Chlamydia pneumoniae persistent infection and its mechanism

目前的研究表明，专性细胞内细菌肺炎衣原体不仅与呼吸系统疾病有关，而且与动脉粥样硬化等慢性疾病有关。心血管疾病患者冠状动脉粥样硬化斑块和外周血中肺炎衣原体DNA或抗原的检测，增加了其可能参与动脉粥样硬化发病机制的可能性。此外，一些研究表明，通过培养和RT-PCR方法，可以在高龄冠心病患者的动脉粥样硬化斑块中检测到存活的肺炎衣原体。我们最近的研究还表明，从健康献血者的外周血单个核细胞(PBMC)中很容易检测到活的肺炎衣原体，这表明血流中活菌的存在可能是动脉粥样硬化发展的危险因素。肺炎衣原体优先感染呼吸道…更多的肠道上皮细胞和巨噬细胞。另一方面，我们以往的研究表明，淋巴细胞是肺炎衣原体感染的另一种宿主细胞，具有持续性。由于淋巴细胞是动脉粥样硬化形成过程中除巨噬细胞外的主要免疫细胞类型，淋巴细胞与肺炎衣原体之间的相互作用可能参与肺炎衣原体相关性慢性炎症性疾病的发病。我们首先试图评估非肥胖糖尿病(NOD)小鼠的糖尿病发展与肺炎衣原体从肺到外周血传播之间的可能联系。用肺炎衣原体16S rRNA的实时荧光定量逆转录-聚合酶链式反应(RT-PCR)方法，对肺炎衣原体进行多次鼻腔接种。NOD合并糖尿病小鼠(38.5%)和ICR小鼠(40%)均可检出细菌，但非糖尿病NOD小鼠(糖尿病前NOD小鼠和非糖尿病非糖尿病NOD小鼠)的细菌感染率很低(4.8%)，仅在NOD合并糖尿病小鼠的外周血单个核细胞(PBMC)中检出细菌(53.8%)。异硫氰酸荧光素标记的抗衣原体单抗免疫染色结果也显示肺组织和RT-PCR判定为阳性的PBMC中存在细菌抗原。结果表明，NOD小鼠糖尿病的发生可能是促进肺炎衣原体从肺向外周血传播的关键因素之一。其次，我们检测了肺炎衣原体感染对人淋巴细胞[Molt-4细胞和外周血单个核细胞(PBMCs)的浓缩淋巴细胞]CD3和CD25表达的可能改变。肺炎衣原体感染可显著降低Molt-4细胞两种分子的表达水平。肺炎衣原体临床分离株也引起感染细胞两者表达的改变。相反，沙眼衣原体对Molt-4细胞的两种表达没有引起任何改变。热灭活菌和HEP-2裂解物对淋巴细胞CD3表达无明显影响。加入NS-398(COX-2抑制剂)或AH-23848(EP4前列腺素受体拮抗剂)均可消除感染细胞CD_3表达的改变。竞争酶联免疫吸附试验也证实感染细胞培养上清液中前列腺素E_2(PGE_2)的产生增强。肺炎衣原体感染外周血单核细胞后，CD3的表达也发生改变，因此肺炎衣原体感染人淋巴细胞后，可通过产生前列腺素E_2而引起CD3表达的改变。由于CD3分子在抗原识别后的信号转导中起重要作用，这种改变可能与肺炎衣原体持续感染淋巴细胞有关。此外，我们还发现，2-氨基-吩恶嗪3-酮(吩恶嗪衍生物：PHX-3)抑制肺炎衣原体在人单核细胞和上皮细胞中的复制，部分依赖于宿主细胞的色氨酸代谢途径。较少

Current studies have revealed that the obligate intracellular bacterium Chlamydia (Chlamydophila) pneumoniae is associated not only with respiratory diseases, but also with chronic diseases such as atherosclerosis. The detection of the C. pneumoniae DNA or antigen in coronary atherosclerotic plaque and peripheral blood of the patients with cardiovascular diseases has strengthened the likelihood of its possible involvement in the pathogenesis of atherosclerosis. Moreover, several studies indicate that viable C. pneumoniae can be detected in atherosclerotic plaques from patients of advanced age with coronary heart disease by both culture and RT-PCR methods. Our recent studies also showed that viable C. pneumoniae are readily detectable in peripheral blood mononuclear cells (PBMCs) obtained from healthy donors, indicating that the presence of viable bacteria in the blood stream might be a risk factor for the development of atherosclerosis. C. pneumoniae preferentially infects respiratory … More tract epithelial cells as well as macrophages. On the other hand, our previous studies revealed that lymphocyte is another host cell permitting C. pneumoniae infection with a persistent nature. Since lymphocytes are a major immune cell type besides macrophages in the development of atherosclerosis, interaction between lymphocytes and this pathogen may contribute to the pathogenesis of chronic inflammatory diseases associated with C. pneumoniae. We first attempted to assess a possible association between development of diabetes in non-obese diabetic (NOD) mice and dissemination of C. pneumoniae from lung to peripheral blood. By real-time reverse transcription-polymerase chain reaction (RT-PCR) with primers for C. pneumoniae 16S rRNA, following multiple intranasal inoculations,. bacteria in lung were detected in NOD mice with diabetes (38.5 %) as well as ICR mice (40 %), but prevalence of bacteria in NOD mice without diabetes (Pre-diabetic NOD mice and non-diabetic retired NOD mice) was very low (4.8 %).The bacteria were only detected in peripheral blood mononuclear cells (PBMCs) cultured withhydrocortisone of the NOD mice with diabetes (53.8 %). Results of immunostaining with fluorescein isothiocyanate-conjugated anti-chlamydia monoclonal antibody also showed the presence of bacterial antigens m the lungs and the PBMCs judged as positive by the RT-PCR. The results clearly showed that the development of diabetes in NOD mouse appears to be one of critical factors for promoting the dissemination of C. pneumoniae from lung to peripheral blood. Second, we examined a possible alteration of CD3 and CD25 expressions of human lymphocytes [Molt-4 cells and enriched lymphocytes from peripheral blood mononuclear cells (PBMCs)] by C. pneumoniae infection. The expression levels of both molecules of Molt-4 cells were significantly decreased by C. pneumoniae infection. C. pneumoniae clinical isolates also caused the alteration of both expressions of the infected cells. In contrast, C. trachomatis did not cause any alteration of both expressions of Molt-4 cells. Heat-killed bacteria and HEp-2 lysate as mock did not cause any alteration of CD3 expression of lymphocytes. Addition of either NS-398 (Cox-2 inhibitor) or AH-23848 (EP4 prostanoid receptorantagonist) tothe culture abolishedthe alteration of CD3 expression ofthe infected cells. The enhanced prostaglandin E_2 (PGE_2) productions in the culture supernatant of infected cells were also confirmed by competitiveELISA. C. pneumoniae infection of enriched lymphocytesfromPBMCs also causedanalteration of CD3 expression.Thus, C. pneumoniae infection of human lymphocytes induces an alteration of CD3 expression mediated by PGE_2 production. Since CD3 molecule has a major role in the signal transduction following antigen recognitions, such alteration may be involved in C.pneumoniae persistent infection of lymphocytes. Also, we foundthat 2-amino-phenoxazine 3-one (phenoxazine derivate: Phx-3)inhibits C. pneumoniae replication in human monocytic cells as well as epithelial cells, partially depending on the tryptophan-metabolic pathway of host cells. Less