Genetic variation in the dimorphic regions of rap-1 genes and rap-1 loci of Babesia bigemina
Genetic variation in the dimorphic regions of rap-1 genes and rap-1 loci of Babesia bigemina
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DOI：
10.1016/s0166-6851(97)00182-5
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发表时间：
1997-12-15
影响因子：
1.5
通讯作者：
Palmer, GH
中科院分区：
文献类型：
--
作者：
Hötzel, I;Suarez, CE;Palmer, GH
母牛巴贝斯虫的虫体相关蛋白-1 （rap1）可诱导保护性免疫反应。RAP-1在羧基端和氨基端分别有两个序列二态性区域。中和敏感的表面暴露的b细胞表位存在于氨基末端变异型1 （NT-1）中，而CD4(+) t细胞表位存在于羧基末端变异型1 （CT-1）中。重要的是，识别NT-1表位的抗体不会与NT-2发生交叉反应，识别CT-1表位的CD4(+) t细胞也不会与CT-2发生交叉反应，这表明RAP-1二态区变异具有免疫学意义。我们对不同地理位置的双芽双歧杆菌rap-1基因二态区rap-1基因座结构和序列变异程度进行了评价。所有菌株均含有NT-1和NT-2，编码序列高度保守，菌株间核苷酸同源性不低于99%。然而，波多黎各菌株编码了NT-1/NT-2杂交序列，这似乎是由基因转换事件产生的。rap-1基因的3'端，包括羧基端变体，在菌株之间是保守的。在所有菌株中鉴定出一种新的保守的CT变异（CT-3），其序列与CT-2相同，序列与CT-1或CT-2均不相关。除了一种菌株外，所有菌株都编码nt和三种CT变体。来自阿根廷的减毒菌株S1A不编码CT-2。虽然NT-1仅与CT-1相关，但NT-2可与RAP-1的所有三种CT变体相关。在基因组内，inp-1基因以串联重复序列排列，但不同菌株间基因拷贝数和排列方式不同。总的来说，数据表明基因转换和不平等重组事件有助于基因变体和菌株之间的总体ray-1序列保守，但也可能产生新的rap-1变体。(C) 1997爱思唯尔科学有限公司
The rhoptry-associated protein-1 (RAP-1) of Babesia bigemina induces protective immune responses in cattle. RAP-1 has two regions of sequence dimorphism at the carboxy and amino terminal ends, respectively. Neutralization-sensitive, surface-exposed B-cell epitopes are present in the amino terminal variant type 1 (NT-1), and CD4(+) T-cell epitopes in the carboxy terminal variant type 1 (CT-1). Importantly, antibodies recognizing NT-1 epitopes do not cross react with NT-2 and CD4(+) T-cells recognizing epitopes in CT-1 do not cross react with CT-2, suggesting that variation in dimorphic regions of RAP-1 is immunologically significant. We evaluated rap-1 locus structure and the extent of sequence variation in the dimorphic regions of rap-1 genes from geographically diverse strains of B. bigemina. All strains contained NT-1 and NT-2 the encoding sequences were highly conserved, with at least 99% nucleotide identity among strains. However, the Puerto Rico strain encoded a hybrid NT-1/NT-2 sequence which appears to have originated by a gene conversion event. The 3' ends of rap-1 genes, which include the carboxy terminal variants, are conserved among strains. A new and conserved CT variant (CT-3), with a region of sequence identity to CT-2 and a sequence not related to either CT-1 or CT-2, was identified in all strains of B. bigemina. All but one strain encode both NTs and the three CT variants. The S1A strain, an attenuated strain from Argentina, does nor encode CT-2. While NT-1 is associated only with CT-1, NT-2 can be associated with all three CT variants in RAP-1. Within the genome, inp-1 genes are arranged in tandem repeats but with different gene copy number and arrangements among strains. Collectively, the data suggest that gene conversion and unequal recombination events contribute to overall ray-1 sequence conservation among gene variants and strains but may also generate new rap-1 variants. (C) 1997 Elsevier Science B.V.