Fetal CMV Infection: Role of the Human Placenta

描述(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。病毒在胎盘感染之前传播给胎儿，感染途径与子宫-胎盘界面的细胞滋养层细胞(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，并传播到锚定绒毛中分化/入侵的CTB和漂浮绒毛中的祖细胞。感染的CTB下调了关键分化分子的表达，并削弱了侵袭性。最近的研究表明，Ig G-病毒子复合体通过合体滋养层细胞跨细胞转运(由新生儿Fc受体介导)，并感染潜在的CTB。免疫染色显示，病毒在发育中的胎盘中的复制位置与功能受体的表达有关，随着细胞的分化而上调。令人惊讶的是，CMV gB与含有小窝蛋白-1的小窝蛋白-1在合体滋养层细胞中共存，形成了小窝小体，病毒粒子可以在中性pH下聚集。Gb中的Caveolin-1结合基序表明病毒诱导的内化。这些新颖的观察证实，病毒粒子内化在自然感染组织的小窝中，并可以解释为什么感染发生在整个妊娠过程中。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到胎儿。GB促进小窝中的病毒粒子内吞和病毒粒子跨细胞作用的假设将通过使用专门的细胞和绒毛外植体进行测试，并在自然感染的胎盘中得到证实。具体目标如下。目的1.检测CMV临床株感染CTB时，细胞黏附、迁移和侵袭等细胞膜近端功能和整合素的异常表达。目的2.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置与发育和空间调节的受体相关。目的3.研究极化细胞中空泡内病毒粒子的转运，评价病毒粒子在细胞间的转运。检查从自然感染的胎盘中分离出来的凹陷体。这些研究将揭示CMV用来突破胎盘屏障并到达胎儿隔室的机制。了解这些过程是设计阻止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.