A single mutation in the prM protein of Zika virus contributes to fetal microcephaly

Structure of the space of taboo-free sequences

Models of sequence evolution typically assume that all sequences are possible. However, restriction enzymes that cut DNA at specific recognition sites provide an example where carrying a recognition site can be lethal. Motivated by this observation, we studied the set of strings over a finite alphabet with taboos, that is, with prohibited substrings. The taboo-set is referred to as \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathbb {T}$$\end{document}T and any allowed string as a taboo-free string. We consider the so-called Hamming graph \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\varGamma _n(\mathbb {T})$$\end{document}Γn(T), whose vertices are taboo-free strings of length n and whose edges connect two taboo-free strings if their Hamming distance equals one. Any (random) walk on this graph describes the evolution of a DNA sequence that avoids taboos. We describe the construction of the vertex set of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\varGamma _n(\mathbb {T})$$\end{document}Γn(T). Then we state conditions under which \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\varGamma _n(\mathbb {T})$$\end{document}Γn(T) and its suffix subgraphs are connected. Moreover, we provide an algorithm that determines if all these graphs are connected for an arbitrary \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathbb {T}$$\end{document}T. As an application of the algorithm, we show that about \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$87\%$$\end{document}87% of bacteria listed in REBASE have a taboo-set that induces connected taboo-free Hamming graphs, because they have less than four type II restriction enzymes. On the other hand, four properly chosen taboos are enough to disconnect one suffix subgraph, and consequently connectivity of taboo-free Hamming graphs could change depending on the composition of restriction sites.

Spatio-Temporal Mutational Profile Appearances of Swedish SARS-CoV-2 during the Early Pandemic

BACKGROUND

During the COVID-19 pandemic, the virus evolved, and we therefore aimed to provide an insight into which genetic variants were enriched, and how they spread in Sweden.

METHODS

We analyzed 348 Swedish SARS-CoV-2 sequences freely available from GISAID obtained from 7 February 2020 until 14 May 2020.

RESULTS

We identified 14 variant sites ≥5% frequency in the population. Among those sites, the D936Y substitution in the viral Spike protein was under positive selection. The variant sites can distinguish 11 mutational profiles in Sweden. Nine of the profiles appeared in Stockholm in March 2020. Mutational profiles 3 (B.1.1) and 6 (B.1), which contain the D936Y mutation, became the predominant profiles over time, spreading from Stockholm to other Swedish regions during April and the beginning of May. Furthermore, Bayesian phylogenetic analysis indicated that SARS-CoV-2 could have emerged in Sweden on 27 December 2019, and community transmission started on February 1st with an evolutionary rate of 1.5425 × 10-3 substitutions per year.

CONCLUSIONS

Our study provides novel knowledge on the spatio-temporal dynamics of Swedish SARS-CoV-2 variants during the early pandemic. Characterization of these viral variants can provide precious insights on viral pathogenesis and can be valuable for diagnostic and drug development approaches.

Zika NS1-induced ER remodeling is essential for viral replication

Zika virus induces the formation of vesicles from ER membrane that form viral replication factories in the ER lumen. Ci et al. show that the Zika NS1 protein plays a key role in this remodeling of the ER as the insertion of the hydrophobic regions of NS1 into the inner leaflet of the ER membrane creates the compartments essential for viral replication.

Zika virus (ZIKV), a recently emerged member of the flavivirus family, forms replication compartments at the ER during its lifecycle. The proteins that are responsible for the biogenesis of replication compartments are not well defined. Here, we show that Zika nonstructural protein 1 (NS1)–induced ER remodeling is essential for viral replication. NS1 expressed in the ER lumen induced ER perinuclear aggregation with an ultrastructure resembling that of the replication compartment. Data from model membrane system indicated that the membrane-binding and membrane-remodeling properties of NS1 depend on its hydrophobic insertion into the membrane. These findings demonstrate that NS1 plays a crucial role in flavivirus replication compartment formation by remodeling the ER structure.

Congenital Zika Virus Infection: a Review with Emphasis on the Spectrum of Brain Abnormalities

Purpose of Review

In 2016, the World Health Organization declared the Zika virus (ZIKV) outbreak a Public Health Emergency of International Concern following a cluster of associated neurological disorders and neonatal malformations. Our aim is to review the clinical and neuroimaging findings seen in congenital Zika syndrome.

Recent Findings

ZIKV injures neural progenitor cells in the hippocampus, a brain region important for learning, memory, cognition, and emotion/stress response. Positron emission tomography has revealed global neuroinflammation in ZIKV infection in animal models.

Summary

Congenital Zika syndrome is associated with a spectrum of brain abnormalities, including microcephaly, parenchymal calcifications, malformations of cortical development and defective neuronal migration, corpus callosum abnormalities, ventriculomegaly, and brainstem and cerebellar abnormalities.

Teratogen update: Zika virus and pregnancy

Zika virus was first identified in Uganda in 1947 but received little attention until 2015 when a large outbreak of Zika virus illness followed by an increased number of babies born with microcephaly occurred in Brazil. Zika virus spread rapidly throughout the Americas, and in 2016 was identified as a cause of microcephaly and other serious birth defects. Since that time, much has been learned about the Zika virus. The virus is primarily spread by the bite of Aedes species mosquitoes; however, other forms of transmission (e.g., sexual and intrauterine) have been recognized. Although postnatal Zika virus infection typically causes mild or no symptoms, effects on infants born to prenatally infected mothers can be severe and include structural birth defects and neurodevelopmental effects. The risk of a structural birth defect among infants born to mothers with confirmed or suspected Zika virus infection during pregnancy has ranged from 5 to 10%. The timing of Zika infection during pregnancy affects risk, with higher risks with the first-trimester infection. Neurodevelopmental effects are seen even in infants who appear normal in the newborn period. Although cases of Zika virus infection have fallen in the Americas, the Zika virus remains an active threat in some regions of the world. The development of a Zika vaccine will require continued focus and investment. Until a Zika vaccine is available, prevention efforts for pregnant women include avoidance of travel to areas with active Zika transmission, avoidance of mosquito bites for those living in or traveling to areas with Zika transmission, and protection against sexual transmission.

N-glycosylation in the Pre-Membrane Protein Is Essential for the Zika Virus Life Cycle

Asparagine (N)-linked protein glycosylation plays an important role in protein synthesis and modification. Two Zika virus (ZIKV) structural proteins, the pre-membrane (prM) and envelope (E) protein are N-glycosylated. The prM protein of all ZIKV strains contains a single N-linked glycosylation site, while not all strains contain an N-linked site in the E protein. Our aim was to examine the impact of prM and E N-linked glycosylation on ZIKV infectivity and cell trafficking. Using a ZIKV infectious clone, we found that when the N-glycan sites were removed, the prM- and the prM/E-double mutants did not produce an infectious virus in the supernatant. Further, by using ZIKV prME constructs, we found that N-glycosylation was necessary for effective secretion of ZIKV virions. The absence of the N-glycan on prM or E caused protein aggregation in the rough endoplasmatic reticulum (ER) compartment. The aggregation was more pronounced for the prM-mutation, and the mutant virus lost the ER-Golgi intermediate compartment (ERGIC) localization. In addition, lack of the N-glycan on prM induced nuclear translocation of CCAAT-enhancer-binding protein homologous protein (CHOP), an ER stress marker. To conclude, we show that the prM N-glycan is essential for the ZIKV infectious cycle, and plays an important role in viral protein trafficking, protein folding, and virion assembly.

