Zika Virus Infects Intermediate Progenitor Cells and Post-mitotic Committed Neurons in Human Fetal Brain Tissues

Lipid droplets in Zika neuroinfection: Potential targets for intervention?

Lipid droplets (LD) are evolutionarily conserved lipid-enriched organelles with a diverse array of cell- and stimulus-regulated proteins. Accumulating evidence demonstrates that intracellular pathogens exploit LD as energy sources, replication sites, and part of the mechanisms of immune evasion. Nevertheless, LD can also favor the host as part of the immune and inflammatory response to pathogens. The functions of LD in the central nervous system have gained great interest due to their presence in various cell types in the brain and for their suggested involvement in neurodevelopment and neurodegenerative diseases. Only recently have the roles of LD in neuroinfections begun to be explored. Recent findings reveal that lipid remodelling and increased LD biogenesis play important roles for Zika virus (ZIKV) replication and pathogenesis in neural cells. Moreover, blocking LD formation by targeting DGAT-1 in vivo inhibited virus replication and inflammation in the brain. Therefore, targeting lipid metabolism and LD biogenesis may represent potential strategies for anti-ZIKV treatment development. Here, we review the progress in understanding LD functions in the central nervous system in the context of the host response to Zika infection.

ZIKV infection differentially affects the transcriptional profiles in HTR8 and U251 cells

The mechanism by which Zika virus (ZIKV) causes severe birth defects in pregnant women remains unclear. Cell tropisms in placenta and brain play a crucial role in ZIKV pathogenesis, leading to congenital Zika syndrome (CZS). To identify the host factors involved in ZIKV infection, we compared the transcriptional profiles of ZIKV-infected human first-trimester placental trophoblast cells HTR8/SVneo and a human glioblastoma astrocytoma cell line U251. Our results demonstrated that ZIKV exhibited lower rates of mRNA replication and protein expression in HTR8 than in U251 cells, while showing a higher release of infectious viral particles. However, a greater number of differentially expressed genes (DEGs) were found in ZIKV-infected U251 cells than in ZIKV-infected HTR8 cells. Several of these DEGs were enriched in distinct biological processes related to the characteristics of each cell type that may contribute to foetal damage. Both cell types exhibited activation of common interferons, inflammatory cytokines, and chemokine production upon ZIKV infection. Moreover, the neutralization of tumour necrosis factor-alpha (TNF-α) promoted ZIKV infection in both trophoblasts and glioblastoma astrocytoma cells. Overall, we identified multiple DEGs associated with ZIKV pathogenesis.

Zika Virus Neuropathogenesis: The Different Brain Cells, Host Factors and Mechanisms Involved

Zika virus (ZIKV), despite being discovered six decades earlier, became a major health concern only after an epidemic in French Polynesia and an increase in the number of microcephaly cases in Brazil. Substantial evidence has been found to support the link between ZIKV and neurological complications in infants. The virus targets various cells in the brain, including radial glial cells, neural progenitor cells (NPCs), astrocytes, microglial and glioblastoma stem cells. It affects the brain cells by exploiting different mechanisms, mainly through apoptosis and cell cycle dysregulation. The modulation of host immune response and the inflammatory process has also been demonstrated to play a critical role in ZIKV induced neurological complications. In addition to that, different ZIKV strains have exhibited specific neurotropism and unique molecular mechanisms. This review provides a comprehensive and up-to-date overview of ZIKV-induced neuroimmunopathogenesis by dissecting its main target cells in the brain, and the underlying cellular and molecular mechanisms. We highlighted the roles of the different ZIKV host factors and how they exploit specific host factors through various mechanisms. Overall, it covers key components for understanding the crosstalk between ZIKV and the brain.

Apoptosis during ZIKA Virus Infection: Too Soon or Too Late?

Cell death by apoptosis is a major cellular response in the control of tissue homeostasis and as a defense mechanism in the case of cellular aggression such as an infection. Cell self-destruction is part of antiviral responses, aimed at limiting the spread of a virus. Although it may contribute to the deleterious effects in infectious pathology, apoptosis remains a key mechanism for viral clearance and the resolution of infection. The control mechanisms of cell death processes by viruses have been extensively studied. Apoptosis can be triggered by different viral determinants through different pathways as a result of virally induced cell stresses and innate immune responses. Zika virus (ZIKV) induces Zika disease in humans, which has caused severe neurological forms, birth defects, and microcephaly in newborns during the last epidemics. ZIKV also surprised by revealing an ability to persist in the genital tract and in semen, thus being sexually transmitted. Mechanisms of diverting antiviral responses such as the interferon response, the role of cytopathic effects and apoptosis in the etiology of the disease have been widely studied and debated. In this review, we examined the interplay between ZIKV infection of different cell types and apoptosis and how the virus deals with this cellular response. We illustrate a duality in the effects of ZIKV-controlled apoptosis, depending on whether it occurs too early or too late, respectively, in neuropathogenesis, or in long-term viral persistence. We further discuss a prospective role for apoptosis in ZIKV-related therapies, and the use of ZIKV as an oncolytic agent.

