Brian J. Geiss

Castanospermine, a Potent Inhibitor of Dengue Virus Infection In Vitro and In Vivo

ABSTRACT Previous studies have suggested that α-glucosidase inhibitors such as castanospermine and deoxynojirimycin inhibit dengue virus type 1 infection by disrupting the folding of the structural proteins prM and E, a step crucial to viral secretion. We extend these studies by evaluating the inhibitory activity of castanospermine against a panel of clinically important flaviviruses including all four serotypes of dengue virus, yellow fever virus, and West Nile virus. Using in vitro assays we demonstrated that infections by all serotypes of dengue virus were inhibited by castanospermine. In contrast, yellow fever virus and West Nile virus were partially and almost completely resistant to the effects of the drug, respectively. Castanospermine inhibited dengue virus infection at the level of secretion and infectivity of viral particles. Importantly, castanospermine prevented mortality in a mouse model of dengue virus infection, with doses of 10, 50, and 250 mg/kg of body weight per day being highly effective at promoting survival (P ≤ 0.0001). Correspondingly, castanospermine had no adverse or protective effect on West Nile virus mortality in an analogous mouse model. Overall, our data suggest that castanospermine has a strong antiviral effect on dengue virus infection and warrants further development as a possible treatment in humans.

Paper-Based Microfluidic Devices: Emerging Themes and Applications

Applications Yuanyuan Yang,† Eka Noviana,† Michael P. Nguyen,† Brian J. Geiss,‡ David S. Dandy, and Charles S. Henry*,†,§ †Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, United States ‡Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado 80523, United States Department of Chemical and Biological Engineering, Colorado State University, Fort Collins, Colorado 80523, United States ■ CONTENTS Fabrication 71 Hydrophobic/Solvent Barrier 72 Deposition 73 Flow and Injection Control 74 Three-Dimensional Devices 75 Incorporating Nonsensing Electrodes 75 Colorimetric Detection 75 Detectors and Readout 75 Reflectance-Based Measurement 75 Transmittance-Based Measurement 77 Instrument-Free Measurement 77 Biomedical Applications 77 Enzymatic Methods 77 Immunoassays 78 Other 79 Environmental Applications 79 Other Applications 80 Electrochemical Detection 80 Electrodes 80 Carbon Electrodes 81 Metallic Electrodes 81 Biological Applications 82 Glucose Sensors 82 Immunosensors 84 Other Examples 84 Environmental Applications 84 Other Technologies 85 Chemiluminescence and Electrochemiluminescence 85 Fluorescence 85 Surface-Enhanced Raman Spectroscopy 85 Separation 86 Preconcentration 86 Conclusions and Future Directions 87 Author Information 87 Corresponding Author 87 ORCID 87 Notes 87 Biographies 87 Acknowledgments 88 References 88

The FDA-approved drug sofosbuvir inhibits Zika virus infection

&NA; The rapidly expanding Zika virus (ZIKV) epidemic has affected thousands of individuals with severe cases causing Guillain‐Barré syndrome, congenital malformations, and microcephaly. Currently, there is no available vaccine or therapy to prevent or treat ZIKV infection. We evaluated whether sofosbuvir, an FDA‐approved nucleotide polymerase inhibitor for the distantly related hepatitis C virus, could have antiviral activity against ZIKV infection. Cell culture studies established that sofosbuvir efficiently inhibits replication and infection of several ZIKV strains in multiple human tumor cell lines and isolated human fetal‐derived neuronal stem cells. Moreover, oral treatment with sofosbuvir protected against ZIKV‐induced death in mice. These results suggest that sofosbuvir may be a candidate for further evaluation as a therapy against ZIKV infection in humans. HighlightsSofosbuvir reduces replication of multiple ZIKV isolates in human liver and placental cells.Sofosbuvir protects human neuronal stem cells from ZIKV infection.Oral administration of sofosbuvir via drinking reduces ZIKV death in mice.Sofosbuvir should be evaluated as an anti‐ZIKV treatment in non‐rodent species.

Disruption of virion host shutoff activity improves the immunogenicity and protective capacity of a replication-incompetent herpes simplex virus type 1 vaccine strain.

