Screening and identification of inhibitors against influenza A virus from a US drug collection of 1280 drugs

Ent-atisane diterpenoids from Euphorbia wallichii and their anti-influenza A virus activity

The study entailed the investigation of the roots of Euphorbia wallichii, which resulted in the isolation of 29 ent-atisane diterpenoids (1-29), 14 of which were previously unknown. These previously undescribed ones were named euphorwanoids A-N (3-5, 7, 9, and 10-18). Various techniques, including comprehensive spectroscopic methods and calculated electronic circular dichroism, were employed to determine their molecular structures. Additionally, the absolute configurations of ten ent-atisane diterpenoids (1, 2, 5, 6, 8, 9, 11, 12, 14 and 16) were established through X-ray crystallographic analyses. All isolated compounds' potential to inhibit the influenza A virus in vitro were evaluated. Compounds 18, 20, and 24 exhibited notable antiviral activity against the A/Puerto Rico/8/1934 strain. Their effective concentrations for reducing viral activity (EC50 values) were found to be 8.56, 1.22, and 4.97 μM, respectively. An intriguing aspect of this research is that it marks the first instance of ent-atisane diterpenes displaying anti-H1N1 activity. Empirical NMR rules were established with Δδ to distinguish the R/S configurations of C-13 and C-16 in ent-atisanes.

In Memory of the Virologist Jianguo Wu, 1957-2022

It is with deep sorrow that we mourn the passing of the virologist Professor Jianguo Wu [...].

Virtual screening of plant-derived compounds against SARS-CoV-2 viral proteins using computational tools

The new SARS-CoV-2, responsible for the COVID-19 pandemic, has been threatening public health worldwide for more than a year. The aim of this work was to evaluate compounds of natural origin, mainly from medicinal plants, as potential SARS-CoV-2 inhibitors through docking studies. The viral spike (S) glycoprotein and the main protease M^pro, involved in the recognition of virus by host cells and in viral replication, respectively, were the main molecular targets in this study. Molecular docking was performed using AutoDock, which allowed us to select the plant actives with the highest affinity towards the viral targets and to identify the interaction molecular sites with the SARS-CoV2 proteins. The best energy binding values for S protein were, in kcal/mol: -19.22 for glycyrrhizin, -17.84 for gitoxin, -12.05 for dicumarol, -10.75 for diosgenin, and -8.12 for delphinidin. For M^pro were, in kcal/mol: -9.36 for spirostan, -8.75 for N-(3-acetylglycyrrhetinoyl)-2-amino-propanol, -8.41 for α-amyrin, -8.35 for oleanane, -8.11 for taraxasterol, and -8.03 for glycyrrhetinic acid. In addition, the synthetic drugs umifenovir, chloroquine, and hydroxychloroquine were used as controls for S protein, while atazanavir and nelfinavir were used for M^pro. Key hydrogen bonds and hydrophobic interactions between natural compounds and the respective viral proteins were identified, allowing us to explain the great affinity obtained in those compounds with the lowest binding energies. These results suggest that these natural compounds could potentially be useful as drugs to be experimentally evaluated against COVID-19.

The Modulation of Cholesterol Metabolism Is Involved in the Antiviral Effect of Nitazoxanide

We previously investigated the role of Nitazoxanide (NTZ), a thiazolide endowed with antiviral and antiparasitic activity, in HIV-1 infection. NTZ treatment in primary isolated PBMCs was able to reduce HIV-1 infection in vitro by inducing the expression of a number of type-I interferon-stimulated genes. Among them, NTZ was able to induce cholesterol-25-hydroxylase (CH25H), which is involved in cholesterol metabolism. In the present study, we wanted to deepen our knowledge about the antiviral mechanism of action of NTZ. Indeed, by inducing CH25H, which catalyzes the formation of 25-hydroxycholesterol from cholesterol, NTZ treatment repressed cholesterol biosynthetic pathways and promoted cholesterol mobilization and efflux from the cell. Such effects were even more pronounced upon stimulation with FLU antigens in combination. It is already well known how lipid metabolism and virus replication are tightly interconnected; thus, it is not surprising that the antiviral immune response employs genes related to cholesterol metabolism. Indeed, NTZ was able to modulate cholesterol metabolism in vitro and, by doing so, enhance the antiviral response. These results give us the chance to speculate about the suitability of NTZ as adjuvant for induction of specific natural immunity. Moreover, the putative application of NTZ to alimentary-related diseases should be investigated.

