A generic screening platform for inhibitors of virus induced cell fusion using cellular electrical impedance

Exploring therapeutic potential of claudin in Flavivirus infection: A review on current advances and future perspectives

Flavivirus such as Dengue, Zika, West Nile, Japanese encephalitis, and yellow fever virus, composed of single-stranded positive-sense RNA, predominantly contaminated through arthropods. Flavivirus infection characterises from asymptomatic signs to severe hemorrhagic fever and encephalitis. The host's immune system detects these viruses and provides a defence mechanism to sustain their life and growth. However, flaviviruses through different mechanisms compromise the host's immune defence. The current pharmacotherapeutic strategies against Flavivirus infection target different stages of the Flavivirus life cycle and its proteins. On the contrary, the host's immune defence mechanism is equally important to restrict their growth. It has been suggested that flaviviruses compromise claudins to sustain their life and growth inside the mammalian cells. This review primarily focuses on the effect of Flavivirus on claudins (CLDNs), transmembrane proteins that form tight junctions in mammalian cells. CLDNs are crucial in viral entry and pathogenesis by regulating paracellular permeability, particularly in tissues and the blood-brain barrier. Recent studies indicate that the Dengue and Zika viruses can potentially be treated by targeting specific CLDNs-specifically CLDN 1, CLDN 5, and CLDN 7 to inhibit viral entry and fusion. Additionally, it highlights the current challenges and future prospects in developing claudin-based antiviral agents against Flavivirus infections.

Impedance-based method for the quantification of infectious SARS-CoV-2

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the etiologic agent involved in the coronavirus disease 2019 (COVID-19) pandemic. The development of infectious titration methods is crucial to provide data for a better understanding of transmission routes, as well as to validate the efficacy of inactivation treatments. Nevertheless, the low-throughput analytical capacity of traditional methods may be a limiting factor for a large screening of samples. The aim of the study was to develop a Real-Time Cell Analysis (RTCA) assay based on the measurement of cell impedance to quantify infectious SARS-CoV-2. The kinetics of cell impedance showed a virus-specific Cell Index (CI) drop. This enabled the correlation between viral concentrations and time at which a 50 % drop in CI values was observed (tCI50), with establishment of a standard curve. In parallel, the improved Spearman and Kärber method was used to quantify infectious titer since the virus-induced CI drop is correlated to the Cytopathic Effect. The estimated uncertainty was respectively 0.57, 0.36, and 0.26 log10 with 4, 8, and 16 wells per dilution. Thus, the RTCA assay is a powerful tool with a greatly simplified workflow for effective risk assessment in the field of food and environmental virology.

Interaction of the Wolbachia surface protein with a novel pro-viral protein from Aedes aegypti

Dengue virus (DENV) and other flaviviruses are prevented from replicating in mosquitoes by Wolbachia. To date, several reports have appeared that highlight multiple molecular and cellular pathways involved in the blocking mechanism, which underlines the complicated nature of the mechanism. Here, we developed a hypothesis on whether Wolbachia proteins interact with pro-viral host proteins by using a unique approach to study the antiviral mechanism based on Wolbachia-host protein-protein interaction. We selected Wolbachia surface protein (WSP) for co-immunoprecipitation because of its abundance and possible secretion. We first confirmed WSP's secretion in mosquito cells and found two host proteins, Ae. aegypti serine-threonine kinase (STK) and synaptic vesicle membrane (SVM) protein VAT-1, and one Wolbachia protein (wGroEL) interacting with WSP. We examined the role of STK and SVM genes in relation to DENV replication in Ae. aegypti mosquitoes and mosquito cell lines with and without Wolbachia. In DENV-infected Aag2 cells, the expression of SVM and STK was significantly increased. However, although these genes were induced in Wolbachia-infected Aag2 cells, they were downregulated after DENV infection. Silencing of STK, but not SVM, reduced DENV replication in Aag2 cells and mosquitoes. Conversely, RNA activation of STK, by utilizing promoter induction via short activating oligos, resulted in higher DENV replication in Wolbachia-infected and uninfected cell lines. Overall, our findings suggest that STK is a pro-viral gene, and Wolbachia WSP binds to STK, possibly making it less accessible for DENV replication.

IMPORTANCE

Wolbachia is an endosymbiotic bacterium that blocks the replication of arboviruses in transinfected Aedes aegypti mosquitoes. In this study, we focused on identifying the potential interaction of Wolbachia proteins with the host pro-viral proteins. For this, we embarked on identifying the interacting proteins with a major Wolbachia protein, WSP, which is both structural and also secreted into the host cells. An Ae. aegypti STK was identified, which is induced in DENV and Wolbachia-infected cells. Silencing or induction of the gene led to reduced and increased DENV replication in vitro. Consistently, knocking down the gene in mosquitoes resulted in decreased virus replication. We hypothesize that WSP may sequester STK, which is pro-viral, contributing to Wolbachia virus blocking.

Evaluation of three alternative methods to the plaque reduction neutralizing assay for measuring neutralizing antibodies to dengue virus serotype 2

BACKGROUND

Dengue is a global public health challenge which requires accurate diagnostic methods for surveillance and control. The gold standard for detecting dengue neutralizing antibodies (nAbs) is the plaque reduction neutralization test (PRNT), which is both labor-intensive and time-consuming. This study aims to evaluate three alternative approaches, namely, the MTT-based (or (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) microneutralization assay, the xCELLigence real-time cell analysis (RTCA), and the immuno-plaque assay-focus reduction neutralization test (iPA-FRNT).

