Center for Evolutionary and Theoretical Immunology and Department of Biology, University of New Mexico, Albuquerque, NM, USA.
BMC Genomics. 2021 Feb 23;22(1):130. doi: 10.1186/s12864-021-07437-0.
Toxoplasma gondii is a globally distributed protozoan parasite that establishes life-long asymptomatic infection in humans, often emerging as a life-threatening opportunistic pathogen during immunodeficiency. As an intracellular microbe, Toxoplasma establishes an intimate relationship with its host cell from the outset of infection. Macrophages are targets of infection and they are important in early innate immunity and possibly parasite dissemination throughout the host. Here, we employ an RNA-sequencing approach to identify host and parasite transcriptional responses during infection of mouse bone marrow-derived macrophages (BMDM). We incorporated into our analysis infection with the high virulence Type I RH strain and the low virulence Type II strain PTG. Because the well-known TLR-MyD88 signaling axis is likely of less importance in humans, we examined transcriptional responses in both MyD88 and MyD88 BMDM. Long noncoding (lnc) RNA molecules are emerging as key regulators in infection and immunity, and were, therefore, included in our analysis.
We found significantly more host genes were differentially expressed in response to the highly virulent RH strain rather than with the less virulent PTG strain (335 versus 74 protein coding genes for RH and PTG, respectively). Enriched in these protein coding genes were subsets associated with the immune response as well as cell adhesion and migration. We identified 249 and 83 non-coding RNAs as differentially expressed during infection with RH and PTG strains, respectively. Although the majority of these are of unknown function, one conserved lncRNA termed mir17hg encodes the mir17 microRNA gene cluster that has been implicated in down-regulating host cell apoptosis during T. gondii infection. Only a minimal number of transcripts were differentially expressed between MyD88 knockout and wild type cells. However, several immune genes were among the differences. While transcripts for parasite secretory proteins were amongst the most highly expressed T. gondii genes during infection, no differentially expressed parasite genes were identified when comparing infection in MyD88 knockout and wild type host BMDM.
The large dataset presented here lays the groundwork for continued studies on both the MyD88-independent immune response and the function of lncRNAs during Toxoplasma gondii infection.
刚地弓形虫是一种分布广泛的原生动物寄生虫,在人类中建立了长期无症状的感染,通常在免疫缺陷时成为危及生命的机会性病原体。作为一种细胞内微生物,弓形虫从感染开始就与宿主细胞建立了密切的关系。巨噬细胞是感染的靶标,它们在早期固有免疫和寄生虫在宿主中的可能传播中很重要。在这里,我们采用 RNA 测序方法来鉴定感染小鼠骨髓来源的巨噬细胞(BMDM)时宿主和寄生虫的转录反应。我们将高毒力 I 型 RH 株和低毒力 II 型 PTG 株的感染纳入分析。由于 TLR-MyD88 信号轴在人类中可能不太重要,因此我们在 MyD88 和 MyD88 BMDM 中检查了转录反应。长非编码(lnc)RNA 分子作为感染和免疫的关键调节剂而出现,因此也包括在我们的分析中。
我们发现,与低毒力的 PTG 株相比,高毒力 RH 株引起的宿主基因差异表达明显更多(RH 和 PTG 株分别有 335 个和 74 个蛋白编码基因差异表达)。在这些蛋白编码基因中,富集了与免疫反应以及细胞粘附和迁移相关的亚群。我们分别鉴定出 249 个和 83 个非编码 RNA 在感染 RH 和 PTG 株时差异表达。尽管其中大多数的功能未知,但一个保守的 lncRNA 称为 mir17hg 编码 mir17 微 RNA 基因簇,该基因簇在下调弓形虫感染期间宿主细胞凋亡中起作用。MyD88 敲除和野生型细胞之间差异表达的转录本数量很少。然而,一些免疫基因也存在差异。虽然寄生虫分泌蛋白的转录物是感染期间表达最高的弓形虫基因之一,但在比较 MyD88 敲除和野生型宿主 BMDM 感染时,没有鉴定到差异表达的寄生虫基因。
本研究提供的大量数据集为继续研究 MyD88 非依赖性免疫反应以及长非编码 RNA 在弓形虫感染中的功能奠定了基础。