Spatz Stephen J, Petherbridge Lawrence, Zhao Yuguang, Nair Venugopal
Southeast Poultry Research Laboratory, Agricultural Research Service, United States Department of Agriculture, Athens, GA 30605, USA.
Institute for Animal Health, Compton, Berkshire RG20 7NN, UK.
J Gen Virol. 2007 Apr;88(Pt 4):1080-1096. doi: 10.1099/vir.0.82600-0.
The complete DNA sequence of the Marek's disease virus serotype 1 vaccine strain CVI988 was determined and consists of 178 311 bp with an overall gene organization identical to that of the oncogenic strains. In examining open reading frames (ORFs), nine differ between vaccine and oncogenic strains. A 177 bp insertion was identified in the overlapping genes encoding the Meq, RLORF6 and 23 kDa proteins of CVI988. Three ORFs are predicted to encode truncated proteins. One, designated 49.1, overlaps the gene encoding the large tegument protein UL36 and encodes a severely truncated protein of 34 aa. The others, ORF5.5/ORF75.91 and ORF3.0/78.0, located in the repeat regions (diploid), encode a previously unidentified ORF of 52 aa and a truncated version of the virus-encoded chemokine (vIL-8), respectively. Subtle genetic changes were identified in the two ORFs encoding tegument proteins UL36 and UL49. Only one diploid ORF (ORF6.2/ORF75.6) present in the genomes of the three virulent strains is absent in the CVI988-BAC genome. Seventy non-synonymous amino acid substitutions were identified that could differentiate CVI988-BAC from all three oncogenic strains collectively. Estimates of the non-synonymous to synonymous substitution ratio (omega) indicate that CVI988 ORFs are generally under purifying selection (omega<1), whereas UL39, UL49, UL50, RLORF6 and RLORF7 (Meq) appear to evolve under relaxed selective constraints. No CVI988 ORF was found to be under positive evolutionary selection (omega>>1).
确定了1型马立克氏病病毒疫苗株CVI988的完整DNA序列，其由178311个碱基对组成，总体基因组织与致癌株相同。在检查开放阅读框（ORF）时，疫苗株和致癌株之间有9个不同之处。在编码CVI988的Meq、RLORF6和23 kDa蛋白的重叠基因中鉴定出一个177 bp的插入片段。预测有三个ORF编码截短蛋白。其中一个命名为49.1，与编码大被膜蛋白UL36的基因重叠，编码一个34个氨基酸的严重截短蛋白。另外两个，位于重复区域（二倍体）的ORF5.5/ORF75.91和ORF3.0/78.0，分别编码一个52个氨基酸的先前未鉴定的ORF和病毒编码趋化因子（vIL-8）的截短版本。在编码被膜蛋白UL36和UL49的两个ORF中发现了细微的基因变化。CVI988-BAC基因组中不存在三种强毒株基因组中存在的唯一一个二倍体ORF（ORF6.2/ORF75.6）。共鉴定出70个非同义氨基酸替换，可将CVI988-BAC与所有三种致癌株区分开来。非同义与同义替换率（ω）的估计表明，CVI988的ORF通常处于纯化选择之下（ω<1），而UL39、UL49、UL50、RLORF6和RLORF7（Meq）似乎在宽松的选择约束下进化。未发现CVI988的ORF处于正进化选择之下（ω>>1）。
