Drugs for Influenza Treatment: Is There Significant News?

Treating influenza with neuraminidase inhibitors: an update of the literature

INTRODUCTION

Influenza affects individuals of all ages and poses a significant threat during pandemics, epidemics, and sporadic outbreaks. Neuraminidase inhibitors (NAIs) are currently the first choice in the treatment and prevention of influenza, but their use can be hindered by viral resistance.

AREAS COVERED

This review summarizes current NAIs pharmacological profiles, their current place in therapy, and the mechanisms of viral resistance and outlines possible new indications, ways of administration, and novel candidate NAIs compounds.

EXPERT OPINION

NAIs represent a versatile group of compounds with diverse administration methods and pharmacokinetics. While the prevalence of influenza virus resistance to NAIs remains low, there is heightened vigilance due to the pandemic potential of influenza. Several novel NAIs and derivatives are currently under assessment at various stages of development for the treatment and prevention of influenza.

Tackling Influenza A virus by M2 ion channel blockers: Latest progress and limitations

Influenza outbreaks cause pandemics in millions of people. The treatment of influenza remains a challenge due to significant genetic polymorphism in the influenza virus. Also, developing vaccines to protect against seasonal and pandemic influenza infections is constantly impeded. Thus, antibiotics are the only first line of defense against antigenically distinct strains or new subtypes of influenza viruses. Among several anti-influenza targets, the M2 protein of the influenza virus performs several activities. M2 protein is an ion channel that permits proton conductance through the virion envelope and the deacidification of the Golgi apparatus. Both these functions are critical for viral replication. Thus, targeting the M2 protein of the influenza virus is an essential target. Rimantadine and amantadine are two well-known drugs that act on the M2 protein. However, these drugs acquired resistance to influenza and thus are not recommended to treat influenza infections. This review discusses an overview of anti-influenza therapy, M2 ion channel functions, and its working principle. It also discusses the M2 structure and its role, and the change in the structure leads to mutant variants of influenza A virus. We also shed light on the recently identified compounds acting against wild-type and mutated M2 proteins of influenza virus A. These scaffolds could be an alternative to M2 inhibitors and be developed as antibiotics for treating influenza infections.

Discovery of cyperenoic acid as a potent and novel entry inhibitor of influenza A virus

Influenza therapeutics with new targets and modes of action are urgently needed due to the frequent emergence of mutants resistant to currently available anti-influenza drugs. Here we report the in vitro and in vivo anti-influenza A virus activities of cyperenoic acid, a natural compound, which was isolated from a Chinese medicine Croton crassifolius Geise. Cyperenoic acid could potently suppress H1N1, H3N2 and H9N2 virus replication with IC50 values ranging from 0.12 to 15.13 μM, and showed a low cytotoxicity against MDCK cells (CC50 = 939.2 ± 60.0 μM), with selectivity index (SI) values ranging from 62 to 7823. Oral or intraperitoneal treatment of cyperenoic acid effectively protected mice against a lethal influenza virus challenge, comparable to the efficacy of Tamiflu. Additionally, cyperenoic acid also significantly reduced lung virus titers and alleviated influenza-induced acute lung injury in infected mice. Mechanism-of-action studies revealed that cyperenoic acid exhibited its anti-influenza activity during the entry stage of viral replication by inhibiting HA-mediated viral fusion. Simulation docking analyses of cyperenoic acid with the HA structures implied that cyperenoic acid binds to the stalk domain of HA in a cavity near the fusion peptide. Collectively, these results demonstrate that cyperenoic acid is a promising lead compound for the anti-influenza drug development and this research provides a useful small-molecule probe for studying the HA-mediated viral entry process.

