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During host cell traversal and cell-to-cell passage, Toxoplasma gondii sporozoites inhabit the parasitophorous vacuole and posteriorly release dense granule protein-associated membranous trails.
International Journal for Parasitology ( IF 4 ) Pub Date : 2020-08-31 , DOI: 10.1016/j.ijpara.2020.06.012
Irene Tartarelli 1 , Antonella Tinari 2 , Alessia Possenti 1 , Simona Cherchi 1 , Mario Falchi 3 , Jitender P Dubey 4 , Furio Spano 1
Affiliation  

Toxoplasma gondii has a worldwide distribution and infects virtually all warm-blooded animals, including humans. Ingestion of the environmentally resistant oocyst stage, excreted only in the feces of cats, is central to transmission of this apicomplexan parasite. There is vast literature on the host and T. gondii tachyzoite (proliferative stage of the parasite) but little is known of the host-parasite interaction and conversion of the free-living stage (sporozoite inside the oocyst) to the parasitic stage. Here, we present events that follow invasion of host cells with T. gondii sporozoites by using immunofluorescence (IF) and transmission electron microscopy (TEM). Several human type cell cultures were infected with T. gondii sporozoites of the two genotypes (Type II, ME49 and Type III, VEG) most prevalent worldwide. For the first known time, using anti-rhoptry neck protein 4 (RON4) antibodies, the moving junction was visualized in sporozoites during the invasion process and shortly after its completion. Surprisingly, IF and TEM evaluation revealed that intracellular sporozoites release, at their posterior end, long membranous tails, herein named sporozoite-specific trails (SSTs). Differential permeabilization and IF experiments showed that the SSTs are associated with several dense granule proteins (GRAs) and that their membranous component is of parasite origin. Furthermore, TEM observations demonstrated that SST-associated sporozoites are delimited by a typical parasitophorous vacuole, which is retained during parasite exit from the host cell and during cell-to-cell passage. Our data strongly suggest that host cell traversal by T. gondii sporozoites relies on a novel force-producing mechanism, based on the massive extrusion at the parasite posterior pole of GRA-associated membranous material derived from the same pool of membranes forming the intravacuolar network.



中文翻译:

在宿主细胞穿越和细胞间传代过程中,弓形虫子孢子栖息在寄生液泡中,并向后释放致密的颗粒蛋白相关膜状痕迹。

弓形虫在世界范围内都有分布,几乎感染所有温血动物,包括人类。摄入仅在猫的粪便中排泄的耐环境卵囊阶段是这种顶复体寄生虫传播的核心。有大量关于宿主和刚地弓形虫速殖子(寄生虫的增殖阶段)的文献,但对宿主-寄生虫相互作用以及自由生活阶段(卵囊内的子孢子)到寄生阶段的转化知之甚少。在这里,我们通过使用免疫荧光 (IF) 和透射电子显微镜 (TEM) 展示了随着弓形虫子孢子侵入宿主细胞而发生的事件。几种人类类型细胞培养物被弓形虫感染世界上最流行的两种基因型(II 型,ME49 和 III 型,VEG)的子孢子。在已知的第一次,使用抗蛇颈蛋白 4 (RON4) 抗体,在入侵过程中和入侵完成后不久,在子孢子中观察到移动连接。令人惊讶的是,IF 和 TEM 评估显示细胞内子孢子在其后端释放长膜状尾部,本文称为子孢子特异性轨迹 (SST)。差异透化和 IF 实验表明,SST 与几种致密颗粒蛋白 (GRA) 相关,并且它们的膜成分是寄生虫来源的。此外,TEM 观察表明 SST 相关的子孢子被典型的寄生液泡划定,它在寄生虫离开宿主细胞和细胞间传代过程中保留下来。我们的数据强烈表明宿主细胞通过T. gondii子孢子依赖于一种新的产生力的机制,该机制基于来自形成液泡内网络的同一膜池的 GRA 相关膜材料在寄生虫后极的大量挤压。

更新日期:2020-11-09
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