Pathogenomics of Chlamydial Infection

沙眼衣原体是可预防失明的主要原因，也是性传播疾病的主要原因。衣原体是专性细胞内细菌，其特征在于其独特的复杂的双相生长周期，其在称为基本体（EB）的感染性颗粒和称为网状体（RB）的非感染性代谢活性颗粒之间进行调节。在IFN-γ的存在下，衣原体在体外产生持续感染，这是一种宿主-寄生虫相互作用，被认为介导体内慢性炎症性疾病。控制双相发育周期和IFN-γ介导的持续感染的基因尚不清楚。 我们已经使用DNA微阵列转录分析衣原体基因表达在自然感染生长周期和持久性，并从持久性激活。这种方法导致了一小部分基因的鉴定，这些基因控制着周期的初级（即早期基因）和次级（晚期基因）分化阶段。即时早期基因产物启动细菌代谢并潜在地修饰细菌吞噬体以逃避与溶酶体的融合。一个立即早期基因（CT 147）是人类早期内体抗原-1，定位于衣原体吞噬体;这表明CT 147在建立寄生虫空泡中的非融合途径的功能作用。晚期基因产物终止细菌细胞分裂，并构成结构组分和参与形成高度二硫键交联的外膜复合物的重塑活动，所述外膜复合物在新宿主细胞的附着和侵入中起作用。许多基因表达的早期和晚期分化阶段是衣原体特异性的，并在真核细胞谱系的进化起源。 参与色氨酸利用、DNA修复和重组、磷脂利用、蛋白质翻译和一般应激的基因在持久性过程中上调。持续生长过程中下调的基因是衣原体晚期基因，以及参与蛋白水解、肽转运和细胞分裂的基因。持久性的特点是改变，但积极的生物合成过程与染色体的持续复制。去除IFN-γ后，衣原体迅速重新进入正常发育周期，并逆转与细胞因子治疗相关的转录变化。对IFN-γ的协调转录反应意味着衣原体反应刺激物已经进化为控制病原体的急性和持续生长之间的过渡。与坚持作为一般应激反应的范例相反，我们的研究结果表明，坚持是衣原体避免宿主炎症反应的另一种生命周期 总之，我们的研究结果确定了新的早期和晚期基因，这些基因在修改宿主对感染的反应以及在从RB到EB的过渡中衣原体细胞壁和外膜的重塑中具有重要功能。此外，持续感染的转录组分析揭示了衣原体反应刺激，解释了衣原体如何在细胞中持续存在，以及它们如何从持续存在中重新激活。这些发现对于开发新的和新颖的抗衣原体感染药物具有相当大的潜力。

Chlamydia trachomatis is the leading cause of preventable blindness and a major cause of sexually transmitted disease. Chlamydiae are obligate intracellular bacteria that are characterized by their unique complex biphasic growth cycle that modulates between infectious particles termed elementary bodies (EB) and non-infectious metabolical active particles termed reticulate bodies (RB). In the presence of IFN-gamma chlamydiae produce persistent infections in vitro, a host-parasite interaction that is believed to mediate in vivo chronic inflammatory disease. The genes that control the biphasic developmental cycle and IFN-gamma mediated persistent infection are unknown. We have used DNA microarray for transcriptional profiling chlamydial gene expression both during the natural infection growth cycle and during persistence, and reactivation from persistence. This approach has led to the identification of a small subset of genes that control the primary (immediate-early genes) and secondary (late genes) differentiation stages of the cycle. Immediate-early gene products initiate bacterial metabolism and potentially modify the bacterial phagosome to escape fusion with lysosomes. One immediate early gene (CT147) is of the human early endosomal antigen-1 that is localized to the chlamydial phagosome; suggesting a functional role for CT147 in establishing the parasitophorous vacuole in a non-fusogenic pathway. Late gene products terminate bacterial cell division and constitute structural components and remodeling activities involved in the formation of the highly disulfide cross-linked outer-membrane complex that functions in attachment and invasion of new host cells. Many of the genes expressed during the immediate-early and late differentiation stages are chlamydia-specific and have evolutionary origins in eukaryotic lineages. Genes involved in tryptophan utilization, DNA repair and recombination, phospholipid utilization, protein translation and general stress were up-regulated during persistence. Down-regulated genes during persistent growth were chlamydial late genes, and genes involved in proteolysis, peptide transport, and cell division. Persistence was characterized by altered but active biosynthetic processes with continued replication of the chromosome. Upon removal of IFN-gamma chlamydiae rapidly re-entered the normal developmental cycle and reversed transcriptional changes associated with cytokine treatment. The coordinated transcriptional response to IFN-gamma implies a chlamydial response stimulon has evolved to control the transition between acute and persistent growth of the pathogen. In contrast to the paradigm of persistence as a general stress response, our findings suggest persistence is an alternative life cycle employed by chlamydiae to avoid host inflammatory responses In summary, our findings identify new early and late genes that have important functions in modifying the host response to infection and in the remodeling of the chlamydial cell wall and outer membrane in transition form RB to EB. Moreover, transcriptome analysis of persistent infection has uncovered a chlamydial response stimulon that explains how chlamydiae persistent in cells and how they can become reactivated form persistence. These findings have considerable potential for the development of new and novel anti-chlamydial infectives.