The Dual Regulation of Apoptosis by Flavivirus

Apoptosis is a form of programmed cell death, which maintains cellular homeostasis by eliminating pathogen-infected cells. It contains three signaling pathways: death receptor pathway, mitochondria-mediated pathway, and endoplasmic reticulum pathway. Its importance in host defenses is highlighted by the observation that many viruses evade, hinder or destroy apoptosis, thereby weakening the host’s immune response. Flaviviruses such as Dengue virus, Japanese encephalitis virus, and West Nile virus utilize various strategies to activate or inhibit cell apoptosis. This article reviews the research progress of apoptosis mechanism during flaviviruses infection, including flaviviruses proteins and subgenomic flaviviral RNA to regulate apoptosis by interacting with host proteins, as well as various signaling pathways involved in flaviviruses-induced apoptosis, which provides a scientific basis for understanding the pathogenesis of flaviviruses and helps in developing an effective antiviral therapy.

Molecular mechanisms of zika virus pathogenesis: An update

Zika virus (ZIKV), member of the family Flaviviridae belonging to genus Flavivirus, is an arthropod-borne virus. The ZIKV is known to cause severe congenital birth defects in neonates. Due to a large number of worldwide outbreaks and associated neurological complications with ZIKV, a public health emergency was declared by the World Health Organization on February 1, 2016. The virus exhibits neurotropism and has a specific propensity towards neural precursor cells of the developing brain. In utero ZIKV infection causes massive cell death in the developing brain resulting in various motor and cognitive disabilities in newborns. The virus modulates cell machinery at several levels to replicate itself and inhibits toll like receptors-3 signalling, deregulates microRNA circuitry and induces a chronic inflammatory response in affected cells. Several significant advances have been made to understand the mechanisms of neuropathogenesis, its prevention and treatment. The current review provides an update on cellular and molecular mechanisms of ZIKV-induced alterations in the function of various brain cells.

A Review on the Current Knowledge on ZIKV Infection and the Interest of Organoids and Nanotechnology on Development of Effective Therapies against Zika Infection

Zika virus (ZIKV) acquired a special relevance due to the pandemic that occurred in the Americas in 2015, when an important number of fetal microcephaly cases occurred. Since then, numerous studies have tried to elucidate the pathogenic mechanisms and the potential therapeutic approaches to combat the virus. Cellular and animal models have proved to be a basic resource for this research, with the more recent addition of organoids as a more realistic and physiological 3D culture for the study of ZIKV. Nanotechnology can also offer a promising therapeutic tool, as the nanoparticles developed by this field can penetrate cells and deliver a wide array of drugs in a very specific and controlled way inside the cells. These two state-of-the-art scientific tools clearly provide a very relevant resource for the study of ZIKV, and will help researchers find an effective treatment or vaccine against the virus.

Intermediate progenitors support migration of neural stem cells into dentate gyrus outer neurogenic niches

The hippocampal dentate gyrus (DG) is a unique brain region maintaining neural stem cells (NCSs) and neurogenesis into adulthood. We used multiphoton imaging to visualize genetically defined progenitor subpopulations in live slices across key stages of mouse DG development, testing decades old static models of DG formation with molecular identification, genetic-lineage tracing, and mutant analyses. We found novel progenitor migrations, timings, dynamic cell-cell interactions, signaling activities, and routes underlie mosaic DG formation. Intermediate progenitors (IPs, Tbr2+) pioneered migrations, supporting and guiding later emigrating NSCs (Sox9+) through multiple transient zones prior to converging at the nascent outer adult niche in a dynamic settling process, generating all prenatal and postnatal granule neurons in defined spatiotemporal order. IPs (Dll1+) extensively targeted contacts to mitotic NSCs (Notch active), revealing a substrate for cell-cell contact support during migrations, a developmental feature maintained in adults. Mouse DG formation shares conserved features of human neocortical expansion.