METHODS

Twenty-two residual serum samples were tested for DENV-2 nAbs using all four assays at three neutralization endpoints of 50%, 70% and 90% inhibition in virus growth. For each neutralization endpoint, results were compared using linear regression and correlation analyses. Test performance characteristics were further obtained for iPA-FRNT using 38 additional serum samples.

RESULTS

Positive correlation of DENV-2 neutralization titers for the MTT-based microneutralization assay and the PRNT assay was only observed at the neutralization endpoint of 50% (r = 0.690). In contrast, at all three neutralization end points, a linear trend and positive correlation of DENV-2 neutralization titers for the xCELLigence RTCA and the PRNT assays were observed, yielding strong or very strong correlation (r = 0.829 to 0.967). This was similarly observed for the iPA-FRNT assay (r = 0.821 to 0.916), which also offered the added advantage of measuring neutralizing titers to non-plaque forming viruses.

CONCLUSION

The xCELLigence RTCA and iPA-FRNT assays could serve as suitable alternatives to PRNT for dengue serological testing. The decision to adopt these methods may depend on the laboratory setting, and the utility of additional applications offered by these technologies.

Antiviral Activities of Heparan Sulfate Mimetic RAFT Polymers Against Mosquito-borne Viruses

Mosquito-borne viruses are a major worldwide health problem associated with high morbidity and mortality rates and significant impacts on national healthcare budgets. The development of antiviral drugs for both the treatment and prophylaxis of these diseases is thus of considerable importance. To address the need for therapeutics with antiviral activity, a library of heparan sulfate mimetic polymers was screened against dengue virus (DENV), Yellow fever virus (YFV), Zika virus (ZIKV), and Ross River virus (RRV). The polymers were prepared by RAFT polymerization of various acidic monomers with a target MW of 20 kDa (average Mn ∼ 27 kDa by GPC). Among the polymers, poly(SS), a homopolymer of sodium styrenesulfonate, was identified as a broad spectrum antiviral with activity against all the tested viruses and particularly potent inhibition of YFV (IC50 = 310 pM). Our results further uncovered that poly(SS) exhibited a robust inhibition of ZIKV infection in both mosquito and human cell lines, which points out the potential functions of poly(SS) in preventing mosquito-borne viruses associated diseases by blocking viral transmission in their mosquito vectors and mitigating viral infection in patients.

Cellular electrical impedance to profile SARS-CoV-2 fusion inhibitors and to assess the fusogenic potential of spike mutants

Despite the vaccination campaigns for COVID-19, we still cannot control the spread of SARS-CoV-2, as evidenced by the ongoing circulation of the Omicron variants of concern. This highlights the need for broad-spectrum antivirals to further combat COVID-19 and to be prepared for a new pandemic with a (re-)emerging coronavirus. An interesting target for antiviral drug development is the fusion of the viral envelope with host cell membranes, a crucial early step in the replication cycle of coronaviruses. In this study, we explored the use of cellular electrical impedance (CEI) to quantitatively monitor morphological changes in real time, resulting from cell-cell fusion elicited by SARS-CoV-2 spike. The impedance signal in CEI-quantified cell-cell fusion correlated with the expression level of SARS-CoV-2 spike in transfected HEK293T cells. For antiviral assessment, we validated the CEI assay with the fusion inhibitor EK1 and measured a concentration-dependent inhibition of SARS-CoV-2 spike mediated cell-cell fusion (IC₅₀ value of 0.13 μM). In addition, CEI was used to confirm the fusion inhibitory activity of the carbohydrate-binding plant lectin UDA against SARS-CoV-2 (IC₅₀ value of 0.55 μM), which complements prior in-house profiling activities. Finally, we explored the utility of CEI in quantifying the fusogenic potential of mutant spike proteins and in comparing the fusion efficiency of SARS-CoV-2 variants of concern. In summary, we demonstrate that CEI is a powerful and sensitive technology that can be applied to studying the fusion process of SARS-CoV-2 and to screening and characterizing fusion inhibitors in a label-free and non-invasive manner.

Analysing inhibition of dengue virus in Wolbachia-infected mosquito cells following the removal of Wolbachia

Wolbachia pipientis is known to block replication of positive sense RNA viruses. Previously, we created an Aedes aegypti Aag2 cell line (Aag2.wAlbB) transinfected with the wAlbB strain of Wolbachia and a matching tetracycline-cured Aag2.tet cell line. While dengue virus (DENV) was blocked in Aag2.wAlbB cells, we found significant inhibition of DENV in Aag2.tet cells. RNA-Seq analysis of the cells confirmed removal of Wolbachia and lack of expression of Wolbachia genes that could have been due to lateral gene transfer in Aag2.tet cells. However, we noticed a substantial increase in the abundance of phasi charoen-like virus (PCLV) in Aag2.tet cells. When RNAi was used to reduce the PCLV levels, DENV replication was significantly increased. Further, we found significant changes in the expression of antiviral and proviral genes in Aag2.tet cells. Overall, the results reveal an antagonistic interaction between DENV and PCLV and how PCLV-induced changes could contribute to DENV inhibition.