The Zika Virus Capsid Disrupts Corticogenesis by Suppressing Dicer Activity and miRNA Biogenesis

Zika virus (ZIKV) causes microcephaly and disrupts neurogenesis. Dicer-mediated miRNA biogenesis is required for embryonic brain development and has been suggested to be disrupted upon ZIKV infection. Here we mapped the ZIKV-host interactome in neural stem cells (NSCs) and found that Dicer is specifically targeted by the capsid from ZIKV, but not other flaviviruses, to facilitate ZIKV infection. We identified a capsid mutant (H41R) that loses this interaction and does not suppress Dicer activity. Consistently, ZIKV-H41R is less virulent and does not inhibit neurogenesis in vitro or corticogenesis in utero. Epidemic ZIKV strains contain capsid mutations that increase Dicer binding affinity and enhance pathogenicity. ZIKV-infected NSCs show global dampening of miRNA production, including key miRNAs linked to neurogenesis, which is not observed after ZIKV-H41R infection. Together these findings show that capsid-dependent suppression of Dicer is a major determinant of ZIKV immune evasion and pathogenesis and may underlie ZIKV-related microcephaly.

A Zika virus envelope mutation preceding the 2015 epidemic enhances virulence and fitness for transmission

Arboviruses maintain high mutation rates due to lack of proofreading ability of their viral polymerases, in some cases facilitating adaptive evolution and emergence. Here we show that, just before its 2013 spread to the Americas, Zika virus (ZIKV) underwent an envelope protein V473M substitution (E-V473M) that increased neurovirulence, maternal-to-fetal transmission, and viremia to facilitate urban transmission. A preepidemic Asian ZIKV strain (FSS13025 isolated in Cambodia in 2010) engineered with the V473M substitution significantly increased neurovirulence in neonatal mice and produced higher viral loads in the placenta and fetal heads in pregnant mice. Conversely, an epidemic ZIKV strain (PRVABC59 isolated in Puerto Rico in 2015) engineered with the inverse M473V substitution reversed the pathogenic phenotypes. Although E-V473M did not affect oral infection of Aedes aegypti mosquitoes, competition experiments in cynomolgus macaques showed that this mutation increased its fitness for viremia generation, suggesting adaptive evolution for human viremia and hence transmission. Mechanistically, the V473M mutation, located at the second transmembrane helix of the E protein, enhances virion morphogenesis. Overall, our study revealed E-V473M as a critical determinant for enhanced ZIKV virulence, intrauterine transmission during pregnancy, and viremia to facilitate urban transmission.

Differential gene expression elicited by ZIKV infection in trophoblasts from congenital Zika syndrome discordant twins

Zika virus (ZIKV) causes congenital Zika syndrome (CZS), which is characterized by fetal demise, microcephaly and other abnormalities. ZIKV in the pregnant woman circulation must cross the placental barrier that includes fetal endothelial cells and trophoblasts, in order to reach the fetus. CZS occurs in ~1-40% of cases of pregnant women infected by ZIKV, suggesting that mothers' infection by ZIKV during pregnancy is not deterministic for CZS phenotype in the fetus. Therefore, other susceptibility factors might be involved, including the host genetic background. We have previously shown that in three pairs of dizygotic twins discordant for CZS, neural progenitor cells (NPCs) from the CZS-affected twins presented differential in vitro ZIKV susceptibility compared with NPCs from the non-affected. Here, we analyzed human-induced-pluripotent-stem-cell-derived (hiPSC-derived) trophoblasts from these twins and compared by RNA-Seq the trophoblasts from CZS-affected and non-affected twins. Following in vitro exposure to a Brazilian ZIKV strain (ZIKVBR), trophoblasts from CZS-affected twins were significantly more susceptible to ZIKVBR infection when compared with trophoblasts from the non-affected. Transcriptome profiling revealed no differences in gene expression levels of ZIKV candidate attachment factors, IFN receptors and IFN in the trophoblasts, either before or after ZIKVBR infection. Most importantly, ZIKVBR infection caused, only in the trophoblasts from CZS-affected twins, the downregulation of genes related to extracellular matrix organization and to leukocyte activation, which are important for trophoblast adhesion and immune response activation. In addition, only trophoblasts from non-affected twins secreted significantly increased amounts of chemokines RANTES/CCL5 and IP10 after infection with ZIKVBR. Overall, our results showed that trophoblasts from non-affected twins have the ability to more efficiently activate genes that are known to play important roles in cell adhesion and in triggering the immune response to ZIKV infection in the placenta, and this may contribute to predict protection from ZIKV dissemination into fetuses' tissues.

Zika circulation, congenital syndrome, and current guidelines: making sense of it all for the traveller

PURPOSE OF REVIEW

Zika virus (ZIKV) swept through the Americas and led to recognition of its neurotropism. Zika circulation elsewhere in the world, nonvector transmission including maternal-fetal/sexual/transfusion routes, and additional reports on congenital Zika syndrome (CZS) and Guillain-Barré syndrome (GBS) have been published.

RECENT FINDINGS

In 2018-2019, ZIKV transmission occurred in Cuba, India, and is suspected to appear sporadically in other countries. Maternal-fetal ZIKV transmission appears to occur in about 26% of ZIKV-infected pregnant women. The US ZIKV Pregnancy and Infant Registry identified 6% of live births to have at least one ZIKV-associated birth defect; 9% had at least one neurodevelopmental abnormality; 1% had both. Infectious virus was rarely isolated from semen of ZIKV-infected male patients beyond day 38 after symptom onset. Brazilian blood donations had low ZIKV prevalence in 2015-2016; in the United States, screening donations was cost-effective only in the high mosquito season in Puerto Rico.

SUMMARY

ZIKV transmission continues; many countries with competent mosquitoes are at risk. Transmission can occur without detection where surveillance is poor and laboratory capacity limited. Travelers are important sentinels. Variations exist among ZIKV strains and Aedes mosquitoes that influence competence for transmission. Maternal-fetal transmission results in significant rates of abnormality. Identification of infectious virus in semen clarifies sexual transmission risk, with updated recommendations for preconception planning. ZIKV neurotropism requires further research and long-term follow-up.

A global lipid map defines a network essential for Zika virus replication

Zika virus (ZIKV), an arbovirus of global concern, remodels intracellular membranes to form replication sites. How ZIKV dysregulates lipid networks to allow this, and consequences for disease, is poorly understood. Here, we perform comprehensive lipidomics to create a lipid network map during ZIKV infection. We find that ZIKV significantly alters host lipid composition, with the most striking changes seen within subclasses of sphingolipids. Ectopic expression of ZIKV NS4B protein results in similar changes, demonstrating a role for NS4B in modulating sphingolipid pathways. Disruption of sphingolipid biosynthesis in various cell types, including human neural progenitor cells, blocks ZIKV infection. Additionally, the sphingolipid ceramide redistributes to ZIKV replication sites, and increasing ceramide levels by multiple pathways sensitizes cells to ZIKV infection. Thus, we identify a sphingolipid metabolic network with a critical role in ZIKV replication and show that ceramide flux is a key mediator of ZIKV infection.

Immunopathology of Zika virus infection

Zika virus (ZIKV) is a mosquito-borne virus of the flavivirus genus in the Flaviviridae family. Flaviviruses are single-stranded, positive-sense RNA viruses that have been responsible for numerous human epidemics. Notable flaviviruses include mosquito-borne viruses such as yellow fever virus (YFV), Dengue virus (DENV), West Nile virus (WNV), Japanese encephalitis virus (JEV), as well as tick-borne viruses including Powassan virus (POWV) and tick-borne encephalitis virus (TBEV). Despite having been relatively obscure until the past decade, ZIKV has become a major global health concern, and is a topic of active research following multiple outbreaks across the globe. Here, we discuss ZIKV pathogenesis and the associated immunopathology, as well as advances in research, therapies, and vaccines developed using models of ZIKV pathogenesis.

Phylogenetic and genetic analyses of the emerging Nipah virus from bats to humans

Little is known about the genetic features of Nipah virus (NiV) associated with virulence and transmission. Herein, phylogenetic and genetic analyses for all available NiV strains revealed sequence variations between the two genetic lineages of NiV with pathogenic differences, as well as among different strains within Bangladesh lineage. A total of 143 conserved amino acid differences, distributed among viral nucleocapsid (N), phosphoprotein (P), matrix protein (M), fusion protein (F) and glycoprotein (G), were revealed. Structural modeling revealed one key substitution (S3554N) in the viral G protein that might mediate a 12-amino-acid structural change from a loop into a β sheet. Multiple key amino acids substitutions in viral G protein were observed, which may alter viral fitness and transmissibility from bats to humans.

