Emerging antiviral therapies and drugs for the treatment of influenza

Optimization and biological evaluation of l-DOPA derivatives as potent influenza PAN endonuclease inhibitors with multi-site binding characteristics

Emerging and potential influenza pandemics still are an enormous worldwide public health challenge. The PAN endonuclease has been proved to be a promising target for anti-influenza drug design. Here, we report the discovery and optimization of potent Y-shaped PAN inhibitors featuring multi-site binding characteristics with l-DOPA as a starting point. We systematically modified the hit 1 bearing two-binding characteristics based on structure-based rational design combined with multisite binding and conformational constraint strategies, generating four families of l-DOPA derivatives for SARs analysis. Among these substances, N, 3-di-substituted 1, 2, 3, 4-tetrahydroisoquinoline derivative T-31 displayed superior properties as a lead PAN endonuclease inhibitor and antiviral agent. The lead T-31 inhibited PAN endonuclease activity with an IC50 value of 0.15 μM and showed broad and submicromolar anti-influenza potency in cell-based assays. More importantly, T-31 could simultaneously target both influenza HA and the RdRp complex, thus interfering with virus entry into host cells and viral replication. This study offers a set of novel PAN endonuclease inhibitors with multi-site binding characteristics starting from the l-DOPA skeleton.

Qingjin Huatan decoction protects mice against influenza a virus pneumonia via the chemokine signaling pathways

ETHNOPHARMACOLOGICAL RELEVANCE

Qingjin Huatan Decoction (QJHTT) consists of 11 herbal medicines: Scutellaria baicalensis Georgi, Gardenia jasminoides J.Ellis, Platycodon grandiflorus (Jacq.) A.DC., Ophiopogon japonicus (Thunb.) Ker Gawl., Morus alba L., Fritillaria thunbergii Miq., Anemarrhena asphodeloides Bunge, Trichosanthes kirilowii Maxim., Citrus reticulata Blanco, Poria cocos (Schw.) Wolf, and Glycyrrhiza uralensis Fisch. As a traditional compound Chinese medicinal formula, QJHTT has been used for more than 400 years in China. Historically, it was used to treat respiratory diseases and had shown beneficial clinical results for diseases related to lung inflammation.

AIM OF THE STUDY

To investigate the therapeutic effect of QJHTT on influenza A virus (IAV) pneumonia in mice and explore its possible mechanism of action.

MATERIALS AND METHODS

The components in QJHTT were analyzed by UPLC-Q-TOF-MS and some antiviral active components reported in the literature were determined and quantified by HPLC. The protective effects of QJHTT were investigated using lethal and sublethal doses (2 LD50 or 0.8 LD50 viral suspension, separately) of H1N1-infected mice. Mortality and lung lesions in H1N1-infected mice were used to evaluate the efficacy of QJHTT. The potential mechanism of QJHTT in the treatment of viral pneumonia was determined at the gene level by RNA sequencing and validated by qRT-PCR. Following this, the changes in protein levels of JAK2/STAT3 were analyzed since it is a key downstream target of the chemokine signaling pathways. Preliminary elucidation of the mechanism of QJHTT to protect mice against IAV pneumonia through this pathway was conducted.

RESULTS

In this study, 12 antiviral active constituents including baicalin, geniposide, and mangiferin were identified from QJHTT. In vivo treatment of QJHTT reduced the virus titers of lung tissue significantly and improved the survival rate, lung index, and pulmonary histopathological changes; additionally, a reduction in the serum levels of TNF-α, IL-1β, IL-6, and IFN-γ inflammatory factors in H1N1-infected mice was observed. RNA-seq analysis and qRT-PCR showed that QJHTT primarily reversed the activities CCL2, CCL7, CCR1, and other chemokines and their reception-related genes, suggesting that QJHTT may produce disease-resistant pneumonia by inhibiting the downstream JAK2/STAT3 pathway. Western blot analysis confirmed that QJHTT effectively reduced the protein levels of JAK2, STAT3, and related phosphorylated products in the lung tissue of H1N1-infected mice.

CONCLUSIONS

Our results indicated that QJHTT alleviated IAV pneumonia in mice by regulating related chemokines and their receptor-related genes in lung tissue, thereby inhibiting JAK2/STAT3 pathway. This could pave way for the design of novel therapeutic strategies to treat viral pneumonia.

