Oseltamivir-resistant pandemic H1N1 influenza

Retracted and republished from: "The current state of research on influenza antiviral drug development: drugs in clinical trial and licensed drugs"

Influenza viruses (IVs) threaten global human health due to the high morbidity, infection, and mortality rates. Currently, the influenza drugs recommended by the Food and Drug Administration are oseltamivir, zanamivir, peramivir, and baloxavir marboxil. These recommended antivirals are currently effective for major subtypes of IVs as the compounds target conserved domains in neuraminidase or polymerase acidic (PA) protein. However, this trend may gradually change due to the selection of antiviral drugs and the natural evolution of IVs. Therefore, there is an urgent need to develop drugs related to the treatment of influenza to deal with the next pandemic. Here, we summarized the cutting-edge research in mechanism of action, inhibitory activity, and clinical efficacy of drugs that have been approved and drugs that are still in clinical trials for influenza treatment. We hope this review will provide up-to-date and comprehensive information on influenza antivirals and generate hypotheses for screens and development of new broad-spectrum influenza drugs in the near future.

The current state of research on influenza antiviral drug development: drugs in clinical trial and licensed drugs

Influenza viruses (IVs) threaten global human health due to the high morbidity, infection, and mortality rates. Currently, the influenza drugs recommended by the FDA are oseltamivir, zanamivir, peramivir, and baloxavir marboxil. Notably, owing to the high variability of IVs, no drug exists that can effectively treat all types and subtypes of IVs. Moreover, the current trend of drug resistance is likely to continue as the viral genome is constantly mutating. Therefore, there is an urgent need to develop drugs related to the treatment of influenza to deal with the next pandemic. Here, we summarized the cutting-edge research in mechanism of action, inhibitory activity, and clinical efficacy of drugs that have been approved and drugs that are still in clinical trials for influenza treatment. We hope this review will provide up-to-date and comprehensive information on influenza antivirals and generate hypotheses for screens and development of new broad-spectrum influenza drugs in the near future.

A novel compound to overcome influenza drug resistance in endonuclease inhibitors

Influenza is a seasonal respiratory illness that kills hundreds of thousands of people every year. Currently, neuraminidase inhibitors and endonuclease inhibitors are used in antiviral therapy. However, both drug types have encountered drug-resistant influenza strains in the human body. Fortunately, there is currently no resistance to endonuclease inhibitors in wild strains of influenza. We obtained the molecules with endonuclease inhibitor activity independent of the existing drug-resistant strains through computer-aided drug design, and we hope the obtained results can lay a theoretical foundation for the development of high-activity endonucleases. Combining a traditional fragment-based drug discovery approach with AI-directed fragment growth, we selected and designed a compound that achieved antiviral activity on drug-resistant strains by avoiding mutable residues and drug-resistant residues. We predicted the related properties using an ADMET model. Finally, we obtained a compound similar to baloxavir in terms of binding free energy but not affected by baloxavir resistance.

Anti-influenza A virus activity of flavonoids in vitro: a structure-activity relationship

Secondary plant metabolites from food extracts, namely daidzein, quercetin, and luteolin, exhibit anti-influenza virus effects, with IC₅₀ values of 143.6, 274.8, and 8.0 μM, respectively. The activities of these metabolites differ depending on the functional groups. Therefore, in this study, we focused on members of the flavonoid group, and investigated the anti-influenza viral effects of different flavonoid classes (flavone, isoflavone, flavonol, flavanone, and flavan-3-ol) in vitro. The IC₅₀ values were 4.9-82.8 μM, 143.6 μM, 62.9-477.8 μM, 290.4-881.1 μM, and 22.9-6717.2 μM, respectively, confirming their activity. The modifying group factors (number, position, type) in the flavonoid skeleton may be significantly related to the anti-influenza virus activity. Moreover, time-of-addition assay revealed that the mechanism of inhibition varied for the different classes; for example, flavonoids that inhibit virus adsorption or the early stage of viral growth. Interestingly, all the examined flavonoids inhibited the late stages of viral growth, suggesting that flavonoids mainly inhibit the late events in viral growth before the release of viral particles. Additionally, apigenin might be effective against oseltamivir-resistant strains. Our results may be important in the development of anti-influenza virus therapeutic strategies in the future.