A direct-acting antiviral drug abrogates viremia in Zika virus-infected rhesus macaques

Zika virus infection in humans has been associated with serious reproductive and neurological complications. At present, no protective antiviral drug treatment is available. Here, we describe the testing and evaluation of the antiviral drug, galidesivir, against Zika virus infection in rhesus macaques. We conducted four preclinical studies in rhesus macaques to assess the safety, antiviral efficacy, and dosing strategies for galidesivir (BCX4430) against Zika virus infection. We treated 70 rhesus macaques infected by various routes with the Puerto Rico or Thai Zika virus isolates. We evaluated galidesivir administered as early as 90 min and as late as 72 hours after subcutaneous Zika virus infection and as late as 5 days after intravaginal infection. We evaluated the efficacy of a range of galidesivir doses with endpoints including Zika virus RNA in plasma, saliva, urine, and cerebrospinal fluid. Galidesivir dosing in rhesus macaques was safe and offered postexposure protection against Zika virus infection. Galidesivir exhibited favorable pharmacokinetics with no observed teratogenic effects in rats or rabbits at any dose tested. The antiviral efficacy of galidesivir observed in the blood and central nervous system of infected animals warrants continued evaluation of this compound for the treatment of flaviviral infections.

A Molecular Determinant of West Nile Virus Secretion and Morphology as a Target for Viral Attenuation

West Nile virus (WNV) is a worldwide (re)emerging mosquito-transmitted Flavivirus causing fatal neurological diseases in humans. However, no human vaccine has been yet approved. One of the most effective live-attenuated vaccines was empirically obtained by serial passaging of wild-type yellow fever Flavivirus. However, such an approach is not acceptable nowadays, and the development of a rationally designed vaccine is necessary. Generating molecular infectious clones and mutating specific residues known to be involved in Flavivirus virulence constitute a powerful tool to promote viral attenuation. WNV membrane glycoprotein is thought to carry such essential determinants. Here, we identified two residues of this protein whose substitutions are key to the full and stable attenuation of WNV in vivo, most likely through inhibition of secretion and possible alteration of morphology. Applied to other flaviviruses, this approach should help in designing new vaccines against these viruses, which are an increasing threat to global human health.

West Nile virus (WNV), a member of the Flavivirus genus and currently one of the most common arboviruses worldwide, is associated with severe neurological disease in humans. Its high potential to reemerge and rapidly disseminate makes it a bona fide global public health problem. The surface membrane glycoprotein (M) has been associated with Flavivirus-induced pathogenesis. Here, we identified a key amino acid residue at position 36 of the M protein whose mutation impacts WNV secretion and promotes viral attenuation. We also identified a compensatory site at position M-43 whose mutation stabilizes M-36 substitution both in vitro and in vivo. Moreover, we found that introduction of the two mutations together confers a full attenuation phenotype and protection against wild-type WNV lethal challenge, eliciting potent neutralizing-antibody production in mice. Our study thus establishes the M protein as a new viral target for rational design of attenuated WNV strains.

IMPORTANCE West Nile virus (WNV) is a worldwide (re)emerging mosquito-transmitted Flavivirus causing fatal neurological diseases in humans. However, no human vaccine has been yet approved. One of the most effective live-attenuated vaccines was empirically obtained by serial passaging of wild-type yellow fever Flavivirus. However, such an approach is not acceptable nowadays, and the development of a rationally designed vaccine is necessary. Generating molecular infectious clones and mutating specific residues known to be involved in Flavivirus virulence constitute a powerful tool to promote viral attenuation. WNV membrane glycoprotein is thought to carry such essential determinants. Here, we identified two residues of this protein whose substitutions are key to the full and stable attenuation of WNV in vivo, most likely through inhibition of secretion and possible alteration of morphology. Applied to other flaviviruses, this approach should help in designing new vaccines against these viruses, which are an increasing threat to global human health.

Comparative analysis of a Thai congenital-Zika-syndrome-associated virus with a Thai Zika-fever-associated virus

In this study, we compared the characteristics of two strains of Zika virus (ZIKV) isolated in Thailand, one isolated from a febrile patient and one isolated from tissues of a fetus medically terminated due to congenital Zika syndrome (CZS). Replication profiles showed that the isolate from the fetal tissues replicated significantly more slowly than the fever-associated isolate in human lung A549 cells during the first 24 hours postinfection but showed a similar growth profile over longer-term infection. A much smaller difference was observed in Aedes albopictus C6/36 cells. In a quasispecies analysis, a high proportion (approximately 20%) of nonfunctional genomes was identified, caused by an adenine insertion in the prM gene. This insertion was found to be present in two Thai fever strains and as such may represent a common feature of Thai endemic ZIKV. Comparison between viral RNA copy number and viral titer showed that the isolate from fetal tissues was produced more efficiently than the fever-associated isolate. Together, these results suggest that different ZIKV isolates differ in their replication capacity, and this might contribute to the fetotropic potential of a particular strain.

Microscopy analysis of Zika virus morphogenesis in mammalian cells

Zika virus (ZIKV) is an arbovirus that recently emerged in the Americas as an important pathogen mainly because of its expanded pathogenesis, and elevated tropism for neuronal cells, transposition across the placental barrier, and replication in reproductive tract cells. Thus, transmission modes are eventually independent of an invertebrate vector, which is an atypical behavior for the flavivirus genus and indicates the need to study the replication of this virus in different cell types. Although ZIKV became a target for public health programs, the interaction of this flavivirus with the infected cell is still poorly understood. Herein, we analyzed the main stages of virus morphogenesis in mammalian cells, from establishment of the viroplasm-like zone to viral release from infected cells, using super-resolution fluorescence microscopy and electron microscopy. In addition, we compared this with other host cell types and other members of the Flaviviridae family that present a similar dynamic.

Maternal Zika Virus (ZIKV) Infection following Vaginal Inoculation with ZIKV-Infected Semen in Timed-Pregnant Olive Baboons

Zika virus (ZIKV) infection is now firmly linked to congenital Zika syndrome (CZS), including fetal microcephaly. While Aedes species of mosquito are the primary vector for ZIKV, sexual transmission of ZIKV is a significant route of infection. ZIKV has been documented in human, mouse, and nonhuman primate (NHP) semen. It is critical to establish NHP models of the vertical transfer of ZIKV that recapitulate human pathogenesis. We hypothesized that vaginal deposition of ZIKV-infected baboon semen would lead to maternal infection and vertical transfer in the olive baboon (Papio anubis). Epidemiological studies suggest an increased rate of CZS in the Americas compared to the original link to CZS in French Polynesia; therefore, we also compared the French Polynesian (FP) ZIKV isolate to the Puerto Rican (PR) isolate. Timed-pregnant baboons (n = 6) were inoculated via vaginal deposition of baboon semen containing 10⁶ focus-forming units (FFU) of ZIKV (n = 3 for FP isolate H/PF/2013; n = 3 for PR isolate PRVABC59) at midgestation (86 to 95 days of gestation [dG]; term, 183 dG) on day 0 (all dams) and then at 7-day intervals through 3 weeks. Maternal blood, saliva, and cervicovaginal wash (CVW) samples were obtained. Animals were euthanized at 28 days (n = 5) or 39 days (n = 1) after the initial inoculation, and maternal/fetal tissues were collected. Viremia was achieved in 3/3 FP ZIKV-infected dams and 2/3 PR ZIKV-infected dams. ZIKV RNA was detected in CVW samples of 5/6 dams. ZIKV RNA was detected in lymph nodes but not the ovaries, uterus, cervix, or vagina in FP isolate-infected dams. ZIKV RNA was detected in lymph nodes (3/3), uterus (2/3), and vagina (2/3) in PR isolate-infected dams. Placenta, amniotic fluid, and fetal tissues were ZIKV RNA negative in the FP isolate-infected dams, whereas 2/3 PR isolate-infected dam placentas were ZIKV RNA positive. We conclude that ZIKV-infected semen is a means of ZIKV transmission during pregnancy in primates. The PR isolate appeared more capable of widespread dissemination to tissues, including reproductive tissues and placenta, than the FP isolate.IMPORTANCE Zika virus remains a worldwide health threat, with outbreaks still occurring in the Americas. While mosquitos are the primary vector for the spread of the virus, sexual transmission of Zika virus is also a significant means of infection, especially in terms of passage from an infected to an uninfected partner. While sexual transmission has been documented in humans, and male-to-female transmission has been reported in mice, ours is the first study in nonhuman primates to demonstrate infection via vaginal deposition of Zika virus-infected semen. The latter is important since a recent publication indicated that human semen inhibited, in a laboratory setting, Zika virus infection of reproductive tissues. We also found that compared to the French Polynesian isolate, the Puerto Rican Zika virus isolate led to greater spread throughout the body, particularly in reproductive tissues. The American isolates of Zika virus appear to have acquired mutations that increase their efficacy.

