J. Jordan Steel

Bio: J. Jordan Steel is an academic researcher from United States Air Force Academy. The author has contributed to research in topics: Sindbis virus & Alphavirus. The author has an hindex of 7, co-authored 20 publications receiving 175 citations. Previous affiliations of J. Jordan Steel include Colorado State University–Pueblo & Colorado State University.

Benzothiazole and Pyrrolone Flavivirus Inhibitors Targeting the Viral Helicase

Abstract: The flavivirus nonstructural protein 3 (NS3) is a protease and helicase, and on the basis of its similarity to its homologue encoded by the hepatitis C virus (HCV), the flavivirus NS3 might be a promising drug target. Few flavivirus helicase inhibitors have been reported, in part, because few specific inhibitors have been identified when nucleic acid unwinding assays have been used to screen for helicase inhibitors. To explore the possibility that compounds inhibiting NS3-catalyzed ATP hydrolysis might function as antivirals even if they do not inhibit RNA unwinding in vitro, we designed a robust dengue virus (DENV) NS3 ATPase assay suitable for high-throughput screening. Members of two classes of inhibitory compounds were further tested in DENV helicase-catalyzed RNA unwinding assays, assays monitoring HCV helicase action, subgenomic DENV replicon assays, and cell viability assays and for their ability to inhibit West Nile virus (Kunjin subtype) replication in cells. The first class contained analogues of NIH molecular probe ML283, a benzothiazole oligomer derived from the dye primuline, and they also inhibited HCV helicase and DENV NS3-catalyzed RNA unwinding. The most intriguing ML283 analogue inhibited DENV NS3 with an IC50 value of 500 nM and was active against the DENV replicon. The second class contained specific DENV ATPase inhibitors that did not inhibit DENV RNA unwinding or reactions catalyzed by HCV helicase. Members of this class contained a 4-hydroxy-3-(5-methylfuran-2-carbonyl)-2H-pyrrol-5-one scaffold, and about 20 μM of the most potent pyrrolone inhibited both DENV replicons and West Nile virus replication in cells by 50%.

Stearoly-CoA desaturase 1 differentiates early and advanced dengue virus infections and determines virus particle infectivity

Abstract: Positive strand RNA viruses, such as dengue virus type 2 (DENV2) expand and structurally alter ER membranes to optimize cellular communication pathways that promote viral replicative needs. These complex rearrangements require significant protein scaffolding as well as changes to the ER chemical composition to support these structures. We have previously shown that the lipid abundance and repertoire of host cells are significantly altered during infection with these viruses. Specifically, enzymes in the lipid biosynthesis pathway such as fatty acid synthase (FAS) are recruited to viral replication sites by interaction with viral proteins and displayed enhanced activities during infection. We have now identified that events downstream of FAS (fatty acid desaturation) are critical for virus replication. In this study we screened enzymes in the unsaturated fatty acid (UFA) biosynthetic pathway and found that the rate-limiting enzyme in monounsaturated fatty acid biosynthesis, stearoyl-CoA desaturase 1 (SCD1), is indispensable for DENV2 replication. The enzymatic activity of SCD1, was required for viral genome replication and particle release, and it was regulated in a time-dependent manner with a stringent requirement early during viral infection. As infection progressed, SCD1 protein expression levels were inversely correlated with the concentration of viral dsRNA in the cell. This modulation of SCD1, coinciding with the stage of viral replication, highlighted its function as a trigger of early infection and an enzyme that controlled alternate lipid requirements during early versus advanced infections. Loss of function of this enzyme disrupted structural alterations of assembled viral particles rendering them non-infectious and immature and defective in viral entry. This study identifies the complex involvement of SCD1 in DENV2 infection and demonstrates that these viruses alter ER lipid composition to increase infectivity of the virus particles.

Infectious alphavirus production from a simple plasmid transfection

Abstract: We have developed a new method for producing infectious double subgenomic alphaviruses from plasmids transfected into mammalian cells. A double subgenomic Sindbis virus (TE3'2J) was transcribed from a cytomegalovirus PolII promoter, which results in the production of infectious virus. Transfection of as little as 125 ng of plasmid is able to produce 1 × 108 plaque forming units/ml (PFU/ml) of infectious virus 48 hours post-transfection. This system represents a more efficient method for producing recombinant Sindbis viruses.

Murine Efficacy and Pharmacokinetic Evaluation of the Flaviviral NS5 Capping Enzyme 2-Thioxothiazolidin-4-One Inhibitor BG-323.