Therapeutic Potential of Nitazoxanide: An Appropriate Choice for Repurposing versus SARS-CoV-2?

The rapidly growing COVID-19 pandemic is the most serious global health crisis since the "Spanish flu" of 1918. There is currently no proven effective drug treatment or prophylaxis for this coronavirus infection. While developing safe and effective vaccines is one of the key focuses, a number of existing antiviral drugs are being evaluated for their potency and efficiency against SARS-CoV-2 in vitro and in the clinic. Here, we review the significant potential of nitazoxanide (NTZ) as an antiviral agent that can be repurposed as a treatment for COVID-19. Originally, NTZ was developed as an antiparasitic agent especially against Cryptosporidium spp.; it was later shown to possess potent activity against a broad range of both RNA and DNA viruses, including influenza A, hepatitis B and C, and coronaviruses. Recent in vitro assessment of NTZ has confirmed its promising activity against SARS-CoV-2 with an EC50 of 2.12 μM. Here we examine its drug properties, antiviral activity against different viruses, clinical trials outcomes, and mechanisms of antiviral action from the literature in order to highlight the therapeutic potential for the treatment of COVID-19. Furthermore, in preliminary PK/PD analyses using clinical data reported in the literature, comparison of simulated TIZ (active metabolite of NTZ) exposures at two doses with the in vitro potency of NTZ against SARS-CoV-2 gives further support for drug repurposing with potential in combination chemotherapy approaches. The review concludes with details of second generation thiazolides under development that could lead to improved antiviral therapies for future indications.

In vitro anti-influenza activity of in silico repurposed candidate drug cycrimine

BACKGROUND

Due to the limitations of current antiviral therapies because of drug resistance and the emergence of new circulating viral strains, novel effective antivirals are urgently needed. Results of the previous drug repurposing by virtual screening of DrugBank revealed the anticholinergic drug cycrimine as a possible inhibitor of the influenza virus infection.

METHODS

In this study we examined the potential antiviral activity of cycrimine in vitro.

RESULTS

The experimental results showed the anti-influenza activity of cycrimine against two different influenza A subtypes in cell culture.

CONCLUSIONS

The findings of this study suggest cycrimine as a potential therapeutic agent for influenza.

Anthralin Suppresses the Proliferation of Influenza Virus by Inhibiting the Cap-Binding and Endonuclease Activity of Viral RNA Polymerase

Influenza virus RNA-dependent RNA polymerase (vRdRp) does not have capping activity and relies on the capped RNAs produced by the host RNA polymerase II (RNAPII). The viral polymerases process the capped RNAs to produce short capped RNA fragments that are used as primers to initiate the transcription of viral mRNAs. This process, known as cap-snatching, can be targeted by antiviral therapeutics. Here, anthralin was identified as an inhibitor against influenza a virus (IAV) infection by targeting the cap-snatching activity of the viral polymerase. Anthralin, an FDA-approved drug used in the treatment of psoriasis, shows antiviral activity against IAV infection in vitro and in vivo. Importantly, anthralin significantly reduces weight loss, lung injury, and mortality caused by IAV infection in mice. The mechanism of action study revealed that anthralin inhibits the cap-binding function of PB2 subunit and endonuclease activity of PA. As a result, viral mRNA transcription is blocked, leading to the decreases in viral RNA replication and viral protein expression. In conclusion, anthralin has been demonstrated to have the potential of an alternative antiviral against influenza virus infection. Also, targeting the captive pocket structure that includes the N-terminus of PA endonuclease domain and the C-terminal of PB2 cap-binding domain of IAV RdRp may be an excellent strategy for developing anti-influenza drugs.