Wolbachia RNase HI contributes to virus blocking in the mosquito Aedes aegypti

The endosymbiotic bacterium Wolbachia pipientis blocks replication of several arboviruses in transinfected Aedes aegypti mosquitoes. However, the mechanism of virus blocking remains poorly understood. Here, we characterized an RNase HI gene from Wolbachia, which is rapidly induced in response to dengue virus (DENV) infection. Knocking down w RNase HI using antisense RNA in Wolbachia-transinfected mosquito cell lines and A. aegypti mosquitoes led to increased DENV replication. Furthermore, overexpression of wRNase HI, in the absence of Wolbachia, led to reduced replication of a positive sense RNA virus, but had no effect on a negative sense RNA virus, a familiar scenario in Wolbachia-infected cells. Altogether, our results provide compelling evidence for the missing link between early Wolbachia-mediated virus blocking and degradation of viral RNA. These findings and the successful pioneered knockdown of Wolbachia genes using antisense RNA in cell line and mosquitoes enable new ways to manipulate and study the complex endosymbiont-host interactions.

Human Claudin-Derived Peptides Block the Membrane Fusion Process of Zika Virus and Are Broad Flavivirus Inhibitors

Zika virus (ZIKV) is a mosquito-borne flavivirus that emerged in the Pacific islands in 2007 and spread to the Americas in 2015. The infection remains asymptomatic in most cases but can be associated with severe neurological disorders. Despite massive efforts, no specific drug or vaccine against ZIKV infection is available to date. Claudins are tight-junction proteins that favor the entry of several flaviviruses, including ZIKV. In this study, we identified two peptides derived from the N-terminal sequences of claudin-7 and claudin-1, named CL7.1 and CL1.1, respectively, that inhibited ZIKV infection in a panel of human cell lines. Using cell-to-cell fusion assays, we demonstrated that these peptides blocked the ZIKV E-mediated membrane fusion. A comparison of the antiviral efficacy of CL1.1 and CL7.1 pointed to the importance of the peptide amphipathicity. Electron microscopic analysis revealed that CL1.1 altered the ultrastructure of the viral particles likely by binding the virus lipid envelope. However, amphipathicity could not fully explain the antiviral activity of CL1.1. In silico docking simulations suggested that CL1.1 may also interact with the E protein, near its stem region. Overall, our data suggested that claudin-derived peptides inhibition may be linked to simultaneous interaction with the E protein and the viral lipid envelope. Finally, we found that CL1.1 also blocked infection by yellow fever and Japanese encephalitis viruses but not by HIV-1 or SARS-CoV-2. Our results provide a basis for the future development of therapeutics against a wide range of endemic and emerging flaviviruses. IMPORTANCE Zika virus (ZIKV) is a flavivirus transmitted by mosquito bites that have spread to the Pacific Islands and the Americas over the past decade. The infection remains asymptomatic in most cases but can cause severe neurological disorders. ZIKV is a major public health threat in areas of endemicity, and there is currently no specific antiviral drug or vaccine available. We identified two antiviral peptides deriving from the N-terminal sequences of claudin-7 and claudin-1 with the latter being the most effective. These peptides block the envelope-mediated membrane fusion. Our data suggested that the inhibition was likely achieved by simultaneously interacting with the viral lipid envelope and the E protein. The peptides also inhibited other flaviviruses. These results could provide the basis for the development of therapies that might target a wide array of flaviviruses from current epidemics and possibly future emergences.

Knockout of Dicer-2 in the Sf9 cell line enhances the replication of Spodoptera frugiperda rhabdovirus and conditionally increases baculovirus replication

The Sf9 cell line, originally isolated from the ovarian tissue of Spodoptera frugiperda larvae, is widely used in academia and industry for the baculovirus-mediated production of recombinant proteins and virus-like particles. RNA interference (RNAi) is a conserved antiviral pathway present in eukaryotic organisms and is the primary antiviral defence mechanism in insects. Recent evidence has implicated RNAi as an antiviral response to baculovirus infection in Sf9 cells. To test this hypothesis, CRISPR/Cas9 technology was used to disable the RNAi pathway in Sf9 cells by knocking out Dicer-2, the protein responsible for cleaving viral double-stranded RNA precursors into short interfering RNAs. Infection of Dicer-2 knockout Sf9 cells with either the wild-type baculovirus Autographa californica nucleopolyhedrovirus (AcMNPV), recombinant AcMNPV (rAcMNPV) expressing β-galactosidase (β-gal), or rAcMNPV expressing a wasp venom protein (Vn50) at a multiplicity of infection (m.o.i.) of 1 resulted in a modest increase in virus replication compared to control Sf9 cells under adherent culture conditions. In contrast, Dicer-2 knockout Sf9 monolayer or suspension cultures infected by the rAcMNPV expressing β-gal at higher m.o.i.s (3.5 and 20) did not exhibit increases in either viral DNA replication or β-gal production. Intriguingly, during long-term passaging in suspension, Dicer-2 knockout Sf9 cultures underwent transient crashes in cell proliferation and viability. It was discovered that these periods of low growth and viability coincided with a dramatic increase in the RNA levels of S. frugiperda rhabdovirus, a recently identified adventitious virus that persistently infects the Sf9 cell line, suggesting a role for Dicer-2 in managing chronic viral infections in this industrially relevant insect cell line.