In vivo imaging of Zika virus reveals dynamics of viral invasion in immune-sheltered tissues and vertical propagation during pregnancy

Rationale: Zika virus (ZIKV) is a pathogenic virus known to cause a wide range of congenital abnormalities, including microcephaly, Guillain-Barre syndrome, meningoencephalitis, and other neurological complications, in humans. This study investigated the noninvasive detection of ZIKV infection in vivo, which is necessary for elucidating the virus's mechanisms of viral replication and pathogenesis, as well as to accelerate the development of anti-ZIKV therapeutic strategies.

Methods: In this study, a recombinant ZIKV harbouring Nluc gene (ZIKV-Nluc) was designed, recovered, and purified. The levels of bioluminescence were directly correlated with viral loads in vitro and in vivo. The dynamics of ZIKV infection in A129 (interferon (IFN)-α/β receptor deficient), AG6 (IFN-α/β and IFN-γ receptor deficient), and C57BL/6 mice were characterized. Pregnant dams were infected with ZIKV-Nluc at E10 via intra footpad injection. Then, the pooled immune sera (anti-ZIKV neutralizing antibodies) #22-1 in ZIKV-Nluc virus-infected mice were visualized.

Results: ZIKV-Nluc showed a high genetic stability and replicated well in cells with similar properties to the wild-type ZIKV (ZIKVwt). Striking bioluminescence signals were consistently observed in animal organs, including spleen, intestine, testis, uterus/ovary, and kidney. The ileocecal junction was found to be the crucial visceral target. Infection of pregnant dams with ZIKV-Nluc showed that ZIKV was capable of crossing the maternal-fetal barrier to infect the fetuses via vertical transmission. Furthermore, it was visualized that treatment with the pooled immune sera was found to greatly restrict the spread of the ZIKV-Nluc virus in mice.

Conclusions: This study is the first to report the real-time noninvasive tracking of the progression of ZIKV invading immune-sheltered tissues and propagating vertically during pregnancy. The results demonstrate that ZIKV-Nluc represents a powerful tool for the study of the replication, dissemination, pathogenesis, and treatment of ZIKV in vitro and in vivo.

Immune-profiling of ZIKV-infected patients identifies a distinct function of plasmacytoid dendritic cells for immune cross-regulation

Zika virus (ZIKV) is a mosquito-borne pathogen with increasing public health significance. To characterize immune responses to ZIKV, here we examine transcriptional signatures of CD4 T, CD8 T, B, and NK cells, monocytes, myeloid dendritic cells (mDCs), and plasmacytoid dendritic cells (pDCs) from three individuals with ZIKV infection. While gene expression patterns from most cell subsets display signs of impaired antiviral immune activity, pDCs from infected host have distinct transcriptional response associated with activation of innate immune recognition and type I interferon signaling pathways, but downregulation of key host factors known to support ZIKV replication steps; meanwhile, pDCs exhibit a unique expression pattern of gene modules that are correlated with alternative cell populations, suggesting collaborative interactions between pDCs and other immune cells, particularly B cells. Together, these results point towards a discrete but integrative function of pDCs in the human immune responses to ZIKV infection.

The continued threat of emerging flaviviruses

Flaviviruses are vector-borne RNA viruses that can emerge unexpectedly in human populations and cause a spectrum of potentially severe diseases including hepatitis, vascular shock syndrome, encephalitis, acute flaccid paralysis, congenital abnormalities and fetal death. This epidemiological pattern has occurred numerous times during the last 70 years, including epidemics of dengue virus and West Nile virus, and the most recent explosive epidemic of Zika virus in the Americas. Flaviviruses are now globally distributed and infect up to 400 million people annually. Of significant concern, outbreaks of other less well-characterized flaviviruses have been reported in humans and animals in different regions of the world. The potential for these viruses to sustain epidemic transmission among humans is poorly understood. In this Review, we discuss the basic biology of flaviviruses, their infectious cycles, the diseases they cause and underlying host immune responses to infection. We describe flaviviruses that represent an established ongoing threat to global health and those that have recently emerged in new populations to cause significant disease. We also provide examples of lesser-known flaviviruses that circulate in restricted areas of the world but have the potential to emerge more broadly in human populations. Finally, we discuss how an understanding of the epidemiology, biology, structure and immunity of flaviviruses can inform the rapid development of countermeasures to treat or prevent human infections as they emerge.

Environmental risk assessment (ERA) of pyriproxyfen in non-target aquatic organisms

Pyriproxyfen (PPF) is a synthetic substance and an insect juvenile hormone agonist with growth regulating effect. It is used worldwide as a pesticide in agriculture and public health campaigns, including the control of Aedes aegypti proliferation. It has low volatility, high Kow value and high lability in aerobic aquatic systems but is considered persistent in anaerobic systems, with a half-life of 288.9 days. The objective of this study is to survey the environmental contamination by pyriproxyfen in aquatic environmental matrices, to review the acute and chronic toxicity in non-target aquatic organisms and to make a risk assessment for the organisms addressed in the bibliographic survey. Pyriproxyfen quantification studies in aquatic environmental matrices are quite scarce and punctual-not representative of regional and global contamination. The water of the River Júcar (Spain) presented the highest concentration of PPF (99.59 ng L^-1) among the matrices analysed, which is equivalent to 1% of the maximum dose allowed by the World Health Organization for use in drinking water. Acute and chronic aquatic toxicity studies with LC50, EC50, LOEC and NOEC values of PPF were compiled and interpreted to evaluate possible risks to non-target aquatic organisms. Pyriproxyfen caused a high risk at concentrations detected in aquatic environments for Daphnia magna, with probable reproductive effects and occasional survival risk. This species was the most sensitive to the pesticide, with the lowest estimated concentration of 50 % of effect values, followed by a freshwater fish (Xiphophorus maculatus) and estuarine crustaceans (Eurytemora affinis and Leander tenuicornis). The most resistant organisms to PPF within the endpoints addressed in this review were Danio rerio (zebrafish) and Capitella sp. (polychaete). Through the species sensitivity distribution (SSD), it was possible to estimate HC5 at 0.214 μg L^-1 and that 2.3 % of the species present high sensitivity to pyriproxyfen in the environmental concentration detected in river water and 25.82 % of the species are affected in the concentration allowed for lavicidal use. In order to obtain more accurate risk estimates, we suggest ecotoxicological assessments in other species, covering various taxa, with emphasis on microcrustaceans due to their fundamental role in the aquatic food web and taxonomic proximity to pesticide target organisms. Furthermore, additional studies of contamination in aquatic environmental matrices are required, with particular attention to freshwater and estuarine environments due to the proximity to the sources of pyriproxyfen and environmental characteristics suggesting high accumulation. Thus, it will be possible to estimate realistic exposure levels and risks in different environments, contributing to effective and safe decision making, integrating development, public health and environmental policy.