ABSTRACT The virion host shutoff (vhs) protein encoded by herpes simplex virus type 1 (HSV-1) destabilizes both viral and host mRNAs. An HSV-1 strain with a mutation in vhs is attenuated in virulence and induces immune responses in mice that are protective against corneal infection with virulent HSV-1, but it has the capacity to establish latency. Similarly, a replication-incompetent HSV-1 strain with a mutation in ICP8 elicits an immune response protective against corneal challenge, but it may be limited in viral antigen production. We hypothesized therefore that inactivation of vhs in an ICP8− virus would yield a replication-incompetent mutant with enhanced immunogenicity and protective capacity. In this study, a vhs−/ICP8− HSV-1 mutant was engineered. BALB/c mice were immunized with incremental doses of the vhs−/ICP8− double mutant or vhs−or ICP8− single mutants, or the mice were mock immunized, and protective immunity against corneal challenge with virulent HSV-1 was assessed. Mice immunized with the vhs−/ICP8− mutant showed prechallenge serum immunoglobulin G titers comparable to those immunized with replication-competent vhs− virus and exceed those of mice immunized with the ICP8− single mutant. Following corneal challenge, the degrees of protection against ocular disease, weight loss, encephalitis, and establishment of latency were similar for vhs−/ICP8− and vhs−virus-vaccinated mice. Moreover, the double deleted vhs−/ICP8− virus protected mice better in all respects than the single deleted ICP8− mutant virus. The data indicate that inactivation of vhs in a replication-incompetent virus significantly enhances its protective efficacy while retaining its safety for potential human vaccination. Possible mechanisms of enhanced immunogenicity are discussed.

Identification of a Novel Antiviral Inhibitor of the Flavivirus Guanylyltransferase Enzyme

ABSTRACT Arthropod-borne flavivirus infection causes serious morbidity and mortality worldwide, but there are currently no effective antiflaviviral chemotherapeutics available for human use. Therefore, it is critical that new therapeutics against virus-specific targets be developed. To identify new compounds that may be used as broadly active flavivirus therapeutics, we have performed a high-throughput screening of 235,456 commercially available compounds for small-molecule inhibitors of the dengue virus NS5 RNA capping enzyme. We identified a family of compounds, the 2-thioxothiazolidin-4-ones, that show potent biochemical inhibition of capping enzyme GTP binding and guanylyltransferase function. During the course of structure-activity relationship analysis, a molecule within this family, (E)-{3-[5-(4-tert-butylbenzylidene)-4-oxo-2-thioxo-1,3-thiazolidin-3-yl]propanoic acid} (BG-323), was found to possess significant antiviral activity in a dengue virus subgenomic replicon assay. Further testing of BG-323 demonstrated that this molecule is able to reduce the replication of infectious West Nile virus and yellow fever virus in cell culture with low toxicity. The results of this study describe the first inhibitor that targets the GTP-binding/guanylyltransferase activity of the flavivirus RNA capping enzyme.

Focus on flaviviruses: current and future drug targets.

BACKGROUND Infection by mosquito-borne flaviviruses (family Flaviviridae) is increasing in prevalence worldwide. The vast global, social and economic impact due to the morbidity and mortality associated with the diseases caused by these viruses necessitates therapeutic intervention. There is currently no effective clinical treatment for any flaviviral infection. Therefore, there is a great need for the identification of novel inhibitors to target the virus life cycle. DISCUSSION In this article, we discuss structural and nonstructural viral proteins that are the focus of current target validation and drug discovery efforts. Both inhibition of essential enzymatic activities and disruption of necessary protein–protein interactions are considered. In addition, we address promising new targets for future research. CONCLUSION As our molecular and biochemical understanding of the flavivirus life cycle increases, the number of targets for antiviral therapeutic discovery grows and the possibility for novel drug discovery continues to strengthen.

Identification of Novel Small-Molecule Inhibitors of West Nile Virus Infection

ABSTRACT West Nile virus (WNV) has spread throughout the United States and Canada and now annually causes a clinical spectrum of human disease ranging from a self-limiting acute febrile illness to acute flaccid paralysis and lethal encephalitis. No therapy or vaccine is currently approved for use in humans. Using high-throughput screening assays that included a luciferase expressing WNV subgenomic replicon and an NS1 capture enzyme-linked immunosorbent assay, we evaluated a chemical library of over 80,000 compounds for their capacity to inhibit WNV replication. We identified 10 compounds with strong inhibitory activity against genetically diverse WNV and Kunjin virus isolates. Many of the inhibitory compounds belonged to a chemical family of secondary sulfonamides and have not been described previously to inhibit WNV or other related or unrelated viruses. Several of these compounds inhibited WNV infection in the submicromolar range, had selectivity indices of greater than 10, and inhibited replication of other flaviviruses, including dengue and yellow fever viruses. One of the most promising compounds, AP30451, specifically blocked translation of a yellow fever virus replicon but not a Sindbis virus replicon or an internal ribosome entry site containing mRNA. Overall, these compounds comprise a novel class of promising inhibitors for therapy against WNV and other flavivirus infections in humans.

