Identification of Compounds Targeting Hepatitis B Virus Core Protein Dimerization through a Split Luciferase Complementation Assay

Arbidol: The current demand, strategies, and antiviral mechanisms

BACKGROUND

High morbidity and mortality of influenza virus infection have made it become one of the most lethal diseases threatening public health; the lack of drugs with strong antiviral activity against virus strains exacerbates the problem.

METHODS

Two independent researchers searched relevant studies using Embase, PubMed, Web of Science, Google Scholar, and MEDLINE databases from its inception to December 2022.

RESULTS

Based on the different antiviral mechanisms, current antiviral strategies can be mainly classified into virus-targeting approaches such as neuraminidase inhibitors, matrix protein 2 ion channel inhibitors, polymerase acidic protein inhibitors and other host-targeting antivirals. However, highly viral gene mutation has underscored the necessity of novel antiviral drug development. Arbidol (ARB) is a Russian-made indole-derivative small molecule licensed in Russia and China for the prevention and treatment of influenza and other respiratory viral infections. ARB also has inhibitory effects on many other viruses such as severe acute respiratory syndrome coronavirus 2, Coxsackie virus, respiratory syncytial virus, Hantaan virus, herpes simplex virus, and hepatitis B and C viruses. ARB is a promising drug which can not only exert activity against virus at different steps of virus replication cycle, but also directly target on hosts before infection to prevent virus invasion.

CONCLUSION

ARB is a broad-spectrum antiviral drug that inhibits several viruses in vivo and in vitro, with high safety profile and low resistance; the antiviral mechanisms of ARB deserve to be further explored and more high-quality clinical studies are required to establish the efficacy and safety of ARB.

Development and characterization of an inducible assay system to measure Zika virus capsid interactions

The global spread of the mosquito-borne Zika virus (ZIKV) infection and its complications including Guillain-Barré syndrome and fetus microcephaly in 2015 have made ZIKV as a significant public health threat. The capsid protein plays crucial roles in ZIKV replication and thus represents an attractive therapeutic target. However, inhibitors of ZIKV capsid assembly have not been rigorously identified due to the lack of a target-based screening system. In this study, we developed a novel ZIKV capsid interaction method based on a split-luciferase complementation assay, which can be used to measure and quantify ZIKV capsid-capsid (C-C) interaction by the restored luciferase signal when capsid proteins interact with each other. Furthermore, a Tet-on inducible stable cell line was generated to screen inhibitors of capsid dimerization. By using of this system, peptides (Pep.15-24 in the N-terminal region of ZIKV capsid protein and Pep.44-58 in the α2 helix of ZIKV capsid protein) were identified to inhibit ZIKV C-C interaction. Overall, this study developed a novel inducible assay system to measure ZIKV capsid interaction and identify ZIKV capsid multimerization inhibitors, which will be applied for future discovery of ZIKV assembly inhibitors.

Experimental and Analytical Framework for "Mix-and-Read" Assays Based on Split Luciferase

The use of immunodetection assays including the widely used enzyme-linked immunosorbent assay (ELISA) in applications such as point-of-care detection is often limited by the need for protein immobilization and multiple binding and washing steps. Here, we describe an experimental and analytical framework for the development of simple and modular "mix-and-read" enzymatic complementation assays based on split luciferase that enable sensitive detection and quantification of analytes in solution. In this assay, two engineered protein binders targeting nonoverlapping epitopes on the target analyte were each fused to nonactive fragments of luciferase to create biosensor probes. Binding proteins to two model targets, lysozyme and Sso6904, were isolated from a combinatorial library of Sso7d mutants using yeast surface display. In the presence of the analyte, probes were brought into close proximity, reconstituting enzymatic activity of luciferase and enabling detection of low picomolar concentrations of the analyte by chemiluminescence. Subsequently, we constructed an equilibrium binding model that relates binding affinities of the binding proteins for the target, assay parameters such as the concentrations of probes used, and assay performance (limit of detection and concentration range over which the target can be quantified). Overall, our experimental and analytical framework provides the foundation for the development of split luciferase assays for detection and quantification of various targets.

