Chary-Reddy S, Graves D C
Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City 73190, USA.
J Clin Microbiol. 1996 Jul;34(7):1660-5. doi: 10.1128/JCM.34.7.1660-1665.1996.
Pneumocystis carinii has been shown to cause extra-alveolar infections in humans, but the lack of a reproducible animal model has hindered the elucidation of mechanisms of P. carinii dissemination. In the present study, PCR and the immunosuppressed rat model were used to gain further insight into the dissemination of P. carinii organisms in extrapulmonary (EP) tissues. Primer sequences specific to major surface glycoprotein (MSG) and dihydrofolate reductase (DHFR) were used to detect P. carinii in lungs and EP tissues. Sprague-Dawley rats were grouped into two classes: one group included rats that had primary episodes of pneumocystosis and the other group included rats that had undergone treatment for P. carinii infection and that had second episodes of pneumocystosis. PCR analysis with MSG primers with tissues obtained from both groups of rats showed the presence of P. carinii DNA in adrenal tissue, bone marrow, blood, and heart, kidney, liver, lymph node, spleen, and thyroid tissues. Reverse transcriptase-PCR (RT-PCR) analysis was carried out with DHFR primers with lung, spleen, heart, kidney, and liver tissues from both groups of rats. Only those tissues that showed a positive PCR result and hybridization signal for the MSG gene were used for the RT-PCR experiments. RT-PCR analysis showed that the P. carinii DHFR gene is actively transcribed in these tissues, thereby indicating the presence of viable P. carinii organisms in EP tissues. Our observations suggest that P. carinii dissemination is influenced by factors other than P. carinii chemotherapy and that heavy organism load and destruction of lung tissue may contribute to the dissemination of P. carinii. The study provides an animal model that can be used for further investigations of the causes of EP pneumocystosis.
卡氏肺孢子虫已被证明可在人类中引起肺泡外感染，但缺乏可重复的动物模型阻碍了对卡氏肺孢子虫传播机制的阐明。在本研究中，使用聚合酶链反应（PCR）和免疫抑制大鼠模型来进一步深入了解卡氏肺孢子虫在肺外（EP）组织中的传播情况。使用针对主要表面糖蛋白（MSG）和二氢叶酸还原酶（DHFR）的引物序列来检测肺和EP组织中的卡氏肺孢子虫。将斯普拉格-道利大鼠分为两类：一组包括患有原发性肺孢子虫病的大鼠，另一组包括接受过卡氏肺孢子虫感染治疗且患有继发性肺孢子虫病的大鼠。用MSG引物对两组大鼠获得的组织进行PCR分析，结果显示在肾上腺组织、骨髓、血液以及心脏、肾脏、肝脏、淋巴结、脾脏和甲状腺组织中存在卡氏肺孢子虫DNA。用DHFR引物对两组大鼠的肺、脾脏、心脏、肾脏和肝脏组织进行逆转录聚合酶链反应（RT-PCR）分析。仅将那些对MSG基因显示出阳性PCR结果和杂交信号的组织用于RT-PCR实验。RT-PCR分析表明，卡氏肺孢子虫DHFR基因在这些组织中活跃转录，从而表明在EP组织中存在活的卡氏肺孢子虫。我们的观察结果表明，卡氏肺孢子虫的传播受卡氏肺孢子虫化疗以外的因素影响，并且大量的病原体负荷和肺组织破坏可能有助于卡氏肺孢子虫的传播。该研究提供了一种可用于进一步研究EP肺孢子虫病病因的动物模型。