Temporal Regulation of Herpes Simplex Virus Type 2 VP22 Expression and Phosphorylation

ABSTRACT The VP22 protein of herpes simplex virus type 2 (HSV-2) is a major component of the virion tegument. Previous work with HSV-1 indicated that VP22 is phosphorylated during infection, and phosphorylation may play a role in modulating VP22 localization in infected cells. It is not clear, however, when phosphorylation occurs in infected cells or how it is regulated. Less is known about the synthesis and phosphorylation of HSV-2 VP22. To study the complete biosynthetic history of HSV-2 VP22, we generated a monoclonal antibody to the carboxy terminus of VP22. Using immunoprecipitation and Western blot analyses, we show that HSV-2 VP22 can be found in three distinct isoforms in infected cells, two of which are phosphorylated. Like HSV-1 VP22, HSV-2 VP22 is synthesized ca. 4 h after infection, and the isoform later incorporated into virions is hypophosphorylated. In addition, we demonstrate for the first time (i) that newly synthesized VP22 is phosphorylated rapidly after synthesis, (ii) that this phosphorylation occurs in a virus-dependent manner, (iii) that the HSV-2 kinase UL13 is capable of inducing phosphorylation of VP22 in the absence of other viral proteins, (iv) that phosphorylated VP22 is very stable in infected cells, (v) that phosphorylated isoforms of VP22 are gradually dephosphorylated late in infection to produce the virion tegument form, and (vi) that this dephosphorylation occurs independently of viral DNA replication or virion assembly. These results indicate that HSV-2 VP22 is a stable protein that undergoes highly regulated, virus-dependent phosphorylation events in infected cells.

Development and Characterization of Recombinant Virus Generated from a New World Zika Virus Infectious Clone.

ABSTRACT Zika virus (ZIKV; family Flaviviridae, genus Flavivirus) is a rapidly expanding global pathogen that has been associated with severe clinical manifestations, including devastating neurological disease in infants. There are currently no molecular clones of a New World ZIKV available that lack significant attenuation, hindering progress toward understanding determinants of transmission and pathogenesis. Here we report the development and characterization of a novel ZIKV reverse genetics system based on a 2015 isolate from Puerto Rico (PRVABC59). We generated a two-plasmid infectious clone system from which infectious virus was rescued that replicates in human and mosquito cells with growth kinetics representative of wild-type ZIKV. Infectious clone-derived virus initiated infection and transmission rates in Aedes aegypti mosquitoes comparable to those of the primary isolate and displayed similar pathogenesis in AG129 mice. This infectious clone system provides a valuable resource to the research community to explore ZIKV molecular biology, vaccine development, antiviral development, diagnostics, vector competence, and disease pathogenesis. IMPORTANCE ZIKV is a rapidly spreading mosquito-borne pathogen that has been linked to Guillain-Barré syndrome in adults and congenital microcephaly in developing fetuses and infants. ZIKV can also be sexually transmitted. The viral molecular determinants of any of these phenotypes are not well understood. There is no reverse genetics system available for the current epidemic virus that will allow researchers to study ZIKV immunity, develop novel vaccines, or develop antiviral drugs. Here we provide a novel infectious clone system generated from a recent ZIKV isolated from a patient infected in Puerto Rico. This infectious clone produces virus with in vitro and in vivo characteristics similar to those of the primary isolate, providing a critical tool to study ZIKV infection and disease.

PAIRpred: Partner-specific prediction of interacting residues from sequence and structure

We present a novel partner‐specific protein–protein interaction site prediction method called PAIRpred. Unlike most existing machine learning binding site prediction methods, PAIRpred uses information from both proteins in a protein complex to predict pairs of interacting residues from the two proteins. PAIRpred captures sequence and structure information about residue pairs through pairwise kernels that are used for training a support vector machine classifier. As a result, PAIRpred presents a more detailed model of protein binding, and offers state of the art accuracy in predicting binding sites at the protein level as well as inter‐protein residue contacts at the complex level. We demonstrate PAIRpreds performance on Docking Benchmark 4.0 and recent CAPRI targets. We present a detailed performance analysis outlining the contribution of different sequence and structure features, together with a comparison to a variety of existing interface prediction techniques. We have also studied the impact of binding‐associated conformational change on prediction accuracy and found PAIRpred to be more robust to such structural changes than existing schemes. As an illustration of the potential applications of PAIRpred, we provide a case study in which PAIRpred is used to analyze the nature and specificity of the interface in the interaction of human ISG15 protein with NS1 protein from influenza A virus. Python code for PAIRpred is available at http://combi.cs.colostate.edu/supplements/pairpred/. Proteins 2014; 82:1142–1155.