Development of molecular clamp stabilized hemagglutinin vaccines for Influenza A viruses

Influenza viruses cause a significant number of infections and deaths annually. In addition to seasonal infections, the risk of an influenza virus pandemic emerging is extremely high owing to the large reservoir of diverse influenza viruses found in animals and the co-circulation of many influenza subtypes which can reassort into novel strains. Development of a universal influenza vaccine has proven extremely challenging. In the absence of such a vaccine, rapid response technologies provide the best potential to counter a novel influenza outbreak. Here, we demonstrate that a modular trimerization domain known as the molecular clamp allows the efficient production and purification of conformationally stabilised prefusion hemagglutinin (HA) from a diverse range of influenza A subtypes. These clamp-stabilised HA proteins provided robust protection from homologous virus challenge in mouse and ferret models and some cross protection against heterologous virus challenge. This work provides a proof-of-concept for clamp-stabilised HA vaccines as a tool for rapid response vaccine development against future influenza A virus pandemics.

Vaccine design and delivery approaches for COVID-19

COVID-19 is still a deadly disease that remains yet a major challenge for humans. In recent times, many large pharmaceutical and non-pharmaceutical companies have invested a lot of time and cost in fighting this disease. In this regard, today's scientific knowledge shows that designing and producing an effective vaccine is the best possible way to diminish the disease burden and dissemination or even eradicate the disease. Due to the urgent need, many vaccines are now available earlier than scheduled. New technologies have also helped to produce much more effective vaccines, although the potential side effects must be taken into account. Thus, in this review, the types of vaccines and vaccine designs made against COVID-19, the vaccination programs, as well as the delivery methods and molecules that have been used to deliver some vaccines that need a carrier will be described.

制备人脐静脉内皮细胞和人肺腺癌细胞融合细胞的新方法

Purpose:

Human umbilical endothelial cells (HUVECs) have been proved to be an effective whole-cell vaccine inhibiting tumor angiogenesis. In this study, we fused HUVECs with human lung adenocarcinoma cells A549 s, aiming at preparing lung cancer vaccine to achieve dual effects of anti-tumor angiogenesis and specific immunity to tumor cells.

Methods:

A549 cells were induced by ethyl methane sulfonate (EMS) and 8-azaguanine (8-AG) to get hypoxanthine guanine phosphoribosyl transferase (HGPRT) auxotrophic A549 cells. Then Fused HGPRT auxotrophic A549 cells with primary HUVEC cells by combining electrofusion with polyethylene glycol (PEG). Afterward the fusion cells were screened by HAT and HT selective medium and sorted by flow cell sorter to obtain high-purity HUVEC-A549 cells. Finally, HUVEC-A549 cells were identified by karyotype analysis and western blotting.

Results:

The fusion efficiency of HUVEC-A549 cells prepared by combining electrofusion with polyethylene glycol (PEG) was significantly higher than that of electrofusion and PEG (43.0% vs 17.60% vs 2.71%, P < 0.05). After screened by HAT and HT selective medium and sorted by flow cell sorter, the proportion of HUVEC-A549 cells can count for 71.2% ± 3.2%. The mode of chromosomes in HUVEC-A549 cells was 68, and the chromosome was triploid. VE-cadherin and platelet endothelial cell adhesion molecule-1 (CD31) were highly expressed in HUVECs and HUVEC-A549 cells, but not in A549 cells.

Conclusions:

These results indicate that HUVEC-A549 cells retain the biological characteristics of human umbilical vein endothelial cells and A549 cells. It can be used in the experimental study of lung cancer cell vaccine.

Respiratory syntycial virus: Current treatment strategies and vaccine approaches

Respiratory Syncytial Virus is a yearly respiratory virus that causes significant frequencies of morbidities, particularly in the young and elderly populations. However, preventive vaccines and/or treatment therapies are generally lacking, although much attention is now being placed on this virus. Moreover, there are now multiple strategies currently being explored in a race to the first licensed vaccine. While vaccines are being developed, multiple treatment strategies are being explored to attenuate the severity of infection and thus reduce hospitalization rates in vulnerable populations. This review outlines current strategies to prevent or treat this virus in the hopes of reducing significant human morbidity and mortality that occurs yearly with this seasonal virus.

A broadly protective antibody that targets the flavivirus NS1 protein

There are no approved flaviviral therapies and the development of vaccines against flaviruses has the potential of being undermined by antibody-dependent enhancement (ADE). The flavivirus nonstructural protein 1 (NS1) is a promising vaccine antigen with low ADE risk but has yet to be explored as a broad-spectrum therapeutic antibody target. Here, we provide the structural basis of NS1 antibody cross-reactivity through cocrystallization of the antibody 1G5.3 with NS1 proteins from dengue and Zika viruses. The 1G5.3 antibody blocks multi-flavivirus NS1-mediated cell permeability in disease-relevant cell lines, and therapeutic application of 1G5.3 reduces viremia and improves survival in dengue, Zika, and West Nile virus murine models. Finally, we demonstrate that 1G5.3 protection is independent of effector function, identifying the 1G5.3 epitope as a key site for broad-spectrum antiviral development.

An Optimized High-Throughput Immuno-Plaque Assay for SARS-CoV-2

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has been identified as the causative agent of coronavirus disease 2019 and is capable of human-to-human transmission and rapid global spread. The rapid emergence and global spread of SARS-CoV-2 has encouraged the establishment of a rapid, sensitive, and reliable viral detection and quantification methodology. Here, we present an alternative assay, termed immuno-plaque assay (iPA), which utilizes a combination of plaque assay and immunofluorescence techniques. We have extensively optimized the conditions for SARS-CoV-2 infection and demonstrated the great flexibility of iPA detection using several antibodies and dual-probing with two distinct epitope-specific antibodies. In addition, we showed that iPA could be utilized for ultra-high-throughput viral titration and neutralization assay within 24 h and is amenable to a 384-well format. These advantages will significantly accelerate SARS-CoV-2 research outcomes during this pandemic period.