Luciferase-Based Biosensors in the Era of the COVID-19 Pandemic

Luciferase-based biosensors have a wide range of applications and assay formats, including their relatively recent use in the study of viruses. Split luciferase, bioluminescence resonance energy transfer, circularly permuted luciferase, cyclic luciferase, and dual luciferase systems have all been used to interrogate the structure and function of prominent viruses infecting humans, animals, and plants. The utility of these assays is demonstrated by numerous studies which have not only successfully characterized interactions between viral and host cell proteins but that have also used these systems to identify viral inhibitors. In the present COVID-19 pandemic, luciferase-based biosensors are already playing a critical role in the study of the culprit virus SARS-CoV-2 as well as in the development of serological assays and drug development via high-throughput screening. In this review paper, we provide a summary of existing luciferase-based biosensors and their applications in virology.

Efficacy and safety of arbidol (umifenovir) in patients with COVID-19: A systematic review and meta-analysis

OBJECTIVE

To provide the latest evidence for the efficacy and safety of arbidol (umifenovir) in COVID-19 treatment.

METHODS

A literature systematic search was carried out in PubMed, Cochrane Library, Embase, and medRxiv up to May 2021. The Cochrane risk of bias tool and Newcastle-Ottawa scale were used to assess the quality of included studies. Meta-analysis was performed using RevMan 5.3.

RESULTS

Sixteen studies were met the inclusion criteria. No significant difference was observed between arbidol and non-antiviral treatment groups neither for primary outcomes, including the negative rate of PCR (NR-PCR) on Day 7 (risk ratio [RR]: 0.94; 95% confidence interval (CI): 0.78-1.14) and Day 14 (RR: 1.10; 95% CI: 0.96-1.25), and PCR negative conversion time (PCR-NCT; mean difference [MD]: 0.74; 95% CI: -0.87 to 2.34), nor secondary outcomes (p > .05). However, arbidol was associated with higher adverse events (RR: 2.24; 95% CI: 1.06-4.73). Compared with lopinavir/ritonavir, arbidol showed better efficacy for primary outcomes (p < .05). Adding arbidol to lopinavir/ritonavir also led to better efficacy in terms of NR-PCR on Day 7 and PCR-NCT (p < .05). There was no significant difference between arbidol and chloroquine in primary outcomes (p > .05). No remarkable therapeutic effect was observed between arbidol and other agents (p > .05).

CONCLUSION

The present meta-analysis showed no significant benefit of using arbidol compared with non-antiviral treatment or other therapeutic agents against COVID-19 disease. High-quality studies are needed to establish the efficacy and safety of arbidol for COVID-19.

Pharmacokinetic comparison of four arbidol hydrochloride preparations in beagle dogs

This study aimed to compare the pharmacokinetic properties of four preparations (dispersible tablets, ordinary tablets, capsules and granules) of arbidol hydrochloride, a broad-spectrum antiviral drug, in beagle dogs. Briefly, a single dose of 100 mg of the four preparations of arbidol hydrochloride was orally administered to dogs; blood was then collected from the veins of the foreleg at different times after administration to prepare plasma samples. The plasma concentration of arbidol hydrochloride was measured using a validated liquid chromatography-tandem mass spectrometry (LC-MS/MS). The results showed that when orally administered with dispersible tablets, ordinary tablets, capsules and granules suspended with water, there were no significant differences in the pharmacokinetic parameters (including peak time, peak concentration, elimination half-life, area under the curve (AUC_0-t ), and mean retention time) of arbidol hydrochloride. However, in the case of the dispersible tablets, the pharmacokinetics of arbidol hydrochloride was significantly affected by the mode of administration. Compared with direct feeding, peak time [0.50 (0.13, 0.50) vs. 1.00 (0.50, 2.00)] was significantly shortened (P = 0.033) and the AUC_{0-48 h} (8726.5 ± 2509.3 vs. 3650.8 ± 1536.9 ng h/ml) was significantly increased (P = 0.012) when the dispersible tablets were orally administered as water dispersion. In conclusion, the pharmacokinetics of four preparations of arbidol hydrochloride were not significant different in beagle dogs. However, compared with direct feeding, the absorption of arbidol hydrochloride was faster and the bioavailability was better when the dispersible tablets were orally administered as water dispersion.

