Zika Virus in the Americas--Yet Another Arbovirus Threat

Cross-reactive antibodies enhance live attenuated virus infection for increased immunogenicity

Vaccination has achieved remarkable successes in the control of childhood viral diseases. To control emerging infections, however, vaccines will need to be delivered to older individuals who, unlike infants, probably have had prior infection or vaccination with related viruses and thus have cross-reactive antibodies against the vaccines. Whether and how these cross-reactive antibodies impact live attenuated vaccination efficacy is unclear. Using an open-label randomized trial design, we show that subjects with a specific range of cross-reactive antibody titres from a prior inactivated Japanese encephalitis vaccination enhanced yellow fever (YF) immunogenicity upon YF vaccination. Enhancing titres of cross-reactive antibodies prolonged YF vaccine viraemia, provoked greater pro-inflammatory responses, and induced adhesion molecules intrinsic to the activating Fc-receptor signalling pathway, namely immune semaphorins, facilitating immune cell interactions and trafficking. Our findings clinically demonstrate antibody-enhanced infection and suggest that vaccine efficacy could be improved by exploiting cross-reactive antibodies.

ZikaVR: An Integrated Zika Virus Resource for Genomics, Proteomics, Phylogenetic and Therapeutic Analysis

Current Zika virus (ZIKV) outbreaks that spread in several areas of Africa, Southeast Asia, and in pacific islands is declared as a global health emergency by World Health Organization (WHO). It causes Zika fever and illness ranging from severe autoimmune to neurological complications in humans. To facilitate research on this virus, we have developed an integrative multi-omics platform; ZikaVR (http://bioinfo.imtech.res.in/manojk/zikavr/), dedicated to the ZIKV genomic, proteomic and therapeutic knowledge. It comprises of whole genome sequences, their respective functional information regarding proteins, genes, and structural content. Additionally, it also delivers sophisticated analysis such as whole-genome alignments, conservation and variation, CpG islands, codon context, usage bias and phylogenetic inferences at whole genome and proteome level with user-friendly visual environment. Further, glycosylation sites and molecular diagnostic primers were also analyzed. Most importantly, we also proposed potential therapeutically imperative constituents namely vaccine epitopes, siRNAs, miRNAs, sgRNAs and repurposing drug candidates.

New Paradigms for Virus Detection, Surveillance and Control of Zika Virus Vectors in the Settings of Southeast Asia

Zika virus (ZIKV) has now become a global public health concern. The vectors for ZIKV are Aedes aegypti and A. albopictus. Both these mosquitoes are predominant in Southeast Asia and are also responsible for the spread of other arboviral diseases like dengue virus and chikungunya virus. The incidence of dengue has been increasing over the years and this is of concern to public health workers. Simple laboratory tools for the detection of ZIKV is also lacking. In the absence of drugs and vaccine for these arboviral diseases, vector control is the main option for surveillance and control. Aedes larval surveys have been the hallmark of dengue control along with larviciding and fogging when cases are reported. However, we need new paradigms and options for control of these vectors. The current situation in Southeast Asia clearly proves that effective strategies for vector control need to be proactive and not reactive. This will be the way forward to control epidemics of these diseases inclusive of ZIKV until a vaccine becomes available.

Structures of NS5 Methyltransferase from Zika Virus

The Zika virus (ZIKV) poses a major public health emergency. To aid in the development of antivirals, we present two high-resolution crystal structures of the ZIKV NS5 methyltransferase: one bound to S-adenosylmethionine (SAM) and the other bound to SAM and 7-methyl guanosine diphosphate (7-MeGpp). We identify features of ZIKV NS5 methyltransferase that lend to structure-based antiviral drug discovery. Specifically, SAM analogs with functionalities on the Cβ atom of the methionine portion of the molecules that occupy the RNA binding tunnel may provide better specificity relative to human RNA methyltransferases.

Protective efficacy of multiple vaccine platforms against Zika virus challenge in rhesus monkeys

Zika virus (ZIKV) is responsible for a major ongoing epidemic in the Americas and has been causally associated with fetal microcephaly. The development of a safe and effective ZIKV vaccine is therefore an urgent global health priority. Here we demonstrate that three different vaccine platforms protect against ZIKV challenge in rhesus monkeys. A purified inactivated virus vaccine induced ZIKV-specific neutralizing antibodies and completely protected monkeys against ZIKV strains from both Brazil and Puerto Rico. Purified immunoglobulin from vaccinated monkeys also conferred passive protection in adoptive transfer studies. A plasmid DNA vaccine and a single-shot recombinant rhesus adenovirus serotype 52 vector vaccine, both expressing ZIKV premembrane and envelope, also elicited neutralizing antibodies and completely protected monkeys against ZIKV challenge. These data support the rapid clinical development of ZIKV vaccines for humans.

Zika Virus-Associated Microcephaly and Eye Lesions in the Newborn

On February 1, 2016, Zika virus (ZIKV) was designated as a Public Health Emergency of International Concern by the director of the World Health Organization. Zika virus has spread to numerous countries throughout the Americas, affecting up to an estimated 1.3 million people since the first reports from Brazil in early 2015. Although ZIKV infections are self-limiting, fetal microcephaly and ophthalmic anomalies have been associated with ZIKV infection as a possible result of perinatal transmission. The causal link between maternal ZIKV infection and newborn microcephaly and eye lesions has not been proven beyond doubt and is currently debated. We discuss the possibility of causality by ZIKV using Koch's postulates and the more appropriate Bradford Hill criteria. In this review, we summarize and consolidate the current literature on newborn microcephaly and eye lesions associated with ZIKV infection and discuss current perspectives and controversies.