Micro-fusion inhibition tests: quantifying antibody neutralization of virus-mediated cell-cell fusion

Although enveloped viruses canonically mediate particle entry through virus-cell fusion, certain viruses can spread by cell-cell fusion, brought about by receptor engagement and triggering of membrane-bound, viral-encoded fusion proteins on the surface of cells. The formation of pathogenic syncytia or multinucleated cells is seen in vivo, but their contribution to viral pathogenesis is poorly understood. For the negative-strand paramyxoviruses respiratory syncytial virus (RSV) and Nipah virus (NiV), cell-cell spread is highly efficient because their oligomeric fusion protein complexes are active at neutral pH. The recently emerged severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has also been reported to induce syncytia formation in infected cells, with the spike protein initiating cell-cell fusion. Whilst it is well established that fusion protein-specific antibodies can block particle attachment and/or entry into the cell (canonical virus neutralization), their capacity to inhibit cell-cell fusion and the consequences of this neutralization for the control of infection are not well characterized, in part because of the lack of specific tools to assay and quantify this activity. Using an adapted bimolecular fluorescence complementation assay, based on a split GFP-Renilla luciferase reporter, we have established a micro-fusion inhibition test (mFIT) that allows the identification and quantification of these neutralizing antibodies. This assay has been optimized for high-throughput use and its applicability has been demonstrated by screening monoclonal antibody (mAb)-mediated inhibition of RSV and NiV fusion and, separately, the development of fusion-inhibitory antibodies following NiV vaccine immunization in pigs. In light of the recent emergence of coronavirus disease 2019 (COVID-19), a similar assay was developed for SARS-CoV-2 and used to screen mAbs and convalescent patient plasma for fusion-inhibitory antibodies. Using mFITs to assess antibody responses following natural infection or vaccination is favourable, as this assay can be performed entirely at low biocontainment, without the need for live virus. In addition, the repertoire of antibodies that inhibit cell-cell fusion may be different to those that inhibit particle entry, shedding light on the mechanisms underpinning antibody-mediated neutralization of viral spread.

Targeted Therapies for Epstein-Barr Virus-Associated Lymphomas

Simple Summary

Epstein-Barr virus (EBV) is the first-discovered and important human tumor virus. It infects more than 90% of human population and induces various lymphomas. Development of specific targeted therapies is very critical for treatment of EBV-induced lymphomas, but it remains a great challenge. In this review, we introduced the current progress of EBV-specific therapies and the promising approaches that can be developed as novel targeted therapies, which involve protective or therapeutic strategies to target these lymphomas on different levels. This work will provide new insights into the development of new targeted therapies against EBV-associated lymphomas.

Abstract

The Epstein-Barr virus (EBV) is the first human tumor virus identified that can transform quiescent B lymphocytes into lymphoblastoid cell lines (LCLs) in vitro. EBV can establish asymptomatic life-long persistence and is associated with multiple human malignancies, including non-Hodgkin lymphoma and Hodgkin lymphoma, as well as infectious mononucleosis. Although EBV-associated lymphomagenesis has been investigated for over 50 years, viral-mediated transformation is not completely understood, and the development of EBV-specific therapeutic strategies to treat the associated cancers is still a major challenge. However, the rapid development of several novel therapies offers exciting possibilities to target EBV-induced lymphomas. This review highlights targeted therapies with potential for treating EBV-associated lymphomas, including small molecule inhibitors, immunotherapy, cell therapy, preventative and therapeutic vaccines, and other potent approaches, which are novel strategies for controlling, preventing, and treating these viral-induced malignances.

Protective Efficacy of a Chimeric Insect-Specific Flavivirus Vaccine against West Nile Virus

Virulent strains of West Nile virus (WNV) are highly neuro-invasive and human infection is potentially lethal. However, no vaccine is currently available for human use. Here, we report the immunogenicity and protective efficacy of a vaccine derived from a chimeric virus, which was constructed using the structural proteins (prM and E) of the Kunjin strain of WNV (WNV_KUN) and the genome backbone of the insect-specific flavivirus Binjari virus (BinJV). This chimeric virus (BinJ/WNV_KUN-prME) exhibits an insect-specific phenotype and does not replicate in vertebrate cells. Importantly, it authentically presents the prM-E proteins of WNV_KUN, which is antigenically very similar to other WNV strains and lineages. Therefore BinJ/WNV_KUN-prME represents an excellent candidate to assess as a vaccine against virulent WNV strains, including the highly pathogenic WNV_NY99. When CD1 mice were immunized with purified BinJ/WNV_KUN-prME, they developed robust neutralizing antibody responses after a single unadjuvanted dose of 1 to 5 μg. We further demonstrated complete protection against viremia and mortality after lethal challenge with WNV_NY99, with no clinical or subclinical pathology observed in vaccinated animals. These data suggest that BinJ/WNV_KUN-prME represents a safe and effective WNV vaccine candidate that warrants further investigation for use in humans or in veterinary applications.

