Identification of influenza polymerase inhibitors targeting C-terminal domain of PA through surface plasmon resonance screening

T-705-Derived Prodrugs Show High Antiviral Efficacies against a Broad Range of Influenza A Viruses with Synergistic Effects When Combined with Oseltamivir

Emerging influenza A viruses (IAV) bear the potential to cause pandemics with unpredictable consequences for global human health. In particular, the WHO has declared avian H5 and H7 subtypes as high-risk candidates, and continuous surveillance of these viruses as well as the development of novel, broadly acting antivirals, are key for pandemic preparedness. In this study, we sought to design T-705 (Favipiravir) related inhibitors that target the RNA-dependent RNA polymerase and evaluate their antiviral efficacies against a broad range of IAVs. Therefore, we synthesized a library of derivatives of T-705 ribonucleoside analogues (called T-1106 pronucleotides) and tested their ability to inhibit both seasonal and highly pathogenic avian influenza viruses in vitro. We further showed that diphosphate (DP) prodrugs of T-1106 are potent inhibitors of H1N1, H3N2, H5N1, and H7N9 IAV replication. Importantly, in comparison to T-705, these DP derivatives achieved 5- to 10-fold higher antiviral activity and were non-cytotoxic at the therapeutically active concentrations. Moreover, our lead DP prodrug candidate showed drug synergy with the neuraminidase inhibitor oseltamivir, thus opening up another avenue for combinational antiviral therapy against IAV infections. Our findings may serve as a basis for further pre-clinical development of T-1106 prodrugs as an effective countermeasure against emerging IAVs with pandemic potential.

Interaction of Influenza A Nucleoprotein with Host hnRNP-C Is Implicated in Viral Replication

The host interactome of influenza viral proteins is ever-expanding. In this work, we report the identification of host heterogeneous nuclear ribonucleoprotein C (hnRNP-C) as an interacting partner of influenza A virus nucleoprotein (NP). We confirmed that this interaction exists across different influenza A subtypes and strains. Using biochemical methods, we determined that hnRNP-C interacts with NP via its C-terminal auxiliary domain. Further, we determined that the hnRNP-C is a negative regulator of influenza viral growth. Its interaction with NP is implicated in the promotion of host cell apoptosis during viral infection. It is the first time that the interaction between influenza nucleoprotein and host heterogeneous nuclear ribonucleoprotein C is characterized in detail. Overall, these findings not only characterize the interaction between NP and its host interacting partner hnRNP-C but also clarify the functional significance of this interaction. This work may lead to a new therapeutic target for the development of anti-influenza drugs.

Design, Synthesis, Molecular Docking Analysis and Biological Evaluations of 4-[(Quinolin-4-yl)amino]benzamide Derivatives as Novel Anti-Influenza Virus Agents

In this study, a series of 4-[(quinolin-4-yl)amino]benzamide derivatives as the novel anti-influenza agents were designed and synthesized. Cytotoxicity assay, cytopathic effect assay and plaque inhibition assay were performed to evaluate the anti-influenza virus A/WSN/33 (H1N1) activity of the target compounds. The target compound G07 demonstrated significant anti-influenza virus A/WSN/33 (H1N1) activity both in cytopathic effect assay (EC₅₀ = 11.38 ± 1.89 µM) and plaque inhibition assay (IC₅₀ = 0.23 ± 0.15 µM). G07 also exhibited significant anti-influenza virus activities against other three different influenza virus strains A/PR/8 (H1N1), A/HK/68 (H3N2) and influenza B virus. According to the result of ribonucleoprotein reconstitution assay, G07 could interact well with ribonucleoprotein with an inhibition rate of 80.65% at 100 µM. Furthermore, G07 exhibited significant activity target PA−PB1 subunit of RNA polymerase according to the PA−PB1 inhibitory activity prediction by the best pharmacophore Hypo1. In addition, G07 was well drug-likeness based on the results of Lipinski’s rule and ADMET prediction. All the results proved that 4-[(quinolin-4-yl)amino]benzamide derivatives could generate potential candidates in discovery of anti-influenza virus agents.