Zika Virus: A Review of Management Considerations and Controversies at Six Months

Zika virus continues to pose a significant global health threat. While the outbreak pattern may seemingly mirror those of other arboviruses, unique transmission characteristics and clinical outcomes warrant a different approach to traditional public health practices. Sexual transmission and virus-associated fetal and nonfetal neurologic disorders specifically challenge conventional methods of disease protection and prevention with regard to vector control, disease surveillance, and health risk communication. The protocols for outbreak and case limitation led by the World Health Organization (in accordance with Public Health Emergency of International Concern declaration) may be augmented by localized risk categorization and assignment for Zika and future emergent outbreaks. There is currently a great deal of "behind the scenes" discussion about modifications to the formal process described in the International Health Regulations. A scalable, adaptable, and flexible process is needed that can be customized to a specific threat. (Disaster Med Public Health Preparedness. 2017;11:279-284).

Green synthesized nanoparticles in the fight against mosquito-borne diseases and cancer-a brief review

Nanobiomedicine and parasitology are facing a number of key challenges, which mostly deal with the paucity of effective preventive and curative tools against mosquito-borne diseases and cancer. In this scenario, the employ of botanical and invertebrate extracts as reducing, stabilizing and capping agents for the synthesis of nanoparticles is advantageous over chemical and physical methods, since it is one-pot, cheap, and does not require high pressure, energy, temperature, or the use of highly toxic chemicals. Considering the overlooked connection between mosquito vector activity and the spread of cancer in USA, this review focused on the current knowledge available about green synthesized nanoparticles with efficacy against mosquito-borne diseases and cancer. Green fabricated metal nanoparticles showed antiplasmodial activity that often encompasses the efficacy of currently marked drugs for malaria treatment. They have been also reported as growth inhibitors against dengue virus (serotype DEN-2), with moderate cytotoxicity on mammalian cells. However, this feature is strongly dependent to the botanical agents employed during nanosynthesis. In addition, green nanoparticles have been successfully used to reduce mosquito young instar populations in the field. The final section focuses on some issues for future research, with special reference to the chemical standardization of the botanical extracts used for nanosynthesis and the potential effects on green fabricated nanoparticles on non-target organisms.

Arbovirus and insect-specific virus discovery in Kenya by novel six genera multiplex high-resolution melting analysis

A broad diversity of arthropod-borne viruses (arboviruses) of global health concern are endemic to East Africa, yet most surveillance efforts are limited to just a few key viral pathogens. Additionally, estimates of arbovirus diversity in the tropics are likely to be underestimated as their discovery has lagged significantly over past decades due to limitations in fast and sensitive arbovirus identification methods. Here, we developed a nearly pan-arbovirus detection assay that uses high-resolution melting (HRM) analysis of RT-PCR products from highly multiplexed assays to differentiate broad diversities of arboviruses. We differentiated 15 viral culture controls and seven additional synthetic viral DNA sequence controls, within Flavivirus, Alphavirus, Nairovirus, Phlebovirus, Orthobunyavirus and Thogotovirus genera. Among Bunyamwera, sindbis, dengue and Thogoto virus serial dilutions, detection by multiplex RT-PCR-HRM was comparable to the gold standard Vero cell plaque assays. We applied our low-cost method for enhanced broad-range pathogen surveillance from mosquito samples collected in Kenya and identified diverse insect-specific viruses, including a new clade in anopheline mosquitoes, and Wesselsbron virus, an arbovirus that can cause viral haemorrhagic fever in humans and has not previously been isolated in Kenya, in Culex spp. and Anopheles coustani mosquitoes. Our findings demonstrate how multiplex RT-PCR-HRM can identify novel viral diversities and potential disease threats that may not be included in pathogen detection panels of routine surveillance efforts. This approach can be adapted to other pathogens to enhance disease surveillance and pathogen discovery efforts, as well as the study of pathogen diversity and viral evolutionary ecology.

Pathology of congenital Zika syndrome in Brazil: a case series

BACKGROUND

Zika virus is an arthropod-borne virus that is a member of the family Flaviviridae transmitted mainly by mosquitoes of the genus Aedes. Although usually asymptomatic, infection can result in a mild and self-limiting illness characterised by fever, rash, arthralgia, and conjunctivitis. An increase in the number of children born with microcephaly was noted in 2015 in regions of Brazil with high transmission of Zika virus. More recently, evidence has been accumulating supporting a link between Zika virus and microcephaly. Here, we describe findings from three fatal cases and two spontaneous abortions associated with Zika virus infection.

METHODS

In this case series, formalin-fixed paraffin-embedded tissue samples from five cases, including two newborn babies with microcephaly and severe arthrogryposis who died shortly after birth, one 2-month-old baby, and two placentas from spontaneous abortions, from Brazil were submitted to the Infectious Diseases Pathology Branch at the US Centers for Disease Control and Prevention (Atlanta, GA, USA) between December, 2015, and March, 2016. Specimens were assessed by histopathological examination, immunohistochemical assays using a mouse anti-Zika virus antibody, and RT-PCR assays targeting the NS5 and envelope genes. Amplicons of RT-PCR positive cases were sequenced for characterisation of strains.

