Oakley Miranda S M, Kumar Sanjai, Anantharaman Vivek, Zheng Hong, Mahajan Babita, Haynes J David, Moch J Kathleen, Fairhurst Rick, McCutchan Thomas F, Aravind L
Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases/NIH, Rockville, MD 20892, USA.
Infect Immun. 2007 Apr;75(4):2012-25. doi: 10.1128/IAI.01236-06. Epub 2007 Feb 5.
Intermittent episodes of febrile illness are the most benign and recognized symptom of infection with malaria parasites, although the effects on parasite survival and virulence remain unclear. In this study, we identified the molecular factors altered in response to febrile temperature by measuring differential expression levels of individual genes using high-density oligonucleotide microarray technology and by performing biological assays in asexual-stage Plasmodium falciparum parasite cultures incubated at 37 degrees C and 41 degrees C (an elevated temperature that is equivalent to malaria-induced febrile illness in the host). Elevated temperature had a profound influence on expression of individual genes; 336 of approximately 5,300 genes (6.3% of the genome) had altered expression profiles. Of these, 163 genes (49%) were upregulated by twofold or greater, and 173 genes (51%) were downregulated by twofold or greater. In-depth sensitive sequence profile analysis revealed that febrile temperature-induced responses caused significant alterations in the major parasite biologic networks and pathways and that these changes are well coordinated and intricately linked. One of the most notable transcriptional changes occurs in genes encoding proteins containing the predicted Pexel motifs that are exported into the host cytoplasm or inserted into the host cell membrane and are likely to be associated with erythrocyte remodeling and parasite sequestration functions. Using our sensitive computational analysis, we were also able to assign biochemical or biologic functional predictions for at least 100 distinct genes previously annotated as "hypothetical." We find that cultivation of P. falciparum parasites at 41 degrees C leads to parasite death in a time-dependent manner. The presence of the "crisis forms" and the terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling-positive parasites following heat treatment strongly support the notion that an apoptosis-like cell death mechanism might be induced in response to febrile temperatures. These studies enhance the possibility of designing vaccines and drugs on the basis of disruption in molecules and pathways of parasite survival and virulence activated in response to febrile temperatures.
间歇性发热疾病发作是疟原虫感染最良性且广为人知的症状，尽管其对寄生虫存活和毒力的影响仍不清楚。在本研究中，我们通过使用高密度寡核苷酸微阵列技术测量单个基因的差异表达水平，并在37摄氏度和41摄氏度（相当于宿主中疟疾引起的发热疾病的升高温度）孵育的无性阶段恶性疟原虫寄生虫培养物中进行生物学测定，确定了响应发热温度而改变的分子因素。升高的温度对单个基因的表达有深远影响；约5300个基因中的336个（占基因组的6.3%）表达谱发生了改变。其中，163个基因（49%）上调了两倍或更多，173个基因（51%）下调了两倍或更多。深入的敏感序列谱分析表明，发热温度诱导的反应导致主要寄生虫生物学网络和途径发生显著改变，并且这些变化协调良好且错综复杂地联系在一起。最显著的转录变化之一发生在编码含有预测的Pexel基序的蛋白质的基因中，这些蛋白质被输出到宿主细胞质或插入宿主细胞膜，可能与红细胞重塑和寄生虫滞留功能有关。通过我们敏感的计算分析，我们还能够为至少100个先前注释为“假设的”不同基因赋予生化或生物学功能预测。我们发现，在41摄氏度培养恶性疟原虫寄生虫会导致寄生虫随时间依赖性死亡。热处理后“危机形式”的存在以及末端脱氧核苷酸转移酶介导的dUTP-生物素缺口末端标记阳性寄生虫有力地支持了这样一种观点，即可能会因发热温度诱导类似凋亡的细胞死亡机制。这些研究增加了基于破坏寄生虫存活和毒力的分子及途径来设计疫苗和药物的可能性，这些分子和途径是在响应发热温度时被激活的。
