Zika Virus in the Americas--Yet Another Arbovirus Threat

Zika Virus Pathogenesis: A Battle for Immune Evasion

Zika virus (ZIKV) infection and its associated congenital and other neurological disorders, particularly microcephaly and other fetal developmental abnormalities, constitute a World Health Organization (WHO) Zika Virus Research Agenda within the WHO’s R&D Blueprint for Action to Prevent Epidemics, and continue to be a Public Health Emergency of International Concern (PHEIC) today. ZIKV pathogenicity is initiated by viral infection and propagation across multiple placental and fetal tissue barriers, and is critically strengthened by subverting host immunity. ZIKV immune evasion involves viral non-structural proteins, genomic and non-coding RNA and microRNA (miRNA) to modulate interferon (IFN) signaling and production, interfering with intracellular signal pathways and autophagy, and promoting cellular environment changes together with secretion of cellular components to escape innate and adaptive immunity and further infect privileged immune organs/tissues such as the placenta and eyes. This review includes a description of recent advances in the understanding of the mechanisms underlying ZIKV immune modulation and evasion that strongly condition viral pathogenesis, which would certainly contribute to the development of anti-ZIKV strategies, drugs, and vaccines.

Detection of SARS-CoV-2 DNA Targets Using Femtoliter Optofluidic Waveguides

Chip-scale SARS-CoV-2 testing was demonstrated using silicon nitride (Si3N4) nanoslot fluidic waveguides to detect a tagged oligonucleotide with a coronavirus DNA sequence. The slot waveguides were fabricated using complementary metal-oxide-semiconductor (CMOS) fabrication processes, including multiscale lithography and selective reactive ion etching (RIE), forming femtoliter fluidic channels. Finite difference method (FDM) simulation was used to calculate the optical field distribution of the waveguide mode when the waveguide sensor was excited by transverse electric (TE) and transverse magnetic (TM) polarized light. For the TE polarization, a strong optical field was created in the slot region and its field intensity was 14× stronger than the evanescent sensing field from the TM polarization. The nanoscale confinement of the optical sensing field significantly enhanced the light-analyte interaction and improved the optical sensitivity. The sensitivity enhancement was experimentally demonstrated by measuring the polarization-dependent fluorescence emission from the tagged oligonucleotide. The photonic chips consisting of femtoliter Si3N4 waveguides provide a low-cost and high throughput platform for real-time virus identification, which is critical for point-of-care (PoC) diagnostic applications.

Assessment of knowledge, attitudes, and practices towards Zika virus among healthcare workers in St. Kitts

Background

Healthcare workers are usually the first responders during outbreaks and are instrumental in educating the populace about the prevention of different diseases and illnesses. The aim of this study was to assess the association between healthcare workers’ characteristics and knowledge, attitudes and practices toward Zika virus.

Methods

This was a cross-sectional study that collected data from healthcare workers at 3 medical facilities using a validated self-administered questionnaire between July 2017 – September 2017. Logistic regression models were used to examine the association between sociodemographic and knowledge, attitudes, and practices.

Results

A total of 190 healthcare workers were analyzed. Of these, 60, 72.6 and 64.7% had good knowledge, positive attitudes, and good practices toward Zika virus, respectively. Healthcare workers without a formal degree were less likely to have good knowledge of Zika virus (adjusted odds ratio (AOR) = 0:49; 95% confidence interval (CI) = 0.24–0.99) compared to those with a formal degree. Reduced odds for positive attitude towards Zika virus were observed in healthcare workers with low income as compared to those with high income (AOR = 0.31; 95% CI =0.13–0.75). Being younger than 40 years old was associated with poor Zika virus practices (AOR = 0:34; 95% CI = 0.15–0.79).

Conclusions

Significant association between healthcare workers’ sociodemographic characteristics and Zika virus knowledge, attitudes and practices were observed. Public health interventions that seek to increase Zika virus awareness should aim to train healthcare workers who are younger, without formal degree and those earning low income.

In vitro study of Hesperetin and Hesperidin as inhibitors of zika and chikungunya virus proteases

The potential outcome of flavivirus and alphavirus co-infections is worrisome due to the development of severe diseases. Hundreds of millions of people worldwide live under the risk of infections caused by viruses like chikungunya virus (CHIKV, genus Alphavirus), dengue virus (DENV, genus Flavivirus), and zika virus (ZIKV, genus Flavivirus). So far, neither any drug exists against the infection by a single virus, nor against co-infection. The results described in our study demonstrate the inhibitory potential of two flavonoids derived from citrus plants: Hesperetin (HST) against NS2B/NS3pro of ZIKV and nsP2pro of CHIKV and, Hesperidin (HSD) against nsP2pro of CHIKV. The flavonoids are noncompetitive inhibitors and the determined IC50 values are in low µM range for HST against ZIKV NS2B/NS3pro (12.6 ± 1.3 µM) and against CHIKV nsP2pro (2.5 ± 0.4 µM). The IC50 for HSD against CHIKV nsP2pro was 7.1 ± 1.1 µM. The calculated ligand efficiencies for HST were > 0.3, which reflect its potential to be used as a lead compound. Docking and molecular dynamics simulations display the effect of HST and HSD on the protease 3D models of CHIKV and ZIKV. Conformational changes after ligand binding and their effect on the substrate-binding pocket of the proteases were investigated. Additionally, MTT assays demonstrated a very low cytotoxicity of both the molecules. Based on our results, we assume that HST comprise a chemical structure that serves as a starting point molecule to develop a potent inhibitor to combat CHIKV and ZIKV co-infections by inhibiting the virus proteases.

Construction of a recombinant avipoxvirus expressing the env gene of Zika virus as a novel putative preventive vaccine

Background

Zika virus (ZIKV) has been declared a public health emergency that requires development of an effective vaccine, as it might represent an international threat.

Methods

Here, two novel DNA-based (pVAXzenv) and fowlpox-based (FPzenv) recombinant putative vaccine candidates were constructed that contained the cPrME genes of ZIKV. The env gene inserted into the fowlpox vector was verified for correct transgene expression by Western blotting and by immunofluorescence in different cell lines. The production of virus-like particles as a result of env gene expression was also demonstrated by electron microscopy. BALB/c mice were immunosuppressed with dexamethasone and immunized following a prime–boost strategy in a heterologous protocol where pVAXzenv was followed by FPzenv, to evaluate the immunogenicity of the Env protein. The mice underwent a challenge with an epidemic ZIKV after the last boost.

Results

These data show that the ZIKV Env protein was correctly expressed in both normal human lung fibroblasts (MRC-5 cells) and green monkey kidney (Vero) cells infected with FPzenv, and that the transgene expression lasted for more than 2 weeks. After mucosal administration of FPzenv, the immunized mice showed specific and significantly higher humoral responses compared to the control mice. However, virus neutralizing antibodies were not detected using plaque reduction assays.

Conclusions

Although BALB/c mice appear to be an adequate model for ZIKV infection, as it mimics the natural mild infection in human beings, inadequate immune suppression seemed to occur by dexamethasone and different immune suppression strategies should be applied before challenge to reveal any protection of the mice.

Seasonality of Aedes albopictus in North and Central Mississippi

Container-breeding mosquitoes are increasingly important in public health due to recent outbreaks of Zika virus, chikungunya, and dengue. This paper documents seasonality of the most prevalent container-breeding mosquito species in Mississippi-Aedes albopictus. Ten sites in 5 counties in both northern and central Mississippi (20 sites, 10 counties total) were sampled by larval dipping and oviposition traps biweekly from September 2016 to June 2019, totaling 22 months and potentially yielding 440 egg or larval collections. However, 22 collections were missed due to inclement weather and personnel issues during the study period, so actually only 418 site visits were performed. Sites were chosen to maximize chances of finding Ae. albopictus. Of the total 1,310 mosquito larvae collected during the study period, 717 larvae and 50 positive egg papers belonged to Ae. albopictus. Aedes albopictus was found in all 10 northern and central counties. No eggs were collected at any of the sites from December through February, although larvae were occasionally collected during that time frame. This study demonstrates that Ae. albopictus is active in central and northern Mississippi beginning in March each year and continuing through November or December. There is little activity during the coldest months of the year (January and February). These data represent the first extensive analysis of Ae. albopictus seasonality in Mississippi, and as such, allow for better public health awareness of diseases transmitted by this species and design of more effective vector control programs.

