耶氏肺孢子菌基因组信息研究进展

Research Development of Genomic Analysis of Pneumocystis Jirovecii

耶氏肺孢子菌(Pj)引起的肺孢子菌肺炎是免疫缺陷患者重要的致死原因之一,基因组测序分析揭示了Pj对人宿主依赖性的新机制。研究发现,Pj十分适应生存于人类的肺部,依赖肺部环境获取气体和营养物质,具有逃避宿主先天免疫和适应性免疫的能力。Pj不使用几丁质和N-甘露聚糖,仅在包囊期合成使用β-1,3-葡聚糖。Pj有球形的包囊和滋养体两种生存形态。包囊期是肺孢子菌有性繁殖和对外传播期,机体吸入空气中的肺孢子菌包囊而感染,成熟包囊进入肺泡后破裂,囊内小体脱囊后发育为滋养体,滋养体期细胞壁薄且具有变形能力和胞吞功能,能与宿主肺泡Ⅰ型细胞吸附,增殖并导致弥漫间质性肺炎。

Pneumocystis jirovecii（ Pj） is one of the major causes of life-threatening Pneumocystis pneumonia,in immunosuppressed patients yet surprisingly little is known about the biology of this fungal pathogen. Genome analysis has revealed new mechanism of the dependence of Pj on human hosts. Pj presumably must obtain nutrients and proliferate in the lung environment,and at the same time it must withstand host innate and adaptive immune defenses for sufficient periods to allow direct transmission to another susceptible host. Unexpectedly,the key fungal cell wall components chitin and outer chain N-mannans are absent in Pj. Furthermore,β-1,3-glucan has only been observed in the cystic stage. Pj has two forms： the cyst form and the trophic form. The cyst is the sexual reproduction and transmission form. Patients inhale the Pj cysts in the air and get infected. The mature cysts rupture after entering into the alveolar,and then the small capsular cysts develop into trophozoites. The trophozoites have thin,flexible cell walls with endocytosis function which are often tightly attached to typeⅠ pneumocytes in lung alveoli to proliferate and cause diffuse interstitial pneumonia.