Arboviruses: A global public health threat

A conference on «ARBOVIRUSES, A GLOBAL PUBLIC HEALTH THREAT» was organized on June 20–22, 2018 at the Merieux Foundation Conference Center in Veyrier du Lac, France, to review and raise awareness to the global public health threat of epidemic arboviruses, and to advance the discussion on the control and prevention of arboviral diseases. The presentations by scientists and public health officials from Asia, the Americas, Europe and Africa strengthened the notion that arboviral diseases of both humans and domestic animals are progressively becoming dominant public health problems in the world. The repeated occurrence of recent deadly epidemics strongly reinforces the call for action against these viral diseases, and the need for developing effective vaccines, drugs, vector control tools and strong prevention programs.

Current Efforts in the Development of Vaccines for the Prevention of Zika and Chikungunya Virus Infections

Arboviruses represent major challenges to public health, particularly in tropical, and subtropical regions, and a substantial risk to other parts of the world as respective vectors extend their habitats. In recent years, two viruses transmitted by Aedes mosquitoes, Chikungunya and Zika virus, have gathered increased interest. After decades of regionally constrained outbreaks, both viruses have recently caused explosive outbreaks on an unprecedented scale, causing immense suffering and massive economic burdens in affected regions. Chikungunya virus causes an acute febrile illness that often transitions into a chronic manifestation characterized by debilitating arthralgia and/or arthritis in a substantial subset of infected individuals. Zika infection frequently presents as a mild influenza-like illness, often subclinical, but can cause severe complications such as congenital malformations in pregnancy and neurological disorders, including Guillain-Barré syndrome. With no specific treatments or vaccines available, vector control remains the most effective measure to manage spread of these diseases. Given that both viruses cause antibody responses that confer long-term, possibly lifelong protection and that such responses are cross-protective against the various circulating genetic lineages, the development of Zika and Chikungunya vaccines represents a promising route for disease control. In this review we provide a brief overview on Zika and Chikungunya viruses, the etiology and epidemiology of the illnesses they cause and the host immune response against them, before summarizing past and current efforts to develop vaccines to alleviate the burden caused by these emerging diseases. The development of the urgently needed vaccines is hampered by several factors including the unpredictable epidemiology, feasibility of rapid clinical trial implementation during outbreaks and regulatory pathways. We will give an overview of the current developments.

Iminosugars With Endoplasmic Reticulum α-Glucosidase Inhibitor Activity Inhibit ZIKV Replication and Reverse Cytopathogenicity in vitro

Zika virus (ZIKV), a vector-borne virus of the family Flaviviridae, continues to spread and remains a significant global public health threat. Currently, there are no approved vaccines or antivirals against ZIKV. We investigated the anti-ZIKV ability of three iminosugars with endoplasmic reticulum α-glucosidase inhibitor (ER-AGI) activity, namely deoxynojirimycin (DNJ), castanospermine, and celgosivir. None of the three iminosugars showed any significant cytotoxicity in Vero or human microglia CHME3 cells when applied for 72 h at concentrations up to 100 μM. Iminosugar treatment of Vero or CHME3 cells prior to ZIKV infection resulted in significant inhibition of ZIKV replication over 48 h. Reduction in ZIKV replication in iminosugar-treated cells was not associated with any significant change in the expression levels of key antiviral genes. Following infection with three different strains of ZIKV, iminosugar-treated Vero or CHME3 cells showed no cell death, whereas vehicle-treated control cells exhibited 50–60% cell death at 72 h post-infection (hpi). While there was no significant difference in apoptosis between iminosugar-treated and control cells, iminosugar-treated cells exhibited a substantial reduction of necrosis at 72 hpi following ZIKV infection. In summary, iminosugars with ER-AGI activity inhibit ZIKV replication and significantly reduce necrosis without altering the antiviral gene expression and apoptosis of infected human cells. The results of this study strongly suggest that iminosugars are promising anti-ZIKV antiviral agents and such warrant further in vivo studies.

Genomic Epidemiology as a Public Health Tool to Combat Mosquito-Borne Virus Outbreaks

Next-generation sequencing technologies, exponential increases in the availability of virus genomic data, and ongoing advances in phylogenomic methods have made genomic epidemiology an increasingly powerful tool for public health response to a range of mosquito-borne virus outbreaks. In this review, we offer a brief primer on the scope and methods of phylogenomic analyses that can answer key epidemiological questions during mosquito-borne virus public health emergencies. We then focus on case examples of outbreaks, including those caused by dengue, Zika, yellow fever, West Nile, and chikungunya viruses, to demonstrate the utility of genomic epidemiology to support the prevention and control of mosquito-borne virus threats. We extend these case studies with operational perspectives on how to best incorporate genomic epidemiology into structured surveillance and response programs for mosquito-borne virus control. Many tools for genomic epidemiology already exist, but so do technical and nontechnical challenges to advancing their use. Frameworks to support the rapid sharing of multidimensional data and increased cross-sector partnerships, networks, and collaborations can support advancement on all scales, from research and development to implementation by public health agencies.

C19orf66 interrupts Zika virus replication by inducing lysosomal degradation of viral NS3

The rapidly emerging human health crisis associated with the Zika virus (ZIKV) epidemic and its link to severe complications highlights the growing need to identify the mechanisms by which ZIKV accesses hosts. Interferon response protects host cells against viral infection, while the cellular factors that mediate this defense are the products of interferon-stimulated genes (ISGs). Although hundreds of ISGs have been identified, only a few have been characterized for their antiviral potential, target specificity and mechanisms of action. In this work, we focused our investigation on the possible antiviral effect of a novel ISG, C19orf66 in response to ZIKV infection and the associated mechanisms. We found that ZIKV infection could induce C19orf66 expression in ZIKV-permissive cells, and such an overexpression of C19orf66 remarkably suppressed ZIKV replication. Conversely, the depletion of C19orf66 led to a significant increase in viral replication. Furthermore, C19orf66 was found to interact and co-localize with ZIKV nonstructural protein 3 (NS3), thus inducing NS3 degradation via a lysosome-dependent pathway. Taken together, this study identified C19orf66 as a novel ISG that exerts antiviral effects against ZIKV by specifically degrading a viral nonstructural protein. These findings uncovered an intriguing mechanism of C19orf66 that targeting NS3 protein of ZIKV, providing clues for understanding the actions of innate immunity, and affording the possible availability of new drug targets that can be used for therapeutic intervention.

ZIKV represents a serious threat to global health with particular relevance to microcephaly and other congenital abnormalities in newborns, and Guillain-Barré syndrome, meningoencephalitis, multi-organ failure in adults. Despite the global health threat of Zika virus infection, there is currently no vaccine or effective antiviral therapy available for the disease. As widely recognized, interferon signaling is key to establishing a strong antiviral state in host cells, mainly mediated through the anti-viral effects of numerous interferon-stimulated genes (ISGs). This work described our novel finding of the antiviral effect of a novel ISG, C19orf66, and its underlying mechanisms. We identified C19orf66 as a novel ISG that exerts antiviral effects against ZIKV by specifically interacting and colocalizing with the ZIKV nonstructural (NS) protein NS3, which inducing NS3 degradation via a lysosome-dependent pathway. Thus, this work broadens the understanding of the pivotal roles of C19orf66 in the interaction between the host and ZIKV, which might further provide a rational basis for developing novel anti-ZIKV strategies.

