Department of Parasitology, National Institute of Infectious Diseases, Tokyo, Japan.
Laboratory of Bacterial Genomics, Pathogen Genomics Center, National Institute of Infectious Diseases, Tokyo, Japan.
PLoS Pathog. 2018 Mar 19;14(3):e1006882. doi: 10.1371/journal.ppat.1006882. eCollection 2018 Mar.
The disease state of amebiasis, caused by Entamoeba histolytica, varies from asymptomatic to severe manifestations that include dysentery and extraintestinal abscesses. The virulence factors of the pathogen, and host defense mechanisms, contribute to the outcomes of infection; however, the underlying genetic factors, which affect clinical outcomes, remain to be fully elucidated. To identify these genetic factors in E. histolytica, we used Illumina next-generation sequencing to conduct a comparative genomic analysis of two clinical isolates obtained from diarrheal and asymptomatic patients (strains KU50 and KU27, respectively). By mapping KU50 and KU27 reads to the genome of a reference HM-1:IMSS strain, we identified two genes (EHI_089440 and EHI_176590) that were absent in strain KU27. In KU27, a single AIG1 (avrRpt2-induced gene 1) family gene (EHI_176590) was found to be deleted, from a tandem array of three AIG1 genes, by homologous recombination between the two flanking genes. Overexpression of the EHI_176590 gene, in strain HM-1:IMSS cl6, resulted in increased formation of cell-surface protrusions and enhanced adhesion to human erythrocytes. The EHI_176590 gene was detected by PCR in 56% of stool samples from symptomatic patients infected with E. histolytica, but only in 15% of stool samples from asymptomatic individuals. This suggests that the presence of the EHI_176590 gene is correlated with the outcomes of infection. Taken together, these data strongly indicate that the AIG1 family protein plays a pivotal role in E. histolytica virulence via regulation of host cell adhesion. Our in-vivo experiments, using a hamster liver abscess model, showed that overexpression or gene silencing of EHI_176590 reduced and increased liver abscess formation, respectively. This suggests that the AIG1 genes may have contrasting roles in virulence depending on the genetic background of the parasite and host environment.
由溶组织内阿米巴原虫引起的阿米巴病的病变状态从无症状到严重表现不等，包括痢疾和肠外脓肿。病原体的毒力因子和宿主防御机制导致了感染的结果；然而，影响临床结果的潜在遗传因素仍有待充分阐明。为了鉴定溶组织内阿米巴中的这些遗传因素，我们使用 Illumina 下一代测序对从腹泻和无症状患者中获得的两个临床分离株（菌株 KU50 和 KU27）进行了比较基因组分析。通过将 KU50 和 KU27 的读取映射到参考 HM-1:IMSS 菌株的基因组上，我们鉴定了两个在 KU27 中缺失的基因（EHI_089440 和 EHI_176590）。在 KU27 中，通过两个侧翼基因之间的同源重组，单个 AIG1（avrRpt2 诱导基因 1）家族基因（EHI_176590）被删除，该基因位于三个 AIG1 基因的串联阵列中。在 HM-1:IMSS cl6 菌株中过表达 EHI_176590 基因导致细胞表面突起的形成增加，并增强了对人红细胞的黏附。PCR 检测到 56%的症状性溶组织内阿米巴感染患者的粪便样本中存在 EHI_176590 基因，但只有 15%的无症状个体的粪便样本中存在该基因。这表明 EHI_176590 基因的存在与感染的结果相关。总之，这些数据强烈表明，AIG1 家族蛋白通过调节宿主细胞黏附在溶组织内阿米巴的毒力中发挥关键作用。我们使用仓鼠肝脓肿模型的体内实验表明，EHI_176590 的过表达或基因沉默分别减少和增加了肝脓肿的形成。这表明 AIG1 基因在毒力中可能根据寄生虫的遗传背景和宿主环境发挥相反的作用。
