Neuroteratogenic Viruses and Lessons for Zika Virus Models

Fetal brain response to maternal inflammation requires microglia

In utero infection and maternal inflammation can adversely impact fetal brain development. Maternal systemic illness, even in the absence of direct fetal brain infection, is associated with an increased risk of neuropsychiatric disorders in affected offspring. The cell types mediating the fetal brain response to maternal inflammation are largely unknown, hindering the development of novel treatment strategies. Here, we show that microglia, the resident phagocytes of the brain, highly express receptors for relevant pathogens and cytokines throughout embryonic development. Using a rodent maternal immune activation (MIA) model in which polyinosinic:polycytidylic acid is injected into pregnant mice, we demonstrate long-lasting transcriptional changes in fetal microglia that persist into postnatal life. We find that MIA induces widespread gene expression changes in neuronal and non-neuronal cells; importantly, these responses are abolished by selective genetic deletion of microglia, indicating that microglia are required for the transcriptional response of other cortical cell types to MIA. These findings demonstrate that microglia play a crucial durable role in the fetal response to maternal inflammation, and should be explored as potential therapeutic cell targets.

Mechanisms of Zika astrocyte infection and neuronal toxicity

Objectives

Zika virus (ZIKV) has become an epidemic in several countries and was declared a major public health issue by the WHO. Although ZIKV infection is asymptomatic or shows mild fever-related symptoms in most people, the virus can be transmitted from a pregnant mother to the fetus, resulting in severe brain developmental abnormalities, including microcephaly. Multiple groups have identified developmental neuronal and neuronal progenitor compromise during ZIKV infection within the fetal brain, but little is known about whether ZIKV could infect human astrocytes and its effect on the developing brain. Thus, our objective was to determine astrocyte ZiKV infection in a developmental-dependent manner.

Methods

We analyze infection of pure cultures of astrocytes and mixed cultures of neurons and astrocytes in response to ZIKV using plaque assays, confocal, and electron microscopy to identify infectivity, ZIKV accumulation and intracellular distribution as well as apoptosis and interorganelle dysfunction.

Results

Here, we demonstrated that ZIKV enters, infects, replicates, and accumulates in large quantities in human fetal astrocytes in a developmental-dependent manner. Astrocyte infection and intracellular viral accumulation resulted in neuronal apoptosis, and we propose astrocytes are a ZIKV reservoir during brain development.

Conclusions

Our data identify astrocytes in different stages of development as major contributors to the devastating effects of ZIKV in the developing brain.

Differential Susceptibility of Fetal Retinal Pigment Epithelial Cells, hiPSC- Retinal Stem Cells, and Retinal Organoids to Zika Virus Infection

Zika virus (ZIKV) causes microcephaly and congenital eye disease. The cellular and molecular basis of congenital ZIKV infection are not well understood. Here, we utilized a biologically relevant cell-based system of human fetal retinal pigment epithelial cells (FRPEs), hiPSC-derived retinal stem cells (iRSCs), and retinal organoids to investigate ZIKV-mediated ocular cell injury processes. Our data show that FRPEs were highly susceptible to ZIKV infection exhibiting increased apoptosis, whereas iRSCs showed reduced susceptibility. Detailed transcriptomics and proteomics analyses of infected FRPEs were performed. Nucleoside analogue drug treatment inhibited ZIKV replication. Retinal organoids were susceptible to ZIKV infection. The Asian genotype ZIKV exhibited higher infectivity, induced profound inflammatory response, and dysregulated transcription factors involved in retinal organoid differentiation. Collectively, our study shows that ZIKV affects ocular cells at different developmental stages resulting in cellular injury and death, further providing molecular insight into the pathogenesis of congenital eye disease.

Application of a Human Blood Brain Barrier Organ-on-a-Chip Model to Evaluate Small Molecule Effectiveness against Venezuelan Equine Encephalitis Virus

The blood brain barrier (BBB) is a multicellular microenvironment that plays an important role in regulating bidirectional transport to and from the central nervous system (CNS). Infections by many acutely infectious viruses such as alphaviruses and flaviviruses are known to impact the integrity of the endothelial lining of the BBB. Infection by Venezuelan Equine Encephalitis Virus (VEEV) through the aerosol route causes significant damage to the integrity of the BBB, which contributes to long-term neurological sequelae. An effective therapeutic intervention strategy should ideally not only control viral load in the host, but also prevent and/or reverse deleterious events at the BBB. Two dimensional monocultures, including trans-well models that use endothelial cells, do not recapitulate the intricate multicellular environment of the BBB. Complex in vitro organ-on-a-chip models (OOC) provide a great opportunity to introduce human-like experimental models to understand the mechanistic underpinnings of the disease state and evaluate the effectiveness of therapeutic candidates in a highly relevant manner. Here we demonstrate the utility of a neurovascular unit (NVU) in analyzing the dynamics of infection and proinflammatory response following VEEV infection and therapeutic effectiveness of omaveloxolone to preserve BBB integrity and decrease viral and inflammatory load.