A protectin DX (PDX) analog with in vitro activity against influenza A(H1N1) viruses

Antiviral therapy based on neuraminidase (oseltamivir) or polymerase (baloxavir marboxil) inhibitors plays an important role in the management of influenza infections. However, the emergence of drug resistance and the uncontrolled inflammatory response are major limitations in the treatment of severe influenza disease. Protectins D1 (PD1) and DX (PDX), part of a family of pro-resolving mediators, have previously demonstrated anti-influenza activity as well as anti-inflammatory properties in various clinical contexts. Herein, we synthetized a series of simplified PDX analogs and assessed their in vitro antiviral activity against influenza A(H1N1) viruses, including oseltamivir- and baloxavir-resistant variants. In ST6GalI-MDCK cells, the PDX analog AN-137B reduced viral replication in a dose-dependent manner with IC50 values of 23.8 for A/Puerto Rico/8/1934 (H1N1) and between 32.6 and 36.7 µM for susceptible and resistant A(H1N1)pdm09 viruses. In MTS-based cell viability experiments, AN-137B showed a 50% cellular cytotoxicity (CC50 ) of 638.7 µM with a resulting selectivity index of 26.8. Of greater importance, the combination of AN-137B with oseltamivir or baloxavir resulted in synergistic and additive in vitro effects, respectively. Treatment of lipopolysaccharide (LPS)-stimulated macrophages with AN-137B resulted in a decrease of iNOS activity as shown by the reduction of nitrite production, suggesting an anti-inflammatory effect. In conclusion, our results indicate that the protectin analog AN-137B constitutes an interesting therapeutic modality against influenza A virus, warranting further evaluation in animal models.

Antiviral Compounds to Address Influenza Pandemics: An Update from 2016-2022

In recent decades, the world has gained experience of the dangerous effects of pandemic events caused by emerging respiratory viruses. In particular, annual epidemics of influenza are responsible for severe illness and deaths. Even if conventional influenza vaccines represent the most effective tool for preventing virus infections, they are not completely effective in patients with severe chronic disease and immunocompromised and new small molecules have emerged to prevent and control the influenza viruses. Thus, the attention of chemists is continuously focused on the synthesis of new antiviral drugs able to interact with the different molecular targets involved in the virus replication cycle. To date, different classes of influenza viruses inhibitors able to target neuraminidase enzyme, hemagglutinin protein, Matrix-2 (M2) protein ion channel, nucleoprotein or RNAdependent RNA polymerase have been synthesized using several synthetic strategies comprising the chemical modification of currently used drugs. The best results, in terms of inhibitory activity, are in the nanomolar range and have been obtained from the chemical modification of clinically used drugs such as Peramivir, Zanamivir, Oseltamir, Rimantadine, as well as sialylated molecules, and hydroxypyridinone derivatives. The aim of this review is to report, covering the period 2016-2022, the most recent routes related to the synthesis of effective influenza virus inhibitors.

Interplay of Modified Sialic Acid Inhibitors and the Human Parainfluenza Virus 1 Hemagglutinin-Neuraminidase Active Site

In the search for effective antivirals against Paramyxoviridae, the dynamics of human parainfluenza virus type 1 hemagglutinin-neuraminidase (hPIV1-HN) inhibition offers a promising perspective. This study focuses on the potential of C5- and C4-modified 2,3-unsaturated sialic acid (DANA) inhibitors and highlights their interaction with the hPIV1-HN enzyme. We show that a strategic substitution, replacing the C5 isopropyl group in BCX 2798 with a trifluoroacetyl function, increases inhibitory potency 3- to 4-fold. At the same time, we explore the special properties of the catalytic site of hPIV1-HN, which harbors only small substituents and favors a C4 sulfonylamido function over a carbonyl function, in contrast to the C4 pocket of Newcastle disease virus hemagglutinin-neuraminidase (NDV-HN). Based on these findings, we present a newly identified potent inhibitor that has the preferred C5 trifluoroacetamido and C4 trifluorosulfonylamide groups. The results of this study pave the way for a deeper understanding of the C4 and C5 binding pockets of hPIV1-HN and promote the development of new, more selective inhibitors.

Discovery of novel potent drugs for influenza by inhibiting the vital function of neuraminidase via fragment-based drug design (FBDD) and molecular dynamics simulation strategies

The current work describes a fragment linking methodology to generate new neuraminidase inhibitors. A total number of 28,977 fragments from Zinc 20 have been obtained and screened for neuraminidase receptor affinity. Using Schrödinger software, the highest-scoring 270 fragment hits (with scores greater than -7.6) were subjected to fragment combining to create 100 new molecules. These 100 novel compounds were studied using XP docking to evaluate the molecular interaction modes and their binding affinity to neuraminidase receptor. The top ten molecules were selected, for ADMET, drug-likeness features. Based on these characteristics, the best four developed molecules and Zanamivir were submitted to a molecular dynamics simulation investigation to estimate their dynamics within the neuraminidase receptor using Gromacs software. All MD simulation findings show that the generated complexes are very stable when compared to the clinical inhibitor (Zanamivir). In addition, the four designed neuraminidase inhibitors formed very stable complexes with neuraminidase receptor (with total binding energies ranging from -83.50 to -107.85 Kj/mol) according to the total binding energy calculated by MM-PBSA. For the objective of developing new influenza medications, these novel molecules have the potential to be further evaluated in vitro and in vivo for influenza drug discovery.Communicated by Ramaswamy H. Sarma.

