Role of Host Cells in Invasive Listeriosis

描述（由申请人提供）：感染是妊娠并发症的主要原因；然而，人们对其潜在的分子和细胞机制知之甚少。我们的长期目标是了解病原体如何破坏人类母胎界面的免疫防御，导致母体和胎儿的发病率和死亡率。我们关注的是人类细胞内单核增生李斯特菌（NIAID B类优先病原体），它会导致包括自然流产、早产和新生儿疾病在内的妊娠并发症。我们已经开发了一种新的怀孕豚鼠李斯特菌病模型，复制人类疾病，因为豚鼠的胎盘结构与人类非常相似。我们在这个模型中检查了胎盘感染的动力学，发现胎盘相对不受定植的保护。我们对人类胎盘器官培养的初步研究证实了这些发现：我们有证据表明单核增生乳杆菌在感染胎盘时受到多重瓶颈。我们发现，构成胎盘表面大部分并沐浴在母体血液中的合胞滋养细胞对单核增生乳杆菌感染具有高度抗性。进入胎盘的主要通道是一小群胎儿来源的细胞（胞外滋养细胞），它们将胎盘固定在蜕膜（妊娠子宫的内膜）中。细胞外滋养细胞不易从母体血流中进入，这就解释了为什么几乎所有胎盘病原体都有细胞内生命周期：它们必须到达母体细胞内的蜕膜才能扩散到胎盘。我们也有证据表明，细胞滋养细胞能够抑制李斯特菌的生长，因此很可能是单核增生乳杆菌必须克服的下一个瓶颈。我们假设胎盘已经进化出多种抵抗感染的机制。我们建议使用原代人胎盘细胞和器官培养来表征单核增生乳杆菌如何破坏母胎屏障以及细胞滋养细胞如何限制李斯特菌的生长。我们将在李斯特菌病的怀孕豚鼠模型体内测试我们的发现的重要性。具体目的是：(1)确定单核增生乳杆菌突破母胎屏障的机制。(2)观察单核增生乳杆菌对分离的原代胎盘细胞的感染。(3)研究胞外滋养细胞对单核增生乳杆菌感染的转录反应。

DESCRIPTION (provided by applicant): Infections are a leading cause of pregnancy complications; yet, little is known about their underlying molecular and cellular mechanisms. Our long-term goal is to understand how pathogens breach the immune defenses at the human maternal-fetal interface, causing maternal and fetal morbidity and mortality. We have focused on the human intracellular pathogen Listeria monocytogenes (NIAID Category B Priority Pathogen), which causes pregnancy complications including spontaneous abortion, preterm labor, and neonatal disease. We have developed a novel pregnant guinea pig model of listeriosis that replicates human disease, as the placental architecture of guinea pigs closely resembles humans. We have examined the kinetics of placental infection in this model and found that the placenta is relatively protected from colonization. Our preliminary studies in primary human placental organ cultures corroborate these findings: we have evidence that L. monocytogenes is subjected to multiple bottlenecks when infecting the placenta. We found that the syncytiotrophoblast, which constitutes most of the placental surface and is bathed in maternal blood, was highly resistant to L. monocytogenes infection. The main portal of entry into the placenta was a small subpopulation of fetally derived cells (extravillous cytotrophoblasts), which anchor the placenta in the decidua, the lining of the pregnant uterus. Extravillous cytotrophoblasts are not readily accessible from the maternal blood stream, which provides a novel explanation why almost all placental pathogens have intracellular life cycles: they have to reach the decidua inside of maternal cells to spread to the placenta. We also have evidence that cytotrophoblasts are able to inhibit listerial growth and therefore most likely represent the next bottleneck L. monocytogenes has to overcome. We hypothesize that the placenta has evolved multiple mechanisms to resist infection. We propose to use primary human placental cell and organ cultures to characterize how L. monocytogenes breaches the maternal-fetal barrier and how cytotrophoblasts restrict listerial growth. We will test the importance of our findings in vivo in the pregnant guinea pig model of listeriosis. The specific aims are: (1) To determine the mechanisms utilized by L. monocytogenes to breach the maternal-fetal barrier. (2) To characterize infection of isolated primary placental cells with L. monocytogenes. (3) To characterize the transcriptional response of extravillous cytotrophoblasts to infection with L. monocytogenes. PUBLIC HEALTH RELEVANCE: Infection is a major cause for pregnancy complications, and resultant maternal and fetal morbidity and mortality. The proposed studies will lead to better understanding of the underlying mechanisms, a prerequisite for developing new strategies for prevention and treatment to improve of the health of women and children.