Schwenkenbecher Jan M, Albonico Marco, Bickle Quentin, Kaplan Ray M
Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, 501 D.W. Brooks Drive, Athens, GA 30602, USA.
Mol Biochem Parasitol. 2007 Dec;156(2):167-74. doi: 10.1016/j.molbiopara.2007.07.019. Epub 2007 Aug 3.
Human hookworms (Ancylostoma duodenale, Necator americanus) are a major cause of malnutrition and anemia, particularly in children, and high worm burdens can lead to stunted growth and mental retardation. Mass drug administration (MDA) with benzimidazole (BZ) anthelmintics has the potential to greatly reduce morbidity and infection prevalence. However, such treatment strategies may apply significant selection pressure on resistance alleles. In several Strongylid parasites of livestock, resistance to BZ drugs is associated with single nucleotide polymorphisms (SNPs) in the beta-tubulin isotype-1 gene at codons 167 and 200. As an initial investigation into the possible development of BZ resistance in hookworms, we have cloned and sequenced the beta-tubulin isotype-1 genes of the canine hookworm Ancylostoma caninum and the two human hookworm species A. duodenale and N. americanus. The genomic sequences are highly conserved as evidenced by a similar structure of exons and introns; the 10 exons are of the same length in all three species and code for the same amino acids. The genomic sequences were then used to develop a real-time PCR assay for detecting polymorphisms in codons 167 and 200 in all three species. Hookworm specimens previously obtained from Pemba Island school children who had demonstrated a reduced response to treatment with mebendazole were then examined using the real-time PCR assay. None of the samples revealed significant levels of polymorphisms at these loci. If BZ resistance is present in the hookworm populations examined, the results do not support the hypothesis that changes in codons 167 and 200 of beta-tubulin isotype-1 are responsible for any resistance.
人体钩虫（十二指肠钩口线虫、美洲板口线虫）是营养不良和贫血的主要病因，尤其是在儿童中，高虫负荷会导致生长发育迟缓及智力发育迟缓。使用苯并咪唑（BZ）驱虫药进行群体药物驱虫（MDA）有可能大幅降低发病率和感染率。然而，此类治疗策略可能会对耐药等位基因施加显著的选择压力。在几种家畜的圆线虫寄生虫中，对BZ药物的耐药性与β-微管蛋白同型-1基因第167和200位密码子处的单核苷酸多态性（SNP）有关。作为对钩虫可能产生BZ耐药性的初步调查，我们克隆并测序了犬钩虫犬钩口线虫以及两种人体钩虫十二指肠钩口线虫和美洲板口线虫的β-微管蛋白同型-1基因。基因组序列高度保守，外显子和内含子结构相似即为证明；所有三个物种的10个外显子长度相同，编码相同的氨基酸。然后利用基因组序列开发了一种实时PCR检测方法，用于检测所有三个物种第167和200位密码子处的多态性。随后使用实时PCR检测方法对之前从奔巴岛学童中采集的、对甲苯达唑治疗反应降低的钩虫样本进行了检测。没有一个样本在这些位点显示出显著水平的多态性。如果在所检测的钩虫群体中存在BZ耐药性，那么结果不支持β-微管蛋白同型-1第167和200位密码子的变化导致任何耐药性的假设。