Tonate Virus and Fetal Abnormalities, French Guiana, 2019

We report a case of vertical transmission of Tonate virus in a pregnant woman from French Guiana. The fetus showed severe necrotic and hemorrhagic lesions of the brain and spinal cord. Clinicians should be made aware of possible adverse fetal outcomes in pregnant women infected with Tonate virus.

Causes of Phenotypic Variability and Disabilities after Prenatal Viral Infections

Prenatal viral infection can lead to a spectrum of neurodevelopmental disabilities or fetal demise. These can include microencephaly, global developmental delay, intellectual disability, refractory epilepsy, deafness, retinal defects, and cortical-visual impairment. Each of these clinical conditions can occur on a semi-quantitative to continuous spectrum, from mild to severe disease, and often as a collective of phenotypes. Such serious outcomes result from viruses’ overlapping neuropathology and hosts’ common neuronal and gene regulatory response to infections. The etiology of variability in clinical outcomes is not yet clear, but it may be related to viral, host, vector, and/or environmental risk and protective factors that likely interact in multiple ways. In this perspective of the literature, we work toward understanding the causes of phenotypic variability after prenatal viral infections by highlighting key aspects of the viral lifecycle that can affect human disease, with special attention to the 2015 Zika pandemic. Therefore, this work offers important insights into how viral infections and environmental teratogens affect the prenatal brain, toward our ultimate goal of preventing neurodevelopmental disabilities.

Immune cells enhance Zika virus-mediated neurologic dysfunction in brain of mice with humanized immune systems

Zika virus (ZIKV) can generate a number of neurological dysfunctions in infected humans. Here, we tested the potential of human immune cells to protect against ZIKV infection in genetically humanized MISTRG mice. FACS analysis showed robust reconstitution of the mouse spleen with human T cells. Peripheral ZIKV inoculation resulted in infection within the brains of MISTRG mice. Mice that were reconstituted with human peripheral blood mononuclear cells (PBMC) showed a more rapid lethal response to ZIKV than the control mice lacking these immune cells. Immunocytochemical analysis of T cell markers CD3, CD45, or CD8 showed strong T cell presence in the brain, together with robust infection by ZIKV particularly in the excitatory pyramidal and granule neurons of the hippocampus. Infection was also found in cortex, striatum, the dopamine neurons of the substantia nigra, and other brain loci. Infection was considerably less in other regions such as the septum and hypothalamus. These data support the perspective that, rather than exerting a protective function, T cells may underlie some ZIKV-mediated neuropathology in the brain.

Tembusu Virus entering the central nervous system caused nonsuppurative encephalitis without disrupting the blood-brain barrier

Tembusu Virus (TMUV) is an emerging and re-emerging zoonotic pathogen that adversely affects poultry industry in recent years. TMUV disease is characterized by nonsuppurative encephalitis in ducklings. The duckling infection model was established to study the mechanism of TMUV crossing the blood-brain barrier (BBB) into the central nervous system (CNS). Here, we showed that no obvious clinical symptoms and enhancement of BBB permeability occurred at the early stage of infection (3∼5 dpi). While simultaneously virus particles were observed by transmission electron microscopy in the brain, inducing the accumulation of inflammatory cytokines. Neurological symptoms and disruption of BBB appeared at the intermediate stage of infection (7∼9 dpi). It was confirmed that TMUV could survive and propagate in brain microvascular endothelial cells (BMECs), but did not affect the permeability of BBB in vivo and in vitro at an early date. In conclusion, TMUV enters the CNS then causes encephalitis, and finally destruct the BBB, which may be due to the direct effect of TMUV on BMECs and the subsequent response of "inflammatory storm".IMPORTANCE The TMUV disease has caused huge losses to the poultry industry in Asia, which is potentially harmful to public health. Neurological symptoms and their sequelae are the main characters of this disease. However, the mechanism of how this virus enters the brain and causes encephalitis is unclear. In this study, we confirmed that the virus entered the CNS and then massively destroyed BBB and the BBB damage was closely associated with the subsequent outbreak of inflammation. TMUV may enter the CNS through the transcellular and "Trojan horse" pathways. These findings can fill the knowledge gap in the pathogenesis of TMUV-infected poultry and be benefit for the treatment of TMUV disease. What's more, TMUV is a representative to study the infection of avian flavivirus. Therefore, our studies have significances both for understanding of the full scope of mechanisms of TMUV and other flavivirus infection, and conceivably, for therapeutics.