The Eco-Bio-Social Factors That Modulate Aedes aegypti Abundance in South Texas Border Communities

Simple Summary

The Aedes aegypti mosquito is distributed worldwide and has become a major public health concern due to its proclivity for the urban environment, human feeding behavior, and ability to transmit agents of diseases such as Zika, chikungunya, and dengue. In the continental United States, the region known as the Lower Rio Grande Valley is one of the few areas with local mosquito transmission of these pathogens transmitted by Ae. aegypti. With limited resources for mosquito control in this region, understanding the ecological, biological, and social factors that affect Ae. aegypti population can help guide and improve current control efforts. We were able to observe widespread knowledge regarding Zika, but with very low importance given to mosquitoes as a problem. We found that the presence of window-mounted air conditioning units, number of windows and doors, characteristics of the property, and presence of children in the household all influenced the abundance of Ae. aegypti. The current results not only show a need for improved community engagement for increasing disease and mosquito risk awareness, but also provide risk factors that can guide current vector control activities.

Abstract

Aedes aegypti control requires dedicated resources that are usually scarce, limiting the reach and sustainability of vector control programs. This generates a need to focus on areas at risk of disease transmission and also understand the factors that might modulate local mosquito abundance. We evaluated the eco-bio-social factors that modulate indoor and outdoor relative abundance of female Ae. aegypti in communities of South Texas. We conducted housing quality and Knowledge Attitudes and Practices surveys in households that were part of a weekly mosquito surveillance program in November of 2017 and 2018. Our results showed widespread knowledge of mosquitoes and Zika virus by our participants. However, less than 35% considered them as serious problems in this region. The presence of window-mounted air conditioning units increased the risk of female mosquito relative abundance indoors. An increase in outdoor relative abundance was associated with larger properties and a higher number of children between 6 to 17 years of age. Interestingly, we observed that an increasing number of children <5 years of age modulated both indoor and outdoor relative abundance, with a 52% increase indoors and 30% decrease outdoors. The low perception of mosquito and disease risk highlights engagement needs for vector-borne disease prevention in this region. The identified risk factors can help guide public health officials in their efforts to reduce human and vector contact.

Differential Longevity of Memory CD4 and CD8 T Cells in a Cohort of the Mothers With a History of ZIKV Infection and Their Children

Background: Zika virus (ZIKV) infection causes for mild and self-limiting disease in healthy adults. In newborns, it can occasionally lead to a spectrum of malformations, the congenital Zika syndrome (CZS). Thus, little is known if mothers and babies with a history of ZIKV infection were able to develop long-lasting T-cell immunity. To these issues, we measure the prevalence of ZIKV T-cell immunity in a cohort of mothers infected to the ZIKV during pregnancy in the 2016–2017 Zika outbreak, who gave birth to infants affected by neurological complications or asymptomatic ones.

Results: Twenty-one mothers and 18 children were tested for IFN-γ ELISpot and T-cell responses for flow cytometry assays in response to CD4 ZIKV and CD8 ZIKV megapools (CD4 ZIKV MP and CD8 ZIKV MP). IFN-γ ELISpot responses to ZIKV MPs showed an increased CD4 and CD8 T-cell responses in mothers compared to children. The degranulation activity and IFN-γ-producing CD4 T cells were detected in most mothers, and children, while in CD8 T-cells, low responses were detected in these study groups. The total Temra T cell subset is enriched for IFN-γ+ CD4 T cells after stimulation of CD4 ZIKV MP.

Conclusion: Donors with a history of ZIKV infection demonstrated long-term CD4 T cell immunity to ZIKV CD4 MP. However, the same was not observed in CD8 T cells with the ZIKV CD8 MP. One possibility is that the cytotoxic and pro-inflammatory activities of CD8 T cells are markedly demonstrated in the early stages of infection, but less detected in the disease resolution phase, when the virus has already been eliminated. The responses of mothers' T cells to ZIKV MPs do not appear to be related to their children's clinical outcome. There was also no marked difference in the T cell responses to ZIKV MP between children affected or not with CZS. These data still need to be investigated, including the evaluation of the response of CD8 T cells to other ZIKV peptides.

Internet of medical things (IoMT)-integrated biosensors for point-of-care testing of infectious diseases

On global scale, the current situation of pandemic is symptomatic of increased incidences of contagious diseases caused by pathogens. The faster spread of these diseases, in a moderately short timeframe, is threatening the overall population wellbeing and conceivably the economy. The inadequacy of conventional diagnostic tools in terms of time consuming and complex laboratory-based diagnosis process is a major challenge to medical care. In present era, the development of point-of-care testing (POCT) is in demand for fast detection of infectious diseases along with “on-site” results that are helpful in timely and early action for better treatment. In addition, POCT devices also play a crucial role in preventing the transmission of infectious diseases by offering real-time testing and lab quality microbial diagnosis within minutes. Timely diagnosis and further treatment optimization facilitate the containment of outbreaks of infectious diseases. Presently, efforts are being made to support such POCT by the technological development in the field of internet of medical things (IoMT). The IoMT offers wireless-based operation and connectivity of POCT devices with health expert and medical centre. In this review, the recently developed POC diagnostics integrated or future possibilities of integration with IoMT are discussed with focus on emerging and re-emerging infectious diseases like malaria, dengue fever, influenza A (H1N1), human papilloma virus (HPV), Ebola virus disease (EVD), Zika virus (ZIKV), and coronavirus (COVID-19). The IoMT-assisted POCT systems are capable enough to fill the gap between bioinformatics generation, big rapid analytics, and clinical validation. An optimized IoMT-assisted POCT will be useful in understanding the diseases progression, treatment decision, and evaluation of efficacy of prescribed therapy.

Further SAR on the (Phenylsulfonyl)piperazine Scaffold as Inhibitors of the Aedes aegypti Kir1 (AeKir) Channel and Larvicides

Zika virus (ZIKV), dengue fever (DENV) and chikungunya (CHIKV) are arboviruses that are spread to humans from the bite of an infected adult female Aedes aegypti mosquito. As there are no effective vaccines or therapeutics for these diseases, the primary strategy for controlling the spread of these viruses is to prevent the mosquito from biting humans through the use of insecticides. Unfortunately, the commonly used classes of insecticides have seen a significant increase in resistance, thus complicating control efforts. Inhibiting the renal inward rectifier potassium (Kir) channel of the mosquito vector Aedes aegypti has been shown to be a promising target for the development of novel mosquitocides. We have shown that Kir1 channels play key roles in mosquito diuresis, hemolymph potassium homeostasis, flight, and reproduction. Previous work from our laboratories identified a novel (phenylsulfonyl)piperazine scaffold as potent AeKir channel inhibitors with activity against both adult and larval mosquitoes. Herein, we report further SAR work around this scaffold and have identified additional compounds with improved in vitro potency and mosquito larvae toxicity.

Two immunogenic recombinant protein vaccine candidates showed disparate protective efficacy against Zika virus infection in rhesus macaques

Zika virus (ZIKV) infection has caused major public health problems recently. To develop subunit vaccines for ZIKV, we have previously constructed recombinant ZIKV envelope protein domain III (EDIII), and the entire ectodomain (E80, which comprises EDI, EDII and EDIII), as vaccine candidates and showed both of them being immunogenic and protective in murine models. In this follow-up study, we compared these vaccine candidates in non-human primates. Both of them elicited neutralizing antibody responses, but only E80 immunization inhibited ZIKV infection in both peripheral blood and monkey tissues, whereas EDIII increased blood ZIKV RNA through possibly antibody-dependent enhancement. Further investigations revealed that the virion-binding antibody response in E80 immunized monkeys persisted longer and stronger than in EDIII immunized monkeys. These results demonstrate that E80 is superior to EDIII as a vaccine candidate, and that the magnitude, quality and durability of virion-binding neutralizing antibodies are correlates of protection.

