Higazi Tarig B, Filiano Anthony, Katholi Charles R, Dadzie Yankum, Remme Jan H, Unnasch Thomas R
Division of Geographic Medicine, University of Alabama at Birmingham, BBRB 203, 1530 3rd Avenue South, Birmingham, AL 35294-2170, USA.
Mol Biochem Parasitol. 2005 May;141(1):109-12. doi: 10.1016/j.molbiopara.2005.02.006.
Epidemiological, clinical and genetic data have all suggested that the filarial parasite Onchocerca volvulus, the causative agent of onchocerciasis (or river blindness) exists as two strains in West Africa. The severe strain induces severe ocular disease in a large proportion of the infected population, while the mild strain induces little ocular disease. Although DNA probes based upon a non-coding repeat sequence family can distinguish the two strains, the underlying basis for this difference in pathogenicity is not understood. Recently, several studies have implicated products produced by the Wolbachia endosymbiotic bacterium of O. volvulus in the pathogenesis of onchocerciasis. This suggested the hypothesis that differences in the Wolbachia endosymbiont population might be responsible for the pathogenic differences noted in the two strains. To test this hypothesis, quantitative PCR assays were used to measure the amount of Wolbachia DNA per nuclear genome in a collection of well characterized samples of mild and severe strain O. volvulus. The median ratio of Wolbachia DNA to nuclear DNA was significantly greater in severe strain parasites than in mild strain parasites. These data support the hypothesis that the pathogenic differences seen in severe and mild strain O. volvulus may be a function of their relative Wolbachia burden and provide additional support to the hypothesis that Wolbachia products may play a central role in the pathogenesis of ocular onchocerciasis.
流行病学、临床和遗传学数据均表明，盘尾丝虫病（又称河盲症）的病原体——丝虫寄生虫盘尾丝虫在西非以两种毒株形式存在。严重毒株会在很大一部分受感染人群中引发严重眼部疾病，而温和毒株引发的眼部疾病很少。尽管基于非编码重复序列家族的DNA探针能够区分这两种毒株，但对于这种致病性差异的潜在原因尚不清楚。最近，多项研究表明，盘尾丝虫的内共生菌沃尔巴克氏体产生的产物与盘尾丝虫病的发病机制有关。这就提出了一种假说，即沃尔巴克氏体内共生菌群的差异可能是导致两种毒株致病性差异的原因。为了验证这一假说，研究人员使用定量PCR检测法，对一系列特征明确的温和毒株和严重毒株盘尾丝虫样本中的每个核基因组的沃尔巴克氏体DNA含量进行了测定。严重毒株寄生虫中沃尔巴克氏体DNA与核DNA的中位比率显著高于温和毒株寄生虫。这些数据支持了这样一种假说，即严重毒株和温和毒株盘尾丝虫的致病性差异可能与其相对的沃尔巴克氏体负荷有关，并为沃尔巴克氏体产物可能在眼部盘尾丝虫病发病机制中起核心作用这一假说提供了更多支持。