Performance of Zika Assays in the Context of Toxoplasma gondii, Parvovirus B19, Rubella Virus, and Cytomegalovirus (TORCH) Diagnostic Assays

Infections during pregnancy that may cause congenital abnormalities have been recognized for decades, but their diagnosis is challenging. This was again illustrated with the emergence of Zika virus (ZIKV), highlighting the inherent difficulties in estimating the extent of pre- and postnatal ZIKV complications because of the difficulties in establishing definitive diagnoses. We reviewed the epidemiology, infection kinetics, and diagnostic methods used for Toxoplasma gondii, parvovirus B19, rubella virus, and cytomegalovirus (TORCH) infections and compared the results with current knowledge of ZIKV diagnostic assays to provide a basis for the inclusion of ZIKV in the TORCH complex evaluations. Similarities between TORCH pathogens and ZIKV support inclusion of ZIKV as an emerging TORCH infection. Our review evaluates the diagnostic performance of various TORCH diagnostic assays for maternal screening, fetal screening, and neonatal screening. We show that the sensitivity, specificity, and positive and negative predictive value of TORCH complex pathogens are widely variable, stressing the importance of confirmatory testing and the need for novel techniques for earlier and accurate diagnosis of maternal and congenital infections. In this context it is also important to acknowledge different needs and access to care for different geographic and resource settings.

Identification of potential Zika virus NS2B-NS3 protease inhibitors via docking, molecular dynamics and consensus scoring-based virtual screening

The Zika virus has recently become a subject of acute interest after the discovery of the link between viral infection and microcephaly in infants. Though a number of treatments are under active investigation, there are currently no approved treatments for the disease. To address this critical need, we screened more than 7 million compounds targeting the NS2B-NS3 protease in an attempt to identify promising inhibitor candidates. Starting with commercially and freely available compounds, we identified six hits utilizing an exhaustive consensus screening protocol, followed by molecular dynamics simulation and binding energy estimation using MM/GBSA and MM/PBSA methods. These compounds feature a variety of cores and functionalities, and all are predicted to have good pharmacokinetic profiles, making them promising candidates for screening assays. Graphical abstract Virtual screen of potential Zika virus NS2B-NS3 protease inhibitors.

Zika virus and the nonmicrocephalic fetus: why we should still worry

Zika virus is a mosquito-transmitted flavivirus and was first linked to congenital microcephaly caused by a large outbreak in northeastern Brazil. Although the Zika virus epidemic is now in decline, pregnancies in large parts of the Americas remain at risk because of ongoing transmission and the potential for new outbreaks. This review presents why Zika virus is still a complex and worrisome public health problem with an expanding spectrum of birth defects and how Zika virus and related viruses evade the immune response to injure the fetus. Recent reports indicate that the spectrum of fetal brain and other anomalies associated with Zika virus exposure is broader and more complex than microcephaly alone and includes subtle fetal brain and ocular injuries; thus, the ability to prenatally diagnose fetal injury associated with Zika virus infection remains limited. New studies indicate that Zika virus imparts disproportionate effects on fetal growth with an unusual femur-sparing profile, potentially providing a new approach to identify viral injury to the fetus. Studies to determine the limitations of prenatal and postnatal testing for detection of Zika virus-associated birth defects and long-term neurocognitive deficits are needed to better guide women with a possible infectious exposure. It is also imperative that we investigate why the Zika virus is so adept at infecting the placenta and the fetal brain to better predict other viruses with similar capabilities that may give rise to new epidemics. The efficiency with which the Zika virus evades the early immune response to enable infection of the mother, placenta, and fetus is likely critical for understanding why the infection may either be fulminant or limited. Furthermore, studies suggest that several emerging and related viruses may also cause birth defects, including West Nile virus, which is endemic in many parts of the United States. With mosquito-borne diseases increasing worldwide, there remains an urgent need to better understand the pathogenesis of the Zika virus and related viruses to protect pregnancies and child health.