Rice yellow stunt virus activates polyamine biosynthesis to promote viral propagation in insect vectors by disrupting ornithine decarboxylase antienzyme function

Intracellular polyamines (putrescine, spermidine, and spermine) have emerged as important molecules for viral infection; however, how viruses activate polyamines biosynthesis to promote viral infection remains unclear. Ornithine decarboxylase 1 (ODC1) and its antienzyme 1 (OAZ1) are major regulators of polyamine biosynthesis in animal cells. Here, we report that rice yellow stunt virus (RYSV), a plant rhabdovirus, could activate putrescine biosynthesis in leafhoppers to promote viral propagation by inhibiting OAZ1 expression. We observed that the reduction of putrescine biosynthesis by treatment with difluormethylornithine (DFMO), a specific nontoxic inhibitor of ODC1, or with in vitro synthesized dsRNAs targeting ODC1 mRNA could inhibit viral infection. In contrast, the supplement of putrescine or the increase of putrescine biosynthesis by treatment with dsRNAs targeting OAZ1 mRNA could facilitate viral infection. We further determined that both RYSV matrix protein M and ODC1 directly bind to the ODC-binding domain at the C-terminus of OAZ1. Thus, viral propagation in leafhoppers would decrease the ability of OAZ1 to target and mediate the degradation of ODC1, which finally activates putrescine production to benefit viral propagation. This work reveals that polyamine-metabolizing enzymes are directly exploited by a vector-borne virus to increase polyamine production, thereby facilitating viral infection in insect vectors.

High concentrations of membrane-fed ivermectin are required for substantial lethal and sublethal impacts on Aedes aegypti

Background

With widespread insecticide resistance in mosquito vectors, there is a pressing need to evaluate alternatives with different modes of action. Blood containing the antihelminthic drug ivermectin has been shown to have lethal and sub-lethal effects on mosquitoes. Almost all work to date has been on Anopheles spp., but impacts on other anthropophagic vectors could provide new options for their control, or additional value to anti-malarial ivermectin programmes.

Methods

Using dose-response assays, we evaluated the effects of ivermectin delivered by membrane feeding on daily mortality (up to 14 days post-blood feed) and fecundity of an Indian strain of Aedes aegypti.

Results

The 7-day lethal concentration of ivermectin required to kill 50% of adult mosquitoes was calculated to be 178.6 ng/ml (95% confidence intervals 142.3–218.4) for Ae. aegypti, which is much higher than that recorded for Anopheles spp. in any previous study. In addition, significant effects on fecundity and egg hatch rates were only recorded at high ivermectin concentrations (≥ 250 ng/ul).

Conclusion

Our results suggest that levels of ivermectin present in human blood at current dosing regimes in mass drug administration campaigns, or even those in a recent higher-dose anti-malaria trial, are unlikely to have a substantial impact on Ae. aegypti. Moreover, owing to the strong anthropophagy of Ae. aegypti, delivery of higher levels of ivermectin in livestock blood is also unlikely to be an effective option for its control. However, other potential toxic impacts of ivermectin metabolites, accumulation in tissues, sublethal effects on behaviour, or antiviral action might increase the efficacy of ivermectin against Ae. aegypti and the arboviral diseases it transmits, and require further investigation.

Plant nutrient quality impacts survival and reproductive fitness of the dengue vector Aedes aegypti

BACKGROUND

In a recent study using DNA barcoding, we identified the plants fed upon by four Afro-tropical mosquito species that vector dengue, malaria, and Rift Valley fever. Herein, we have expanded on this study by investigating the role of three of the plants, Pithecellobium dulce (Fabaceae), Leonotis nepetifolia (Lamiaceae), and Opuntia ficus-indica (Cactaceae), on the survival, fecundity, and egg viability of the dengue vector Aedes aegypti.

METHODS

We tested these effects using females that received (i) an initial three rations of blood meals and (ii) no blood meal at all. Two controls were included: age-matched females fed on glucose solution with or without an initial blood meal and those fed exclusively on blood meals. Data were collected daily over a 30-day period. The amino acid contents of Ae. aegypti guts and their respective diets were detected by coupled liquid chromatography-mass spectrometry.

RESULTS

Females fed on P. dulce and an exclusively blood meal diet had a shorter survival than those fed on glucose. On the other hand, females fed on L. nepetifolia survived longer than those fed exclusively on blood meals, whereas those fed on O. ficus-indica had the shortest survival time. With an initial blood meal, females fed on L. nepetifolia laid 1.6-fold more eggs while those fed on the other diets laid fewer eggs compared to those fed exclusively on blood meals. Hatching rates of the eggs laid varied with the diet. Mass spectroscopic analysis of gut contents of mosquitoes exposed to the different diets showed qualitative and quantitative differences in their amino acid levels.

CONCLUSION

Our findings highlight the central role of plant nutrients in the reproductive fitness of dengue vectors, which may impact their disease transmission potential.

Generation and preliminary characterization of vertebrate-specific replication-defective Zika virus

Zika virus (ZIKV) is a mosquito-borne flavivirus that replicates in both vertebrate and insect cells, whereas insect-specific flaviviruses (ISF) replicate only in insect cells. We sought to convert ZIKV, from a dual-tropic flavivirus, into an insect-specific virus for the eventual development of a safe ZIKV vaccine. Reverse genetics was used to introduce specific mutations into the furin cleavage motif within the ZIKV pre-membrane protein (prM). Mutant clones were selected, which replicated well in C6/36 insect cells but exhibited reduced replication in non-human primate (Vero) cells. Further characterization of the furin cleavage site mutants indicated they replicated poorly in both human (HeLa, U251), and baby hamster kidney (BHK-21) cells. One clone with the induced mutation in the prM protein and at positions 291and 452 within the NS3 protein was totally and stably replication-defective in vertebrate cells (VSRD-ZIKV). Preliminary studies in ZIKV sensitive, immunodeficient mice demonstrated that VSRD-ZIKV-infected mice survived and were virus-negative. Our study indicates that a reverse genetic approach targeting the furin cleavage site in prM can be used to select an insect-specific ZIKV with the potential utility as a vaccine strain.

Comparative Analysis of the Gut Microbiota of Adult Mosquitoes From Eight Locations in Hainan, China

The midgut microbial community composition, structure, and function of field-collected mosquitoes may provide a way to exploit microbial function for mosquito-borne disease control. However, it is unclear how adult mosquitoes acquire their microbiome, how the microbiome affects life history traits and how the microbiome influences community structure. We analyzed the composition of 501 midgut bacterial communities from field-collected adult female mosquitoes, including Aedes albopictus, Aedes galloisi, Culex pallidothorax, Culex pipiens, Culex gelidus, and Armigeres subalbatus, across eight habitats using the HiSeq 4000 system and the V3-V4 hyper-variable region of 16S rRNA gene. After quality filtering and rarefaction, a total of 1421 operational taxonomic units, belonging to 29 phyla, 44 families, and 43 genera were identified. Proteobacteria (75.67%) were the most common phylum, followed by Firmicutes (10.38%), Bacteroidetes (6.87%), Thermi (4.60%), and Actinobacteria (1.58%). The genera Rickettsiaceae (33.00%), Enterobacteriaceae (20.27%), Enterococcaceae (7.49%), Aeromonadaceae (7.00%), Thermaceae (4.52%), and Moraxellaceae (4.31%) were dominant in the samples analyzed and accounted for 76.59% of the total genera. We characterized the midgut bacterial communities of six mosquito species in Hainan province, China. The gut bacterial communities were different in composition and abundance, among locations, for all mosquito species. There were significant differences in the gut microbial composition between some species and substantial variation in the gut microbiota between individuals of the same mosquito species. There was a marked variation in different mosquito gut microbiota within the same location. These results might be useful in the identification of microbial communities that could be exploited for disease control.