Identification of pyrvinium pamoate as an anti-tuberculosis agent in vitro and in vivo by SOSA approach amongst known drugs

Tuberculosis (TB), caused by Mycobacterium tuberculosis (M.tb) bacteria, is a leading infectious cause of mortality worldwide. The emergence of drug-resistant M. tb has made control of TB more difficult. The selective optimization of side activities (SOSA) approach uses old drugs for new pharmacological targets. In the present study by using SOSA approach, we have successfully identified pyrvinium pamoate (PP) which is capable of inhibiting the growth of mycobacteria, including M. tb H37Rv, Mycobacterium smegmatis, Bacille Calmette-Guérin (BCG), M. tb H37Ra, and drug-resistant M. tb clinical isolates in vitro from 1280 known drugs library. The MIC₉₉ of PP, the minimum inhibitory concentration that inhibits more than 99% of M. tb H37Rv and the drug-resistant M. tb clinical isolates, ranges from 1.55 to 4.8 µg/mL. Importantly, PP could reduce the bacterial colony-forming units (CFUs) in lung, spleen and liver tissues, and effectively inhibit inflammatory response in M. tb H37Rv, multidrug-resistant (MDR) M. tb and extensively drug-resistant (XDR) M.tb-infected mice. Our results clearly show that the PP has the potential application for treatment of TB.

Identification of new antiviral agents against Kaposi's sarcoma-associated herpesvirus (KSHV) by high-throughput drug screening reveals the role of histamine-related signaling in promoting viral lytic reactivation

Kaposi's sarcoma-associated herpesvirus (KSHV) causes several human cancers, such as Kaposi's sarcoma (KS) and primary effusion lymphoma (PEL). Current treatment options for KSHV infection and virus associated diseases are sometimes ineffective, therefore, more effectively antiviral agents are urgently needed. As a herpesvirus, lytic replication is critical for KSHV pathogenesis and oncogenesis. In this study, we have established a high-throughput screening assay by using an inducible KSHV+ cell-line, iSLK.219. After screening a compound library that consisted of 1280 Food and Drug Administration (FDA)-approved drugs, 15 hit compounds that effectively inhibited KSHV virion production were identified, most of which have never been reported with anti-KSHV activities. Interestingly, 3 of these drugs target histamine receptors or signaling. Our data further confirmed that antagonists targeting different histamine receptors (HxRs) displayed excellent inhibitory effects on KSHV lytic replication from induced iSLK.219 or BCBL-1 cells. In contrast, histamine and specific agonists of HxRs promoted viral lytic replication from induced iSLK.219 or KSHV-infected primary cells. Mechanistic studies indicated that downstream MAPK and PI3K/Akt signaling pathways were required for histamine/receptors mediated promotion of KSHV lytic replication. Direct knockdown of HxRs in iSLK.219 cells effectively blocked viral lytic gene expression during induction. Using samples from a cohort of HIV+ patients, we found that the KSHV+ group has much higher levels of histamine in their plasma and saliva than the KSHV- group. Taken together, our data have identified new anti-KSHV agents and provided novel insights into the molecular bases of host factors that contribute to lytic replication and reactivation of this oncogenic herpesvirus.

Three New Compounds from the Actinomycete Actinocorallia aurantiaca

Aurantiadioic acids A (1) and B (2), two new furan-containing polyketides, and aurantoic acid A (3), a new natural product, were isolated from the liquid fermentation of the sika deer dung-derived actinomycete Actinocorallia aurantiaca. The structures of the new compounds were established by extensive spectroscopic methods, including 1D & 2D NMR, HRESIMS spectroscopic analysis. The absolute configuration of 3 was assigned by comparison of the specific optical rotations with the reported derivatives. Biological activity evaluations suggested that compounds 1-3 showed weak inhibition on NO production in the murine monocytic RAW 264.7 macrophages with IC₅₀ values of 35.8, 41.8, 45.2 μM, respectively. Compound 3 showed weak inhibition on influenza A virus (A/PuertoRico/8/1934, H1N1) with an EC₅₀ value of 35.9 μM, and a selective index higher than 13.3.

