Toxoplasma gondii Dense Granule Proteins 7, 14, and 15 Are Involved in Modification and Control of the Immune Response Mediated via NF-κB Pathway
Toxoplasma gondii Dense Granule Proteins 7, 14, and 15 Are Involved in Modification and Control of the Immune Response Mediated via NF-κB Pathway
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DOI：
10.3389/fimmu.2020.01709
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发表时间：
2020-07-31
影响因子：
7.3
通讯作者：
Nishikawa, Yoshifumi
中科院分区：
文献类型：
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作者：
Ihara, Fumiaki;Fereig, Ragab M.;Nishikawa, Yoshifumi
弓形虫感染几乎所有的温血动物，包括人类，导致宿主的细胞和体液免疫反应。弓形虫的毒力是菌株特有的，由分泌的干扰宿主免疫的效应蛋白定义。在这里，我们集中在核因子-kappa B(核因子-kappa B)信号，它调节T辅助细胞1型免疫的诱导。荧光素酶试验筛选对依赖于核因子kappa B的报告质粒具有生物活性的效应蛋白，包括ROPS和GRAS，发现II型菌株的GRA7、14和15的过度表达导致了较强的活性。因此，我们的研究旨在通过对这三个分子的比较分析，了解核因子kappaB在弓形虫病发病机制中的作用。我们发现GRA7和GRA14部分参与了核因子kappaB的激活，而GRA15对核因子kappaB的激活是必不可少的。在II型Prugniaud(PrU)株中，GRA7、GRA14和GRA15的缺失导致了relA核转位的缺陷。感染Pru Delta Gra15寄生虫的细胞显示抑制物kappa Bα的磷酸化水平降低。GRA7、GRA14和GRA15缺乏降低了RAW246.7细胞中IL-6的水平，RNA-seq分析表明，GRA7、GRA14和GRA15缺乏主要导致核因子kappa B介导的基因表达下调。所有突变株的毒力都增加了，但Pru Delta gra14的毒力仅略有增加。然而，足垫内注射高毒力的I RH Delta Gra14寄生虫会导致小鼠的毒力增加。这项研究表明，GRA7、14和15通过核因子kappaB诱导宿主免疫限制了寄生虫的扩张。
Toxoplasma gondii infects almost all warm-blooded animals, including humans, leading to both cellular and humoral immune responses in the host. The virulence of T. gondii is strain specific and is defined by secreted effector proteins that disturb host immunity. Here, we focus on nuclear factor-kappa B (NF kappa B) signaling, which regulates the induction of T-helper type 1 immunity. A luciferase assay for screening effector proteins, including ROPs and GRAs that have biological activity against an NF kappa B-dependent reporter plasmid, found that overexpression of GRA7, 14, and 15 of a type II strain resulted in a strong activity. Thus, our study was aimed at understanding the involvement of NF kappa B in the pathogenesis of toxoplasmosis through a comparative analysis of these three molecules. We found that GRA7 and GRA14 were partially involved in the activation of NF kappa B, whereas GRA15 was essential for NF kappa B activation. The deletion of GRA7, GRA14, and GRA15 in the type II Prugniaud (Pru) strain resulted in a defect in the nuclear translocation of RelA. Cells infected with the Pru Delta gra15 parasite showed reduced phosphorylation of inhibitor-kappa B alpha. GRA7, GRA14, and GRA15 deficiency decreased the levels of interleukin-6 in RAW246.7 cells, and RNA-seq analysis revealed that GRA7, GRA14, and GRA15 deficiency predominantly resulted in downregulation of gene expression mediated by NF kappa B. The virulence of all mutant strains increased, but Pru Delta gra14 only showed a slight increase in virulence. However, the intra-footpad injection of the highly-virulent type I RH Delta gra14 parasites in mice resulted in increased virulence. This study shows that GRA7, 14, and 15-induced host immunity via NF kappa B limits parasite expansion.