Zika virus crosses an in vitro human blood brain barrier model

Zika virus (ZIKV) is a flavivirus that is highly neurotropic causing congenital abnormalities and neurological damage to the central nervous systems (CNS). In this study, we used a human induced pluripotent stem cell (iPSC)-derived blood brain barrier (BBB) model to demonstrate that ZIKV can infect brain endothelial cells (i-BECs) without compromising the BBB barrier integrity or permeability. Although no disruption to the BBB was observed post-infection, ZIKV particles were released on the abluminal side of the BBB model and infected underlying iPSC-derived neural progenitor cells (i-NPs). AXL, a putative ZIKV cellular entry receptor, was also highly expressed in ZIKV-susceptible i-BEC and i-NPs. This iPSC-derived BBB model can help elucidate the mechanism by which ZIKV can infect BECs, cross the BBB and gain access to the CNS.

Emerging Viral Infections in Sub-Saharan Africa and the Developing Nervous System: A Mini Review

The global public health concern is heightened over the increasing number of emerging viruses, i.e., newly discovered or previously known that have expanded into new geographical zones. These viruses challenge the health-care systems in sub-Saharan Africa (SSA) countries from which several of them have originated and been transmitted by insects worldwide. Some of these viruses are neuroinvasive, but have been relatively neglected by neuroscientists. They may provide experiments by nature to give a time window for exposure to a new virus within sizeable, previously non-infected human populations, which, for instance, enables studies on potential long-term or late-onset effects on the developing nervous system. Here, we briefly summarize studies on the developing brain by West Nile, Zika, and Chikungunya viruses, which are mosquito-borne and have spread worldwide out of SSA. They can all be neuroinvasive, but their effects vary from malformations caused by prenatal infections to cognitive disturbances following perinatal or later infections. We also highlight Ebola virus, which can leave surviving children with psychiatric disturbances and cause persistent infections in the non-human primate brain. Greater awareness within the neuroscience community is needed to emphasize the menace evoked by these emerging viruses to the developing brain. In particular, frontline neuroscience research should include neuropediatric follow-up studies in the field on long-term or late-onset cognitive and behavior disturbances or neuropsychiatric disorders. Studies on pathogenetic mechanisms for viral-induced perturbations of brain maturation should be extended to the vulnerable periods when neurocircuit formations are at peaks during infancy and early childhood.

Maternal-fetal transmission of the zika virus: An intriguing interplay

In this review, we give an overview of aspects related to the congenital transmission of the Zika virus (ZIKV). Although we acknowledge that important advances in research on ZIKV pathogenesis have come from studies using animal models, particularly non-human primates, this review emphasizes studies using ex-vivo human cells and tissues as well as natural infections in pregnant women. The possible routes used by ZIKV to cross or breach the placental barrier and infect the fetal central nervous system are presented. Understanding the viral infection biology and ZIKV pathogenesis during pregnancy may guide the design of affordable antiviral strategies to benefit pregnant women in areas at risk.

Development of Zika Virus Vaccines

Zika virus (ZIKV) is a mosquito-borne flavivirus that emerged as a global threat following the most recent outbreak in Brazil in 2015. ZIKV infection of pregnant women is associated with fetal abnormalities such as microcephaly, and infection of adults can lead to Guillain-Barré syndrome, an autoimmune disease characterized by neurological deficits. Although there are currently licensed vaccines for other flaviviruses, there remains an urgent need for preventative vaccines against ZIKV infection. Herein we describe the current efforts to accelerate the development of ZIKV vaccines using various platforms, including live attenuated virus, inactivated virus, DNA and RNA, viral vectors, and in silico-predicted immunogenic viral epitopes. Many of these approaches have leveraged lessons learned from past experience with Dengue and other flavivirus vaccines.

