An in vitro model of intestinal infection reveals a developmentally regulated transcriptome of Toxoplasma sporozoites and a NF-?B-like signature in infected host cells

Toxoplasmosis is a zoonotic infection affecting approximately 30% of the world’s human population. After sexual reproduction in the definitive feline host, Toxoplasma oocysts, each containing 8 sporozoites, are shed into the environment where they can go on to infect humans and other warm-blooded intermediate hosts. Here, we use an in vitro model to assess host transcriptomic changes that occur in the earliest stages of such infections. We show that infection of rat intestinal epithelial cells with mature sporozoites primarily results in higher expression of genes associated with Tumor Necrosis Factor alpha (TNFa) signaling via NF-?B. Furthermore, we find that, consistent with their biology, these mature, invaded sporozoites display a transcriptome intermediate between the previously reported day 10 oocysts and that of their tachyzoite counterparts. Thus, this study uncovers novel host and pathogen factors that may be critical for the establishment of a successful intracellular niche following sporozoite-initiated infection. Overall design: Rat intestinal epithelial cells were infected in duplicate with either Toxoplasma sporozoites or tachyzoites in the presence or absence of frozen sporozoites for 8 hours. Frozen sporozoites and lysates from uninfected cells were used as controls. The experiment was performed twice. Total RNA was extracted from the resulting 24 samples and the transcriptional profiles of both host and parasites were determined using RNA sequencing on the Illumina NextSeq platform

弓形虫病（Toxoplasmosis）是一种人畜共患传染病，全球约有30%的人类人口受到感染。在终末猫科宿主体内完成有性生殖后，每个内含8个子孢子（sporozoites）的弓形虫卵囊（Toxoplasma oocysts）会被排放至环境中，进而可感染人类及其他温血中间宿主。本研究采用体外模型，评估此类感染早期阶段宿主发生的转录组变化。研究发现，成熟子孢子感染大鼠肠上皮细胞后，主要诱导与经核因子κB（NF-κB）通路传导的肿瘤坏死因子α（Tumor Necrosis Factor alpha, TNFα）信号相关的基因表达上调。此外，结合其生物学特性，我们观察到这些已完成入侵的成熟子孢子的转录组介于此前报道的第10天卵囊与对应速殖子（tachyzoite）的转录组之间。因此，本研究揭示了在子孢子启动的感染后，成功建立细胞内微环境可能至关重要的新型宿主与病原体相关因子。实验设计概述：大鼠肠上皮细胞分别以弓形虫子孢子或速殖子进行复孔感染，感染体系中设置添加或不添加冻存子孢子的组别，感染时长为8小时。以冻存子孢子与未感染细胞的裂解物作为对照。本实验重复开展两次。从最终获取的24份样本中提取总RNA，通过Illumina NextSeq平台进行RNA测序，以测定宿主与寄生虫的转录谱。