Optimization of in vitro trophoblast assay for real-time impedimetric sensing of trophoblast-erythrocyte interactions in Plasmodium falciparum malaria

Sequestration of Plasmodium falciparum-infected erythrocytes (IEs) is responsible for the pathophysiology of placental malaria, leading to serious complications such as intrauterine growth restriction and low birth weight. However, it is an experimental challenge to study the biology of human placenta. Conventional cell culture-based in vitro placental models rely on immunostaining techniques and high-magnification microscopy is limited in providing real-time quantitative analysis. Impedimetric sensing in combination with cell culture may offer a useful tool. In this paper, we report that real-time label-free measurement of cellular electrical impedance using xCELLigence technology can be used to quantify the proliferation, syncytial fusion, and long-term response of BeWo cells to IEs cytoadhesion. Specifically, we optimized key experimental parameters of cell seeding density and concentration of forskolin, a compound used to promote cell syncitiation, based on electrical signals and immunostaining results. Prolonged time of infection with IEs that led to cell-cell junction vanishment in BeWo cells and release of inflammatory cytokines were monitored in real time by continuous change in electrical impedance. The results suggest that the impedimetric technique is sensitive and can offer new opportunities for the study of cellular responses of trophoblast cells to IEs. The developed system can provide potentially a high-throughput screening tool of anti-adhesion or anti-inflammatory drugs for placental malaria infections.

Efficient Delivery of Dengue Virus Subunit Vaccines to the Skin by Microprojection Arrays

Dengue virus is the most important arbovirus impacting global human health, with an estimated 390 million infections annually, and over half the world’s population at risk of infection. While significant efforts have been made to develop effective vaccines to mitigate this threat, the task has proven extremely challenging, with new approaches continually being sought. The majority of protective, neutralizing antibodies induced during infection are targeted by the envelope (E) protein, making it an ideal candidate for a subunit vaccine approach. Using truncated, recombinant, secreted E proteins (sE) of all 4 dengue virus serotypes, we have assessed their immunogenicity and protective efficacy in mice, with or without Quil-A as an adjuvant, and delivered via micropatch array (MPA) to the skin in comparison with more traditional routes of immunization. The micropatch contains an ultra-high density array (21,000/cm²) of 110 μm microprojections. Mice received 3 doses of 1 μg (nanopatch, intradermal, subcutaneous, or intra muscular injection) or 10 μg (intradermal, subcutaneous, or intra muscular injection) of tetravalent sE spaced 4 weeks apart. When adjuvanted with Quil-A, tetravalent sE vaccination delivered via MPA resulted in earlier induction of virus-neutralizing IgG antibodies for all four serotypes when compared with all of the other vaccination routes. Using the infectious dengue virus AG129 mouse infectious dengue model, these neutralizing antibodies protected all mice from lethal dengue virus type 2 D220 challenge, with protected animals showing no signs of disease or circulating virus. If these results can be translated to humans, MPA-delivered sE represents a promising approach to dengue virus vaccination.

Basimarols A, B, and C, Highly Oxygenated Pimarane Diterpenoids from Basilicum polystachyon

The highly oxygenated pimarane diterpenoids basimarols A, B, and C (3-5) were isolated from the plant species Basilicum polystachyon, which was collected within the Australian arid zone. Structure elucidation was performed using a suite of spectroscopic techniques, including X-ray crystallography. Anticancer and anti-DENV activity of 3-5 was explored, but only limited activity was observed. More extensive antiviral evaluation of stachyonic acid A (1), which was also isolated from B. polystachyon, revealed broad spectrum antiviral activity against West Nile virus (Kunjin strain, WNV_Kun) and human influenza viruses H1N1 and H3N2.

Isolation of Neutralizing Human Single Chain Antibodies Against Conserved Hemagglutinin Epitopes of Influenza a Virus H3N2 Strain

BACKGROUND

Immunotherapies using monoclonal antibodies against influenza A hemagglutinin (HA) has been an effective means for controlling Influenza spread. An alternative method for viral prophylaxis and treatment is the development of human single-chain variable fragment (scFv) antibodies with no human anti-mouse antibody (HAMA) response and high specificity. In the present study, two highly conserved sequences of HA were used to select specific neutralizing scFvs against H3N2 strain of influenza A virus.

METHODS

Biopanning process was performed to isolate specific scFv antibodies against highly conserved HA sequences, aa173-181 and 227-239, of the influenza A H3N2 strain from a scFv library. The peptide-binding specificity of the selected clones was examined via phage ELISA. The soluble forms of the clones were prepared and assessed using western blot analysis and neutralization efficiency of the selected clones were examined by TCID50 neutralizing assay and real-time PCR.

RESULTS

scFv 1 and scFv 2 were selected against HA of H3N2 influenza A virus with frequencies of 95% and 30% in the panning process, respectively. Western blot analysis confirmed the scFv band size. Significant neutralization in the presence of scFv 1 and scFv 2 were obtained. Real time PCR revealed significant decrease in viral copy number.

CONCLUSION

Two specific neutralizing scFvs against two highly conserved neutralizing epitopes of the influenza A virus HA glycoprotein were selected. A strong neutralization effect of scFv1, showed the potential of this antibody for H3N2 influenza A controlling in the viral spread.

Stachyonic Acid: A Dengue Virus Inhibitor from Basilicum polystachyon

Stachyonic acid A, arising from the first in-depth phytochemical investigation of the herb Basilicum polystachyon, was found to display potent inhibitory activity against dengue virus, with limited cytotoxicity. Andrographolide, a known dengue virus inhibitor and closely related labdane-type diterpene, is structurally more complex but displayed poor antiviral activity in the PRNT assay, and increased cytotoxicity in comparison. Furthermore, a Diels-Alder reaction with PTAD identified the active pharmacophore of stachyonic acid to be the conjugated diene.