In situ immune response and mechanisms of cell damage in central nervous system of fatal cases microcephaly by Zika virus

Zika virus (ZIKV) has recently caused a pandemic disease, and many cases of ZIKV infection in pregnant women resulted in abortion, stillbirth, deaths and congenital defects including microcephaly, which now has been proposed as ZIKV congenital syndrome. This study aimed to investigate the in situ immune response profile and mechanisms of neuronal cell damage in fatal Zika microcephaly cases. Brain tissue samples were collected from 15 cases, including 10 microcephalic ZIKV-positive neonates with fatal outcome and five neonatal control flavivirus-negative neonates that died due to other causes, but with preserved central nervous system (CNS) architecture. In microcephaly cases, the histopathological features of the tissue samples were characterized in three CNS areas (meninges, perivascular space, and parenchyma). The changes found were mainly calcification, necrosis, neuronophagy, gliosis, microglial nodules, and inflammatory infiltration of mononuclear cells. The in situ immune response against ZIKV in the CNS of newborns is complex. Despite the predominant expression of Th2 cytokines, other cytokines such as Th1, Th17, Treg, Th9, and Th22 are involved to a lesser extent, but are still likely to participate in the immunopathogenic mechanisms of neural disease in fatal cases of microcephaly caused by ZIKV.

In situ immune response and mechanisms of cell damage in central nervous system of fatal cases microcephaly by Zika virus

Zika virus (ZIKV) has recently caused a pandemic disease, and many cases of ZIKV infection in pregnant women resulted in abortion, stillbirth, deaths and congenital defects including microcephaly, which now has been proposed as ZIKV congenital syndrome. This study aimed to investigate the in situ immune response profile and mechanisms of neuronal cell damage in fatal Zika microcephaly cases. Brain tissue samples were collected from 15 cases, including 10 microcephalic ZIKV-positive neonates with fatal outcome and five neonatal control flavivirus-negative neonates that died due to other causes, but with preserved central nervous system (CNS) architecture. In microcephaly cases, the histopathological features of the tissue samples were characterized in three CNS areas (meninges, perivascular space, and parenchyma). The changes found were mainly calcification, necrosis, neuronophagy, gliosis, microglial nodules, and inflammatory infiltration of mononuclear cells. The in situ immune response against ZIKV in the CNS of newborns is complex. Despite the predominant expression of Th2 cytokines, other cytokines such as Th1, Th17, Treg, Th9, and Th22 are involved to a lesser extent, but are still likely to participate in the immunopathogenic mechanisms of neural disease in fatal cases of microcephaly caused by ZIKV.

Distribución espacial de egresos hospitalarios de casos por infección vírica por picadura de mosquito en México entre 2004 y 2014

Objetivo.

Conocer la distribución espacial de los egresos hospitalarios por fiebre vírica por picadura de mosquito (FVPM) en México y caracterizar su evolución histórica en el periodo 2004-2014.

Métodos.

Se realizo un análisis exploratorio e inferencial de corte transversal. Los datos primarios se obtuvieron de los registros de egresos hospitalarios del Sistema Nacional de Información en Salud (SINAIS) del periodo 2004-2014. Para identificar clusters de los casos notificados, se estimaron indicadores de asociación geográfica y establecieron zonas de riesgo sobre la base de determinantes ambientales que se validaron con medidas estimadas de concentración relativa. Para conocer la evolución temporal y determinar la estructura de edad de los casos, se estimaron tasas de crecimiento y se construyeron curvas de densidad.

Resultados.

La distribución geográfica de estos egresos hospitalarios en México sigue un patrón focalizado. En total se detectó alta concentración en clusters integrados por 20 municipios de los cuales 9 se localizaron en el estado de Sinaloa. En 37% de los estados del país las concentraciones de egresos hospitalarios por FVPM fueron mayores que las del país en conjunto y sus índices de localización oscilaron entre 5,79 en Sinaloa y 1,17 en Campeche.

Conclusión.

La información geográfica obtenida, la referente al vínculo encontrado entre las zonas de alto riesgo de transmisión de la infección por la presencia del vector transmisor y la relativa a las condiciones sociales como la pobreza son útiles para diseñar estrategias de prevención y control de las infecciones víricas emergentes transmitidas por artrópodos en México, como la del virus del Zika.