Hydrogen-deuterium exchange mass spectrometry identifies spatially distinct antibody epitopes on domain III of the Zika virus envelope protein

Zika Virus (ZIKV) has become a global public health concern because it causes fetal microcephaly and other neurological complications in humans. Currently, there are no approved treatments or vaccines for ZIKV infection. We describe here the detailed epitopes for six monoclonal antibodies (mAbs) that bind to domain III of the envelope protein of ZIKV, some of which have therapeutic potential. We show that by using hydrogen-deuterium exchange mass spectrometry (HDX-MS), we can identify three spatially distinct epitopes for the six mAbs investigated. The HDX-MS approach identified epitopes for three mAbs that agreed well with recently reported X-ray crystallography data. The HDX-MS determined epitopes for the other three anti-ZIKV mAbs for which there were no crystal structures, and the epitopes were confirmed by structure-guided mutagenesis and biolayer interferometry (BLI) competition binding assay. Our results have implications for the design of vaccine and antibody therapeutics against ZIKV and demonstrate the use of HDX-MS as a rapid and valid approach for epitope mapping.

Phycobilins as Potent Food Bioactive Broad-Spectrum Inhibitors Against Proteases of SARS-CoV-2 and Other Coronaviruses: A Preliminary Study

In the 21st century, we have witnessed three coronavirus outbreaks: SARS in 2003, MERS in 2012, and the ongoing pandemic coronavirus disease 2019 (COVID-19). The search for efficient vaccines and development and repurposing of therapeutic drugs are the major approaches in the COVID-19 pandemic research area. There are concerns about the evolution of mutant strains (e.g., VUI - 202012/01, a mutant coronavirus in the United Kingdom), which can potentially reduce the impact of the current vaccine and therapeutic drug development trials. One promising approach to counter the mutant strains is the "development of effective broad-spectrum antiviral drugs" against coronaviruses. This study scientifically investigates potent food bioactive broad-spectrum antiviral compounds by targeting main protease (M^pro) and papain-like protease (PL^pro) proteases of coronaviruses (CoVs) using in silico and in vitro approaches. The results reveal that phycocyanobilin (PCB) shows potential inhibitor activity against both proteases. PCB had the best binding affinity to Mpro and PLpro with IC₅₀ values of 71 and 62 μm, respectively. Also, in silico studies with M^pro and PL^pro enzymes of other human and animal CoVs indicate broad-spectrum inhibitor activity of the PCB. As with PCB, other phycobilins, such as phycourobilin (PUB), phycoerythrobilin (PEB), and phycoviolobilin (PVB) show similar binding affinity to SARS-CoV-2 M^pro and PL^pro.

Manifestaciones Oculares Posterior a Infecciones por Arbovirus

Introducción: Las infecciones por virus del Dengue, Chikungunya y Zika se han asociado a manifestaciones oculares como neurorretinitis, vasculitis, coroiditis, coriorretinitis, obstrucción venosa, edema macular, foveolitis, entre otras. Objetivo: El propósito del estudio es presentar una serie de casos de pacientes con afección ocular causada por infecciones por arbovirus. Metodología: Estudio es de carácter descriptivo, retrospectivo, en formato de reporte de serie de casos, describiendo los hallazgos de manifestaciones oculares secundarias a infecciones de arbovirus. Resultados: Se presentaron 13 pacientes con Dengue, 5 con Chikungunya y 4 con Zika. Doce de sexo masculino y diez femenino, con edades que oscilan entre 18 y 62 años. Conclusión: El Dengue es la infección con mayor recurrencia de manifestaciones oculares. El tratamiento con esteroides y anti-VEGF utilizado en base a la evidencia disponible demostró un impacto positivo en la evolución de la agudeza visual. El tratamiento conservador en pacientes con obstrucción de vena central de retina fue efectivo en aquellos que no presentaron la variante isquémica. La atrofia óptica fue la complicación más frecuente y presentó mejoría una vez el cuadro inflamatorio ha sido resuelto.

Zika Virus-Induced Neuronal Apoptosis via Increased Mitochondrial Fragmentation

The 2015 to 2016 outbreak of Zika virus (ZIKV) infections in the Americas coincided with a dramatic increase in neurodevelopmental abnormalities, including fetal microcephaly, in newborns born to infected women. In this study, we observed mitochondrial fragmentation and disrupted mitochondrial membrane potential after 24 h of ZIKV infection in human neural stem cells and the SNB-19 glioblastoma cell line. The severity of these changes correlated with the amount of ZIKV proteins expressed in infected cells. ZIKV infection also decreased the levels of mitofusin 2, which modulates mitochondria fusion. Mitochondrial division inhibitor 1 (Mdivi-1), a small molecule inhibiting mitochondria fission, ameliorated mitochondria disruptions and reduced cell death in ZIKV-infected cells. Collectively, this study suggests that abnormal mitochondrial fragmentation contributes to ZIKV-induced neuronal cell death; rebalancing mitochondrial dynamics of fission-fusion could be a therapeutic strategy for drug development to treat ZIKV-mediated neuronal apoptosis.

Do socioeconomic factors drive Aedes mosquito vectors and their arboviral diseases? A systematic review of dengue, chikungunya, yellow fever, and Zika Virus

As the threat of arboviral diseases continues to escalate worldwide, the question of, "What types of human communities are at the greatest risk of infection?" persists as a key gap in the existing knowledge of arboviral diseases transmission dynamics. Here, we comprehensively review the existing literature on the socioeconomic drivers of the most common Aedes mosquito-borne diseases and Aedes mosquito presence/abundance. We reviewed a total of 182 studies on dengue viruses (DENV), chikungunya virus (CHIKV), yellow fever virus (YFVV), Zika virus (ZIKV), and presence of Aedes mosquito vectors. In general, associations between socioeconomic conditions and both Aedes-borne diseases and Aedes mosquitoes are highly variable and often location-specific. Although 50% to 60% of studies found greater presence or prevalence of disease or vectors in areas with lower socioeconomic status, approximately half of the remaining studies found either positive or null associations. We discuss the possible causes of this lack of conclusiveness as well as the implications it holds for future research and prevention efforts.

Mapping the evolutionary landscape of Zika virus infection in immunocompromised mice

The fundamental basis of how arboviruses evolve in nature and what regulates the adaptive process remain unclear. To address this problem, we established a Zika virus (ZIKV) vector-borne transmission system in immunocompromised mice to study the evolutionary characteristics of ZIKV infection. Using this system, we defined factors that influence the evolutionary landscape of ZIKV infection and show that transmission route and specific organ microenvironments impact viral diversity and defective viral genome production. In addition, we identified in mice the emergence of ZIKV mutants previously seen in natural infections, including variants present in currently circulating Asian and American strains, as well as mutations unique to the mouse infections. With these studies, we have established an insect-to-mouse transmission model to study ZIKV evolution in vivo. We also defined how organ microenvironments and infection route impact the ZIKV evolutionary landscape, providing a deeper understanding of the factors that regulate arbovirus evolution and emergence.

Zika structural genes determine the virulence of African and Asian lineages

The Asian lineage of Zika virus (ZIKV) is responsible for the recent epidemics in the Americas and severe disease, whereas the African lineage of ZIKV has not been reported to cause epidemics or severe disease. We constructed a cDNA infectious clone (IC) of an African ZIKV strain, which, together with our previously developed Asian ZIKV strain IC, allowed us to engineer chimeric viruses by swapping the structural and non-structural genes between the two lineages. Recombinant parental and chimeric viruses were analyzed in A129 and newborn CD1 mouse models. In the A129 mice, the African strain developed higher viremia, organ viral loading, and mortality rate. In CD1 mice, the African strain exhibited a higher neurovirulence than the Asian strain. A chimeric virus containing the structural genes from the African strain is more virulent than the Asian strain, whereas a chimeric virus containing the non-structural genes from the African strain exhibited a virulence comparable to the Asian strain. These results suggest that (i) African strain is more virulent than Asian strain and (ii) viral structural genes primarily determine the virulence difference between the two lineages in mouse models. Other factors may contribute to the discrepancy between the mouse and epidemic results.

