Comparative analysis of Marek's disease virus (MDV) glycoprotein-, lytic antigen pp38- and transformation antigen Meq-encoding genes:: association of meq mutations with MDVs of high virulence
Comparative analysis of Marek's disease virus (MDV) glycoprotein-, lytic antigen pp38- and transformation antigen Meq-encoding genes:: association of meq mutations with MDVs of high virulence
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DOI：
10.1016/j.vetmic.2004.06.007
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发表时间：
2004-09-08
影响因子：
3.3
通讯作者：
Parcells, MS
中科院分区：
文献类型：
--
作者：
Shamblin, CE;Greene, N;Parcells, MS
马立克氏病（MD）是一种高度传染性的鸡淋巴增生性和脱髓鞘疾病。MD是由马立克氏病病毒（MDV）引起的，这是一种与细胞相关的急性转化甲型疱疹病毒。三十年来，通过使用活疫苗大大限制了因口蹄疫给家禽业造成的损失。MDV疫苗毒株由最初从鸡（MDV-2）、火鸡（火鸡疱疹病毒，HVT）或MDV-1的减毒致癌毒株（CVI-988）中分离出来的抗原性相关的致病性MDV毒株组成。自从高密度家禽生产和MD疫苗接种开始以来，MDV野毒株的毒力有两个明显的增加。我们的目的是确定主要糖蛋白基因、主要裂解物、抗原磷酸化蛋白38 （pp38）或主要潜伏期/转化抗原Meq （Marek's ecori - q编码蛋白）的常见突变是否与MDV毒力增强有关。为了解决这个问题，我们克隆并测序了5株MDV毒株的主要表面糖蛋白基因（gB、gC、gD、gE、gH、gI和gL），这些毒株分别代表MDV的强毒(v)型、强毒（vv）型和强毒+ (vv+)型。我们发现这些基因中没有一致的突变与毒力水平严格相关。在MDV-1、MDV-2和HVT中最相似的糖蛋白基因（gB和gC，分别接近81%和75%）在整个病理型中最保守。我们在11个vv+ mdv中的4个中发现了指向gL基因中假定的信号切割位点的突变，但在一个vvMDV （643P）中也发现了这种突变，表明它与增强的毒力无关。在对另外12株MDV的进一步分析中，我们发现任何糖蛋白基因都没有明显的多态性。同样，通过PCR和RFLP分析，我们发现编码pp38基因的位点没有多态性，pp38基因是与MDV复制相关的早期裂解期基因。相比之下，我们在潜伏期和转化相关的Marek's ecori - q编码蛋白Meq中发现了明显的突变。通过对26株MDV毒株（9 m/vMDV、5个vvMDV和12个vv+MDV） meq基因的DNA和推断氨基酸序列的检测，我们发现了明显的多态性和点突变，这些多态性和点突变似乎与毒力有关。尽管像MDV毒力这样的复杂性状可能是多基因的，但这些数据描述了第一批似乎与MDV毒力相关的突变。我们的结论是，由于Meq主要在MDV感染的潜伏/转化期表达，并且不被MDV-2或HVT疫苗病毒编码，因此MDV毒力的进化可能是由于潜伏期间MDV-宿主细胞相互作用的选择，而可能不是由针对病毒表达抗原（如表面糖蛋白）的免疫选择介导的。(C) 2004 Elsevier B.V.版权所有
Marek's disease (MD) is a highly contagious lymphoproliferative and demyelinating disorder of chickens. MD is caused by Marek's disease virus (MDV), a cell-associated, acute-transforming alphaherpesvirus. For three decades, losses to the poultry industry due to MD have been greatly limited through the use of live vaccines. MDV vaccine strains are comprised of antigenically related, apathogenic MDVs originally isolated from chickens (MDV-2), turkeys (herpesvirus of turkeys, HVT) or attenuated-oncogenic strains of MDV-1 (CVI-988). Since the inception of high-density poultry production and MD vaccination, there have been two discernible increases in the virulence of MDV field strains. Our objectives were to determine if common mutations in the major glycoprotein genes, a major lytic, antigen phosphoprotein 38 (pp38) or a major latency/transformation antigen Meq (Marek's EcoRI-Q-encoded protein) were associated with enhanced MDV virulence. To address this, we cloned and sequenced the major surface glycoprotein genes (gB, gC, gD, gE, gH, gI, and gL) of five MDV strains that were representative of the virulent (v), very virulent (vv) and very virulent plus (vv+) pathotypes of MDV. We found no consistent mutations in these genes that correlated strictly with virulence level. The glycoprotein genes most similar among MDV-1, MDV-2 and HVT (gB and gC, similar to81 and 75%, respectively) were among the most conserved across pathotype. We found mutations mapping to the putative signal cleavage site in the gL genes in four out of eleven vv+MDVs, but this mutation was also identified in one vvMDV (643P) indicating that it did not correlate with enhanced virulence. In further analysis of an additional 12 MDV strains, we found no gross polymorphism in any of the glycoprotein genes. Likewise, by PCR and RFLP analysis, we found no polymorphism at the locus encoding the pp38 gene, an early lytic-phase gene associated with MDV replication. In contrast, we found distinct mutations in the latency and transformation-associated Marek's EcoRI-Q-encoded protein, Meq. In examination of the DNA and deduced amino acid sequence of meq genes from 26 MDV strains (9 m/vMDV, 5 vvMDV and 12 vv+MDVs), we found distinct polymorphism and point mutations that appeared to correlate with virulence. Although a complex trait like MDV virulence is likely to be multigenic, these data describe the first sets of mutations that appear to correlate with MDV virulence. Our conclusion is that since Meq is expressed primarily in the latent/transforming phase of MDV infection, and is not encoded by MDV-2 or HVT vaccine viruses, the evolution of MDV virulence may be due to selection on MDV-host cell interactions during latency and may not be mediated by the immune selection against virus lyric antigens such as the surface glycoproteins. (C) 2004 Elsevier B.V. All rights reserved.