MicroRNA-9-1 Attenuates Influenza A Virus Replication via Targeting Tankyrase 1

An unstable influenza genome leads to the virus resistance to antiviral drugs that target viral proteins. Thus, identification of host factors essential for virus replication may pave the way to develop novel antiviral therapies. In this study, we investigated the roles of the poly(ADP-ribose) polymerase enzyme, tankyrase 1 (TNKS1), and the endogenous small noncoding RNA, miR-9-1, in influenza A virus (IAV) infection. Increased expression of TNKS1 was observed in IAV-infected human lung epithelial cells and mouse lungs. TNKS1 knockdown by RNA interference repressed influenza viral replication. A screen using TNKS1 3'-untranslation region (3'-UTR) reporter assays and predicted microRNAs identified that miR-9-1 targeted TNKS1. Overexpression of miR-9-1 reduced influenza viral replication in lung epithelial cells as measured by viral mRNA and protein levels as well as virus production. miR-9-1 induced type I interferon production and enhanced the phosphorylation of STAT1 in cell culture. The ectopic expression of miR-9-1 in the lungs of mice by using an adenoviral viral vector enhanced type I interferon response, inhibited viral replication, and reduced susceptibility to IAV infection. Our results indicate that miR-9-1 is an anti-influenza microRNA that targets TNKS1 and enhances cellular antiviral state.

Efficacy of favipiravir against influenza virus resistant to both baloxavir and neuraminidase inhibitors

OBJECTIVES

Widespread resistance of influenza viruses to neuraminidase (NA) inhibitor or polymerase inhibitor, baloxavir, is a major public health concern. The amino acid mutations R152K in NA and I38T in polymerase acidic (PA) are responsible for resistance to NA inhibitors and baloxavir, respectively.

METHODS

We generated recombinant A(H1N1)pdm09 viruses possessing NA-R152K, PA-I38T or both mutations by using a plasmid-based reverse genetics system, characterized their virological properties in vitro and in vivo, and examined whether oseltamivir, baloxavir and favipiravir are effective against these mutant viruses.

RESULTS

The three mutant viruses showed similar or superior growth kinetics and virulence to those of wild-type virus. Although oseltamivir and baloxavir blocked the replication of the wild-type virus in vitro, oseltamivir and baloxavir failed to suppress the replication of the NA-R152K and PA-I38T viruses in vitro, respectively. Mutant virus possessing both mutations grew in the presence of oseltamivir or baloxavir in vitro. Baloxavir treatment protected mice from lethal infection with wild-type or NA-R152K virus, but failed to protect mice from lethal infection with PA-I38T or PA-I38T/NA-R152K virus. Favipiravir treatment protected mice from lethal infection with all viruses tested, whereas oseltamivir treatment did not protect at all.

CONCLUSIONS

Our findings indicate that favipiravir should be used to treat patients with suspected baloxavir-resistant virus infection.

Antisense oligonucleotides: a promising therapeutic option against infectious diseases

Infectious diseases have been one of the biggest health problems of humanity for centuries. Nucleic acid-based therapeutics have received attention in recent years with their effectiveness in the treatment of various infectious diseases and vaccine development studies. This review aims to provide a comprehensive understanding of the basic properties underlying the mechanism of antisense oligonucleotides (ASOs), their applications, and their challenges. The efficient delivery of ASOs is the greatest challenge for their therapeutic success, but this problem is overcome with new-generation antisense molecules developed with chemical modifications. The types, carrier molecules, and gene regions targeted by sequences have been summarized in detail. Research and development of antisense therapy is still in its infancy; however, gene silencing therapies appear to have the potential for faster and longer-lasting activity than conventional treatment strategies. On the other hand, realizing the potential of antisense therapy will require a large initial economic investment to ascertain the pharmacological properties and learn how to optimize them. The ability of ASOs to be rapidly designed and synthesized to target different microbes can reduce drug discovery time from 6 years to 1 year. Since ASOs are not particularly affected by resistance mechanisms, they come to the fore in the fight against antimicrobial resistance. The design-based flexibility of ASOs has enabled it to be used for different types of microorganisms/genes and successful in vitro and in vivo results have been revealed. The current review summarized a comprehensive understanding of ASO therapy in combating bacterial and viral infections.