Nanoluciferase complementation-based bioreporter reveals the importance of N-linked glycosylation of SARS-CoV-2 S for viral entry

The ongoing COVID-19 pandemic has highlighted the immediate need for the development of antiviral therapeutics targeting different stages of the SARS-CoV-2 life cycle. We developed a bioluminescence-based bioreporter to interrogate the interaction between the SARS-CoV-2 viral spike (S) protein and its host entry receptor, angiotensin-converting enzyme 2 (ACE2). The bioreporter assay is based on a nanoluciferase complementation reporter, composed of two subunits, large BiT and small BiT, fused to the S receptor-binding domain (RBD) of the SARS-CoV-2 S protein and ACE2 ectodomain, respectively. Using this bioreporter, we uncovered critical host and viral determinants of the interaction, including a role for glycosylation of asparagine residues within the RBD in mediating successful viral entry. We also demonstrate the importance of N-linked glycosylation to the RBD's antigenicity and immunogenicity. Our study demonstrates the versatility of our bioreporter in mapping key residues mediating viral entry as well as screening inhibitors of the ACE2-RBD interaction. Our findings point toward targeting RBD glycosylation for therapeutic and vaccine strategies against SARS-CoV-2.

SARS-CoV-2 S1 NanoBiT: A nanoluciferase complementation-based biosensor to rapidly probe SARS-CoV-2 receptor recognition

As the COVID-19 pandemic continues, there is an imminent need for rapid diagnostic tools and effective antivirals targeting SARS-CoV-2. We have developed a novel bioluminescence-based biosensor to probe a key host-virus interaction during viral entry: the binding of SARS-CoV-2 viral spike (S) protein to its receptor, angiotensin-converting enzyme 2 (ACE2). Derived from Nanoluciferase binary technology (NanoBiT), the biosensor is composed of Nanoluciferase split into two complementary subunits, Large BiT and Small BiT, fused to the Spike S1 domain of the SARS-CoV-2 S protein and ACE2 ectodomain, respectively. The ACE2-S1 interaction results in reassembly of functional Nanoluciferase, which catalyzes a bioluminescent reaction that can be assayed in a highly sensitive and specific manner. We demonstrate the biosensor's large dynamic range, enhanced thermostability and pH tolerance. In addition, we show the biosensor's versatility towards the high-throughput screening of drugs which disrupt the ACE2-S1 interaction, as well as its ability to act as a surrogate virus neutralization assay. Results obtained with our biosensor correlate well with those obtained with a Spike-pseudotyped lentivirus assay. This rapid in vitro tool does not require infectious virus and should enable the timely development of antiviral modalities targeting SARS-CoV-2 entry.

COVID-19 Antiviral and Treatment Candidates: Current Status

The coronavirus disease 2019 (COVID-19) pandemic caused by the severe acute respiratory syndrome coronavirus 2 has severely impacted global health and economy. There is currently no effective approved treatment for COVID-19; although vaccines have been granted emergency use authorization in several countries, they are currently only administered to high-risk individuals, thereby leaving a gap in virus control measures. The scientific and clinical communities and drug manufacturers have collaborated to speed up the discovery of potential therapies for COVID-19 by taking advantage of currently approved drugs as well as investigatory agents in clinical trials. In this review, we stratified some of these candidates based on their potential targets in the progression of COVID-19 and discuss some of the results of ongoing clinical evaluations.

Repurposing of Antazoline Hydrochloride as an Inhibitor of Hepatitis B Virus DNA Secretion

Hepatitis B virus (HBV) belongs to Hepadnaviridae family and mainly infects hepatocytes, which can cause acute or chronic hepatitis. Currently, two types of antiviral drugs are approved for chronic infection clinically: interferons and nucleos(t)ide analogues. However, the clinical cure for chronic infection is still rare, and it is a huge challenge for all researchers to develop high-efficiency, safe, non-tolerant, and low-toxicity anti-HBV drugs. Antazoline hydrochloride is a first-generation antihistamine with anticholinergic properties, and it is commonly used to relieve nasal congestion and in eye drops. Recently, an in vitro high-throughput evaluation system was constructed to screen nearly 800 compounds from the Food and Drug Administration (FDA)-approved Drug Library. We found that arbidol hydrochloride and antazoline hydrochloride can effectively reduce HBV DNA in the extracellular supernatant in a dose-dependent manner, with EC₅₀ of 4.321 μmol/L and 2.910 μmol/L in HepAD38 cells, respectively. Moreover, the antiviral effects and potential mechanism of action of antazoline hydrochloride were studied in different HBV replication systems. The results indicate that antazoline hydrochloride also has a significant inhibitory effect on HBV DNA in the extracellular supernatant of Huh7 cells, with an EC₅₀ of 2.349 μmol/L. These findings provide new ideas for screening and research related to HBV agents.