Prevalence, Genetics, and Evolutionary Properties of Eurasian Avian-Like H1N1 Swine Influenza Viruses in Liaoning

Swine influenza virus (SIV) is an important zoonosis pathogen. The 2009 pandemic of H1N1 influenza A virus (2009/H1N1) highlighted the importance of the role of pigs as intermediate hosts. Liaoning province, located in northeastern China, has become one of the largest pig-farming areas since 2016. However, the epidemiology and evolutionary properties of SIVs in Liaoning are largely unknown. We performed systematic epidemiological and genetic dynamics surveillance of SIVs in Liaoning province during 2020. In total, 33,195 pig nasal swabs were collected, with an SIV detection rate of 2%. Our analysis revealed that multiple subtypes of SIVs are co-circulating in the pig population in Liaoning, including H1N1, H1N2 and H3N2 SIVs. Furthermore, 24 H1N1 SIVs were confirmed to belong to the EA H1N1 lineage and divided into two genotypes. The two genotypes were both triple reassortant, and the predominant one with polymerase, nucleoprotein (NP), and matrix protein (M) genes originating from 2009/H1N1; hemagglutinin (HA) and neuraminidase (NA) genes originating from EA H1N1; and the nonstructural protein (NS) gene originating from triple reassortant H1N2 (TR H1N2) was detected in Liaoning for the first time. According to our evolutionary analysis, the EA H1N1 virus in Liaoning will undergo further genome variation.

Design, synthesis, and biological activity of a novel series of 2-ureidonicotinamide derivatives against influenza A virus

BACKGROUND

Viral resistance to existing inhibitors and the time-dependent effectiveness of neuraminidase inhibitors have limited the number of antivirals that can be used for prophylaxis and therapeutic treatment of severe influenza infection. Thus, there is an urgent need to develop new drugs to prevent and treat influenza infection.

OBJECTIVE

The aim of this study was to design and synthesize a novel series of 2-ureidonicotinamide derivatives, and evaluate their anti-IAV activities. Furthermore, we predicted the abilities of these compounds inhibiting PA-PB1 subunit and forecasted the docking poses of these compounds with RNA polymerase protein (PDB ID 3CM8).

METHOD

The novel designed compounds were synthesized using classical methods of organic chemistry and tested in vitro for their abilities inhibiting RNP and against influenza A virus. In addition, the 23 synthesized molecules were subjected to the generated pharmacophore Hypo1 to forecast the activity target PA-PB1 subunit of RNA polymerase. The ADMET pharmacokinetic parameters were calculated by the ADMET modules in Discovery Studio 2016. The docking results helped us to demonstrate the possible interactions between these compounds with 3CM8.

RESULTS

The synthesized 2-ureidonicotinamide derivatives were characterized as potent anti-influenza inhibitors. The target compounds 7b and 7c demonstrated significant antiviral activities, and could be considered as novel lead compounds of antiviral inhibitors. In addition, compound 7b revealed suitable ADME properties expressed, and might be a significant RNA polymerase inhibitor targeting PA-PB1 subunit based on the predictable results and the docking results.

CONCLUSION

This study revealed a novel series of compounds that might be useful in the search for an effective drug against influenza virus.

Design and synthesis of 1,3-diphenylpyrimidine-2,4(1H,3H)-dione derivatives as antitumor agents via elevating ROS production to induce apoptosis

The target compound XS23 have exhibited excellent antitumor cell proliferative activity against multiple tumor cell lines and can induce cancer cell apoptosis by elevating ROS production.