Targeting Metalloenzymes: The "Achilles' Heel" of Viruses and Parasites

Metalloenzymes are central to the regulation of a wide range of essential viral and parasitic functions, including protein degradation, nucleic acid modification, and many others. Given the impact of infectious diseases on human health, inhibiting metalloenzymes offers an attractive approach to disease therapy. Metal-chelating agents have been expansively studied as antivirals and antiparasitics, resulting in important classes of metal-dependent enzyme inhibitors. This review provides the recent advances in targeting the metalloenzymes of viruses and parasites that impose a significant burden on global public health, including influenza A and B, hepatitis B and C, and human immunodeficiency viruses as well as Trypanosoma brucei and Trypanosoma cruzi.

Artesunate inhibits PDE4 leading to intracellular cAMP accumulation, reduced ERK/MAPK signaling, and blockade of influenza A virus vRNP nuclear export

Influenza A viruses (IAV) have been a major cause of mortality. Given the potential for future deadly pandemics, effective drugs are needed for the treatment of severe influenzas, such as those caused by H5N1 IAV. The anti-malaria drugs artemisinin and its derivates, including artesunate (AS), have been reported to have broad antiviral activities. Here, we showed AS's antiviral activity against H5N1, H1N1, H3N2 and oseltamivir-resistant influenza A(H1N1)virus in vitro. Moreover, we showed that AS treatment significantly protected mice from lethal challenges with H1N1 and H5N1 IAV. Strikingly, the combination of AS and peramivir treatment significantly improved survival outcomes compared to their monotherapy with either AS or peramivir. Furthermore, we demonstrated mechanistically that AS affected the later stages of IAV replication and limited nuclear export of viral ribonucleoprotein (vRNP) complexes. In A549 cells, we demonstrated for the first time that AS treatment induced cAMP accumulation via inhibiting PDE4, and consequently reduced ERK phosphorylation and blocked IAV vRNP export, and thus suppressed IAV replication. These AS's effects were reversed by the pre-treatment with a cAMP inhibitor SQ22536. Our findings suggest that AS could serve as a novel IAV inhibitor by interfering vRNP nuclear export to prevent and treat IAV infection.

In Vivo Antiviral Activity of Baloxavir against PA/I38T-Substituted Influenza A Viruses at Clinically Relevant Doses

Although the prevalence of polymerase acidic (PA)/I38T strains of influenza virus with reduced susceptibility to baloxavir acid is low, there is a possibility of emergence under selective pressure. Furthermore, the virus may be transmitted between humans. We investigated the in vivo efficacy of baloxavir acid and oseltamivir phosphate against influenza A subtypes H1N1, H1N1pdm09, and H3N2, with PA/I38T substitution, at doses simulating human plasma concentrations. A pharmacokinetic/pharmacodynamic analysis was performed to strengthen the validity of the findings and the applicability in a clinical setting. Although the antiviral effect of baloxavir acid was attenuated in mice infected with PA/I38T-substituted viral strains compared with the wild type (WT), baloxavir acid significantly reduced virus titers at higher-but clinically relevant-doses. The virus titer reduction with baloxavir acid (30 mg/kg subcutaneous single dose) was comparable to that of oseltamivir phosphate (5 mg/kg orally twice daily) against H1N1 and H1N1pdm09 PA/I38T strains in mice, as well as the H3N2 PA/I38T strain in hamsters. Baloxavir acid demonstrated an antiviral effect against PA/I38T-substituted strains, at day 6, with no further viral rebound. In conclusion, baloxavir acid demonstrated dose-dependent antiviral effects comparable to that of oseltamivir phosphate, even though the degree of lung virus titer reduction was diminished in animal models infected with PA/I38T-substituted strains.

