Cell Commun Signal. 2014 Sep 10;12:51. doi: 10.1186/s12964-014-0051-0.
Cryptococcus neoformans is the most common cause of fungal meningitis among individuals with HIV/AIDS, which is uniformly fatal without proper treatment. The underlying mechanism of disease development in the brain that leads to cryptococcal meningoencephalitis remains incompletely understood. We have previously demonstrated that inositol transporters (ITR) are required for Cryptococcus virulence. The itr1aΔ itr3cΔ double mutant of C. neoformans was attenuated for virulence in a murine model of intra-cerebral infection; demonstrating that Itr1a and Itr3c are required for full virulence during brain infection, despite a similar growth rate between the mutant and wild type strains in the infected brain.
To understand the immune pathology associated with infection by the itr1aΔ itr3cΔ double mutant, we investigated the molecular correlates of host immune response during mouse brain infection. We used genome-wide transcriptome shotgun sequencing (RNA-Seq) and quantitative real-time PCR (qRT-PCR) methods to examine the host gene expression profile in the infected brain. Our results show that compared to the wild type, infection of mouse brains by the mutant leads to significant activation of cellular networks/pathways associated with host protective immunity. Most of the significantly differentially expressed genes (SDEG) are part of immune cell networks such as tumor necrosis factor-alpha (TNF-α) and interferon-gamma (IFN-γ) regulon, indicating that infection by the mutant mounts a stronger host immune response compared to the wild type. Interestingly, a significant reduction in glucuronoxylomannan (GXM) secretion was observed in the itr1aΔ itr3cΔ mutant cells, indicating that inositol utilization pathways play a role in capsule production.
Since capsule has been shown to impact the host response during Cryptococcus-host interactions, our results suggest that the reduced GXM production may contribute to the increased immune activation in the mutant-infected animals.
新型隐球菌是 HIV/AIDS 患者中最常见的真菌性脑膜炎病原体，如果不进行适当治疗，该病一律致命。导致隐球菌性脑膜脑炎的疾病在大脑中的发展机制仍不完全清楚。我们之前的研究表明，肌醇转运蛋白（ITR）是新型隐球菌毒力所必需的。新型隐球菌的 itr1aΔ itr3cΔ 双突变体在大脑内感染的小鼠模型中毒力减弱；表明尽管在感染的大脑中突变体和野生型菌株的生长速度相似，但 Itr1a 和 Itr3c 在大脑感染期间是完全毒力所必需的。
为了了解 itr1aΔ itr3cΔ 双突变体感染相关的免疫病理学，我们研究了感染小鼠大脑时宿主免疫反应的分子相关性。我们使用全基因组转录组 shotgun 测序（RNA-Seq）和定量实时 PCR（qRT-PCR）方法检测感染大脑中的宿主基因表达谱。结果表明，与野生型相比，突变体感染小鼠大脑会导致与宿主保护性免疫相关的细胞网络/途径的显著激活。大多数差异表达基因（SDEG）是免疫细胞网络的一部分，如肿瘤坏死因子-α（TNF-α）和干扰素-γ（IFN-γ）调节子，表明与野生型相比，突变体感染引发了更强的宿主免疫反应。有趣的是，在 itr1aΔ itr3cΔ 突变体细胞中观察到葡聚糖（GXM）分泌显著减少，表明肌醇利用途径在荚膜产生中起作用。
由于荚膜已被证明会影响隐球菌与宿主相互作用过程中的宿主反应，我们的结果表明，GXM 产量的降低可能导致突变体感染动物的免疫激活增加。