Identification of Potential Drug Targets of Broad-Spectrum Inhibitors with a Michael Acceptor Moiety Using Shotgun Proteomics

The Michael addition reaction is a spontaneous and quick chemical reaction that is widely applied in various fields. This reaction is performed by conjugating an addition of nucleophiles with α, β-unsaturated carbonyl compounds, resulting in the bond formation of C-N, C-S, C-O, and so on. In the development of molecular materials, the Michael addition is not only used to synthesize chemical compounds but is also involved in the mechanism of drug action. Several covalent drugs that bond via Michael addition are regarded as anticarcinogens and anti-inflammatory drugs. Although drug development is mainly focused on pharmaceutical drug discovery, target-based discovery can provide a different perspective for drug usage. However, considerable time and labor are required to define a molecular target through molecular biological experiments. In this review, we systematically examine the chemical structures of current FDA-approved antiviral drugs for potential Michael addition moieties with α, β-unsaturated carbonyl groups, which may exert an unidentified broad-spectrum inhibitory mechanism to target viral or host factors. We thus propose that profiling the targets of antiviral agents, such as Michael addition products, can be achieved by employing a high-throughput LC-MS approach to comprehensively analyze the interaction between drugs and targets, and the subsequent drug responses in the cellular environment to facilitate drug repurposing and/or identify potential adverse effects, with a particular emphasis on the pros and cons of this shotgun proteomic approach.

A Multiligand Architectural Photosensitizer That Targets Hemagglutinin on Envelope of Influenza Virus for Photodynamic Inactivation

The efficacy of current antiviral drugs used to treat influenza has been declining because of mutations and resistance of the virus. Herein, a light-sensitive multiligand architecture is developed consisting of chitosan conjugated to a photosensitizer and 6'-sialyllactose (SL) to develop an antiviral agent against influenza with a different mechanism of action (SL-chitosan-Chlorin e6, SCC). Saturation transfer difference-nuclear magnetic resonance determined that the ability of SCC to bind to viral hemagglutinin is stronger than that of the monomeric substance. Virus recognition is confirmed by immunofluorescence and transmission electron microscope imaging. SCC induces viral inactivation by causing permanent membrane damage through its photoactivity. Viral membrane is oxidized by the photoactivity of SCC, thus, the virus membrane collapses. Furthermore, using the plaque reduction assay to evaluate the inhibitory effect of SCC on influenza A and B, it is found that its antiviral effects are 23% and 50% higher than the conventional antiviral drug. Additionally, SCC prevents infection by influenza in 100% of mice subjected to laser irradiation. These results indicate that this photodynamic multiligand structure can overcome the limitations of existing antiviral agents and suggest a pertinent methodology of prophylaxis and treatment by preemptively attacking the virus before it enters the host cell.

Inhibition of H1N1 influenza virus infection by zinc oxide nanoparticles: another emerging application of nanomedicine

BACKGROUND

Currently available anti-influenza drugs are often associated with limitations such as toxicity and the appearance of drug-resistant strains. Therefore, there is a pressing need for the development of novel, safe and more efficient antiviral agents. In this study, we evaluated the antiviral activity of zinc oxide nanoparticles (ZnO-NPs) and PEGylated zinc oxide nanoparticles against H1N1 influenza virus.

METHODS

The nanoparticles were characterized using the inductively coupled plasma mass spectrometry, x-ray diffraction analysis, and electron microscopy. MTT assay was applied to assess the cytotoxicity of the nanoparticles, and anti-influenza activity was determined by TCID50 and quantitative Real-Time PCR assays. To study the inhibitory impact of nanoparticles on the expression of viral antigens, an indirect immunofluorescence assay was also performed.