FINDINGS

Viral antigens were localised to glial cells and neurons and associated with microcalcifications in all three fatal cases with microcephaly. Antigens were also seen in chorionic villi of one of the first trimester placentas. Tissues from all five cases were positive for Zika virus RNA by RT-PCR, and sequence analyses showed highest identities with Zika virus strains isolated from Brazil during 2015.

INTERPRETATION

These findings provide strong evidence of a link between Zika virus infection and different congenital central nervous system malformations, including microcephaly as well as arthrogryposis and spontaneous abortions.

FUNDING

None.

Zanotto PM, Iampietro MJ, Badamchi-Zadeh A, Boyd M, Ng’ang’a D, Kirilova M, Nityanandam R, Mercado NB, Li Z, Moseley ET, Bricault CA, Borducchi EN, Giglio PB, Jetton D, Neubauer G, Nkolola JP, Maxfield LF, De La Barrera RA, Jarman RG, Eckels KH, Michael NL, Thomas SJ, Barouch DH. Vaccine protection against Zika virus from Brazil

Zika virus (ZIKV) is a flavivirus that is responsible for the current epidemic in Brazil and the Americas. ZIKV has been causally associated with fetal microcephaly, intrauterine growth restriction, and other birth defects in both humans and mice. The rapid development of a safe and effective ZIKV vaccine is a global health priority, but very little is currently known about ZIKV immunology and mechanisms of immune protection. Here we show that a single immunization with a plasmid DNA vaccine or a purified inactivated virus vaccine provides complete protection in susceptible mice against challenge with a strain of ZIKV involved in the outbreak in northeast Brazil. This ZIKV strain has recently been shown to cross the placenta and to induce fetal microcephaly and other congenital malformations in mice. We produced DNA vaccines expressing ZIKV pre-membrane and envelope (prM-Env), as well as a series of deletion mutants. The prM-Env DNA vaccine, but not the deletion mutants, afforded complete protection against ZIKV, as measured by absence of detectable viraemia following challenge, and protective efficacy correlated with Env-specific antibody titers. Adoptive transfer of purified IgG from vaccinated mice conferred passive protection, and depletion of CD4 and CD8 T lymphocytes in vaccinated mice did not abrogate this protection. These data demonstrate that protection against ZIKV challenge can be achieved by single-shot subunit and inactivated virus vaccines in mice and that Env-specific antibody titers represent key immunologic correlates of protection. Our findings suggest that the development of a ZIKV vaccine for humans is likely to be achievable.

An ultrasensitive electrogenerated chemiluminescence-based immunoassay for specific detection of Zika virus

Zika virus (ZIKV) is a globally emerging mosquito-transmitted flavivirus that can cause severe fetal abnormalities, including microcephaly. As such, highly sensitive, specific, and cost-effective diagnostic methods are urgently needed. Here, we report a novel electrogenerated chemiluminescence (ECL)-based immunoassay for ultrasensitive and specific detection of ZIKV in human biological fluids. We loaded polystyrene beads (PSB) with a large number of ECL labels and conjugated them with anti-ZIKV monoclonal antibodies to generate anti-ZIKV-PSBs. These anti-ZIKV-PSBs efficiently captured ZIKV in solution forming ZIKV-anti-ZIKV-PSB complexes, which were subjected to measurement of ECL intensity after further magnetic beads separation. Our results show that the anti-ZIKV-PSBs can capture as little as 1 PFU of ZIKV in 100 μl of saline, human plasma, or human urine. This platform has the potential for development as a cost-effective, rapid and ultrasensitive assay for the detection of ZIKV and possibly other viruses in clinical diagnosis, epidemiologic and vector surveillance, and laboratory research.

A Full-Length Infectious cDNA Clone of Zika Virus from the 2015 Epidemic in Brazil as a Genetic Platform for Studies of Virus-Host Interactions and Vaccine Development

An arthropod-borne virus, Zika virus (ZIKV), has recently emerged as a major human pathogen. Associated with complications during perinatal development and Guillain-Barré syndrome in adults, ZIKV raises new challenges for understanding the molecular determinants of flavivirus pathogenesis. This underscores the necessity for the development of a reverse genetic system based on an epidemic ZIKV strain. Here, we describe the generation and characterization in cell cultures of an infectious cDNA clone of ZIKV isolated from the 2015 epidemic in Brazil. The cDNA-derived ZIKV replicated efficiently in a variety of cell lines, including those of both neuronal and placental origin. We observed that the growth of cDNA-derived virus was attenuated compared to the growth of the parental isolate in most cell lines, which correlates with substantial differences in sequence heterogeneity between these viruses that were determined by deep-sequencing analysis. Our findings support the role of genetic diversity in maintaining the replicative fitness of viral populations under changing conditions. Moreover, these results indicate that caution should be exercised when interpreting the results of reverse-genetics experiments in attempts to accurately predict the biology of natural viruses. Finally, a Vero cell-adapted cDNA clone of ZIKV was generated that can be used as a convenient platform for studies aimed at the development of ZIKV vaccines and therapeutics.