Super resolution microscopy and deep learning identify Zika virus reorganization of the endoplasmic reticulum

The endoplasmic reticulum (ER) is a complex subcellular organelle composed of diverse structures such as tubules, sheets and tubular matrices. Flaviviruses such as Zika virus (ZIKV) induce reorganization of ER membranes to facilitate viral replication. Here, using 3D super resolution microscopy, ZIKV infection is shown to induce the formation of dense tubular matrices associated with viral replication in the central ER. Viral non-structural proteins NS4B and NS2B associate with replication complexes within the ZIKV-induced tubular matrix and exhibit distinct ER distributions outside this central ER region. Deep neural networks trained to distinguish ZIKV-infected versus mock-infected cells successfully identified ZIKV-induced central ER tubular matrices as a determinant of viral infection. Super resolution microscopy and deep learning are therefore able to identify and localize morphological features of the ER and allow for better understanding of how ER morphology changes due to viral infection.

Recent Development of Aptasensor for Influenza Virus Detection

In nowadays, we have entered the new era of pandemics and the significance of virus detection deeply impacts human society. Viruses with genetic mutations are reported nearly every year, and people have prepared tools to detect the virus and vaccines to ensure proper treatments. Influenza virus (IV) is one of the most harmful viruses reporting various mutations, sub-types, and rapid infection speed for humans and animals including swine and poultry. Moreover, IV infection presents several harmful symptoms including cough, fever, diarrhea, chills, even causing death. To reduce the IV-induced harm, its proper and rapid detection is highly required. Conventional techniques were used against various IV sub-types including H1N1, H3N2, and H5N1. However, some of the techniques are time-consuming, expensive, or labor-intensive for detecting IV. Recently, the nucleic acid-based aptamer has gained attention as a novel bioprobe for constructing a biosensor. In this review, the authors discuss the recent progress in aptasensors for detecting IV in terms of an electrochemical and an optical biosensor.

Antiviral effect of silymarin against Zika virus in vitro

Zika virus (ZIKV) epidemic and its association with severe neurological syndromes have raised worldwide concern. Despite the great clinical relevance of this infection, no vaccine or specific treatment is available and the search for antiviral compounds against ZIKV is extremely necessary. Several natural compounds, such as silymarin, exhibit antioxidant, hepatoprotective, and antiviral properties; however, the antiviral potential of this compound remains partially investigated. Therefore, the objective of this study was to evaluate in vitro the antiviral activity of silymarin against ZIKV infection. Global antiviral activity, dose-dependent, plaque reduction, and time-of-drug-addition assays were used to determine the anti-ZIKV activity of silymarin. Additionally, to start characterizing the mechanisms of action we determined whether silymarin could have a virucidal effect and inhibit viral adsorption and penetration stages. Regarding its global antiviral activity, silymarin showed significant inhibition of ZIKV infection, protecting cells infected with EC₅₀ equal to 34.17μg/mL, with a selectivity index greater than 17 and 4x greater than that of the positive control (ribavirin). Its greatest efficiency was achieved at 125μg/mL, whose cell viability did not differ from the control without infection and treatment. Furthermore, treatment with silymarin reduced viral load by up to two logs (> 90%) concerning viral control, when evaluating virucidal activity and the precocious times of infection. Thus, our results set to show the promising anti-ZIKV activity of silymarin, which does not seem to have a single inhibition mechanism, acting at different times of infection, and still has the advantage of silymarin be a phytotherapy already available on the market.

Engineering Antiviral Vaccines

Despite the vital role of vaccines in fighting viral pathogens, effective vaccines are still unavailable for many infectious diseases. The importance of vaccines cannot be overstated during the outbreak of a pandemic, such as the coronavirus disease 2019 (COVID-19) pandemic. The understanding of genomics, structural biology, and innate/adaptive immunity have expanded the toolkits available for current vaccine development. However, sudden outbreaks and the requirement of population-level immunization still pose great challenges in today's vaccine designs. Well-established vaccine development protocols from previous experiences are in place to guide the pipelines of vaccine development for emerging viral diseases. Nevertheless, vaccine development may follow different paradigms during a pandemic. For example, multiple vaccine candidates must be pushed into clinical trials simultaneously, and manufacturing capability must be scaled up in early stages. Factors from essential features of safety, efficacy, manufacturing, and distributions to administration approaches are taken into consideration based on advances in materials science and engineering technologies. In this review, we present recent advances in vaccine development by focusing on vaccine discovery, formulation, and delivery devices enabled by alternative administration approaches. We hope to shed light on developing better solutions for faster and better vaccine development strategies through the use of biomaterials, biomolecular engineering, nanotechnology, and microfabrication techniques.

Flexible Synthetic Carbohydrate Receptors as Inhibitors of Viral Attachment

Carbohydrate-receptor interactions are often involved in the docking of viruses to host cells, and this docking is a necessary step in the virus life cycle that precedes infection and, ultimately, replication. Despite the conserved structures of the glycans involved in docking, they are still considered "undruggable", meaning these glycans are beyond the scope of conventional pharmacological strategies. Recent advances in the development of synthetic carbohydrate receptors (SCRs), small molecules that bind carbohydrates, could bring carbohydrate-receptor interactions within the purview of druggable targets. Here we discuss the role of carbohydrate-receptor interactions in viral infection, the evolution of SCRs, and recent results demonstrating their ability to prevent viral infections in vitro. Common SCR design strategies based on boronic ester formation, metal chelation, and noncovalent interactions are discussed. The benefits of incorporating the idiosyncrasies of natural glycan-binding proteins-including flexibility, cooperativity, and multivalency-into SCR design to achieve nonglucosidic specificity are shown. These studies into SCR design and binding could lead to new strategies for mitigating the grave threat to human health posed by enveloped viruses, which are heavily glycosylated viroids that are the cause of some of the most pressing and untreatable diseases, including HIV, Dengue, Zika, influenza, and SARS-CoV-2.

Detection of Zika and dengue viruses in wild-caught mosquitoes collected during field surveillance in an environmental protection area in São Paulo, Brazil

Species of the genus Flavivirus are widespread in Brazil and are a major public health concern. The country's largest city, São Paulo, is in a highly urbanized area with a few forest fragments which are commonly used for recreation. These can be considered to present a potential risk of flavivirus transmission to humans as they are home simultaneously to vertebrate hosts and mosquitoes that are potential flavivirus vectors. The aim of this study was to conduct flavivirus surveillance in field-collected mosquitoes in the Capivari-Monos Environmental Protection Area (EPA) and identify the flavivirus species by sequence analysis in flavivirus IFA-positive pools. Monthly mosquito collections were carried out from March 2016 to April 2017 with CO2-baited CDC light traps. Specimens were identified morphologically and grouped in pools of up to 10 individuals according to their taxonomic category. A total of 260 pools of non-engorged females were inoculated into C6/36 cell culture, and the cell suspensions were analyzed by indirect immunofluorescence assay (IFA) after the incubation period. IFA-positive pools were tested by qRT-PCR with genus-specific primers targeting the flavivirus NS5 gene to confirm IFA-positive results and sequenced to identify the species. Anopheles cruzii (19.5%) and Wyeomyia confusa (15.3%) were the most frequent vector species collected. IFA was positive for flaviviruses in 2.3% (6/260) of the sample pools. This was confirmed by qRT-PCR in five pools (83.3%). All five flavivirus-positive pools were successfully sequenced and the species identified. DENV serotype 2 (DENV-2) was detected in Culex spp. and Culex vaxus pools, while ZIKV was identified in An. cruzii, Limatus durhamii and Wy. confusa pools. To the best of our knowledge, detection of flavivirus species of medical importance has never previously been reported in these species of wild-caught mosquitoes. The finding of DENV-2 and ZIKV circulating in wild mosquitoes suggests the existence of an enzootic cycle in the area. In-depth studies of DENV-2 and ZIKV, including investigation of mosquito infection, vector competence and infection in sylvatic hosts, are needed to shed light on the transmission dynamics of these important viruses and the potential risk of future outbreaks of DENV-2 and ZIKV infections in the region.

ZIKV viral proteins and their roles in virus-host interactions

The re-emergence of Zika virus (ZIKV) and its associated neonatal microcephaly and Guillain-Barré syndrome have led the World Health Organization to declare a global health emergency. Until today, many related studies have successively reported the role of various viral proteins of ZIKV in the process of ZIKV infection and pathogenicity. These studies have provided significant insights for the treatment and prevention of ZIKV infection. Here we review the current research advances in the functional characterization of the interactions between each ZIKV viral protein and its host factors.