CpG Oligonucleotides Protect Mice From Alphavirus Encephalitis: Role of NK Cells, Interferons, and TNF

Arboviruses including alphavirus are responsible for most emerging infectious diseases worldwide. Recent outbreaks of chikungunya virus serve as a stark reminder to their pathogenic potential. There are no vaccines or therapeutics currently available to contain alphavirus outbreaks. In this study we evaluated the effect of immunomodulatory CpG ODN on the clinical progression of neurotropic Sindbis virus infection. Neonatal C57Bl-6 mice challenged with Sindbis virus AR339 (25 PFU Subcutaneous) infect neurons in the CNS leading to the development of ataxia, seizures, paralysis, and death. We show that systemic administration of CpG ODN modulates the cytokine and chemokine gene expression levels in the CNS and ultimately protects neonatal mice from lethal neurotropic infection. The protection conferred by CpG ODN is controlled by innate immune response and T and B cells were dispensable. Further, protection required Type I, Type II interferons, and TNF as well as functional NK cells, but did not involve iNOS. This study confirms that administration of innate immune modulators can be used as a strategy to boost host innate immune responses and protect against neurotropic viruses reducing their pathogenic footprint.

Mutations in ANKLE2, a ZIKA Virus Target, Disrupt an Asymmetric Cell Division Pathway in Drosophila Neuroblasts to Cause Microcephaly

The apical Par complex, which contains atypical protein kinase C (aPKC), Bazooka (Par-3), and Par-6, is required for establishing polarity during asymmetric division of neuroblasts in Drosophila, and its activity depends on L(2)gl. We show that loss of Ankle2, a protein associated with microcephaly in humans and known to interact with Zika protein NS4A, reduces brain volume in flies and impacts the function of the Par complex. Reducing Ankle2 levels disrupts endoplasmic reticulum (ER) and nuclear envelope morphology, releasing the kinase Ballchen-VRK1 into the cytosol. These defects are associated with reduced phosphorylation of aPKC, disruption of Par-complex localization, and spindle alignment defects. Importantly, removal of one copy of ballchen or l(2)gl suppresses Ankle2 mutant phenotypes and restores viability and brain size. Human mutational studies implicate the above-mentioned genes in microcephaly and motor neuron disease. We suggest that NS4A, ANKLE2, VRK1, and LLGL1 define a pathway impinging on asymmetric determinants of neural stem cell division.

Atlastin Endoplasmic Reticulum-Shaping Proteins Facilitate Zika Virus Replication

The endoplasmic reticulum (ER) is the site for Zika virus (ZIKV) replication and is central to the cytopathic effects observed in infected cells. ZIKV induces the formation of ER-derived large cytoplasmic vacuoles followed by "implosive" cell death. Little is known about the nature of the ER factors that regulate flavivirus replication. Atlastins (ATL1, -2, and -3) are dynamin-related GTPases that control the structure and the dynamics of the ER membrane. We show here that ZIKV replication is significantly decreased in the absence of ATL proteins. The appearance of infected cells is delayed, the levels of intracellular viral proteins and released virus are reduced, and the cytopathic effects are strongly impaired. We further show that ATL3 is recruited to viral replication sites and interacts with the nonstructural viral proteins NS2A and NS2B3. Thus, proteins that shape and maintain the ER tubular network ensure efficient ZIKV replication.IMPORTANCE Zika virus (ZIKV) is an emerging virus associated with Guillain-Barré syndrome, and fetal microcephaly as well as other neurological complications. There is no vaccine or specific antiviral treatment against ZIKV. We found that endoplasmic reticulum (ER)-shaping atlastin proteins (ATL1, -2, and -3), which induce ER membrane fusion, facilitate ZIKV replication. We show that ATL3 is recruited to the viral replication site and colocalize with the viral proteins NS2A and NS2B3. The results provide insights into host factors used by ZIKV to enhance its replication.

Update on the Animal Models and Underlying Mechanisms for ZIKV-Induced Microcephaly

The circulation of Zika virus (ZIKV) in nearly 80 countries and territories poses a significant global threat to public health. ZIKV is causally linked to severe developmental defects in the brain, recognized as congenital Zika syndrome (CZS), which includes microcephaly and other serious congenital neurological complications. Since the World Health Organization declared the ZIKV outbreak a public health emergency of international concern, remarkable progress has been made in the generation of different ZIKV infection animal models to gain insight into cellular targets and pathogenesis and to explore the associated underlying mechanisms. Here we focus on summarizing our current understanding of the effects of ZIKV on mammalian brain development in different developmental stages and discuss the potential underlying mechanisms of ZIKV-induced CZS, as well as future perspectives.