IMPORTANCE

The availability of genetic tools and laboratory models determines the progress in understanding mechanisms of virus emergence and pathogenesis. Recent large-scale outbreaks of Zika virus (ZIKV) that were linked to complications during perinatal development and Guillain-Barré syndrome in adults emphasize the urgency for the development of a reverse-genetics system based on an epidemic ZIKV strain. Here, we report a stable infectious cDNA clone for ZIKV isolated during the 2015 epidemic in Brazil, as well as a Vero cell-adapted version of it, which will be used for virus-host interaction studies and vaccine development.

Complete Genome Sequences of Three Historically Important, Spatiotemporally Distinct, and Genetically Divergent Strains of Zika Virus: MR-766, P6-740, and PRVABC-59

Here, we report the 10,807-nucleotide-long consensus RNA genome sequences of three spatiotemporally distinct and genetically divergent Zika virus strains, with the functionality of their genomic sequences substantiated by reverse genetics: MR-766 (African lineage, Uganda, 1947), P6-740 (Asian lineage, Malaysia, 1966), and PRVABC-59 (Asian lineage-derived American strain, Puerto Rico, 2015).

Assessing the global threat from Zika virus

First discovered in 1947, Zika virus (ZIKV) infection remained a little-known tropical disease until 2015, when its apparent association with a considerable increase in the incidence of microcephaly in Brazil raised alarms worldwide. There is limited information on the key factors that determine the extent of the global threat from ZIKV infection and resulting complications. Here, we review what is known about the epidemiology, natural history, and public health effects of ZIKV infection, the empirical basis for this knowledge, and the critical knowledge gaps that need to be filled.

A Screen of FDA-Approved Drugs for Inhibitors of Zika Virus Infection

Currently there are no approved vaccines or specific therapies to prevent or treat Zika virus (ZIKV) infection. We interrogated a library of FDA-approved drugs for their ability to block infection of human HuH-7 cells by a newly isolated ZIKV strain (ZIKV MEX_I_7). More than 20 out of 774 tested compounds decreased ZIKV infection in our in vitro screening assay. Selected compounds were further validated for inhibition of ZIKV infection in human cervical, placental, and neural stem cell lines, as well as primary human amnion cells. Established anti-flaviviral drugs (e.g., bortezomib and mycophenolic acid) and others that had no previously known antiviral activity (e.g., daptomycin) were identified as inhibitors of ZIKV infection. Several drugs reduced ZIKV infection across multiple cell types. This study identifies drugs that could be tested in clinical studies of ZIKV infection and provides a resource of small molecules to study ZIKV pathogenesis.

Zika Virus and the Blood Supply: What Do We Know?

Zika virus (ZIKV), a mosquito-borne Flavivirus and emerging infectious disease, is the focus of an international public health emergency after its rapid spread through the Americas and the Caribbean. Although most ZIKV infections are subclinical or characterized by mild febrile illness, ZIKV has been implicated in severe complications, most notably microcephaly in babies born to incident infected mothers during pregnancy. As yet, the extent to which ZIKV is transfusion transmissible remains undefined. Nonetheless, a high prevalence of asymptomatic infection during outbreaks, the demonstration of ZIKV in blood donors, and 4 possible cases of transfusion-transmitted ZIKV in Brazil have raised concern for risk to the blood supply. Consequently, a proactive response is underway by blood collection agencies, regulatory bodies, national funding agencies, and industry alike. Mitigation strategies differ between endemic and nonendemic areas. In the continental United States, the American Association of Blood Banks and Food and Drug Administration guidelines recommend travel-based deferral for those returning from affected areas, and nucleic acid testing is being initiated under an investigational new drug application in Puerto Rico and selected areas of the United States. Options are less clear for countries where autochthonous vector-borne transmission is active. The burden of Zika falls in low-resource countries where high cost and technical barriers associated with testing and pathogen reduction pose barriers to implementation. Additional strategies include maintaining selective inventory for high-risk recipients (eg, pregnant women). We review the available data as of July 2016 on ZIKV in relation to the blood supply including risk, mitigation strategies, and barriers to implementation in addition to the research that is needed to address current uncertainty.

An autochthonous case of Zika due to possible sexual transmission, Florence, Italy, 2014

We report a case of Zika virus infection imported in Florence, Italy ex-Thailand, leading to a secondary autochthonous case, probably through sexual transmission. The two cases occurred in May 2014 but were retrospectively diagnosed in 2016 on the basis of serological tests (plaque reduction neutralisation) performed on stored serum samples. Our report provides further evidence that sexual transmission of Zika virus is possible.

microRNA-309 targets the Homeobox gene SIX4 and controls ovarian development in the mosquito Aedes aegypti