A high-throughput multiplex assay to characterize flavivirus-specific immunoglobulins

Genus Flavivirus, which includes 53 virus species, is the leading cause of arthropod-borne diseases in humans. Diagnosis of these viral diseases is complicated by their overlapping epidemiology and clinical manifestations, and the fact that cross-reactive antibody responses are frequently elicited by individuals in response to infection. We developed a bead-based immunoassay to concomitantly profile the isotype and subclass of antibody responses (five isotypes and four subclasses) in parallel with specificity against multiple antigens. Our panel included 22 envelope (E) and non-structural 1 (NS1) proteins of different flaviviruses (Zika (ZIKV), Dengue (DENV), Yellow Fever (YFV), West Nile (WNV), Japanese Encephalitis (JEV) and Tick-Borne Encephalitis (TBEV)) and the envelope protein of Chikungunya virus (CHIKV). Using 54 samples from 40 individuals with ZIKV infection that had been pre-characterized, we identified 1) stronger ZIKV responses in individuals previously exposed to flavivirus compared to flavivirus-naïve individuals; 2) different antibody isotypes depending on the stage of infection: acute, convalescent and late convalescent; 3) cross-reactive responses; and 4) a potential CHIKV infection. The assay had a broad dynamic range (>5 logs) and has the potential to distinguish antigen-specific responses induced by ZIKV infection from cross-reactive responses. The multidimensional data provided by this high-throughput antibody-profiling platform can advance our understanding of the human immune response to flaviviruses as they expand their global reach.

Reverse genetic approaches for the development of Zika vaccines and therapeutics

In 2015-2016, the little known Zika virus (ZIKV) caused an epidemic, in which it became recognized as a unique human pathogen associated with a range of devastating congenital abnormalities collectively categorized as congenital Zika syndrome (CZS). In adults, the virus can trigger the autoimmune disorder Guillain-Barré syndrome (GBS), characterized by ascending paralysis. In February 2016, the World Health Organization (WHO) declared ZIKV to be a Public Health Emergency of International Concern. The global public health problem prompted academia, industry, and governments worldwide to initiate development of an effective vaccine to prevent another ZIKV epidemic that would put millions at risk. The development of reverse genetic systems for the study and manipulation of RNA viral genomes has revolutionized the field of virology, providing platforms for vaccine and antiviral development. In this review, we discuss the impact of reverse genetic systems on the rapid progress of ZIKV vaccines and antiviral therapeutics.

Hydroalcoholic extract of Caryocar brasiliense Cambess. leaves affect the development of Aedes aegypti mosquitoes

INTRODUCTION:

Curtailing the development of the aquatic immature stages of Aedes aegypti is one of the main measures to limit their spread and the diseases transmitted by them. The use of plant extracts is a promising approach in the development of natural insecticides. Thus, this research aimed to characterize the inhibitory effect of the hydroalcoholic extract of Caryocar brasiliense leaves on the emergence of adult A. aegypti and the main substances that constitute this extract.

METHODS:

C. brasiliense leaf extract was prepared by ethanol (70%) extraction. Bioassays using L3 larvae were performed at concentrations of 200, 300, 400, and 500 ppm. We identified the major secondary metabolites present in this extract, and performed toxicity tests on an off-target organism, Danio rerio.

RESULTS:

We observed a significant delay in the development of A. aegypti larvae mainly at a concentration of 500 ppm, and estimated an emergence inhibition for 50% of the population of 150 ppm. Moreover, the C. brasiliense leaf extracts exhibited low toxicity in D. rerio. The main compounds found in the extract were quercetin, violaxanthin, myricetin3-O-hexoside, methyl-elagic-3-arabinose acid, and isoquercitrin.

CONCLUSIONS:

Herein, we demonstrate the inhibition of mosquito development by the hydroalcoholic extract of C. brasiliense and suggest substances that may act as active principles.

Emerging Pandemic Diseases: How We Got to COVID-19

Infectious diseases prevalent in humans and animals are caused by pathogens that once emerged from other animal hosts. In addition to these established infections, new infectious diseases periodically emerge. In extreme cases they may cause pandemics such as COVID-19; in other cases, dead-end infections or smaller epidemics result. Established diseases may also re-emerge, for example by extending geographically or by becoming more transmissible or more pathogenic. Disease emergence reflects dynamic balances and imbalances, within complex globally distributed ecosystems comprising humans, animals, pathogens, and the environment. Understanding these variables is a necessary step in controlling future devastating disease emergences.

Safety and immunogenicity of a Zika purified inactivated virus vaccine given via standard, accelerated, or shortened schedules: a single-centre, double-blind, sequential-group, randomised, placebo-controlled, phase 1 trial

BACKGROUND

The development of an effective vaccine against Zika virus remains a public health priority. A Zika purified inactivated virus (ZPIV) vaccine candidate has been shown to protect animals against Zika virus challenge and to be well tolerated and immunogenic in humans up to 8 weeks of follow-up. We aimed to assess the safety and immunogenicity of ZPIV in humans up to 52 weeks of follow-up when given via standard or accelerated vaccination schedules.

METHODS

We did a single-centre, double-blind, randomised controlled, phase 1 trial in healthy adults aged 18-50 years with no known history of flavivirus vaccination or infection at Beth Israel Deaconess Medical Center in Boston, MA, USA. Participants were sequentially enrolled into one of three groups: ZPIV given at weeks 0 and 4 (standard regimen), weeks 0 and 2 (accelerated regimen), or week 0 alone (single-dose regimen). Within each group, participants were randomly assigned using a computer-generated randomisation schedule to receive an intramuscular injection of 5 μg ZPIV or saline placebo, in a ratio of 5:1. The sponsor, clinical staff, investigators, participants, and laboratory personnel were masked to treatment assignment. The primary endpoint was safety up to day 364 after final dose administration, and secondary endpoints were proportion of participants with positive humoral immune responses (50% microneutralisation titre [MN50] ≥100) and geometric mean MN50 at observed peak response (ie, the highest neutralising antibody level observed for an individual participant across all timepoints) and week 28. All participants who received at least one dose of ZPIV or placebo were included in the safety population; the analysis of immunogenicity at observed peak included all participants who received at least one dose of ZPIV or placebo and had any adverse events or immunogenicity data after dosing. The week 28 immunogenicity analysis population consisted of all participants who received ZPIV or placebo and had immunogenicity data available at week 28. This trial is registered with ClinicalTrials.gov, NCT02937233.

FINDINGS

Between Dec 8, 2016, and May 17, 2017, 12 participants were enrolled into each group and then randomly assigned to vaccine (n=10) or placebo (n=2). There were no serious or grade 3 treatment-related adverse events. The most common reactions among the 30 participants who received the vaccine were injection-site pain (24 [80%]), fatigue (16 [53%]), and headache (14 [46%]). A positive response at observed peak titre was detected in all participants who received ZPIV via the standard regimen, in eight (80%) of ten participants who received ZPIV via the accelerated regimen, and in none of the ten participants who received ZPIV via the single-dose regimen. The geometric mean of all individual participants' observed peak values was 1153·9 (95% CI 455·2-2925·2) in the standard regimen group, 517·7 (142·9-1875·6) in the accelerated regimen group, and 6·3 (3·7-10·8) in the single-dose regimen group. At week 28, a positive response was observed in one (13%) of eight participants who received ZPIV via the standard regimen and in no participant who received ZPIV via the accelerated (n=7) or single-dose (n=10) regimens. The geomteric mean titre (GMT) at this timepoint was 13·9 (95% CI 3·5-55·1) in the standard regimen group and 6·9 (4·0-11·9) in the accelerated regimen group; antibody titres were undetectable at 28 weeks in participants who received ZPIV via the single-dose regimen. For all vaccine schedules, GMTs peaked 2 weeks after the final vaccination and declined to less than 100 by study week 16. There was no difference in observed peak GMTs between the standard 4-week and the accelerated 2-week boosting regimens (p=0·4494).

INTERPRETATION

ZPIV was safe and well tolerated in humans up to 52 weeks of follow-up. ZPIV immunogenicity required two doses and was not durable. Additional studies of ZPIV to optimise dosing schedules are ongoing.