The Establishment and Validation of the Human U937 Cell Line as a Cellular Model to Screen Immunomodulatory Agents Regulating Cytokine Release Induced by Influenza Virus Infection

Severe influenza infections are often associated with the excessive induction of pro-inflammatory cytokines, which is also referred to as "cytokine storms". Several studies have shown that cytokine storms are directly associated with influenza-induced fatal acute lung injury and acute respiratory distress syndrome. Due to the narrow administration window, current antiviral therapies are often inadequate. The efforts to use immunomodulatory agents alone or in combination with antiviral agents in the treatment of influenza in animal models have resulted in the achievement of protective effects accompanied with reduced cytokine production. Currently, there are no immunomodulatory drugs for influenza available for clinical use. Animal models, despite being ideal to study the anti-inflammatory responses to influenza virus infection, are very costly and time-consuming. Therefore, there is an urgent need to establish fast and economical screening methods using cell-based models to screen and develop novel immunomodulatory agents. In this study, we screened seven human cell lines and found that the human monocytic cell U937 supports the replication of different subtypes of influenza viruses as well as the production of the important pro-inflammatory cytokines and was selected to develop the cell-based model. The U937 cell model was validated by testing a panel of known antiviral and immunomodulatory agents and screening a drug library consisting of 1280 compounds comprised mostly of FDA-approved drugs. We demonstrated that the U937 cell model is robust and suitable for the high-throughput screening of immunomodulators and antivirals against influenza infection.

Mouse lung slices: An ex vivo model for the evaluation of antiviral and anti-inflammatory agents against influenza viruses

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Mouse lung slices stay alive for at least 5 days ex vivo.

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Influenza viruses can replicate in mouse lung slices and trigger robust cytokine and chemokine responses.

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A positive correlation in cytokine and chemokine responses between ex vivo and in vivo exists.

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Neuraminidase and IP-10 can serve as readouts for antiviral and anti-inflammation activities, respectively.

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This ex vivo model may predict efficacy of drug candidates in antiviral and anti-inflammation activities in vivo.

The influenza A virus is notoriously known for its ability to cause recurrent epidemics and global pandemics. Antiviral therapy is effective when treatment is initiated within 48 h of symptom onset, and delaying treatment beyond this time frame is associated with decreased efficacy. Research on anti-inflammatory therapy to ameliorate influenza-induced inflammation is currently underway and seems important to the impact on the clinical outcome. Both antiviral and anti-inflammatory drugs with novel mechanisms of action are urgently needed. Current methods for evaluating the efficacy of anti-influenza drugs rely mostly on transformed cells and animals. Transformed cell models are distantly related to physiological and pathological conditions. Although animals are the best choices for preclinical drug testing, they are not time- or cost-efficient. In this study, we established an ex vivo model using mouse lung slices to evaluate both antiviral and anti-inflammatory agents against influenza virus infection. Both influenza virus PR8 (H1N1) and A/Human/Hubei/3/2005 (H3N2) can replicate efficiently in mouse lung slices and trigger significant cytokine and chemokine responses. The induction of selected cytokines and chemokines were found to have a positive correlation between ex vivo and in vivo experiments, suggesting that the ex vivo cultured lung slices may closely resemble the lung functionally in an in vivo configuration when challenged by influenza virus. Furthermore, a set of agents with known antiviral and/or anti-inflammatory activities were tested to validate the ex vivo model. Our results suggested that mouse lung slices provide a robust, convenient and cost-efficient model for the assessment of both antiviral and anti-inflammatory agents against influenza virus infection in one assay. This ex vivo model may predict the efficacy of drug candidates’ antiviral and anti-inflammatory activities in vivo.

Antiviral activity of maca (Lepidium meyenii) against human influenza virus

OBJECTIVE

To investigate antiviral activity of maca to reduce viral load in Madin-Darby canine kidney (MDCK) cells infected with influenza type A and B viruses (Flu-A and Flu-B, respectively).

METHODS

Maca were extracted with methanol (1:2, v/v). The cell viability and toxicity of the extracts were evaluated on MDCK cells using method MTT assay. Antiviral activity of compounds against Flu-A and Flu-B viruses was assayed using a test for determining the inhibition of the cytopathic effect on cell culture and multiplex RT-PCR.

RESULTS

The methanol extract of maca showed low cytotoxicity and inhibited influenza-induced cytopathic effect significantly, while viral load was reduced via inhibition of viral growth in MDCK infected cells. Maca contains potent inhibitors of Flu-A and Flu-B with a selectivity index [cytotoxic concentration 50%/IC50] of 157.4 and 110.5, respectively.

CONCLUSIONS

In vitro assays demonstrated that maca has antiviral activity not only against Flu-A (like most antiviral agents) but also Flu-B viruses, providing remarkable therapeutic benefits.