Obligatory blood-triggered reproductive strategy is an evolutionary adaptation of mosquitoes for rapid egg development. It contributes to the vectorial capacity of these insects. Therefore, understanding the molecular mechanisms underlying reproductive processes is of particular importance. Here, we report that microRNA-309 (miR-309) plays a critical role in mosquito reproduction. A spatiotemporal expression profile of miR-309 displayed its blood feeding-dependent onset and ovary-specific manifestation in female Aedes aegypti mosquitoes. Antagomir silencing of miR-309 impaired ovarian development and resulted in nonsynchronized follicle growth. Furthermore, the genetic disruption of miR-309 by CRISPR/Cas9 system led to the developmental failure of primary follicle formation. Examination of genomic responses to miR-309 depletion revealed that several pathways associated with ovarian development are down-regulated. Comparative analysis of genes obtained from the high-throughput RNA sequencing of ovarian tissue from the miR-309 antagomir-silenced mosquitoes with those from the in silico computation target prediction identified that the gene-encoding SIX homeobox 4 protein (SIX4) is a putative target of miR-309. Reporter assay and RNA immunoprecipitation confirmed that SIX4 is a direct target of miR-309. RNA interference of SIX4 was able to rescue phenotypic manifestations caused by miR-309 depletion. Thus, miR-309 plays a critical role in mosquito reproduction by targeting SIX4 in the ovary and serves as a regulatory switch permitting a stage-specific degradation of the ovarian SIX4 mRNA. In turn, this microRNA (miRNA)-targeted degradation is required for appropriate initiation of a blood feeding-triggered phase of ovarian development, highlighting involvement of this miRNA in mosquito reproduction.

Zika Fetal Neuropathogenesis: Etiology of a Viral Syndrome

The ongoing Zika virus epidemic in the Americas and the observed association with both fetal abnormalities (primary microcephaly) and adult autoimmune pathology (Guillain-Barré syndrome) has brought attention to this neglected pathogen. While initial case studies generated significant interest in the Zika virus outbreak, larger prospective epidemiology and basic virology studies examining the mechanisms of Zika viral infection and associated pathophysiology are only now starting to be published. In this review, we analyze Zika fetal neuropathogenesis from a comparative pathology perspective, using the historic metaphor of "TORCH" viral pathogenesis to provide context. By drawing parallels to other viral infections of the fetus, we identify common themes and mechanisms that may illuminate the observed pathology. The existing data on the susceptibility of various cells to both Zika and other flavivirus infections are summarized. Finally, we highlight relevant aspects of the known molecular mechanisms of flavivirus replication.

Re-Emergence of Zika Virus: A Review on Pathogenesis, Clinical Manifestations, Diagnosis, Treatment, and Prevention

Zika virus (ZKV) is an arbovirus of the Flaviviridae family, which includes West Nile, dengue fever, yellow fever, and Japanese encephalitis virus. It is transmitted by the Aedes genus of mosquitoes. Before 2015, ZKV outbreaks occurred in areas of Africa, the Pacific Islands, and Southeast Asia. The current large outbreak, which began in Brazil, has also emerged throughout a large part of South/Central America, a number of islands in the Caribbean, including Puerto Rico, the Virgin Islands, and Mexico. A sudden rise in the numbers of infants reported born with microcephaly in Brazil, and the detection of the single-stranded positive RNA virus in the amniotic fluid of affected newborns, has captured medical, mainstream media, and global political attention, causing considerable concern in a post-Ebola global community considerably more focused on the threat of internationally transmissible diseases. The goal of this article is to provide an overview of ZKV for clinicians, with the emphasis on pathogenesis, clinical manifestations, diagnosis, and treatment/preventive measures.

Epidemiology of Zika virus, 1947-2007

INTRODUCTION

Since 1947, Zika virus has been identified sporadically in humans in Africa and Asia; however, clinically consequential Zika virus disease had not been documented prior to the current outbreak in the Americas. Considering 6 decades have passed since the first identification of the virus, it is perhaps unexpected that Zika virus was recognised only recently as capable of causing disease epidemics. Substantial work on understanding the epidemiology of Zika virus has been conducted since the virus' first outbreak in 2007 in Micronesia; however, there has been little study of the earlier data on Zika virus.

METHODS

A systematic literature search was conducted to identify evidence of Zika virus infection in humans from 1947 to 2007. Data extracted included seroprevalence of Zika virus infection, age distributions of positive test results and serologic test modalities used. Country-level and age-specific seroprevalence was calculated. Estimates of seroprevalence by different serologic test modalities were compared.

RESULTS

12 026 citations were retrieved by the literature search, and 76 articles were included in this review. Evidence of Zika virus infection in humans was found in 29 countries in Africa, 8 countries in Asia and 1 country in Europe. Country-level seroprevalence of Zika virus infection ranged from 0.4% to 53.3%. Seroprevalence of Zika virus infection was found to increase across the lifespan; 15-40% of reproductive-age individuals may have been previously infected. No significant difference was found between estimates of seroprevalence by different serologic test modalities.

DISCUSSION

Zika virus has likely been endemic for decades in certain regions of the world; however, the majority of reproductive-age individuals have likely not been infected. Historical evidence of Zika virus infection exists regardless of the serologic test modality used.

Prospects for dengue vaccines for travelers

Travel-acquired dengue cases have been increasing as the overall global dengue burden has expanded. In Korea, imported dengue cases have been reported since 2000 when it first became a notifiable disease. During the first four months of 2016, three times more dengue cases were reported in Korea than during the same period the previous year. A safe and efficacious vaccine for travelers would be beneficial to prevent dengue disease in individual travelers and potentially decrease the risk of virus spread to non-endemic areas. Here, we summarize the characteristics of dengue vaccines for travelers and review dengue vaccines currently licensed or in clinical development.