IL-1 receptor antagonist therapy mitigates placental dysfunction and perinatal injury following Zika virus infection

Zika virus (ZIKV) infection during pregnancy causes significant adverse sequelae in the developing fetus, and results in long-term structural and neurologic defects. Most preventive and therapeutic efforts have focused on the development of vaccines, antivirals, and antibodies. The placental immunologic response to ZIKV, however, has been largely overlooked as a target for therapeutic intervention. The placental inflammatory response, specifically IL-1β secretion and signaling, is induced by ZIKV infection and represents an environmental factor that is known to increase the risk of perinatal developmental abnormalities. We show in a mouse model that maternally administrated IL-1 receptor antagonist (IRA; Kineret, or anakinra), following ZIKV exposure, can preserve placental function (by improving trophoblast invasion and placental vasculature), increase fetal viability, and reduce neurobehavioral deficits in the offspring. We further demonstrate that while ZIKV RNA is highly detectable in placentas, it is not correlated with fetal viability. Beyond its effects in the placenta, we show that IL-1 blockade may also directly decrease fetal neuroinflammation by mitigating fetal microglial activation in a dose-dependent manner. Our studies distinguish the role of placental inflammation during ZIKV-infected pregnancies, and demonstrate that maternal IRA may attenuate fetal neuroinflammation and improve perinatal outcomes.

Glycosaminoglycan Compositional Analysis of Relevant Tissues in Zika Virus Pathogenesis and in Vitro Evaluation of Heparin as an Antiviral against Zika Virus Infection

Zika virus (ZIKV) is an enveloped RNA virus from the flavivirus family that can cause fetal neural abnormalities in pregnant women. Previously, we established that ZIKV-EP (envelope protein) binds to human placental chondroitin sulfate (CS), suggesting that CS may be a potential host cell surface receptor in ZIKV pathogenesis. In this study, we further characterized the GAG disaccharide composition of other biological tissues (i.e., mosquitoes, fetal brain cells, and eye tissues) in ZIKV pathogenesis to investigate the role of tissue specific GAGs. Heparan sulfate (HS) was the major GAG, and levels of HS-6-sulfo, HS 0S (unsulfated HS), and CS 4S disaccharides were the main differences in the GAG composition of Aedes aegypti and Aedes albopictus mosquitoes. In human fetal neural progenitor and differentiated cells, HS 0S and CS 4S were the main disaccharides. A change in disaccharide composition levels was observed between undifferentiated and differentiated cells. In different regions of the bovine eyes, CS was the major GAG, and the amounts of hyaluronic acid or keratan sulfate varied depending on the region of the eye. Next, we examined heparin (HP) of various structures to investigate their potential in vitro antiviral activity against ZIKV and Dengue virus (DENV) infection in Vero cells. All compounds effectively inhibited DENV replication; however, they surprisingly promoted ZIKV replication. HP of longer chain lengths more strongly promoted activity in ZIKV replication. This study further expands our understanding of role of GAGs in ZIKV pathogenesis and carbohydrate-based antivirals against flaviviral infection.

Putative Cellular and Molecular Roles of Zika Virus in Fetal and Pediatric Neuropathologies

Although the World Health Organization declared an end to the recent Zika virus (ZIKV) outbreak and its association with adverse fetal and pediatric outcome, on November 18, 2016, the virus still remains a severe public health threat. Laboratory experiments thus far supported the suspicions that ZIKV is a teratogenic agent. Evidence indicated that ZIKV infection cripples the host cells' innate immune responses, allowing productive replication and potential dissemination of the virus. In addition, studies suggest potential transplacental passage of the virus and subsequent selective targeting of neural progenitor cells (NPCs). Depletion of NPCs by ZIKV is associated with restricted brain growth. And while microcephaly can result from infection at any gestational stages, the risk is greater during the first trimester. Although a number of recent studies revealed some of specific molecular and cellular roles of ZIKV proteins of this mosquito-borne flavivirus, the mechanisms by which it produces it suspected pathophysiological effects are not completely understood. Thus, this review highlights the cellular and molecular evidence that implicate ZIKV in fetal and pediatric neuropathologies.