Patterns, Drivers, and Challenges of Vector-Borne Disease Emergence

Vector-borne diseases are emerging at an increasing rate and comprise a disproportionate share of all emerging infectious diseases. Yet, the key ecological and evolutionary dimensions of vector-borne disease that facilitate their emergence have not been thoroughly explored. This study reviews and synthesizes the existing literature to explore global patterns of emerging vector-borne zoonotic diseases (VBZDs) under changing global conditions. We find that the vast majority of emerging VBZDs are transmitted by ticks (Ixodidae) and mosquitoes (Culicidae) and the pathogens transmitted are dominated by Rickettsiaceae bacteria and RNA viruses (Flaviviridae, Bunyaviridae, and Togaviridae). The most common potential driver of these emerging zoonoses is land use change, but for many diseases, the driver is unknown, revealing a critical research gap. While most reported VBZDs are emerging in the northern latitudes, after correcting for sampling bias, Africa is clearly a region with the greatest share of emerging VBZD. We highlight critical gaps in our understanding of VBZD emergence and emphasize the importance of interdisciplinary research and consideration of deeper evolutionary processes to improve our capacity for anticipating where and how such diseases have and will continue to emerge.

Pluripotent Stem Cell-Based Models: A Peephole into Virus Infections during Early Pregnancy

The rubella virus (RV) was the first virus shown to be teratogenic in humans. The wealth of data on the clinical symptoms associated with congenital rubella syndrome is in stark contrast to an incomplete understanding of the forces leading to the teratogenic alterations in humans. This applies not only to RV, but also to congenital viral infections in general and includes (1) the mode of vertical transmission, even at early gestation, (2) the possible involvement of inflammation as a consequence of an activated innate immune response, and (3) the underlying molecular and cellular alterations. With the progress made in the development of pluripotent stem cell-based models including organoids and embryoids, it is now possible to assess congenital virus infections on a mechanistic level. Moreover, antiviral treatment options can be validated, and newly emerging viruses with a potential impact on human embryonal development, such as that recently reflected by the Zika virus (ZIKV), can be characterized. Here, we discuss human cytomegalovirus (HCMV) and ZIKV in comparison to RV as viruses with well-known congenital pathologies and highlight their analysis on current models for the early phase of human development. This includes the implications of their genetic variability and, as such, virus strain-specific properties for their use as archetype models for congenital virus infections. In this review, we will discuss the use of induced pluripotent stem cells (iPSC) and derived organoid systems for the study of congenital virus infections with a focus on their prominent aetiologies, HCMV, ZIKV, and RV. Their assessment on these models will provide valuable information on how human development is impaired by virus infections; it will also add new insights into the normal progression of human development through the analysis of developmental pathways in the context of virus-induced alterations. These are exciting perspectives for both developmental biology and congenital virology.

ZIKV-Specific NS1 Epitopes as Serological Markers of Acute Zika Virus Infection

BACKGROUND

Zika virus (ZIKV) infections have reemerged as a global health issue due to serious clinical complications. Development of specific serological assays to detect and differentiate ZIKV from other cocirculating flaviviruses for accurate diagnosis remains a challenge.

METHODS

We investigated antibody responses in 51 acute ZIKV-infected adult patients from Campinas, Brazil, including 7 pregnant women who later delivered during the study. Using enzyme-linked immunosorbent assays, levels of antibody response were measured and specific epitopes identified.

RESULTS

Several antibody-binding hot spots were identified in ZIKV immunogenic antigens, including membrane, envelope (E) and nonstructural protein 1 (NS1). Interestingly, specific epitopes (2 from E and 2 from NS1) strongly recognized by ZIKV-infected patients' antibodies were identified and were not cross-recognized by dengue virus (DENV)-infected patients' antibodies. Corresponding DENV peptides were not strongly recognized by ZIKV-infected patients' antibodies. Notably, ZIKV-infected pregnant women had specific epitope recognition for ZIKV NS1 (amino acid residues 17-34), which could be a potential serological marker for early ZIKV detection.

CONCLUSIONS

This study identified 6 linear ZIKV-specific epitopes for early detection of ZIKV infections. We observed differential epitope recognition between ZIKV-infected and DENV-infected patients. This information will be useful for developing diagnostic methods that differentiate between closely related flaviviruses.

Maternal-Fetal Interplay in Zika Virus Infection and Adverse Perinatal Outcomes

During pregnancy, the organization of complex tolerance mechanisms occurs to assure non-rejection of the semiallogeneic fetus. Pregnancy is a period of vulnerability to some viral infections, mainly during the first and second trimesters, that may cause congenital damage to the fetus. Recently, Zika virus (ZIKV) infection has gained great notoriety due to the occurrence of congenital ZIKV syndrome, characterized by fetal microcephaly, which results from the ability of ZIKV to infect placental cells and neural precursors in the fetus. Importantly, in addition to the congenital effects, studies have shown that perinatal ZIKV infection causes a number of disorders, including maculopapular rash, conjunctivitis, and arthralgia. In this paper, we contextualize the immunological aspects involved in the maternal-fetal interface and vulnerability to ZIKV infection, especially the alterations resulting in perinatal outcomes. This highlights the need to develop protective maternal vaccine strategies or interventions that are capable of preventing fetal or even neonatal infection.

Intrinsically disordered protein domains in flavivirus infection

Intrinsically disordered protein regions are at the core of biological processes and involved in key protein-ligand interactions. The Flavivirus proteins, of viruses of great biomedical importance such as Zika and dengue viruses, exemplify this. Several proteins of these viruses have disordered regions that are of the utmost importance for biological activity. Disordered proteins can adopt several conformations, each able to interact with and/or bind to different ligands. In fact, such interactions can help stabilize a particular fold. Moreover, by being promiscuous in the number of target molecules they can bind to, these protein regions increase the number of functions that their small proteome (10 proteins) can achieve. A folding energy waterfall better describes the protein folding landscape of these proteins. A disordered protein can be thought as rolling down the folding energy cascade, in order "to fall, fold and function". This is the case of many viral protein regions, as seen in the flaviviruses proteome. Given their small size, flaviviruses are a good model system for understanding the role of intrinsically disordered protein regions in viral function. Finally, studying these viruses disordered protein regions will certainly contribute to the development of therapeutic approaches against such promising (yet challenging) targets.

Combining genomics and epidemiology to track mumps virus transmission in the United States

Unusually large outbreaks of mumps across the United States in 2016 and 2017 raised questions about the extent of mumps circulation and the relationship between these and prior outbreaks. We paired epidemiological data from public health investigations with analysis of mumps virus whole genome sequences from 201 infected individuals, focusing on Massachusetts university communities. Our analysis suggests continuous, undetected circulation of mumps locally and nationally, including multiple independent introductions into Massachusetts and into individual communities. Despite the presence of these multiple mumps virus lineages, the genomic data show that one lineage has dominated in the US since at least 2006. Widespread transmission was surprising given high vaccination rates, but we found no genetic evidence that variants arising during this outbreak contributed to vaccine escape. Viral genomic data allowed us to reconstruct mumps transmission links not evident from epidemiological data or standard single-gene surveillance efforts and also revealed connections between apparently unrelated mumps outbreaks.

Sequencing of ZIKV genomes directly from Ae. aegypti and Cx. quinquefasciatus mosquitoes collected during the 2015-16 epidemics in Recife

Zika virus (ZIKV) is a negative sense RNA virus from the Flaviviridae family, which was relatively unknown until the first human epidemic in Micronesia, in 2007. Since then, it spread to French Polynesia and the Americas. Recife, the capital of Pernambuco state and epicenter of the Zika epidemic in Brazil, experienced a large number of microcephaly cases and other congenital abnormalities associated to the ZIKV infection from, 2015 to 16. Evidences suggest that both Aedes aegypti and Culex quinquefasciatus mosquitoes from Recife are capable of replicating and transmitting the virus. Here, we conducted high throughput sequencing of ZIKV genomes directly from Ae. aegypti and Cx. quinquefasciatus mosquitoes collected during the ZIKV epidemics in Recife, in order to investigate the variability and evolution of the virus. We obtained 11 draft ZIKV genomes derived from 5 pools from each Ae. aegypti and Cx. quinquefasciatus species. Genome coverage breadth ranged from 16 to 100% and average depth from 45 to 46,584×. Two of these genomes were obtained from pools of Cx. quinquefasciatus females with no sign of blood in the abdomen. Amino acid substitutions found here were not species-specific. In addition, molecular clock dating estimated that ZIKV draft genomes obtained here were co-circulating in other regions of the country during the epidemics. Overall results highlight that viral mutations and even minor variants can be detected in genomes directly sequenced from mosquito samples and insights about natural viral genomic variability and viral evolution can be useful when designing tools for mosquito control programs.

