Toxoplasma gondii is a protozoan parasite that persists in the central nervous system as intracellular chronic-stage bradyzoites that are encapsulated by a thick cyst wall. While the cyst wall separates bradyzoites from the host cytosol, it has been posited that small solutes can traverse the cyst wall to sustain bradyzoites. Recently, it was found that host cytosolic macromolecules can cross the parasitophorous vacuole and are ingested and digested by actively replicating acute-stage tachyzoites. However, the extent to which bradyzoites have an active ingestion pathway remained unknown. To interrogate this, we modified previously published protocols that look at tachyzoite acquisition and digestion of host proteins by measuring parasite accumulation of a host-expressed reporter protein after impairment of an endolysosomal protease (cathepsin protease L [CPL]). Using two cystogenic parasite strains (ME49 and Pru), we demonstrate that T. gondii bradyzoites can ingest host-derived cytosolic mCherry. Bradyzoites acquire host mCherry within 4 h of invasion and after cyst wall formation. This study provides direct evidence that host macromolecules can be internalized by T. gondii bradyzoites across the cyst wall in infected cells.

中文翻译：

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弓形虫缓殖子获得宿主胞浆蛋白


弓形虫是一种原生动物寄生虫，以细胞内慢性阶段缓殖子的形式存在于中枢神经系统中，并被厚厚的囊壁包裹。虽然囊壁将缓殖子与宿主细胞质分开，但有人认为小溶质可以穿过囊壁来维持缓殖子。最近发现宿主胞浆大分子可以穿过寄生液泡并被活跃复制的急性期速殖子摄入和消化。然而，缓殖子具有活跃的摄入途径的程度仍然未知。为了探究这一点，我们修改了之前发布的方案，通过测量内溶酶体蛋白酶（组织蛋白酶 L [CPL]）受损后宿主表达的报告蛋白的寄生虫积累来观察速殖子的获取和宿主蛋白的消化。使用两种囊原性寄生虫菌株（ME49 和 Pru），我们证明弓形虫缓殖子可以摄取宿主来源的胞质 mCherry。缓殖子在入侵后 4 小时内和囊壁形成后获得宿主 mCherry。这项研究提供了直接证据，证明宿主大分子可以被弓形虫缓殖子穿过受感染细胞的包囊壁内化。