Ribosomal biogenesis as an emerging target of neurodevelopmental pathologies

Development of the nervous system is carried out by complex gene expression programs that are regulated at both transcriptional and translational level. In addition, quality control mechanisms such as the TP53-mediated apoptosis or neuronal activity-stimulated survival ensure successful neurogenesis and formation of functional circuitries. In the nucleolus, production of ribosomes is essential for protein synthesis. In addition, it participates in chromatin organization and regulates the TP53 pathway via the ribosomal stress response. Its tight regulation is required for maintenance of genomic integrity. Mutations in several ribosomal components and trans-acting ribosomal biogenesis factors result in neurodevelopmental syndromes that present with microcephaly, autism, intellectual deficits and/or progressive neurodegeneration. Furthermore, ribosomal biogenesis is perturbed by exogenous factors that disrupt neurodevelopment including alcohol or Zika virus. In this review, we present recent literature that argues for a role of dysregulated ribosomal biogenesis in pathogenesis of various neurodevelopmental syndromes. We also discuss potential mechanisms through which such dysregulation may lead to cellular pathologies of the developing nervous system including insufficient proliferation and/or loss of neuroprogenitors cells, apoptosis of immature neurons, altered neuronal morphogenesis, and neurodegeneration.

Zika virus vaccines

The recent epidemic of Zika virus (ZIKV) in the Americas has revealed the devastating consequences of ZIKV infection, particularly in pregnant women. Congenital Zika syndrome, characterized by malformations and microcephaly in neonates as well as developmental challenges in children, highlights the need for the development of a safe and effective vaccine. Multiple vaccine candidates have been developed and have shown promising results in both animal models and phase I clinical trials. However, important challenges remain for the clinical development of these vaccines. In this Progress article, we discuss recent preclinical studies and lessons learned from first-in-human clinical trials with ZIKV vaccines.

Global Interactomics Uncovers Extensive Organellar Targeting by Zika Virus

Zika virus (ZIKV) is a membrane enveloped Flavivirus with a positive strand RNA genome, transmitted by Aedes mosquitoes. The geographical range of ZIKV has dramatically expanded in recent decades resulting in increasing numbers of infected individuals, and the spike in ZIKV infections has been linked to significant increases in both Guillain-Barré syndrome and microcephaly. Although a large number of host proteins have been physically and/or functionally linked to other Flaviviruses, very little is known about the virus-host protein interactions established by ZIKV. Here we map host cell protein interaction profiles for each of the ten polypeptides encoded in the ZIKV genome, generating a protein topology network comprising 3033 interactions among 1224 unique human polypeptides. The interactome is enriched in proteins with roles in polypeptide processing and quality control, vesicle trafficking, RNA processing and lipid metabolism. >60% of the network components have been previously implicated in other types of viral infections; the remaining interactors comprise hundreds of new putative ZIKV functional partners. Mining this rich data set, we highlight several examples of how ZIKV may usurp or disrupt the function of host cell organelles, and uncover an important role for peroxisomes in ZIKV infection.

Evolution of Two Major Zika Virus Lineages: Implications for Pathology, Immune Response, and Vaccine Development

Zika virus (ZIKV) became a public health emergency of global concern in 2015 due to its rapid expansion from French Polynesia to Brazil, spreading quickly throughout the Americas. Its unexpected correlation to neurological impairments and defects, now known as congenital Zika syndrome, brought on an urgency to characterize the pathology and develop safe, effective vaccines. ZIKV genetic analyses have identified two major lineages, Asian and African, which have undergone substantial changes during the past 50 years. Although ZIKV infections have been circulating throughout Africa and Asia for the later part of the 20th century, the symptoms were mild and not associated with serious pathology until now. ZIKV evolution also took the form of novel modes of transmission, including maternal-fetal transmission, sexual transmission, and transmission through the eye. The African and Asian lineages have demonstrated differential pathogenesis and molecular responses in vitro and in vivo. The limited number of human infections prior to the 21st century restricted ZIKV research to in vitro studies, but current animal studies utilize mice deficient in type I interferon (IFN) signaling in order to invoke enhanced viral pathogenesis. This review examines ZIKV strain differences from an evolutionary perspective, discussing how these differentially impact pathogenesis via host immune responses that modulate IFN signaling, and how these differential effects dictate the future of ZIKV vaccine candidates.