FUNDING

The Henry M Jackson Foundation for the Advancement of Military Medicine.

Leveraging multiple data types to estimate the size of the Zika epidemic in the Americas

Several hundred thousand Zika cases have been reported across the Americas since 2015. Incidence of infection was likely much higher, however, due to a high frequency of asymptomatic infection and other challenges that surveillance systems faced. Using a hierarchical Bayesian model with empirically-informed priors, we leveraged multiple types of Zika case data from 15 countries to estimate subnational reporting probabilities and infection attack rates (IARs). Zika IAR estimates ranged from 0.084 (95% CrI: 0.067-0.096) in Peru to 0.361 (95% CrI: 0.214-0.514) in Ecuador, with significant subnational variability in every country. Totaling infection estimates across these and 33 other countries and territories, our results suggest that 132.3 million (95% CrI: 111.3-170.2 million) people in the Americas had been infected by the end of 2018. These estimates represent the most extensive attempt to determine the size of the Zika epidemic in the Americas, offering a baseline for assessing the risk of future Zika epidemics in this region.

MODELING ZIKA TRANSMISSION DYNAMICS: PREVENTION AND CONTROL

The Zika virus (ZIKV) epidemic is depicted to have high spatial diversity and slow growth, attributable to the dynamics of the mosquito vector and mobility of the human populations. In an effort to understand the transmission dynamics of Zika virus, we formulate a new compartmental epidemic model with a system of seven differential equations and 11 parameters incorporating the decaying transmission rate and study the impact of protection measure on basic public health. We do not fit the model to the observed pattern of spread, rather we use parameter values estimated in the past and examine the extent to which the designed model prediction agrees with the pattern of spread seen in Brazil, via reaction–diffusion modeling. Our work includes estimation of key epidemiological parameters such as basic reproduction number ([Formula: see text], and gives a rough estimate of how many individuals can be typically infected during an outbreak if it occurs in India. We used partial rank correlation coefficient method for global sensitivity analysis to identify the most influential model parameters. Using optimal control theory and Pontryagin’s maximum principle, a control model has been proposed and conditions for the optimal control are determined for the deterministic model of Zika virus. The control functions for the strategies (i) vector-to-human contact reduction and (ii) vector elimination are introduced into the system. Numerical simulations are also performed. This work aimed at understanding the potential extent and timing of the ZIKV epidemic can be used as a template for the analysis of future mosquito-borne epidemics.

Detailed Analyses of Zika Virus Tropism in Culex quinquefasciatus Reveal Systemic Refractoriness

The role of Culex quinquefasciatus in Zika virus transmission has been debated since the epidemic of Zika occurred in the Americas in 2015 to 2016. The majority of studies have found no evidence that C. quinquefasciatus or other Culex species are competent vectors of Zika virus, and the few studies that have proposed Zika vector status for C. quinquefasciatus have relied predominantly on quantitative real-time PCR (qRT-PCR) for viral detection. We assessed the infectious range of pre- and post-epidemic Zika virus isolates in order to classify mosquito samples based on titer infectiousness and demonstrated that two strains of C. quinquefasciatus, including one previously found to be competent, are highly resistant to infection with these Zika isolates compared to Aedes aegypti and are not competent for virus transmission. Further dissection of the dynamics of Zika exposure in both A. aegypti and C. quinquefasciatus revealed that while virus transmission by C. quinquefasciatus is blocked at the levels of the midgut and salivary glands, viral RNA persists in these tissues for prolonged periods post-exposure. We assessed Zika entry dynamics in both Aedes and Culex cells, and our results suggest that Zika virus infection in Culex cells may be blocked downstream of cell entry. These findings strongly suggest that C. quinquefasciatus is not a vector of Zika virus and additionally inform the use of qRT-PCR in vector competence assays as well as our understanding of barriers to arbovirus infection in non-susceptible mosquito species.IMPORTANCE Understanding which mosquito species transmit an emerging arbovirus is critical to effective vector control. During the Zika virus epidemic in 2015 to 2016, Aedes mosquitoes were confirmed as vectors. However, studies addressing the vector status of Culex quinquefasciatus mosquitoes presented conflicting evidence and remain an outstanding source of confusion in the field. Here, we established a robust cell-based assay to identify infectious titers of Zika virus and assessed the virus titers in C. quinquefasciatus by quantitative real-time PCR (qRT-PCR). We found that while low levels of virus were detected in C. quinquefasciatus, these titers did not correspond to infectious virus, and these mosquitoes did not transmit virus in the saliva. We also present evidence that the virus may enter Culex cells before infection is disrupted. Our findings are important for future studies incriminating vector species using qRT-PCR for virus detection and offer new information on how virus transmission is blocked by mosquitoes.

Portable and accurate diagnostics for COVID-19: Combined use of the miniPCR thermocycler and a well-plate reader for SARS-CoV-2 virus detection

The coronavirus disease 2019 (COVID-19) pandemic has crudely demonstrated the need for massive and rapid diagnostics. By the first week of July, more than 10,000,000 positive cases of COVID-19 have been reported worldwide, although this number could be greatly underestimated. In the case of an epidemic emergency, the first line of response should be based on commercially available and validated resources. Here, we demonstrate the use of the miniPCR, a commercial compact and portable PCR device recently available on the market, in combination with a commercial well-plate reader as a diagnostic system for detecting genetic material of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causal agent of COVID-19. We used the miniPCR to detect and amplify SARS-CoV-2 DNA sequences using the sets of initiators recommended by the World Health Organization (WHO) for targeting three different regions that encode for the N protein. Prior to amplification, samples were combined with a DNA intercalating reagent (i.e., EvaGreen Dye). Sample fluorescence after amplification was then read using a commercial 96-well plate reader. This straightforward method allows the detection and amplification of SARS-CoV-2 nucleic acids in the range of ~625 to 2×105 DNA copies. The accuracy and simplicity of this diagnostics strategy may provide a cost-efficient and reliable alternative for COVID-19 pandemic testing, particularly in underdeveloped regions where RT-QPCR instrument availability may be limited. The portability, ease of use, and reproducibility of the miniPCR makes it a reliable alternative for deployment in point-of-care SARS-CoV-2 detection efforts during pandemics.

COVID-19 Therapeutic Options Under Investigation

Since its emergence in China in December 2019, COVID-19 has quickly spread around the globe causing a pandemic. Vaccination or the development of herd immunity seems the only way to slow down the spread of the virus; however, both are not achievable in the near future. Therefore, effective treatments to mitigate the burden of this pandemic and reduce mortality rates are urgently needed. Preclinical and clinical studies of potential antiviral and immunomodulatory compounds and molecules to identify safe and efficacious therapeutics for COVID-19 are ongoing. Two compounds, remdesivir, and dexamethasone have been so far shown to reduce COVID-19-associated death. Here, we provide a review of the potential therapeutic agents being considered for the treatment and management of COVID-19 patients.

Ecological processes underlying the emergence of novel enzootic cycles: Arboviruses in the neotropics as a case study

Pathogens originating from wildlife (zoonoses) pose a significant public health burden, comprising the majority of emerging infectious diseases. Efforts to control and prevent zoonotic disease have traditionally focused on animal-to-human transmission, or "spillover." However, in the modern era, increasing international mobility and commerce facilitate the spread of infected humans, nonhuman animals (hereafter animals), and their products worldwide, thereby increasing the risk that zoonoses will be introduced to new geographic areas. Imported zoonoses can potentially "spill back" to infect local wildlife-a danger magnified by urbanization and other anthropogenic pressures that increase contacts between human and wildlife populations. In this way, humans can function as vectors, dispersing zoonoses from their ancestral enzootic systems to establish reservoirs elsewhere in novel animal host populations. Once established, these enzootic cycles are largely unassailable by standard control measures and have the potential to feed human epidemics. Understanding when and why translocated zoonoses establish novel enzootic cycles requires disentangling ecologically complex and stochastic interactions between the zoonosis, the human population, and the natural ecosystem. In this Review, we address this challenge by delineating potential ecological mechanisms affecting each stage of enzootic establishment-wildlife exposure, enzootic infection, and persistence-applying existing ecological concepts from epidemiology, invasion biology, and population ecology. We ground our discussion in the neotropics, where four arthropod-borne viruses (arboviruses) of zoonotic origin-yellow fever, dengue, chikungunya, and Zika viruses-have separately been introduced into the human population. This paper is a step towards developing a framework for predicting and preventing novel enzootic cycles in the face of zoonotic translocations.