Research and development of Zika virus vaccines

Zika virus (ZIKV) is a member of the family Flaviviridae, genus Flavivirus, and is transmitted by Aedes sp. mosquitoes. There are three genetic lineages of ZIKV: the East African, West African and Asian lineages. Until recently, Zika fever (ZF) has normally been considered a rare, mild febrile disease, but reports since 2012 have shown potentially severe complications associated with ZIKV infection, including microcephaly and Guillain-Barré syndrome. There are no licensed vaccines for ZIKV; however, many vaccine platforms/approaches that have been utilised for other flavivirus vaccines are being applied to ZIKV. Given the current outbreak of ZIKV in the Americas with its associated risks to pregnancy, we summarise what is known about the virus, how knowledge of currently licensed flavivirus vaccines can be applied to ZIKV vaccine development and the assessments of potential challenges for ZIKV vaccine testing and evaluation.

Design of virus-based nanomaterials for medicine, biotechnology, and energy

This review provides an overview of recent developments in "chemical virology." Viruses, as materials, provide unique nanoscale scaffolds that have relevance in chemical biology and nanotechnology, with diverse areas of applications. Some fundamental advantages of viruses, compared to synthetically programmed materials, include the highly precise spatial arrangement of their subunits into a diverse array of shapes and sizes and many available avenues for easy and reproducible modification. Here, we will first survey the broad distribution of viruses and various methods for producing virus-based nanoparticles, as well as engineering principles used to impart new functionalities. We will then examine the broad range of applications and implications of virus-based materials, focusing on the medical, biotechnology, and energy sectors. We anticipate that this field will continue to evolve and grow, with exciting new possibilities stemming from advancements in the rational design of virus-based nanomaterials.

Three atypical lethal cases associated with acute Zika virus infection in Suriname

Acute Zika virus infection usually presents with a self-limiting triad of fever, rash and arthritis. There is limited information on severe or lethal cases. We report three cases of lethal acute Zika infection, confirmed with polymerase chain reaction, in adult patients with some co-morbidities. The patients showed rapid clinical deterioration with hemorrhagic and septic shock, and exaggerated acute and innate inflammatory responses with pronounced coagulopathy, and died soon after admission to the hospital. It remains unclear whether the fatal outcomes were due to acute Zika virus infection alone or to the combination with exacerbated underlying prior disease or co-infection. Nonetheless, the severity of these cases implies that increased awareness for atypical presentations of Zika virus infection, and careful clinical assessment of patients with symptoms of Zika, is warranted during current and future outbreaks.

Accelerating Drug Development: Antiviral Therapies for Emerging Viruses as a Model

Drug discovery and development is a lengthy and expensive process. Although no one, simple, single solution can significantly accelerate this process, steps can be taken to avoid unnecessary delays. Using the development of antiviral therapies as a model, we describe options for acceleration that cover target selection, assay development and high-throughput screening, hit confirmation, lead identification and development, animal model evaluations, toxicity studies, regulatory issues, and the general drug discovery and development infrastructure. Together, these steps could result in accelerated timelines for bringing antiviral therapies to market so they can treat emerging infections and reduce human suffering.

A Literature Review of Zika Virus

We summarize what is known about this virus and its global expansion as of mid-February 2016.

Zika virus is a mosquitoborne flavivirus that is the focus of an ongoing pandemic and public health emergency. Previously limited to sporadic cases in Africa and Asia, the emergence of Zika virus in Brazil in 2015 heralded rapid spread throughout the Americas. Although most Zika virus infections are characterized by subclinical or mild influenza-like illness, severe manifestations have been described, including Guillain-Barre syndrome in adults and microcephaly in babies born to infected mothers. Neither an effective treatment nor a vaccine is available for Zika virus; therefore, the public health response primarily focuses on preventing infection, particularly in pregnant women. Despite growing knowledge about this virus, questions remain regarding the virus’s vectors and reservoirs, pathogenesis, genetic diversity, and potential synergistic effects of co-infection with other circulating viruses. These questions highlight the need for research to optimize surveillance, patient management, and public health intervention in the current Zika virus epidemic.

Interferon-Induced Spermidine-Spermine Acetyltransferase and Polyamine Depletion Restrict Zika and Chikungunya Viruses

Polyamines are small, positively charged molecules derived from ornithine and synthesized through an intricately regulated enzymatic pathway. Within cells, they are abundant and play several roles in diverse processes. We find that polyamines are required for the life cycle of the RNA viruses chikungunya virus (CHIKV) and Zika virus (ZIKV). Depletion of spermidine and spermine via type I interferon signaling-mediated induction of spermidine/spermine N1-acetyltransferase (SAT1), a key catabolic enzyme in the polyamine pathway, restricts CHIKV and ZIKV replication. Polyamine depletion restricts these viruses in vitro and in vivo, due to impairment of viral translation and RNA replication. The restriction is released by exogenous replenishment of polyamines, further supporting a role for these molecules in virus replication. Thus, SAT1 and, more broadly, polyamine depletion restrict viral replication and suggest promising avenues for antiviral therapies.