Arboviruses and pregnancy: maternal, fetal, and neonatal effects

Arboviruses are an expanding public health threat, with pregnant women facing unique complications from arbovirus infections. These infections, such as dengue and Crimean-Congo haemorrhagic fever, can be more severe in pregnant women than in the general population. Vertical transmission is reported for many arboviruses and can severely affect pregnancy outcome. Indeed, arboviruses-particularly flaviviruses and alphaviruses-are associated with increased risks of fetal loss and premature birth. Arboviruses can be teratogenic, as is the case for Zika virus and Venezuelan equine encephalitis virus. Finally, intrapartum transmission can result in severe neonatal infections, as is true for chikungunya virus. Although the global burden of arboviruses is well recognised, few studies have provided data on arbovirus infection specifically in the context of maternal and child health. Epidemiological and clinical studies are therefore needed to better assess the burden of arbovirus infections during pregnancy and to improve the prevention and clinical management of these viral infections. In this Review, we analyse the information available and identify gaps in knowledge that require further assessment.

A novel Zika virus mouse model reveals strain specific differences in virus pathogenesis and host inflammatory immune responses

Zika virus (ZIKV) is a mosquito borne flavivirus, which was a neglected tropical pathogen until it emerged and spread across the Pacific Area and the Americas, causing large human outbreaks associated with fetal abnormalities and neurological disease in adults. The factors that contributed to the emergence, spread and change in pathogenesis of ZIKV are not understood. We previously reported that ZIKV evades cellular antiviral responses by targeting STAT2 for degradation in human cells. In this study, we demonstrate that Stat2^-/- mice are highly susceptible to ZIKV infection, recapitulate virus spread to the central nervous system (CNS), gonads and other visceral organs, and display neurological symptoms. Further, we exploit this model to compare ZIKV pathogenesis caused by a panel of ZIKV strains of a range of spatiotemporal history of isolation and representing African and Asian lineages. We observed that African ZIKV strains induce short episodes of severe neurological symptoms followed by lethality. In comparison, Asian strains manifest prolonged signs of neuronal malfunctions, occasionally causing death of the Stat2^-/- mice. African ZIKV strains induced higher levels of inflammatory cytokines and markers associated with cellular infiltration in the infected brain in mice, which may explain exacerbated pathogenesis in comparison to those of the Asian lineage. Interestingly, viral RNA levels in different organs did not correlate with the pathogenicity of the different strains. Taken together, we have established a new murine model that supports ZIKV infection and demonstrate its utility in highlighting intrinsic differences in the inflammatory response induced by different ZIKV strains leading to severity of disease. This study paves the way for the future interrogation of strain-specific changes in the ZIKV genome and their contribution to viral pathogenesis.

Zika virus is the most recent viral pathogen to cause a global public health emergency. It is distinct from other flaviviruses in its ability to cause transplacental infection, fetal abnormalities and vector independent transmission through body fluids in humans. Over the last year, there has been rapid progress in the development of animal models, which can be used to study ZIKV pathogenesis. In this study, we demonstrate for the first time that Stat2^-/- mice are highly susceptible to ZIKV infection and recapitulate aspects of ZIKV pathogenesis and disease. We use this model to delineate whether strain specific differences in ZIKV pathogenesis exist, using diverse strains representing both African and Asian lineages. We show that African strains in general are more virulent than Asian strains and their pathogenicity associates closely with the degree of inflammatory immune response in the CNS of infected mice, and does not necessarily correlate with viral RNA levels. Thus, we establish Stat2^-/- mice as new model to study ZIKV pathogenesis and use it to characterize inherent differences in the virulence among ZIKV strains. More importantly, we also highlight a potential role of the host inflammatory immune response in mediating differential pathogenesis among ZIKV strains.

Intrauterine Zika virus infection of pregnant immunocompetent mice models transplacental transmission and adverse perinatal outcomes

Zika virus (ZIKV) crosses the placenta and causes congenital disease. Here we develop an animal model utilizing direct ZIKV inoculation into the uterine wall of pregnant, immunocompetent mice to evaluate transplacental transmission. Intrauterine inoculation at embryonic day (E) 10, but not E14, with African, Asian or American strains of ZIKV reduces fetal viability and increases infection of placental and fetal tissues. ZIKV inoculation at E10 causes placental inflammation, placental dysfunction and reduces neonatal brain cortical thickness, which is associated with increased activation of microglia. Viral antigen localizes in trophoblast and endothelial cells in the placenta, and endothelial, microglial and neural progenitor cells in the fetal brain. ZIKV infection of the placenta increases production of IFNβ and expression of IFN-stimulated genes 48 h after infection. This mouse model provides a platform for identifying factors at the maternal-fetal interface that contribute to adverse perinatal outcomes in a host with an intact immune system.