Novel influenza inhibitors designed to target PB1 interactions with host importin RanBP5

MicroRNA-205-5p: A potential therapeutic target for influenza A

We are committed to finding host targets for influenza A therapeutics. The nucleoprotein (NP) plays an important role in influenza A virus replication and is an indispensable part of viral transcription and replication. Exploring endogenous substances that can modulate NP is critical for finding host targets. MicroRNAs (miRNAs, miR) are a novel class of powerful, endogenous gene expression regulators. Herein, we used miRanda to analyse the base complementarity between the NP gene and the 14 host miRNAs reported previously by us. MiRanda predicted that miR-431-5p, miR-744-3p and miR-205-5p could complement the NP gene. To understand the effect of these miRNAs on NP expression, we co-transfected 293 T cells with NP gene sequence containing above miRNAs binding site or full sequence of NP gene (transfected into pmirGlo or pcDNA3.1 vectors, respectively), and mimics of miR-205-5p, miR-431-5p and miR-744-3p. Dual luciferase reporter gene or Western blotting assays confirmed that miR-205-5p and miR-431-5p inhibit NP expression by binding with the miRNA binding site of NP gene. Further, we infected Mouse Lung Epithelial (MLE-12) cells overexpressing miR-205-5p and miR-431-5p with influenza A virus and performed Western blotting to examine NP expression. We found that NP expression was significantly reduced in MLE-12 cells overexpressing miR-205-5p during influenza A infection. The miR-205-5p overexpression-induced inhibition of influenza A replication could be attributed to the inhibition of NP expression. Further, we administered oseltamivir and Jinchai Antiviral Capsules (JC, an anti-influenza Chinese medicine) to influenza A virus-infected MLE-12 cells and mice. We found that miR-205-5p was significantly decreased increased in infected cells and lung tissues, and oseltamivir and JC could up-regulate miR-205-5p. In conclusion, we provide new evidence that miR-205-5p plays a role in regulating viral NP protein expression in combating influenza A and may be a potential target for influenza A therapy.

Discovery of Aryl Benzoyl Hydrazide Derivatives as Novel Potent Broad-Spectrum Inhibitors of Influenza A Virus RNA-Dependent RNA Polymerase (RdRp)

Influenza A viruses possess a high antigenic shift, and the approved anti-influenza drugs are extremely limited, which makes the development of novel anti-influenza drugs for the clinical treatment and prevention of influenza outbreaks imperative. Herein, we report a series of novel aryl benzoyl hydrazide analogs as potent anti-influenza agents. Particularly, analogs 10b, 10c, 10g, 11p, and 11q exhibited potent inhibitory activity against the avian H5N1 flu strain with EC₅₀ values ranging from 0.009 to 0.034 μM. Moreover, compound 11q exhibited nanomolar antiviral effects against both the H1N1 virus and Flu B virus and possessed good oral bioavailability and inhibitory activity against influenza A virus in a mouse model. Preliminary mechanistic studies suggested that these compounds exert anti-influenza virus effects mainly by interacting with the PB1 subunit of RNA-dependent RNA polymerase (RdRp). These results revealed that 11q has the potential to become a potent clinical candidate to combat seasonal influenza and influenza pandemics.

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.

How SARS-CoV-2 and Other Viruses Build an Invasion Route to Hijack the Host Nucleocytoplasmic Trafficking System

The host nucleocytoplasmic trafficking system is often hijacked by viruses to accomplish their replication and to suppress the host immune response. Viruses encode many factors that interact with the host nuclear transport receptors (NTRs) and the nucleoporins of the nuclear pore complex (NPC) to access the host nucleus. In this review, we discuss the viral factors and the host factors involved in the nuclear import and export of viral components. As nucleocytoplasmic shuttling is vital for the replication of many viruses, we also review several drugs that target the host nuclear transport machinery and discuss their feasibility for use in antiviral treatment.