Specificity, cross-reactivity, and function of antibodies elicited by Zika virus infection

Zika virus (ZIKV), a mosquito-borne flavivirus with homology to Dengue virus (DENV), has become a public health emergency. By characterizing memory lymphocytes from ZIKV-infected patients, we dissected ZIKV-specific and DENV-cross-reactive immune responses. Antibodies to nonstructural protein 1 (NS1) were largely ZIKV-specific and were used to develop a serological diagnostic tool. In contrast, antibodies against E protein domain I/II (EDI/II) were cross-reactive and, although poorly neutralizing, potently enhanced ZIKV and DENV infection in vitro and lethally enhanced DENV disease in mice. Memory T cells against NS1 or E proteins were poorly cross-reactive, even in donors preexposed to DENV. The most potent neutralizing antibodies were ZIKV-specific and targeted EDIII or quaternary epitopes on infectious virus. An EDIII-specific antibody protected mice from lethal ZIKV infection, illustrating the potential for antibody-based therapy.

Enhancing dengue virus maturation using a stable furin over-expressing cell line

Flaviviruses are positive-stranded RNA viruses that incorporate envelope (E) and premembrane (prM) proteins into the virion. Furin-mediated cleavage of prM defines a required maturation step in the flavivirus lifecycle. Inefficient prM cleavage results in structurally heterogeneous virions with unique antigenic and functional characteristics. Recent studies with dengue virus suggest that viruses produced in tissue culture cells are less mature than those produced in primary cells. In this study, we describe a Vero cell line that ectopically expresses high levels of human furin (Vero-furin) for use in the production of more homogenous mature flavivirus populations. Laboratory-adapted and clinical dengue virus isolates grow efficiently in Vero-furin cells. Biochemical and structural techniques demonstrate efficient prM cleavage in Vero-furin derived virus preparations. These virions also were less sensitive to neutralization by antibodies that bind efficiently to immature virions. This furin-expressing cell line will be of considerable utility for flavivirus neutralization and structural studies.

Coinfections of Zika and Chikungunya Viruses in Bahia, Brazil, Identified by Metagenomic Next-Generation Sequencing

Metagenomic next-generation sequencing (mNGS) of samples from 15 patients with documented Zika virus (ZIKV) infection in Bahia, Brazil, from April 2015 to January 2016 identified coinfections with chikungunya virus (CHIKV) in 2 of 15 ZIKV-positive cases by PCR (13.3%). While generally nonspecific, the clinical presentation corresponding to these two CHIKV/ZIKV coinfections reflected infection by the virus present at a higher titer. Aside from CHIKV and ZIKV, coinfections of other viral pathogens were not detected. The mNGS approach is promising for differential diagnosis of acute febrile illness and identification of coinfections, although targeted arbovirus screening may be sufficient in the current ZIKV outbreak setting.

A vaccine effective against Zika virus is theoretically possible but may not be delivered anytime soon

Following the first report in May 2015 of the unexpected emergence of Zika in north east Brazil, there has been an explosive epidemic of this infection across Latin America. The outbreak has caused alarm among social and news media as to the virulence and transmission potential of the Aedes mosquito-borne virus. This debate is heightened by the proximity, both in time and distance, to the forthcoming Olympic Games to be held in Rio de Janeiro this August, provoking fears for the safety of athletes and spectators alike. The threat, real or perceived, is exacerbated by the movement between nations in the same or separate continents of persons who act unwittingly as asymptomatic carriers. Pregnant females are considered at greatest risk because microcephaly in newborn infants is linked to, if not yet proven as caused by, Zika infection. In February this year, the World Health Organization declared that further to the then unconfirmed association between the virus and the clinical manifestations of microcephaly and also Guillain-Barré syndrome, the Zika epidemic was a “public health emergency of international concern”. No anti-Zika therapy, vaccine or drug, is currently available and while the production of the former has now been prioritized by multiple funding agencies, the history of infectious disease vaccine development indicates that this may take several years to reach the market place. The fact that Zika is a close relative of yellow fever and Japanese encephalitis viruses, for both of which there are already effective vaccines, provides a rational basis for the fast-tracked laboratory-based preparation of a candidate vaccine. However, undertaking clinical trials on pregnant females provides ethical and practical hurdles to overcome before licensure is granted for public administration. Meanwhile, public health management strategies, including mosquito control programs to reduce breeding, are needed to limit the global spread of this re-emerging disease.

Preventing Zika Virus Infection during Pregnancy Using a Seasonal Window of Opportunity for Conception

It has come to light that Zika virus (ZIKV) infection during pregnancy can result in trans-placental transmission to the fetus along with fetal death, congenital microcephaly, and/or Central Nervous System (CNS) malformations. There are projected to be >9,200,000 births annually in countries with ongoing ZIKV transmission. In response to the ZIKV threat, the World Health Organization (WHO) is strategically targeting prevention of infection in pregnant women and funding contraception in epidemic regions. I propose that the damaging effects of ZIKV can be reduced using a seasonal window of opportunity for conception that may minimize maternal exposure. Like other acute viral infections-including the related flavivirus, dengue virus (DENV)-the transmission of ZIKV is anticipated to be seasonal. By seasonally planning pregnancy, this aspect of pathogen ecology can be leveraged to align sensitive periods of gestation with the low-transmission season.

