前未鉴定的突变。此外，一个额外的EcoRI位点被确定在糖蛋白B基因的分离株，株北海道，而糖蛋白L基因，这是经常观察到的vvMDV，被发现在几个分离株从野鸟和鸡。在 ...更多信息 接下来的实验中，我们分析了这些突变对meq基因产物MEQ转录激活的影响。毒力增强的MDV毒株通过MEQ表现出更高的转录激活，MEQ转录激活结构域的突变可能是MDV毒株毒力的决定因素。然而，菌株北海道的MEQ，与新鉴定的突变，没有显示更高的转录激活其MEQ。非致病性MDV疫苗株中存在的L-meq基因产物（L-MEQ）可抑制MEQ的转录激活和vvMDV的体外复制，提示L-MEQ在维持潜伏期中具有重要作用。我们还鉴定了meq基因的一种新的转录变体，称为Δmeq，当诱导凋亡时，其在马立克氏病肿瘤细胞中的表达上调。Δmeq抑制MEQ和L-MEQ的转录激活作用，表明Δmeq可能作为MEQ的负调节因子参与MDV的凋亡或从潜伏期再激活。因此，Δmeq可用于开发仅在vvMDV转化细胞中诱导程序性细胞死亡的新疫苗。少

The aim of this research is molecular characterization of recent isolates of Marek's disease virus (MDV) which can cause vaccine breaks in the field, in order to develop new vaccine strategies against theses very virulent MDV (vvMDV) by using a new MDV vaccine with the modified L-meq gene.Strains of vvMDV were isolated from wild birds such as white-fronted geese or from domestic chickens with vaccine breaks, and their nucleotide sequences were compared with those of known vvMDVs. The nucleotide sequences of the meq gene (a candidate oncogene of MDV) of recent isolates of MDVs in Japan showed high homologies with those of known vvMDVs, but some mutations previously unidentified were also found in these isolates. In addition, an additional EcoRI site was identified in the glycoprotein B gene of an isolate, strain Hokkaido, while a small deletion in the glycoprotein L gene, which had been frequently observed in vvMDV, was found in several isolates from wild birds and from chickens. In the … More next experiment, we analyzed the effects of these mutations on the transcriptional activation by the meq gene product, MEQ. MDV strains with increased virulence showed higher transcriptional activation by their MEQ, and mutations in the transcriptional activation domain of MEQ could be a determinant for the virulence of MDV strains. However, MEQ of strain Hokkaido, with newly identified mutations, did not display higher transcriptional activation by their MEQ. The L-meq gene product (L-MEQ), present in vaccine strains of apathogenic MDV, was shown to suppress both transcriptional activation by MEQ and replication in vitro of vvMDV, suggesting important roles of L-MEQ on the maintenance of latent phase. We also identified a new transcription variant of the meq gene, termed Δmeq, whose expression is up-regulated in Marek's disease tumor cells when apoptosis is induced. Δmeq inhibited the transcriptional activation by MEQ and L-MEQ, showing that Δmeq could play roles as a negative regulator of MEQ on apoptosis or reactivation of MDV from latent phase. Thus, Δmeq can be used to develop a new vaccine which induces programmed cell death only in transformed cells by vvMDV. Less