Respiratory Viral Infections in Recipients of Cellular Therapies: A Review of Incidence, Outcomes, Treatment, and Prevention

Respiratory viral infections (RVIs) are of major clinical importance in immunocompromised patients and represent a substantial cause of morbidity and mortality in patients with hematologic malignancies and those who have undergone hematopoietic cell transplantation. Similarly, patients receiving immunotherapy with CD19-targeted chimeric antigen receptor-modified T cells, natural killer cells, and genetically modified T-cell receptors are susceptible to RVIs and progression to lower respiratory tract infections. In adoptive cellular therapy recipients, this enhanced susceptibility to RVIs results from previous chemotherapy regimens such as lymphocyte-depleting chemotherapy conditioning regimens, underlying B-cell malignancies, immune-related toxicities, and secondary prolonged, profound hypogammaglobulinemia. The aggregated risk factors for RVIs have both immediate and long-term consequences. This review summarizes the current literature on the pathogenesis, epidemiology, and clinical aspects of RVIs that are unique to recipients of adoptive cellular therapy, the preventive and therapeutic options for common RVIs, and appropriate infection control and preventive strategies.

Design, Synthesis, and Antiviral Evaluation of Sialic Acid Derivatives as Inhibitors of Newcastle Disease Virus Hemagglutinin-Neuraminidase: A Translational Study on Human Parainfluenza Viruses

Global infections with viruses belonging to the Paramyxoviridae, such as Newcastle disease virus (NDV) or human parainfluenza viruses (hPIVs), pose a serious threat to animal and human health. NDV-HN and hPIVs-HN (HN hemagglutinin-neuraminidase) share a high degree of similarity in catalytic site structures; therefore, the development of an efficient experimental NDV host model (chicken) may be informative for evaluating the efficacy of hPIVs-HN inhibitors. As part of the broad research in pursuit of this goal and as an extension of our published work on antiviral drug development, we report here the biological results obtained with some newly synthesized C4- and C5-substituted 2,3-unsaturated sialic acid derivatives against NDV. All developed compounds showed high neuraminidase inhibitory activity (IC₅₀ 0.03-13 μM). Four molecules (9, 10, 23, 24) confirmed their high in vitro inhibitory activity, which caused a significant reduction of NDV infection in Vero cells, accompanied by very low toxicity.

Carboxylic Acid Isostere Derivatives of Hydroxypyridinones as Core Scaffolds for Influenza Endonuclease Inhibitors

Among the most important influenza virus targets is the RNA-dependent RNA polymerase acidic N-terminal (PA_N) endonuclease, which is a critical component of the viral replication machinery. To inhibit the activity of this metalloenzyme, small-molecule inhibitors employ metal-binding pharmacophores (MBPs) that coordinate to the dinuclear Mn²⁺ active site. In this study, several metal-binding isosteres (MBIs) were examined where the carboxylic acid moiety of a hydroxypyridinone MBP is replaced with other groups to modulate the physicochemical properties of the compound. MBIs were evaluated for their ability to inhibit PA_N using a FRET-based enzymatic assay, and their mode of binding in PA_N was determined using X-ray crystallography.

Antiviral Potential of Natural Resources against Influenza Virus Infections

Influenza is a severe contagious disease caused by influenza A and B viruses. The WHO estimates that annual outbreaks lead to 3-5 million severe infections of which approximately 10% lead to the death of the patient. While vaccination is the cornerstone of prevention, antiviral drugs represent the most important treatment option of acute infections. Only two classes of drugs are currently approved for the treatment of influenza in numerous countries: M2 channel blockers and neuraminidase inhibitors. In some countries, additional compounds such as the recently developed cap-dependent endonuclease inhibitor baloxavir marboxil or the polymerase inhibitor favipiravir are available. However, many of these compounds suffer from poor efficacy, if not applied early after infection. Furthermore, many influenza strains have developed resistances and lost susceptibility to these compounds. As a result, there is an urgent need to develop new anti-influenza drugs against a broad spectrum of subtypes. Natural products have made an important contribution to the development of new lead structures, particularly in the field of infectious diseases. Therefore, this article aims to review the research on the identification of novel lead structures isolated from natural resources suitable to treat influenza infections.