Abstract: Arthropod-borne flavivirus infection continues to cause significant morbidity and mortality worldwide. Identification of drug targets and novel antiflaviviral compounds to treat these diseases has become a global health imperative. A previous screen of 235,456 commercially available small molecules identified the 2-thioxothiazolidin-4-one family of compounds as inhibitors of the flaviviral NS5 capping enzyme, a promising target for antiviral drug development. Rational drug design methodologies enabled identification of lead compound BG-323 from this series. We have shown previously that BG-323 potently inhibits NS5 capping enzyme activity, displays antiviral effects in dengue virus replicon assays and inhibits growth of West Nile and yellow fever viruses with low cytotoxicity in vitro. In this study we further characterized BG-323’s antiviral activity in vitro and in vivo. We found that BG-323 was able to reduce replication of WNV (NY99) and Powassan viruses in culture, and we were unable to force resistance into WNV (Kunjin) in long-term culture experiments. We then evaluated the antiviral activity of BG-323 in a murine model. Mice were challenged with WNV NY99 and administered BG-323 or mock by IP inoculation immediately post challenge and twice daily thereafter. Mice were bled and viremia was quantified on day three. No significant differences in viremia were observed between BG-323-treated and control groups and clinical scores indicated both BG-323-treated and control mice developed signs of illness on approximately the same day post challenge. To determine whether differences in in vitro and in vivo efficacy were due to unfavorable pharmacokinetic properties of BG-323, we conducted a pharmacokinetic evaluation of this small molecule. Insights from pharmacokinetic studies indicate that BG-323 is cell permeable, has a low efflux ratio and does not significantly inhibit two common cytochrome P450 (CYP P450) isoforms thus suggesting this molecule may be less likely to cause adverse drug interactions. However, the T1/2 of BG-323 was suboptimal and the percent of drug bound to plasma binding proteins was high. Future studies with BG-323 will be aimed at increasing the T1/2 and determining strategies for mitigating the effects of high plasma protein binding, which likely contribute to low in vivo efficacy.

Broad-spectrum agents for flaviviral infections: dengue, Zika and beyond

Abstract: Infections with flaviviruses, such as dengue, West Nile virus and the recently re-emerging Zika virus, are an increasing and probably lasting global risk. This Review summarizes and comments on the opportunities for broad-spectrum agents that are active against multiple flaviviruses. Broad-spectrum activity is particularly desirable to prepare for the next flaviviral epidemic, which could emerge from as-yet unknown or neglected viruses. Potential molecular targets for broad-spectrum antiflaviviral compounds include viral proteins, such as the viral protease or polymerase, and host targets that are exploited by these viruses during entry and replication, including α-glucosidase and proteins involved in nucleoside biosynthesis. Numerous compounds with broad-spectrum antiviral activity have already been identified by target-specific or phenotypic assays. For other compounds, broad-spectrum activity can be anticipated because of their mode of action and molecular targets.

Venezuelan equine encephalitis.

Abstract: Venezuelan equine encephalomyelitis (VEE) viruses are taxonomically classified within the genus Alphavirus of the family Togaviridae (formerly the Group A arboviruses). The VEE complex of viruses includes six antigenic subtypes (I–VI) divided by antigenic variants. Within subtype I there are five antigenic variants (variants AB–F). Originally, subtypes I-A and I-B were considered to be distinct variants, but they are now considered to be identical (I-AB). Antigenic variants I-AB and I-C are associated with epizootic/epidemic activity in equids and humans. The other three variants of subtype I (I-D, I-E, and I-F) and the other five subtypes of VEE (II–VI) circulate in natural enzootic cycles.

Implications of oxidative stress on viral pathogenesis.

Abstract: Reactive species are frequently formed after viral infections. Antioxidant defences, including enzymatic and non-enzymatic components, protect against reactive species, but sometimes these defences are not completely adequate. An imbalance in the production of reactive species and the body's inability to detoxify these reactive species is referred to as oxidative stress. The aim of this review is to analyse the role of oxidative stress in the pathogenesis of viral infections and highlight some major therapeutic approaches that have gained importance, with regards to controlling virus-induced oxidative injury. Attention will be focused on DNA viruses (papillomaviruses, hepadnaviruses), RNA viruses (flaviviruses, orthomyxoviruses, paramyxoviruses, togaviruses) and retroviruses (human immunodeficiency virus). In general, viruses cause an imbalance in the cellular redox environment, which depending on the virus and the cell can result in different responses, e.g. cell signaling, antioxidant defences, reactive species, and other processes. Therefore, the modulation of reactive species production and oxidative stress potentially represents a novel pharmacological approach for reducing the consequences of viral pathogenesis.

Hijacking the Supplies: Metabolism as a Novel Facet of Virus-Host Interaction.

Abstract: Viral replication is a process that involves an extremely high turnover of cellular molecules. Since viruses depend on the host cell to obtain the macromolecules needed for their proper replication, they have evolved numerous strategies to shape cellular metabolism and the biosynthesis machinery of the host according to their specific needs. Technologies for the rigorous analysis of metabolic alterations in cells have recently become widely available and have greatly expanded our knowledge of these crucial host-pathogen interactions. We have learned that most viruses enhance specific anabolic pathways and are highly dependent on these alterations. Since uninfected cells are far more plastic in their metabolism, targeting of the virus-induced metabolic alterations is a promising strategy for specific antiviral therapy and has gained great interest recently. In this review, we summarize the current advances in our understanding of metabolic adaptations during viral infections, with a particular focus on the utilization of this information for therapeutic application.

The Medicinal Chemistry of Dengue Virus.

Abstract: The dengue virus and related flaviviruses are an increasing global health threat. In this perspective, we comment on and review medicinal chemistry efforts aimed at the prevention or treatment of dengue infections. We include target-based approaches aimed at viral or host factors and results from phenotypic screenings in cellular assay systems for viral replication. This perspective is limited to the discussion of results that provide explicit chemistry or structure–activity relationship (SAR), or appear to be of particular interest to the medicinal chemist for other reasons. The discovery and development efforts discussed here may at least partially be extrapolated toward other emerging flaviviral infections, such as West Nile virus. Therefore, this perspective, although not aimed at flaviviruses in general, should also be able to provide an overview of the medicinal chemistry of these closely related infectious agents.