Determining how macrophages regulate immunity to Zika virus infection at the maternal-fetal interface

摘要 胎盘的特征是母体血液与胎儿绒毛膜绒毛紧密接触。这 器官是风疹、巨细胞病毒、单纯疱疹病毒、HIV-1、B和C型肝炎病毒以及细小病毒的目标 B19感染，通过直接或连续感染胎盘细胞层，病毒粒子通过裂口 或通过与细胞相关的运输。最近，寨卡病毒（ZIKV），一种蚊子传播的黄病毒， 在美洲的健康问题，被发现从一个受感染的母亲传播 子宫内发育中的胎儿 , 导致以胎儿脑异常和小头畸形为特征的不良妊娠结果。的 严重胎儿后遗症的最大风险与妊娠早期的ZIKV感染有关，这表明 在妊娠早期和中期增强胎盘细胞的向性。然而， ZIKV确定胎盘和胎儿感染知之甚少。我们试图填补这一知识空白， 对母胎间室中的巨噬细胞如何维持 免疫稳态和限制ZIKV传播到发育中的胎儿。已检测到ZIKV抗原 在慢性绒毛中，特别是在来自女性的胎盘巨噬细胞或Hofbauer细胞（HC）和组织细胞中 生下患有小头畸形的婴儿或在怀孕期间患有活动性ZIKV感染的婴儿。ZIKV RNA还 从人类的胎盘组织和感染ZIKV的妊娠小鼠中分离。一些研究， 包括我们小组最近发表的一项研究，将HC确定为体内病毒感染的靶细胞， 体外我们发现，从足月胎盘中分离出的初级人类HC对生产性 ZIKV当代毒株PRVABC59感染（PR 2015）。ZIKV感染后，HC产生IFN-α， 和促炎细胞因子，然而，我们观察到很少或没有细胞死亡。我们的发现首次 鉴定胎盘中ZIKV感染的允许细胞类型，然而，仍然不清楚蜕膜或 胎儿单核细胞衍生的巨噬细胞在ZIKV感染期间发挥作用，以及这些胎盘细胞是否动态地 怀孕期间的变化，以规划更有效的抗病毒反应，以病毒感染后，怀孕。 基于我们的初步研究，我们的建议将解决中心假设，即巨噬细胞在 妊娠早期的母胎隔室（蜕膜、胎盘和胎儿）更允许ZIKV 与妊娠晚期巨噬细胞相比， 细胞自主抗病毒免疫信号传导的效力。我们的建议分为两个具体目标，寻求： 1)为了确定在妊娠期间母胎界面巨噬细胞中先天免疫信号传导的动力学， 2）确定母胎隔室中的巨噬细胞如何控制ZIKV感染 孕期这些研究将为人类ZIKV免疫提供新的见解，阐明机制， 胎盘内先天免疫控制，并有助于发展迫切需要的有效 抗病毒治疗剂和疫苗。

ABSTRACT The placenta is characterized by intimate contact between the maternal blood and fetal chorionic villi. This organ is a target for rubella, cytomegalovirus, herpes simplex, HIV-1, hepatitis B and C viruses and parvovirus B19 infection, by either direct or contiguous infection of placental cell layers, virion passage through a breach or by cell-associated transport. Most recently, Zika virus (ZIKV), a mosquito-borne flavivirus of significant public health concern in the Americas, was found to transmit from an infected mother to the developing fetus in utero , resulting in adverse pregnancy outcomes characterized by fetal brain abnormalities and microcephaly. The greatest risk of serious fetal sequelae is associated with ZIKV infection early in pregnancy, suggesting enhanced tropism for placental cells during the first- and second-trimester. However the mechanism by which ZIKV establishes placental and fetal infection is poorly understood. We seek to fill this gap in knowledge and develop a deeper mechanistic understanding for how macrophages in the maternal-fetal compartment maintain immune homeostasis and restrict ZIKV transmission to the developing fetus. ZIKV antigen has been detected in chronic villi, specifically within placental macrophages or Hofbauer cells (HCs) and histiocytes from women who gave birth to infants with microcephaly or had active ZIKV infection during pregnancy. ZIKV RNA has also been isolated from placental tissue in humans and from pregnant mice infected with ZIKV. Several studies, including one recently published by our group, identified HCs as target cells of viral infection in vivo and in vitro. We showed that primary human HCs isolated from full-term placentae are permissive to productive infection by a contemporary strain of ZIKV, PRVABC59 (PR 2015). Upon ZIKV infection, HCs produced IFN-α and pro-inflammatory cytokines, however, we observed little to no cell death. Our findings were the first to identify a permissive cell type for ZIKV infection in the placenta, however, it is still unclear what role decidual or fetal monocyte-derived macrophages play during ZIKV infection and whether these placental cells dynamically change during pregnancy to program more potent antiviral responses to virus infection later in pregnancy. Based on our preliminary studies, our proposal will address the central hypothesis that macrophages in the maternal-fetal compartment (decidual, placental and fetal) in early gestation are more permissive for ZIKV infection and replication as compared to late-gestation macrophages, directly corresponding to reduced potency of cell autonomous antiviral immune signaling. Our proposal is divided into two specific aims that seek: 1) To define the dynamics of innate immune signaling in macrophages at the maternal-fetal interface during pregnancy; and 2) To determine how macrophages in the maternal-fetal compartment control ZIKV infection during pregnancy. These studies will provide new insights to ZIKV immunity in humans, elucidate mechanisms of innate immune control within the placenta and contribute to development of urgently needed effective antiviral therapeutics and vaccines.