In silico characterization of aryl benzoyl hydrazide derivatives as potential inhibitors of RdRp enzyme of H5N1 influenza virus

RNA-dependent RNA polymerase (RdRp) is a potential therapeutic target for the discovery of novel antiviral agents for the treatment of life-threatening infections caused by newly emerged strains of the influenza virus. Being one of the most conserved enzymes among RNA viruses, RdRp and its inhibitors require further investigations to design novel antiviral agents. In this work, we systematically investigated the structural requirements for antiviral properties of some recently reported aryl benzoyl hydrazide derivatives through a range of in silico tools such as 2D-quantitative structure-activity relationship (2D-QSAR), 3D-QSAR, structure-based pharmacophore modeling, molecular docking and molecular dynamics simulations. The 2D-QSAR models developed in the current work achieved high statistical reliability and simultaneously afforded in-depth mechanistic interpretability towards structural requirements. The structure-based pharmacophore model developed with the docked conformation of one of the most potent compounds with the RdRp protein of H5N1 influenza strain was utilized for developing a 3D-QSAR model with satisfactory statistical quality validating both the docking and the pharmacophore modeling methodologies performed in this work. However, it is the atom-based alignment of the compounds that afforded the most statistically reliable 3D-QSAR model, the results of which provided mechanistic interpretations consistent with the 2D-QSAR results. Additionally, molecular dynamics simulations performed with the apoprotein as well as the docked complex of RdRp revealed the dynamic stability of the ligand at the proposed binding site of the receptor. At the same time, it also supported the mechanistic interpretations drawn from 2D-, 3D-QSAR and pharmacophore modeling. The present study, performed mostly with open-source tools and webservers, returns important guidelines for research aimed at the future design and development of novel anti-viral agents against various RNA viruses like influenza virus, human immunodeficiency virus-1, hepatitis C virus, corona virus, and so forth.

Iterative Optimization and Structure-Activity Relationship Studies of Oseltamivir Amino Derivatives as Potent and Selective Neuraminidase Inhibitors via Targeting 150-Cavity

With our continuous endeavors in seeking neuraminidase (NA) inhibitors, we reported herein three series of novel oseltamivir amino derivatives with the goal of exploring the druggable chemical space inside the 150-cavity of influenza virus NAs. Among them, around half of the compounds in series C were demonstrated to be better inhibitors against both wild-type and oseltamivir-resistant group-1 NAs than oseltamivir carboxylate (OSC). Notably, compounds 12d, 12e, 15e, and 15i showed more potent or equipotent antiviral activity against H1N1, H5N1, and H5N8 viruses compared to OSC in cellular assays. Furthermore, compounds 12e and 15e exhibited high metabolic stability in human liver microsomes (HLMs) and low inhibitory effect on main cytochrome P450 (CYP) enzymes, as well as low acute/subacute toxicity and certain antiviral efficacy in vivo. Also, pharmacokinetic (PK) and molecular docking studies were performed. Overall, 12e and 15e possess great potential to serve as anti-influenza candidates and are worthy of further investigation.

Peptidic defective interfering gene nanoparticles against Omicron, Delta SARS-CoV-2 variants and influenza A virus in vivo

Defective interfering genes (DIGs) are short viral genomes and interfere with wild-type viral replication. Here, we demonstrate that the new designed SARS-CoV-2 DIG (CD3600) can significantly inhibit the replication of SARS-CoV-2 including Alpha, Delta, Kappa and Omicron variants in human HK-2 cells and influenza DIG (PAD4) can significantly inhibit influenza virus replication in human A549 cells. One dose of influenza DIGs prophylactically protects 90% mice from lethal challenge of A(H1N1)pdm09 virus and CD3600 inhibits SARS-CoV-2 replication in hamster lungs when DIGs are administrated to lungs one day before viral challenge. To further investigate the gene delivery vector in the respiratory tract, a peptidic TAT2-P1&LAH4, which can package genes to form small spherical nanoparticles with high endosomal escape ability, is demonstrated to dramatically increase gene expression in the lung airway. TAT2-P1&LAH4, with the dual-functional TAT2-P1 (gene-delivery and antiviral), can deliver CD3600 to significantly inhibit the replication of Delta and Omicron SARS-CoV-2 in hamster lungs. This peptide-based nanoparticle system can effectively transfect genes in lungs and deliver DIGs to inhibit SARS-CoV-2 variants and influenza virus in vivo, which provides the new insight into the drug delivery system for gene therapy against respiratory viruses.