Placental Inflammation and Fetal Injury in a Rare Zika Case Associated With Guillain-Barré Syndrome and Abortion

Zika virus (ZIKV) is an emerging virus involved in recent outbreaks in Brazil. The association between the virus and Guillain-Barré syndrome (GBS) or congenital disorders has raised a worldwide concern. In this work, we investigated a rare Zika case, which was associated with GBS and spontaneous retained abortion. Using specific anti-ZIKV staining, the virus was identified in placenta (mainly in Hofbauer cells) and in several fetal tissues, such as brain, lungs, kidneys, skin and liver. Histological analyses of the placenta and fetal organs revealed different types of tissue abnormalities, which included inflammation, hemorrhage, edema and necrosis in placenta, as well as tissue disorganization in the fetus. Increased cellularity (Hofbauer cells and TCD8⁺ lymphocytes), expression of local pro-inflammatory cytokines such as IFN-γ and TNF-α, and other markers, such as RANTES/CCL5 and VEGFR2, supported placental inflammation and dysfunction. The commitment of the maternal-fetal link in association with fetal damage gave rise to a discussion regarding the influence of the maternal immunity toward the fetal development. Findings presented in this work may help understanding the ZIKV immunopathogenesis under the rare contexts of spontaneous abortions in association with GBS.

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.

Adverse outcomes of pregnancy-associated Zika virus infection

The spread of Zika virus to the Americas was accompanied by surge in the number of infants with CNS abnormalities leading to a declaration of a health emergency by the WHO. This was accompanied by significant responses from governmental health agencies in the United States and Europe that resulted in significant new information described in the natural history of this perinatal infection in a very short period of time. Although much has been learned about Zika virus infection during pregnancy, limitations of current diagnostics and the challenges for accurate serologic diagnosis of acute Zika virus infection has restricted our understanding of the natural history of this perinatal infection to infants born to women with clinical disease during pregnancy and to Zika exposed infants with obvious clinical stigmata of disease. Thus, the spectrum of disease in infants exposed to Zika virus during pregnancy remains to be defined. In contrast, observations in informative animal models of Zika virus infections have provided rational pathways for vaccine development and existing antiviral drug development programs for other flaviviruses have resulted in accelerated development for potential antiviral therapies. This brief review will highlight some of the current concepts of the natural history of Zika virus during pregnancy.

Innovative in cellulo method as an alternative to in vivo neurovirulence test for the characterization and quality control of human live Yellow Fever virus vaccines: A pilot study

Live attenuated vaccines have proved to be mostly valuable in the prevention of infectious diseases in humans, especially in developing countries. The safety and potency of vaccine, and the consistency of vaccine batch-to-batch manufacturing, must be proven before being administrated to humans. For now, the tests used to control vaccine safety largely involve animal testing. For live viral vaccines, regulations require suppliers to demonstrate the absence of neurovirulence in animals, principally in non-human primates and mice. In a search to reduce the use of animals and embracing the 3Rs principles (Replacement, Reduction, Refinement in the use of laboratory animals), we developed a new Blood-Brain Barrier Minibrain (BBB-Minibrain) in cellulo device to evaluate the neuroinvasiveness/neurovirulence of live Yellow Fever virus (YFV) vaccines. A pilot study was performed using the features of two distinct YFV strains, with the ultimate goal of proposing a companion test to characterize YFV neurovirulence. Here, we demonstrate that the BBB-Minibrain model is a promising alternative to consider for future replacement of YFV vaccine in vivo neurovirulence testing (see graphical abstract).

Congenital Zika virus infection as a silent pathology with loss of neurogenic output in the fetal brain

Zika virus (ZIKV) is a flavivirus with teratogenic effects on fetal brain, but the spectrum of ZIKV-induced brain injury is unknown, particularly when ultrasound imaging is normal. In a pregnant pigtail macaque (Macaca nemestrina) model of ZIKV infection, we demonstrate that ZIKV-induced injury to fetal brain is substantial, even in the absence of microcephaly, and may be challenging to detect in a clinical setting. A common and subtle injury pattern was identified, including (i) periventricular T2-hyperintense foci and loss of fetal noncortical brain volume, (ii) injury to the ependymal epithelium with underlying gliosis and (iii) loss of late fetal neuronal progenitor cells in the subventricular zone (temporal cortex) and subgranular zone (dentate gyrus, hippocampus) with dysmorphic granule neuron patterning. Attenuation of fetal neurogenic output demonstrates potentially considerable teratogenic effects of congenital ZIKV infection even without microcephaly. Our findings suggest that all children exposed to ZIKV in utero should receive long-term monitoring for neurocognitive deficits, regardless of head size at birth.