Host-Adaptive Signatures of H3N2 Influenza Virus in Canine

Wild aquatic birds are the primary natural reservoir of influenza A viruses (IAVs), although a small number of viruses can spill over to mammals and circulate. The focus of IAV infection in mammals was largely limited to humans and swine variants, until the emergence of H3N2 canine influenza viruses (CIVs), which provides new perspective for interspecies transmission of the virus. In this study, we captured 54 canine-adaptive signatures in H3N2 CIVs through entropy computation, which were largely concentrated in the interaction region of polymerase proteins on ribonucleoprotein complex. The receiver operating characteristic curves of these sites showed >95% accuracy in distinguishing between the hosts. Nine of the 54 canine-adaptive signatures were shared in avian–human/equine or equine–canine (PB2-82; PB1-361; PA-277; HA-81, 111, 172, 196, 222, 489), suggesting their involvement in canine adaptation. Furthermore, we found that IAVs can establish persistent transmission in lower mammals with greater ease compared to higher mammals, and 25 common adaptation signatures of H3 IAVs were observed in diverse avian–mammals comparison. There were few human-like residues in H3N2 CIVs, which suggested a low risk of human infection. Our study highlights the necessity of identifying and monitoring the emerging adaptive mutations in companion animals by enhanced surveillance and provides a basis for mammal adaptation of avian influenza viruses.

Inhibition of Influenza Virus Polymerase by Interfering with Its Protein-Protein Interactions

Influenza (flu) virus is a serious threat to global health with the potential to generate devastating pandemics. The availability of broad spectrum antiviral drugs is an unequaled weapon during pandemic events, especially when a vaccine is still not available. One of the most promising targets for the development of new antiflu therapeutics is the viral RNA-dependent RNA polymerase (RdRP). The assembly of the flu RdRP heterotrimeric complex from the individual polymerase acidic protein (PA), polymerase basic protein 1 (PB1), and polymerase basic protein 2 (PB2) subunits is a prerequisite for RdRP functions, such as mRNA synthesis and genome replication. In this Review, we report the known protein-protein interactions (PPIs) occurring by RdRP that could be disrupted by small molecules and analyze their benefits and drawbacks as drug targets. An overview of small molecules able to interfere with flu RdRP functions exploiting the PPI inhibition approach is described. In particular, an update on the most recent inhibitors targeting the well-consolidated RdRP PA-PB1 subunit heterodimerization is mainly reported, together with pioneer inhibitors targeting other virus-virus or virus-host interactions involving RdRP subunits. As demonstrated by the PA-PB1 interaction inhibitors discussed herein, the inhibition of flu RdRP functions by PPI disrupters clearly represents a valid means to identify compounds endowed with a broad spectrum of action and a reduced propensity to develop drug resistance, which are the main issues of antiviral drugs.

Anti-Influenza Drug Discovery and Development: Targeting the Virus and Its Host by All Possible Means

Infections by influenza virus constitute a major and recurrent threat for human health. Together with vaccines, antiviral drugs play a key role in the prevention and treatment of influenza virus infection and disease. Today, the number of antiviral molecules approved for the treatment of influenza is relatively limited, and their use is threatened by the emergence of viral strains with resistance mutations. There is therefore a real need to expand the prophylactic and therapeutic arsenal. This chapter summarizes the state of the art in drug discovery and development for the treatment of influenza virus infections, with a focus on both virus-targeting and host cell-targeting strategies. Novel antiviral strategies targeting other viral proteins or targeting the host cell, some of which are based on drug repurposing, may be used in combination to strengthen our therapeutic arsenal against this major pathogen.

structural characterization of the interaction between the C-terminal domain of the influenza polymerase PA subunit and an optimized small peptide inhibitor

Influenza viruses can cause severe respiratory infections in humans, leading to nearly half a million deaths worldwide each year. Improved antiviral drugs are needed to address the threat of development of novel pandemic strains. Current therapeutic interventions target three key proteins in the viral life cycle: neuraminidase, the M2 channel and RNA-dependent-RNA polymerase. Protein-protein interactions between influenza polymerase subunits are potential new targets for drug development. Using a newly developed assay based on AlphaScreen technology, we screened a peptide panel for protein-protein interaction inhibitors to identify a minimal PB1 subunit-derived peptide that retains high inhibition potential and can be further modified. Here, we present an X-ray structure of the resulting decapeptide bound to the C-terminal domain of PA polymerase subunit from pandemic isolate A/California/07/2009 H1N1 at 1.6 Å resolution and discuss its implications for the design of specific, potent influenza polymerase inhibitors.