Assessment of influenza A (H1N1, H3N2) oseltamivir resistance during 2017-2019 in Iran

Background and Objectives

Neuraminidase inhibitors (NAIs) as an imperative antiviral for influenza prophylaxis and treatment are being consumed worldwide. Increasing use of these antivirals might be associated with drug resistance. Regarding the significance of these variations, this study aimed to investigate the mutations occurring in the NA gene of influenza A viruses leading to oseltamivir resistance during 2017-2019 in Iran.

Materials and Methods

In this cross-sectional study, 40 influenza A (H1N1, H3N2) strains, isolated in National Influenza Center (NIC) from patients with Severe Acute Respiratory Infection (SARI) during 2017-2019 were subjected to RT-PCR and sequencing of NA complete gene. The frequency of oseltamivir resistance and variation of NA amino acids in these strains were investigated.

Results

No significant mutation conferring oseltamivir resistance was detected. However, NA antigenic sites in these strains depicted minor changes compared to the vaccine strains. Among H3N2 isolates, mutations at 329, 344, 346 and 385 and among H1N1 isolates mutations at 143 and 188 residues occurred in NA antigenic regions.

Conclusion

Evaluation of NA gene sequences, showed no resistant viruses to oseltamivir. Given that the viruses in the present study were the last viruses circulating in Iran before COVID-19 pandemic, the results will be beneficial to have a worthy comparison with the strains circulating after the pandemic. Constant monitoring for the emergence of drug-resistant variants and antigenic changes are crucial for all countries.

Contemporary medicinal chemistry strategies for the discovery and optimization of influenza inhibitors targeting vRNP constituent proteins

Influenza is an acute respiratory infectious disease caused by the influenza virus, affecting people globally and causing significant social and economic losses. Due to the inevitable limitations of vaccines and approved drugs, there is an urgent need to discover new anti-influenza drugs with different mechanisms. The viral ribonucleoprotein complex (vRNP) plays an essential role in the life cycle of influenza viruses, representing an attractive target for drug design. In recent years, the functional area of constituent proteins in vRNP are widely used as targets for drug discovery, especially the PA endonuclease active site, the RNA-binding site of PB1, the cap-binding site of PB2 and the nuclear export signal of NP protein. Encouragingly, the PA inhibitor baloxavir has been marketed in Japan and the United States, and several drug candidates have also entered clinical trials, such as favipiravir. This article reviews the compositions and functions of the influenza virus vRNP and the research progress on vRNP inhibitors, and discusses the representative drug discovery and optimization strategies pursued.

Low Dose Pig Anti-Influenza Virus Monoclonal Antibodies Reduce Lung Pathology but Do Not Prevent Virus Shedding

We have established the pig, a large natural host animal for influenza, with many physiological similarities to humans, as a robust model for testing the therapeutic potential of monoclonal antibodies (mAbs). In this study we demonstrated that prophylactic intravenous administration of 15 mg/kg of porcine mAb pb18, against the K160-163 site of the hemagglutinin, significantly reduced lung pathology and nasal virus shedding and eliminated virus from the lung of pigs following H1N1pdm09 challenge. When given at 1 mg/kg, pb18 significantly reduced lung pathology and lung and BAL virus loads, but not nasal shedding. Similarly, when pb18 was given in combination with pb27, which recognized the K130 site, at 1 mg/kg each, lung virus load and pathology were reduced, although without an apparent additive or synergistic effect. No evidence for mAb driven virus evolution was detected. These data indicate that intravenous administration of high doses was required to reduce nasal virus shedding, although this was inconsistent and seldom complete. In contrast, the effect on lung pathology and lung virus load is consistent and is also seen at a one log lower dose, strongly indicating that a lower dose might be sufficient to reduce severity of disease, but for prevention of transmission other measures would be needed.