The evolution of Zika virus from Asia to the Americas

Zika virus (ZIKV) was once considered an obscure member of the large and diverse family of mosquito-borne flaviviruses, and human infections with ZIKV were thought to be sporadic, with mild and self-limiting symptoms. The large-scale ZIKV epidemics in the Americas and the unexpected uncovering of a link to congenital birth defects escalated ZIKV infections to the status of a global public health emergency. Recent studies that combined reverse genetics with modelling in multiple systems have provided evidence that ZIKV has acquired additional amino acid substitutions at the same time as congenital Zika syndrome and other birth defects were detected. In this Progress article, we summarize the evolution of ZIKV during its spread from Asia to the Americas and discuss potential links to pathogenesis.

A natural polymorphism in Zika virus NS2A protein responsible of virulence in mice

Zika virus (ZIKV) infection is currently one of the major concerns in human public health due to its association with neurological disorders. Intensive effort has been implemented for the treatment of ZIKV, however there are not currently approved vaccines or antivirals available to combat ZIKV infection. In this sense, the identification of virulence factors associated with changes in ZIKV virulence could help to develop safe and effective countermeasures to treat ZIKV or to prevent future outbreaks. Here, we have compared the virulence of two related ZIKV strains from the recent outbreak in Brazil (2015), Rio Grande do Norte Natal (RGN) and Paraiba. In spite of both viruses being identified in the same period of time and region, significant differences in virulence and replication were observed using a validated mouse model of ZIKV infection. While ZIKV-RGN has a 50% mouse lethal dose (MLD50) of ~105 focus forming units (FFUs), ZIKV-Paraiba infection resulted in 100% of lethality with less than 10 FFUs. Combining deep-sequencing analysis and our previously described infectious ZIKV-RGN cDNA clone, we identified a natural polymorphism in the non-structural protein 2 A (NS2A) that increase the virulence of ZIKV. Moreover, results demonstrate that the single amino acid alanine to valine substitution at position 117 (A117V) in the NS2A was sufficient to convert the attenuated rZIKV-RGN in a virulent Paraiba-like virus (MLD50 < 10 FFU). The mechanism of action was also evaluated and data indicate that substitution A117V in ZIKV NS2A protein reduces host innate immune responses and viral-induced apoptosis in vitro. Therefore, amino acid substitution A117V in ZIKV NS2A could be used as a genetic risk-assessment marker for future ZIKV outbreaks.

Zika Virus Infection in the Developing Mouse Produces Dramatically Different Neuropathology Dependent on Viral Strain

Zika virus (ZIKV) infection during pregnancy has been causally linked to a constellation of neurodevelopmental deformities in the fetus resulting in a disease termed congenital Zika syndrome (CZS). Here we detail how ZIKV infection produces extensive neuropathology in the developing mouse brain and spinal cord of both sexes. Surprisingly, neuropathology differs depending on viral strain with a French Polynesian isolate producing primarily excitotoxicity and a Brazilian isolate being almost exclusively apoptotic but occurring over a prolonged period that is more likely to produce severe hypoplasia. We also show exposure can produce a characteristic pattern of infection that mirrors neuropathology and ultimately results in gross morphological deformities strikingly similar to CZS. This research provides a valuable mouse model mirroring the clinical course of disease that can be used to test potential therapies to improve treatment and gain a better understanding of the disabilities associated with CZS.SIGNIFICANCE STATEMENT Zika virus (ZIKV) infection during pregnancy has been causally linked to a constellation of neurodevelopmental deformities in the fetus resulting in a disease termed congenital Zika syndrome. Despite its devastating effects, very little is known about how ZIKV infection produces fetal neuropathology. Here we detail the temporal progression of ZIKV infection in the mouse brain and spinal cord resulting in massive neurodegeneration of infected regions. We also report a ZIKV strain from a region of Brazil with high levels of microcephaly (abnormally small head circumference) produces particularly devastating neuropathology.

Inter- and intra-lineage genetic diversity of wild-type Zika viruses reveals both common and distinctive nucleotide variants and clusters of genomic diversity

Zika virus (ZIKV) strains belong to the East African, West African, and Asian/American phylogenetic lineages. RNA viruses, like ZIKV, exist as populations of genetically-related sequences whose heterogeneity may impact viral fitness, evolution, and virulence. Genetic diversity of representative ZIKVs from each lineage was examined using next generation sequencing (NGS) paired with downstream entropy and single nucleotide variant (SNV) analysis. Comparisons showed that inter-lineage diversity was statistically supported, while intra-lineage diversity. Intra-lineage diversity was significant for East but not West Africa strains. Furthermore, intra-lineage diversity for the Asian/American lineage was not supported for human serum isolates; however, a placenta isolate differed significantly. Relative in the pre-membrane/membrane (prM/M) gene of several ZIKV strains. Additionally, the East African lineage contained a greater number of synonymous SNVs, while a greater number of non-synonymous SNVs were identified for American strains. Further, inter-lineage SNVs were dispersed throughout the genome, whereas intra-lineage non-synonymous SNVs for Asian/American strains clustered within prM/M and NS1 gene. This comprehensive analysis of ZIKV genetic diversity provides a repository of SNV positions across lineages. We posit that increased non-synonymous SNV populations and increased relative genetic diversity of the prM/M and NS1 proteins provides more evidence for their role in ZIKV virulence and fitness.

Characteristics of Zika virus infection among international travelers: A prospective study from a Spanish referral unit

BACKGROUND

From the first Zika virus (ZIKV) description, it has progressively widespread worldwide. We analyzed demographic, clinical, microbiologic and travel-related characteristic from returned patients from a ZIKV endemic country in a referral Tropical Medicine Unit.

METHOD

A prospective cohort study performed in a Spanish referral center with the aim of determining the significant factors associated with confirmed Zika virus (ZIKV) infection.

RESULTS

817 patients, (56% women, median age 36 [IQR, Interquartile Range: 32-42]) were enrolled. Most had returned from Latin America (n = 486; 59.4%), travelled for tourism (n = 404; 49.4%) and stayed a median of 18 days (IQR: 10-30). 602 (73.6%) presented symptoms, but only 25 (4%) were finally diagnosed with confirmed ZIKV infection (including two pregnant women, without adverse fetal outcomes), 88% (n:22) presented with fever and 92% (n:23) with rash. 56% (n:14) arthralgia and/or myalgia and 28% (n:7) conjunctivitis. The presence of conjunctivitis, fever and rash were associated with an 8.9 (95% CI: 2.2-34.9), 6.4 (95% CI: 1.2-33.3) and 72.3 (95% CI: 9.2-563.5) times greater probability of confirmed ZIKV infection, respectively.

CONCLUSION

Travel characteristics and clinical presentation may help clinicians to optimize requests for microbiological testing. Diagnosis of arboviriasis in travellers arriving form endemic areas remains a challenge for clinicians, but must be detected for the possible transmission outside endemic areas, where the vector is present.

