Peng Weidong, Yuan Keng, Zhou Xianmin, Hu Min, Abs EL-Osta Youssef G, Gasser Robin B
Department of Veterinary Science, The University of Melbourne, Werribee, Victoria, Australia.
Electrophoresis. 2003 Jul;24(14):2308-15. doi: 10.1002/elps.200305455.
Using a single-strand conformation polymorphism-based approach, we investigated nucleotide variation in part of the first internal transcribed spacer (pITS-1) of nuclear ribosomal DNA within and among a large number of Ascaris individuals from humans and pigs from six endemic regions in China, and examined the frequency of the different genotypes of Ascaris in relation to host species and geographical origin. Five different SSCP genotypes (G1-G5) were recorded for human Ascaris (n = 486), of which three (genotypes G1-G3) were detected for pig Ascaris (n = 329). Of the five Ascaris genotypes detected, genotype G1 predominantly infected humans (approximately 63-74%) whereas genotype G3 infected mainly pigs (approximately 79-86%), indicating that each of these genotypes has a particular host affiliation. In contrast, the frequencies of the other three genotypes was substantially lower for each of the two host species. The findings also suggested that the rate of cross infection of Ascaris between humans and pigs is relatively low and that gene flow between the predominant genotypes is limited, consistent with previous proposals for endemic regions in other countries. While the nature and extent of nucleotide variation in the pITS-1 (and the proposal of host affiliated Ascaris populations) may relate to "introgression" or "lineage sorting and retention of ancentral polymorphism", other explanations are possible. Evidence of multiple pITS-1 sequence types in some Ascaris individuals representing particular genotypes (e.g., G2 and G5) may suggest hybridization between human- and pig-affiliated Ascaris. This aspect and the species status of Ascaris (from each host species) warrant future experimental testing, employing the pig/Ascaris model and the present electrophoretic approach.*
我们采用基于单链构象多态性的方法，研究了来自中国六个流行地区的大量人体和猪体蛔虫个体内核糖体DNA第一内部转录间隔区部分（pITS-1）的核苷酸变异，并考察了蛔虫不同基因型的频率与宿主物种和地理来源的关系。人体蛔虫（n = 486）记录到五种不同的SSCP基因型（G1-G5），猪体蛔虫（n = 329）检测到其中三种（基因型G1-G3）。在检测到的五种蛔虫基因型中，基因型G1主要感染人体（约63-74%），而基因型G3主要感染猪体（约79-86%），表明这些基因型各自具有特定的宿主归属。相比之下，另外三种基因型在两种宿主物种中的频率都显著较低。研究结果还表明，人体和猪体蛔虫之间的交叉感染率相对较低，优势基因型之间的基因流动有限，这与其他国家流行地区的先前推测一致。虽然pITS-1中核苷酸变异的性质和程度（以及宿主归属蛔虫种群的推测）可能与“基因渗入”或“祖先多态性的谱系分选和保留”有关，但也可能有其他解释。在一些代表特定基因型（如G2和G5）的蛔虫个体中存在多种pITS-1序列类型的证据，可能表明人体和猪体蛔虫之间存在杂交。这一方面以及蛔虫（来自每个宿主物种）的物种地位值得未来采用猪/蛔虫模型和当前的电泳方法进行实验测试。