Detection of apoptotic and live pre-osteoblast cell line using impedance-based biosensors with variable electrode design

Electrical impedance-based sensing of cell activity has become a powerful analytical tool that allows the monitoring of several relevant biological processes associated with cell evolution and morphology. In these types of biosensors, the electrode design has a direct impact on the sensitivity because it defines the capability of the biosensor to measure small changes in the impedance resulting from cell activities. Herein, impedance-based biosensors arrays with several configurations were successfully developed and used to study the impact of the electrode layout on the dynamics of cultured pre-osteoblast cells. The biosensor design was initially validated by measuring the effect of electrode design on the capacitance of a dielectric polymer (parylene) that mimics the dielectric characteristics of cell populations, results are shown in the Supplementary information section. Results from in vitro cell growth indicate that the optimized design of single electrodes with a diameter of 50 µm, are the most sensitive to cell motion whereas increasing the number of electrodes allows clear differentiation between living and dead cells after 3 h of inducing apoptosis. Apoptosis death was induced with Staurosporine, a chemical mediator of apoptosis in osteoblasts. These impedance results have been validated with optical imaging and flow cytometry analysis that were performed on parallel cultures. Frequency and electrolyte concentration effects are also discussed.

Rational Engineering and Characterization of an mAb that Neutralizes Zika Virus by Targeting a Mutationally Constrained Quaternary Epitope

Following the recent emergence of Zika virus (ZIKV), many murine and human neutralizing anti-ZIKV antibodies have been reported. Given the risk of virus escape mutants, engineering antibodies that target mutationally constrained epitopes with therapeutically relevant potencies can be valuable for combating future outbreaks. Here, we applied computational methods to engineer an antibody, ZAb_FLEP, that targets a highly networked and therefore mutationally constrained surface formed by the envelope protein dimer. ZAb_FLEP neutralized a breadth of ZIKV strains and protected mice in distinct in vivo models, including resolving vertical transmission and fetal mortality in infected pregnant mice. Serial passaging of ZIKV in the presence of ZAb_FLEP failed to generate viral escape mutants, suggesting that its epitope is indeed mutationally constrained. A single-particle cryo-EM reconstruction of the Fab-ZIKV complex validated the structural model and revealed insights into ZAb_FLEP's neutralization mechanism. ZAb_FLEP has potential as a therapeutic in future outbreaks.

Innovation and trends in the development and approval of antiviral medicines: 1987-2017 and beyond

2017 marked the 30th anniversary of the approval of zidovudine (AZT) as the first HIV/AIDS therapy. Since then, more than eighty antiviral drugs have received FDA approval, half of which treat HIV infection. Here, we provide a retrospective analysis of approved antiviral drugs, including therapeutics against other major chronic infections such as hepatitis B and C, and herpes viruses, over the last thirty years. During this time, only a few drugs were approved to treat acute viral infections, mainly influenza. Analysis of these approved antiviral drugs based on molecular class and mode of action shows that a large majority are small molecules and direct-acting agents as opposed to proteins, peptides, or oligonucleotides and host-targeting therapies. In addition, approvals of combination therapies accelerated over the last five years. We also provide a prospective study of future potential antiviral therapies, based on current clinical research pipelines across the pharmaceutical industry. Comparing past drug approvals with current clinical candidates hints at the future evolution in antiviral therapies and reveals how antiviral medicines are often discovered. Overall, this work helps forecast future trends and innovation in the field of antiviral research and development.

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This review summarizes all approved antiviral drugs over the last thirty years.

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Most are small molecules and direct-acting agents over biologics, oligonucleotides, and host-targeting therapies.

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We provide a prospective study and trend analysis of future potential antivirals based on current clinical research.

Suppression of the pelo protein by Wolbachia and its effect on dengue virus in Aedes aegypti

The endosymbiont Wolbachia is known to block replication of several important arboviruses, including dengue virus (DENV), in the mosquito vector Aedes aegypti. So far, the exact mechanism of this viral inhibition is not fully understood. A recent study in Drosophila melanogaster has demonstrated an interaction between the pelo gene and Drosophila C virus. In this study, we explored the possible involvement of the pelo protein, that is involved in protein translation, in Wolbachia-mediated antiviral response and mosquito-DENV interaction. We found that pelo is upregulated during DENV replication and its silencing leads to reduced DENV virion production suggesting that it facilities DENV replication. However, in the presence of Wolbachia, specifically in female mosquitoes, the pelo protein is downregulated and its subcellular localization is altered, which could contribute to reduction in DENV replication in Ae. aegypti. In addition, we show that the microRNA aae-miR-2940-5p, whose abundance is highly enriched in Wolbachia-infected mosquitoes, might mediate regulation of pelo. Our data reveals identification of pelo as a host factor that is positively involved in DENV replication, and its suppression in the presence of Wolbachia may contribute to virus blocking exhibited by the endosymbiont.