A Novel Mechanism for Zika Virus Host-Cell Binding

Zika virus (ZIKV) recently emerged in the Western Hemisphere with previously unrecognized or unreported clinical presentations. Here, we identify two putative binding mechanisms of ancestral and emergent ZIKV strains featuring the envelope (E) protein residue asparagine 154 (ASN154) and viral phosphatidylserine (PS). Synthetic peptides representing the region containing ASN154 from strains PRVABC59 (Puerto Rico 2015) and MR_766 (Uganda 1947) were exposed to neuronal cells and fibroblasts to model ZIKV E protein/cell interactions and bound MDCK or Vero cells and primary neurons significantly. Peptides significantly inhibited Vero cell infectivity by ZIKV strains MR_766 and PRVABC59, indicating that this region represents a putative binding mechanism of ancestral African ZIKV strains and emergent Western Hemisphere strains. Pretreatment of ZIKV strains MR_766 and PRVABC59 with the PS-binding protein annexin V significantly inhibited replication of PRVABC59 but not MR_766, suggesting that Western hemisphere strains may additionally be capable of utilizing PS-mediated entry to infect host cells. These data indicate that the region surrounding E protein ASN154 is capable of binding fibroblasts and primary neuronal cells and that PS-mediated entry may be a secondary mechanism for infectivity utilized by Western Hemisphere strains.

E and prM proteins of genotype V Japanese encephalitis virus are required for its increased virulence in mice

We previously showed that the Japanese encephalitis virus (JEV) genotype V (GV) strain Muar exhibits significantly higher virulence in mice than the genotype I (GI) JEV strain Mie/41/2002. In this study, we attempted to identify the region responsible for the increased virulence of GV JEV using recombinant intertypic and single mutant JEVs. Intertypic viruses containing the GV E region in the Mie/41/2002 backbone showed increased pathogenicity in mice. The amino acid at position 123 in the E protein (E123) of the Mie/41/2002 and GV JEVs was serine and histidine, respectively. A serine-to-histidine substitution at E123 of the Mie/41/2002 increased its virulence. However, histidine-to-serine changes at E123 in the intertypic mutants with the GV E region remained highly virulent. GV Muar prM-bearing mutants were also highly pathogenic in mice. Our results suggest that the E and prM proteins of GV JEV are responsible for the highly virulent characteristics of GV JEV.

The African strain of Zika virus causes more severe in utero infection than Asian strain in a porcine fetal transmission model

Studies in mice showed that African Zika virus (ZIKV) strains cause more damage in embryos. These studies, however, were limited to the mouse-adapted African MR766 strain or infection at early gestation. Here, we compared infection of Asian and African strains in the fetal pig model at midgestation. Both strains caused fetal infection. ZIKV was detected in placenta, amniotic membrane, amniotic fluid, fetal blood, and brain. The African strain produced more vigorous in utero infection as represented by more efficient virus transmission between siblings, and higher viral loads in fetal organs and membranes. Infection with both strains was associated with reduced fetal brain weight and increased number of placental CD163-positive cells, as well as elevated in utero interferon alpha and cortisol levels. This is the first large animal model study which demonstrated that African strain of ZIKV, with no passage history in experimental animals, can cause persistent infection in fetuses and fetal membranes at midgestation. Our studies also suggest that similar to Asian strains, ZIKV of African lineage might cause silent pathology which is difficult to identify in deceptively healthy fetuses. The findings emphasize the need for further studies to highlight the impact of ZIKV heterogeneity on infection outcomes during pregnancy.

Long non-coding subgenomic flavivirus RNAs have extended 3D structures and are flexible in solution

Most mosquito-borne flaviviruses, including Zika virus (ZIKV), Dengue virus (DENV), and West Nile virus (WNV), produce long non-coding subgenomic RNAs (sfRNAs) in infected cells that link to pathogenicity and immune evasion. Until now, the structural characterization of these lncRNAs remains limited. Here, we studied the 3D structures of individual and combined subdomains of sfRNAs, and visualized the accessible 3D conformational spaces of complete sfRNAs from DENV2, ZIKV, and WNV by small angle X-ray scattering (SAXS) and computational modeling. The individual xrRNA1s and xrRNA2s adopt similar structures in solution as the crystal structure of ZIKV xrRNA1, and all xrRNA1-2s form compact structures with reduced flexibility. While the DB12 of DENV2 is extended, the DB12s of ZIKV and WNV are compact due to the formation of intertwined double pseudoknots. All 3' stem-loops (3'SLs) share similar rod-like structures. Complete sfRNAs are extended and sample a large conformational space in solution. Our work not only provides structural insight into the function of flavivirus sfRNAs, but also highlights strategies of visualizing other lncRNAs in solution by SAXS and computational methods.

The Rescue and Characterization of Recombinant, Microcephaly-Associated Zika Viruses as Single-Round Infectious Particles

Zika virus (ZIKV) is transmitted by Aedes mosquitoes and exhibits genetic variation with African and Asian lineages. ZIKV Natal RGN strain, an Asian-lineage virus, has been identified in brain tissues from fetal autopsy cases with microcephaly and is suggested to be a neurotropic variant. However, ZIKV Natal RGN strain has not been isolated; its biological features are not yet illustrated. This study rescued and characterized recombinant, single-round infectious particles (SRIPs) of the ZIKV Natal RGN strain using reverse genetic and synthetic biology techniques. The DNA-launched replicon of ZIKV Natal RGN was constructed and contains the EGFP reporter, lacks prM-E genes, and replicates under CMV promoter control. The peak in the ZIKV Natal RGN SRIP titer reached 6.25 × 10⁶ TCID50/mL in the supernatant of prM-E-expressing packaging cells 72 h post-transfection with a ZIKV Natal RGN replicon. The infectivity of ZIKV Natal RGN SRIPs has been demonstrated to correlate with the green florescence intensity of the EGFP reporter, the SRIP-induced cytopathic effect, and ZIKV’s non-structural protein expression. Moreover, ZIKV Natal RGN SRIPs effectively self-replicated in rhabdomyosarcoma/muscle, glioblastoma/astrocytoma, and retinal pigmented epithelial cells, displaying unique cell susceptibility with differential attachment activity. Therefore, the recombinant ZIKV Natal RGN strain was rescued as SRIPs that could be used to elucidate the biological features of a neurotropic strain regarding cell tropism and pathogenic components, apply for antiviral agent screening, and develop vaccine candidates.

Development of Universal and Lineage-Specific Primer Sets for Rapid Detection of the Zika Virus (ZIKV) in Blood and Urine Samples Using One-Step Reverse Transcription Loop-Mediated Isothermal Amplification (RT-LAMP)

Zika is a mosquito-borne disease that has been posing a significant threat to public health in recent years. The Zika virus (ZIKV), the causative agent of this disease, is classified into 2 distinct genetic lineages, namely Asian and African. While molecular nucleic acid analysis methods have been shown to be useful for the diagnosis of ZIKV infection, the development of assays based on one-step reverse transcription loop-mediated isothermal amplification (RT-LAMP) offers several advantages, such as shorter incubation times, ease of handling, and rapid detection. In this study, a universal LAMP primer set was developed to target conserved sequences of known ZIKV lineages. Additionally, the Af7462 and As1788 primer sets were designed based on LAMP-based single-nucleotide polymorphism (SNPs) typing for the specific detection of the African and Asian lineages. The developed RT-LAMP assays could specifically detect the African and Asian lineages of ZIKV, with a detection limit ranging from 0.17 FFU/mL to 2.3×10² FFU/mL. As ZIKV viremia ranges between 10² to 10⁶ PFU/mL or 10³ to 10⁶ copies/mL, the data indicate that the viremia range of clinical samples is within the detection range of our assay. Due to the high specificity and sensitivity, as well as the ease of use of our assay, it could potentially be used for early clinical diagnosis applications.

Dissecting the Toxic Effects of Zika Virus Proteins on Neural Progenitor Cells

The mechanisms by which Zika virus (ZIKV) disrupts neurogenesis and causes microcephaly are poorly understood. In this issue of Neuron, Li et al. (2019) demonstrate that ZIKV protease NS2B-NS3 heterodimers cleave Septin-2 and lead to cytokinesis defects.