Zika Virus: An Emergence of a New Arbovirus

The world is facing a new pandemic in progress due to a mosquito-borne flavivirus popularly known as Zika virus. The emergence of this new virus is really alarming with the sudden increment in the cases of microcephaly reported from Brazil. The findings attributing the involvement of Zika virus as the reason for congenital deformations in the babies born in afflicted areas have really shocked the world. The present knowledge about this virus is very limited and in the absence of further studies the precautions seems to be the best way of protection from this virus. The present article is a short review about this new virus.

Zika Virus

Zika virus (ZIKV) is an arthropod-borne virus (arbovirus) in the genus Flavivirus and the family Flaviviridae. ZIKV was first isolated from a nonhuman primate in 1947 and from mosquitoes in 1948 in Africa, and ZIKV infections in humans were sporadic for half a century before emerging in the Pacific and the Americas. ZIKV is usually transmitted by the bite of infected mosquitoes. The clinical presentation of Zika fever is nonspecific and can be misdiagnosed as other infectious diseases, especially those due to arboviruses such as dengue and chikungunya. ZIKV infection was associated with only mild illness prior to the large French Polynesian outbreak in 2013 and 2014, when severe neurological complications were reported, and the emergence in Brazil of a dramatic increase in severe congenital malformations (microcephaly) suspected to be associated with ZIKV. Laboratory diagnosis of Zika fever relies on virus isolation or detection of ZIKV-specific RNA. Serological diagnosis is complicated by cross-reactivity among members of the Flavivirus genus. The adaptation of ZIKV to an urban cycle involving humans and domestic mosquito vectors in tropical areas where dengue is endemic suggests that the incidence of ZIKV infections may be underestimated. There is a high potential for ZIKV emergence in urban centers in the tropics that are infested with competent mosquito vectors such as Aedes aegypti and Aedes albopictus.

Vaccinations for Neuroinfectious Disease: A Global Health Priority

Vaccines for neuroinfectious diseases are becoming an ever-increasing global health priority, as neurologic manifestations and sequelae from existing and emerging central nervous system infections account for significant worldwide morbidity and mortality. The prevention of neurotropic infections can be achieved through globally coordinated vaccination campaigns, which have successfully eradicated nonzoonotic agents such as the variola viruses and, hopefully soon, poliovirus. This review discusses vaccines that are currently available or under development for zoonotic flaviviruses and alphaviruses, including Japanese and tick-borne encephalitis, yellow fever, West Nile, dengue, Zika, encephalitic equine viruses, and chikungunya. Also discussed are nonzoonotic agents, including measles and human herpesviruses, as well as select bacterial, fungal, and protozoal pathogens. While therapeutic vaccines will be required to treat a multitude of ongoing infections of the nervous system, the ideal vaccination strategy is pre-exposure vaccination, with the ultimate goals of minimizing disease associated with zoonotic viruses and the total eradication of nonzoonotic agents.

Evaluation of Alternative Killing Agents for Aedes aegypti (Diptera: Culicidae) in the Gravid Aedes Trap (GAT)

The Gravid Aedes Trap (GAT) uses visual and olfactory cues to attract gravid Aedes aegypti (L.) that are then captured when knocked down by a residual pyrethroid surface spray. However, the use of surface sprays can be compromised by poor availability of the spray and pesticide resistance in the target mosquito. We investigated several "alternative" insecticide and insecticide-free killing agents for use in the GAT. This included long-lasting insecticide-impregnated nets (LLINs), vapor-active synthetic pyrethroids (metofluthrin), canola oil, and two types of dry adhesive sticky card. During bench top assays LLINs, metofluthrin, and dry sticky cards had 24-h knockdown (KD) percentages >80% (91.2 ± 7.2%, 84.2 ± 6.8%, and 83.4 ± 6.1%, respectively), whereas the 24-h KD for canola oil was 70 ± 7.7%, which improved to 90.0 ± 3.7% over 48 h. Importantly, there were no significant differences in the number of Ae. aegypti collected per week or the number of traps positive for Ae. aegypti between the sticky card and canola oil treatments compared with the surface spray and LLIN treatments in semifield and field trials. These results demonstrate that the use of inexpensive and widely available insecticide-free agents such as those described in this study are effective alternatives to pyrethroids in regions with insecticide-resistant populations. The use of such environmentally friendly insecticide-free alternatives will also be attractive in areas where there is substantial resistance to insecticide use due to environmental and public health concerns.

Detection of Zika virus RNA in whole blood of imported Zika virus disease cases up to 2 months after symptom onset, Israel, December 2015 to April 2016

Zika virus RNA presence in serum, whole-blood and urine samples from six Israeli travellers symptomatic for Zika virus disease was examined. Whole-blood samples were positive for as late as 2 months (58 days) post-symptom onset, longer than for urine (26 days) and serum (3 days). These findings suggest the utility of whole blood in Zika infection diagnosis.

Zika: As an emergent epidemic

Zika virus is a new global threat for 2016 that has been swept to almost all Americas and is now posing serious threats to the entire globe. This deadly virus is playing havoc to unborn lives because of its reported association with upsurge of fetal deformation called microcephaly and neuropathic disorders including Guillain-Barré syndrome. Till today, there is no vaccine prospect, antiviral therapy or licensed medical countermeasures to curb the teratogenic outcomes of this destructive viral infection. Diagnosis, treatment, chronicity and pathogenesis are still vague and unsettled. Therefore, this review article addresses all the aspects related to this disease to mitigate the explosive rise in Zika virus infection.