The Heptad Repeat C Domain of the Respiratory Syncytial Virus Fusion Protein Plays a Key Role in Membrane Fusion

Respiratory syncytial virus (RSV) mediates host cell entry through the fusion (F) protein, which undergoes a conformational change to facilitate the merger of viral and host lipid membrane envelopes. The RSV F protein comprises a trimer of disulfide-bonded F₁ and F₂ subunits that is present on the virion surface in a metastable prefusion state. This prefusion form is readily triggered to undergo refolding to bring two heptad repeats (heptad repeat A [HRA] and HRB) into close proximity to form a six-helix bundle that stabilizes the postfusion form and provides the free energy required for membrane fusion. This process can be triggered independently of other proteins. Here, we have performed a comprehensive analysis of a third heptad repeat region, HRC (amino acids 75 to 97), an amphipathic α-helix that lies at the interface of the prefusion F trimer and is a major structural feature of the F₂ subunit. We performed alanine scanning mutagenesis from Lys-75 to Met-97 and assessed all mutations in transient cell culture for expression, proteolytic processing, cell surface localization, protein conformation, and membrane fusion. Functional characterization revealed a striking distribution of activity in which fusion-increasing mutations localized to one side of the helical face, while fusion-decreasing mutations clustered on the opposing face. Here, we propose a model in which HRC plays a stabilizing role within the globular head for the prefusion F trimer and is potentially involved in the early events of triggering, prompting fusion peptide release and transition into the postfusion state.IMPORTANCE RSV is recognized as the most important viral pathogen among pediatric populations worldwide, yet no vaccine or widely available therapeutic treatment is available. The F protein is critical for the viral replication process and is the major target for neutralizing antibodies. Recent years have seen the development of prefusion stabilized F protein-based approaches to vaccine design. A detailed understanding of the specific domains and residues that contribute to protein stability and fusion function is fundamental to such efforts. Here, we present a comprehensive mutagenesis-based study of a region of the RSV F₂ subunit (amino acids 75 to 97), referred to as HRC, and propose a role for this helical region in maintaining the delicate stability of the prefusion form.

Structural and Functional Characterization of a Cross-Reactive Dengue Virus Neutralizing Antibody that Recognizes a Cryptic Epitope

Understanding the molecular basis of the neutralizing antibody response to dengue virus (DENV) is an essential component in the design and development of effective vaccines and immunotherapeutics. Here we present the structure of a cross-reactive, neutralizing antibody, 3E31, in complex with domain III (DIII) of the DENV envelope (E) protein and reveal a conserved, temperature-sensitive, cryptic epitope on DIII that is not available in any of the known conformations of E on the dengue virion. We observed that 3E31 inhibits E-mediated membrane fusion, suggesting that the antibody is able to neutralize virus through binding an as-yet uncharacterized intermediate conformation of DENV E and sterically block trimer formation. Finally, we show that, unlike cross-reactive fusion peptide-specific antibodies, 3E31 does not promote antibody-dependent enhancement of infection at sub-neutralizing concentrations. Our results highlight the 3E31 epitope on the E protein DIII as a promising target for immunotherapeutics or vaccine design.

Induction of high titred, non-neutralising antibodies by self-adjuvanting peptide epitopes derived from the respiratory syncytial virus fusion protein

Respiratory syncytial virus (RSV) causes severe lower respiratory tract illness in infants and young children. The significant morbidity and mortality rates associated with RSV infection make an effective RSV vaccine development a priority. Two neutralising antibody binding sites, Ø and II, located on the pre-fusion RSV F glycoprotein are prime candidates for epitope-focused vaccine design. We report on a vaccine strategy that utilises a lipid core peptide (LCP) delivery system with self-adjuvanting properties in conjunction with either the antigenic site Ø or II (B cell epitopes) along with PADRE as a T helper cell epitope. These LCP constructs adopted the desired helical conformation in solution and were recognised by their cognate antibodies D25 and Motavizumab, specific for site Ø and II on RSV F protein, respectively. The LCP constructs were capable of eliciting higher levels of antigen specific antibodies than those induced by antigens administered with complete Freund's adjuvant, demonstrating the potent adjuvanting properties of LCP delivery. However, the antibodies induced failed to recognise native F protein or neutralise virus infectivity. These results provide a note of caution in assuming that peptide vaccines, successfully designed to structurally mimic minimal linear B cell epitopes, will necessarily elicit the desired immune response.

Downregulation of Aedes aegypti chromodomain helicase DNA binding protein 7/Kismet by Wolbachia and its effect on dengue virus replication

Dengue virus (DENV) is a mosquito-transmitted virus imposing a significant burden on human health around the world. Since current control strategies are not sufficient, there is an urgent need to find alternative methods to control DENV transmission. It has been demonstrated that introduction of Wolbachia pipientis in Aedes aegypti mosquitoes can impede DENV transmission with the mechanism(s) not fully understood. Recently, a number of studies have found the involvement of chromodomain DNA binding helicases in case of Human Immunodeficiency virus (HIV) and Influenza A virus infection. In this study, we have identified three chromodomain helicase DNA binding protein (CHD) genes in Ae. aegypti and looked at their response in the case of Wolbachia and DENV infections. Foremost amongst them we have found that AeCHD7/Kismet is significantly downregulated in the presence of Wolbachia infection only in female mosquitoes. Furthermore, AeCHD7 levels showed significant increase during DENV infection, and AeCHD7 depletion led to severe reduction in the replication of DENV. Our data have identified AeCHD7 as a novel Ae. aegypti host factor that is important for DENV replication, and Wolbachia downregulates it, which may contribute towards the mechanism(s) of limiting DENV replication.