Epidemic Alphaviruses: Ecology, Emergence and Outbreaks

Over the past century, the emergence/reemergence of arthropod-borne zoonotic agents has been a growing public health concern. In particular, agents from the genus Alphavirus pose a significant risk to both animal and human health. Human alphaviral disease presents with either arthritogenic or encephalitic manifestations and is associated with significant morbidity and/or mortality. Unfortunately, there are presently no vaccines or antiviral measures approved for human use. The present review examines the ecology, epidemiology, disease, past outbreaks, and potential to cause contemporary outbreaks for several alphavirus pathogens.

Diversity and circulation of Jingmen tick virus in ticks and mammals

Since its initial identification in ticks in 2010, Jingmen tick virus (JMTV) has been described in cattle, rodents, and primates. To better understand the diversity, evolution, and transmission of JMTV, we sampled 215 ticks, 104 cattle bloods, 216 bats, and 119 rodents in Wenzhou city, Zhejiang Province, China as well as 240 bats from Guizhou and Henan Provinces. JMTV was identified in 107 ticks (from two species), 54 bats (eleven species), 8 rodents (three species), and 10 cattle, with prevalence levels of 49.8, 11.8, 6.7, and 9.6 per cent, respectively, suggesting that bats may be a natural reservoir of JMTV. Phylogenetic analyses revealed that all the newly identified JMTVs were closely related to each other and to previously described viruses. Additionally, all tick and mammalian JMTV sampled in Wenzhou shared a consistent genomic structure, suggesting that the virus can cocirculate between ticks and mammals without observable variation in genome organization. All JMTVs sampled globally could be divided into two phylogenetic groups, Mantel tests suggested that geographic isolation, rather than host species, may be the main driver of JMTV diversity. However, the exact geographical origin of JMTV was difficult to determine, suggesting that this virus has a complex evolutionary history.

Resting behavior of Aedes aegypti in southeastern Senegal

BACKGROUND

Only the sylvatic and zoophilic population of Aedes aegypti was formerly identified in southeastern Senegal. A newly established anthropophilic population was detected in the urban area of the Kedougou city. Because of its new behavior, this species could play a primary role in the transmission of dengue and other arboviruses in this area. Because these arboviruses have no vaccine and specific treatments, vector control remains the only effective way to control their outbreaks. Effective vector control strategies require to understand some aspects of the bioecology of the vector, specially resting behavior. The aims of this study were to investigate the sites and resting behavior of Ae. aegypti in southeastern Senegal.

METHODS

Mosquitoes were collected in several potential resting places (rooms, tires, bricks and scrap metal) by two technicians using a CDC back-pack aspirator in the Kedougou bus station and other sites within the city and the nearby rural area. Collected mosquitoes were identified and classified.

RESULTS

A total of 1291 mosquitoes belonging to 6 genera and 20 species were collected. Aedes aegypti was the dominant species in all the resting places investigated. This species was found resting equally in rooms, bricks, tires and scrap metal. The average number of Ae. aegypti collected in resting places was higher in the bus station (center of the city) compared to the other areas. The rates of unfed and fed females varied significantly in the different resting places while the proportions of gravid females which varied between 7.8% in tires and 1.8% in rooms were comparable.

CONCLUSIONS

This study showed that Ae. aegypti could be found resting indoors and in several sites, including in used tires outdoors. These data will be helpful in setting better arboviruses surveillance and vector control strategies.

Determinants of dengue virus dispersal in the Americas

Dengue viruses (DENVs) are classified into four serotypes, each of which contains multiple genotypes. DENV genotypes introduced into the Americas over the past five decades have exhibited different rates and patterns of spatial dispersal. In order to understand factors underlying these patterns, we utilized a statistical framework that allows for the integration of ecological, socioeconomic, and air transport mobility data as predictors of viral diffusion while inferring the phylogeographic history. Predictors describing spatial diffusion based on several covariates were compared using a generalized linear model approach, where the support for each scenario and its contribution is estimated simultaneously from the data set. Although different predictors were identified for different serotypes, our analysis suggests that overall diffusion of DENV-1, -2, and -3 in the Americas was associated with airline traffic. The other significant predictors included human population size, the geographical distance between countries and between urban centers and the density of people living in urban environments.

Safety and immunogenicity of a mosquito saliva peptide-based vaccine: a randomised, placebo-controlled, double-blind, phase 1 trial

BACKGROUND

In animal models, immunity to mosquito salivary proteins protects animals against mosquito-borne disease. These findings provide a rationale to vaccinate against mosquito saliva instead of the pathogen itself. To our knowledge, no vector salivary protein-based vaccine has been tested for safety and immunogenicity in humans. We aimed to assess the safety and immunogenicity of Anopheles gambiae saliva vaccine (AGS-v), a peptide-based vaccine derived from four A gambiae salivary proteins, in humans.

METHODS

In this randomised, placebo-controlled, double-blind, phase 1 trial, participants were enrolled at the National Institutes of Health Clinical Center in Bethesda, MD, USA. Participants were eligible if they were healthy adults, aged 18-50 years with no history of severe allergic reactions to mosquito bites. Participants were randomly assigned (1:1:1), using block randomisation and a computer-generated randomisation sequence, to treatment with either 200 nmol of AGS-v vaccine alone, 200 nmol of AGS-v with adjuvant (Montanide ISA 51), or sterile water as placebo. Participants and clinicians were masked to treatment assignment. Participants were given a subcutaneous injection of their allocated treatment at day 0 and day 21, followed by exposure to feeding by an uninfected Aedes aegypti mosquito at day 42 to assess subsequent risk to mosquito bites in a controlled setting. The primary endpoints were safety and immunogenicity at day 42 after the first immunisation. Participants who were given at least one dose of assigned treatment were assessed for the primary endpoints and analysis was by intention to treat. The trial was registered with ClinicalTrials.gov, NCT03055000, and is closed for accrual.

FINDINGS

Between Feb 15 and Sept 10, 2017, we enrolled and randomly assigned 49 healthy adult participants to the adjuvanted vaccine (n=17), vaccine alone (n=16), or placebo group (n=16). Five participants did not complete the two-injection regimen with mosquito feeding at day 42, but were included in the safety analyses. No systemic safety concerns were identified; however, one participant in the adjuvanted vaccine group developed a grade 3 erythematous rash at the injection site. Pain, swelling, erythema, and itching were the most commonly reported local symptoms and were significantly increased in the adjuvanted vaccine group compared with both other treatment groups (nine [53%] of 17 participants in the adjuvanted vaccine group, two [13%] of 16 in the vaccine only group, and one [6%] of 16 in the placebo group; p=0·004). By day 42, participants who were given the adjuvanted vaccine had a significant increase in vaccine-specific total IgG antibodies compared with at baseline than did participants who were give vaccine only (absolute difference of log10-fold change of 0·64 [95% CI 0·39 to 0·89]; p=0·0002) and who were given placebo (0·62 [0·34 to 0·91]; p=0·0001). We saw a significant increase in IFN-γ production by peripheral blood mononuclear cells at day 42 in the adjuvanted vaccine group compared with in the placebo group (absolute difference of log10 ratio of vaccine peptide-stimulated vs negative control 0·17 [95% CI 0·061 to 0·27]; p=0·009) but we saw no difference between the IFN-γ production in the vaccine only group compared with the placebo group (0·022 [-0·072 to 0·116]; p=0·63).

INTERPRETATION

AGS-v was well tolerated, and, when adjuvanted, immunogenic. These findings suggest that vector-targeted vaccine administration in humans is safe and could be a viable option for the increasing burden of vector-borne disease.

FUNDING

Office of the Director and the Division of Intramural Research at the National Institute of Allergy and Infectious Diseases, and National Institutes of Health.