Fetal CMV Infection: Role of the Human Placenta

描述（由申请人提供）：在美国，先天性巨细胞病毒（CMV）感染每年影响1%的婴儿，导致死亡和永久性残疾。胎盘的病毒感染先于胎儿，感染途径与子宫-胎盘界面的细胞滋养层（CTB）相互作用有关。对妊娠早期胎盘活检标本的研究表明，CMV感染子宫并扩散到锚定绒毛中的分化/侵入CTB和漂浮绒毛中的祖细胞。感染的CTB下调关键分化分子并损害侵袭性。最近的研究表明，IgG-病毒体复合物跨合体滋养层被转胞吞（由新生儿Fc受体介导）并感染潜在的CTB。免疫染色显示，病毒在胎盘发育中的复制位点与细胞分化时上调的功能性受体的表达相关。令人惊讶的是，CMV gB共定位与小窝蛋白-1包含在合胞滋养层的车厢，形成小窝体的病毒粒子可以积累在中性pH值。小窝蛋白-1结合基序在gB表明病毒诱导的内化。这些新的观察结果表明，病毒粒子在自然感染的组织中的小窝中内化，并可以解释为什么感染发生在整个妊娠期。长期目标是了解经胎盘传播的机制，防止病毒感染胎盘并传播给胎儿。将使用特化细胞和绒毛膜绒毛外植体测试gB促进病毒粒子内吞作用于小窝和病毒粒子转胞吞作用的假设，并在自然感染的胎盘中证实。具体目标如下。目标1.检查失调的整合素和膜近端功能-细胞粘附，迁移和侵袭-在临床CMV株感染的分化CTB中。目标二。完成对CTB和特化细胞中作为CMV受体的分子的分析。评估小窝蛋白-1-脂筏和gB在病毒粒子摄取中的作用。感染胎盘中的病毒复制位点与发育和空间调节受体相关。目标3：研究极化细胞中小窝囊泡中病毒粒子的转运，并评估病毒粒子的细胞间传递。检查从自然感染的胎盘中分离出的囊泡体。这些研究将揭示CMV破坏胎盘屏障并到达胎儿室的机制。了解这些过程是设计阻断病毒传播和增强胎盘屏障功能的新方法的第一步，以防止这种重要的人类病原体在先天性疾病中造成的损害。

DESCRIPTION (provided by applicant): Congenital cytomegalovirus (CMV) infection affects 1% of babies in the United States annually, causing mortality and permanent disabilities. Virus infection of the placenta precedes transmission to the fetus, and the routes of infection are linked to cytotrophoblast (CTB) interactions at the uterine-placental interface. Studies of biopsy specimens from early-gestation placentas revealed that CMV infects the uterus and spreads to differentiating/invading CTBs in anchoring villi and to progenitor cells in floating villi. Infected CTBs downregulate key differentiation molecules and impair invasiveness. Recent studies showed that IgG- virion complexes are transcytosed (mediated by the neonatal Fc receptor) across the syncytiotrophoblast and infect underlying CTBs. Immunostaining showed that sites of viral replication in the developing placenta correlate with expression of functional receptors upregulated as the cells differentiate. Surprisingly, CMV gB colocalized with caveolin-1 containing compartments in the syncytiotrophoblast, forming caveosomes where virions could accumulate at neutral pH. Caveolin-1-binding motifs in gB suggest virus-induced internalization. These novel observations establish that virions internalize in caveolae in naturally infected tissues and could explain why infection occurs throughout gestation. The long-term objectives are to understand mechanisms of transplacental transmission and prevent virus infection of the placenta and spread to the fetus. The hypothesis that gB promotes virion endocytosis in caveolae and virion transcytosis will be tested using specialized cells and chorionic villus explants and confirmed in naturally infected placentas. The specific aims are as follows. Aim 1. Examine dysregulated integrins and membrane-proximal functions-cell adhesion, migration and invasion-in differentiating CTBs infected with clinical CMV strains. Aim 2. Complete the analysis of molecules that function as CMV receptors in CTBs and specialized cells. Assess the role of caveolin-1-lipid rafts and gB in virion uptake. Correlate viral replication sites in infected placentas with developmentally and spatially regulated receptors. Aim 3. Investigate virion transport in caveolar vesicles in polarized cells and evaluate cell-cell transmission of virions. Examine caveosomes isolated from naturally infected placentas. These studies will uncover mechanisms used by CMV to breach the placental barrier and reach the fetal compartment. Understanding these processes is the first step in the design of novel approaches to block viral spread and enhance the barrier function of the placenta to prevent damage caused by this important human pathogen in congenital disease.