RESULTS

Post-exposure of influenza virus with PEGylated ZnO-NPs and bare ZnO-NPs at the highest non-toxic concentrations could be led to 2.8 and 1.2 log10 TCID50 reduction in virus titer when compared to the virus control, respectively (P < 0.0001). At the highest non-toxic concentrations, the PEGylated and unPEGylated ZnO-NPs led to inhibition rates of 94.6 and 52.2%, respectively, which were calculated based on the viral loads. There was a substantial decrease in fluorescence emission intensity in viral-infected cell treated with PEGylated ZnO-NPs compared to the positive control.

CONCLUSIONS

Taken together, our study indicated that PEGylated ZnO-NPs could be a novel, effective, and promising antiviral agent against H1N1 influenza virus infection, and future studies can be designed to explore the exact antiviral mechanism of these nanoparticles.

Preventive Activity against Influenza (H1N1) Virus by Intranasally Delivered RNA-Hydrolyzing Antibody in Respiratory Epithelial Cells of Mice

The antiviral effect of a catalytic RNA-hydrolyzing antibody, 3D8 scFv, for intranasal administration against avian influenza virus (H1N1) was described. The recombinant 3D8 scFv protein prevented BALB/c mice against H1N1 influenza virus infection by degradation of the viral RNA genome through its intrinsic RNA-hydrolyzing activity. Intranasal administration of 3D8 scFv (50 μg/day) for five days prior to infection demonstrated an antiviral activity (70% survival) against H1N1 infection. The antiviral ability of 3D8 scFv to penetrate into epithelial cells from bronchial cavity via the respiratory mucosal layer was confirmed by immunohistochemistry, qRT-PCR, and histopathological examination. The antiviral activity of 3D8 scFv against H1N1 virus infection was not due to host immune cytokines or chemokines, but rather to direct antiviral RNA-hydrolyzing activity of 3D8 scFv against the viral RNA genome. Taken together, our results suggest that the RNase activity of 3D8 scFv, coupled with its ability to penetrate epithelial cells through the respiratory mucosal layer, directly prevents H1N1 virus infection in a mouse model system.

High throughput screening for small molecule enhancers of the interferon signaling pathway to drive next-generation antiviral drug discovery

Most of current strategies for antiviral therapeutics target the virus specifically and directly, but an alternative approach to drug discovery might be to enhance the immune response to a broad range of viruses. Based on clinical observation in humans and successful genetic strategies in experimental models, we reasoned that an improved interferon (IFN) signaling system might better protect against viral infection. Here we aimed to identify small molecular weight compounds that might mimic this beneficial effect and improve antiviral defense. Accordingly, we developed a cell-based high-throughput screening (HTS) assay to identify small molecules that enhance the IFN signaling pathway components. The assay is based on a phenotypic screen for increased IFN-stimulated response element (ISRE) activity in a fully automated and robust format (Z'>0.7). Application of this assay system to a library of 2240 compounds (including 2160 already approved or approvable drugs) led to the identification of 64 compounds with significant ISRE activity. From these, we chose the anthracycline antibiotic, idarubicin, for further validation and mechanism based on activity in the sub-µM range. We found that idarubicin action to increase ISRE activity was manifest by other members of this drug class and was independent of cytotoxic or topoisomerase inhibitory effects as well as endogenous IFN signaling or production. We also observed that this compound conferred a consequent increase in IFN-stimulated gene (ISG) expression and a significant antiviral effect using a similar dose-range in a cell-culture system inoculated with encephalomyocarditis virus (EMCV). The antiviral effect was also found at compound concentrations below the ones observed for cytotoxicity. Taken together, our results provide proof of concept for using activators of components of the IFN signaling pathway to improve IFN efficacy and antiviral immune defense as well as a validated HTS approach to identify small molecules that might achieve this therapeutic benefit.