Identification of catalytically active domain epitopes in neuraminidase protein of H9N2 subtype of avian influenza virus

H9N2 subtype of avian influenza virus (AIV) is primarily a bird virus, which is widespread in clinical avian disease, and reported in cases of human infection. As one of the surface proteins of AIV, the neuraminidase (NA) protein plays an important role mainly in viral budding. However, vaccine development and detection methods for NA of H9N2 AIVs are in urgent clinical need. In this study, a truncated NA gene (205-900 bp) was cloned from the NA sequence of H9N2 strain, and then expressed using pET-28a (+) vector. This purified recombinant NA protein was used to immunize BALB/c mice, and the monoclonal antibodies were screened through the indirect enzyme-linked immunosorbent assay (ELISA). Next, eight prokaryotic expression vectors were constructed for epitope identification. After cell fusion, three hybridoma cell lines producing the antibodies special to NA protein were screened by ELISA, western blotting, and indirect immunofluorescence; these were named 1B10, 2B6, and 5B2, respectively. Epitope scanning techniques were used to identify three B-cell epitopes recognized by these three monoclonal antibodies, 196KNATASIIYDGMLVD210, 210DSIGSWSKNIL220 and 221RTQESECVCI230. The subsequent homology analysis revealed the three epitopes were highly conserved in H9N2 AIV strains. The structural predictions of the antigenic epitopes indicated that all three epitopes were located in the catalytic region of NA. These results provide a basis for studying the function of the NA protein of H9N2 AIV and technical support for the development of a universal detection method based on anti-NA monoclonal antibodies.

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.

Fc-Effector-Independent in vivo Activity of a Potent Influenza B Neuraminidase Broadly Neutralizing Antibody

Influenza B virus (IBV) contributes to substantial influenza-mediated morbidity and mortality, particularly among children. Similar to influenza A viruses (IAV), the hemagglutinin (HA) and neuraminidase (NA) of IBV undergo antigenic drift, necessitating regular reformulation of seasonal influenza vaccines. NA inhibitors, such as oseltamivir, have reduced activity and clinical efficacy against IBV, while M2 channel inhibitors are only effective against IAV, highlighting the need for improved vaccine and therapeutics for the treatment of seasonal IBV infections. We have previously described a potent human monoclonal antibody (hMAb), 1092D4, that is specific for IBV NA and neutralizes a broad range of IBVs. The anti-viral activity of MAbs can include direct mechanisms such as through neutralization and/or Fc-mediated effector functions that are dependent on accessory cells expressing Fc receptors and that could be impacted by potential host-dependent variability. To discern if the in vivo efficacy of 1092D4 was dependent on Fc-effector function, 1092D4 hMAb with reduced ability to bind to Fc receptors (1092D4-LALAPG) was generated and tested. 1092D4-LALAPG had comparable in vitro binding, neutralization, and inhibition of NA activity to 1092D4. 1092D4-LALAPG was effective at protecting against a lethal challenge of IBV in mice. These results suggest that hMAb 1092D4 in vivo activity is minimally dependent on Fc-effector functions, a characteristic that may extend to other hMAbs that have potent NA inhibition activity.

Antiviral Activity of Beebread, Bee-Collected Pollen and Artificially Fermented Follen against Influenza A Virus

Bee-collected pollen (BCP) and the naturally fermented BCP product known as bee bread (BB) are functional foods renowned for their nutritious, antioxidant, antibacterial and other therapeutic properties. This is the first study employed to assess the antiviral activity of BCP and BB against influenza A virus (IAV) H1N1 along with their proteinaceous, aqueous and n-butanol fractions. Additionally, artificially fermented BCP has been evaluated against IAV (H1N1). Antiviral activity was assessed in vitro by comparative real-time PCR assay. IC₅₀ values ranged from 0.022 to 10.04 mg/mL, and Selectivity Index (SI) values ranged from 1.06 to 338.64. Artificially fermented BCP samples AF5 and AF17 demonstrated higher SI values than unfermented BCP, and proteinaceous fractions demonstrated the highest SI values. The chemical profile of BCP and BB samples, analyzed using NMR and LC-MS, revealed the presence of specialized metabolites that may contribute toward the antiviral activity. Overall, the significant anti-IAV activity of BB and BCP harvested in Thessaly (Greece) could be attributed to chemical composition (especially undiscovered yet proteinaceous compounds) and possibly to microbiome metabolism. Further research regarding the antiviral properties of BCP and BB will elucidate the mode of action and could lead to new treatments against IAV or other viral diseases.