RIGI, TLR7, and TLR3 Genes Were Predicted to Have Immune Response Against Avian Influenza in Indigenous Ducks

Avian influenza is a disease with every possibility to evolve as a human-to-human pandemic arising out of frequent mutations and genetic reassortment or recombination of avian influenza (AI) virus. The greatest concern is that till date, no satisfactory medicine or vaccines are available, leading to massive culling of poultry birds, causing huge economic loss and ban on export of chicken products, which emphasizes the need to develop an alternative strategy for control of AI. In the current study, we attempt to explore the molecular mechanism of innate immune potential of ducks against avian influenza. In the present study, we have characterized immune response molecules such as duck TLR3, TLR7, and RIGI that are predicted to have potent antiviral activities against the identified strain of avian influenza through in silico studies (molecular docking) followed by experimental validation with differential mRNA expression analysis. Future exploitation may include immunomodulation with the recombinant protein, and transgenic or gene-edited chicken resistant to bird flu.

COVID-19 pandemic: lessons learned from more than a century of pandemics and current vaccine development for pandemic control

Pandemic dynamics and health care responses are markedly different during the COVID-19 pandemic than in earlier outbreaks. Compared with established infectious disease such as influenza, we currently know relatively little about the origin, reservoir, cross-species transmission and evolution of SARS-CoV-2. Health care services, drug availability, laboratory testing, research capacity and global governance are more advanced than during 20th century pandemics, although COVID-19 has highlighted significant gaps. The risk of zoonotic transmission and an associated new pandemic is rising substantially. COVID-19 vaccine development has been done at unprecedented speed, with the usual sequential steps done in parallel. The pandemic has illustrated the feasibility of this approach and the benefits of a globally coordinated response and infrastructure. Some of the COVID-19 vaccines recently developed or currently in development might offer flexibility or sufficiently broad protection to swiftly respond to antigenic drift or emergence of new coronaviruses. Yet many challenges remain, including the large-scale production of sufficient quantity of vaccines, delivery of vaccines to all countries and ensuring vaccination of relevant age groups. This wide vaccine technology approach will be best employed in tandem with active surveillance for emerging variants or new pathogens using antigen mapping, metagenomics and next generation sequencing.

Metabolic Modifications by Common Respiratory Viruses and Their Potential as New Antiviral Targets

Respiratory viruses are known to be the most frequent causative mediators of lung infections in humans, bearing significant impact on the host cell signaling machinery due to their host-dependency for efficient replication. Certain cellular functions are actively induced by respiratory viruses for their own benefit. This includes metabolic pathways such as glycolysis, fatty acid synthesis (FAS) and the tricarboxylic acid (TCA) cycle, among others, which are modified during viral infections. Here, we summarize the current knowledge of metabolic pathway modifications mediated by the acute respiratory viruses respiratory syncytial virus (RSV), rhinovirus (RV), influenza virus (IV), parainfluenza virus (PIV), coronavirus (CoV) and adenovirus (AdV), and highlight potential targets and compounds for therapeutic approaches.

Analysis of the Genetic Diversity Associated With the Drug Resistance and Pathogenicity of Influenza A Virus Isolated in Bangladesh From 2002 to 2019

The subtype prevalence, drug resistance- and pathogenicity-associated mutations, and the distribution of the influenza A virus (IAV) isolates identified in Bangladesh from 2002 to 2019 were analyzed using bioinformatic tools. A total of 30 IAV subtypes have been identified in humans (4), avian species (29), and environment (5) in Bangladesh. The predominant subtypes in human and avian species are H1N1/H3N2 and H5N1/H9N2, respectively. However, the subtypes H5N1/H9N2 infecting humans and H3N2/H1N1 infecting avian species have also been identified. Among the avian species, the maximum number of subtypes (27) have been identified in ducks. A 3.56% of the isolates showed neuraminidase inhibitor (NAI) resistance with a prevalence of 8.50, 1.33, and 2.67% in avian species, humans, and the environment, respectively, the following mutations were detected: V116A, I117V, D198N, I223R, S247N, H275Y, and N295S. Prevalence of adamantane-resistant IAVs was 100, 50, and 30.54% in humans, the environment, and avian species, respectively, the subtypes H3N2, H1N1, H9N2, and H5N2 were highly prevalent, with the subtype H5N1 showing a comparatively lower prevalence. Important PB2 mutations such D9N, K526R, A588V, A588I, G590S, Q591R, E627K, K702R, and S714R were identified. A wide range of IAV subtypes have been identified in Bangladesh with a diversified genetic variation in the NA, M2, and PB2 proteins providing drug resistance and enhanced pathogenicity. This study provides a detailed analysis of the subtypes, and the host range of the IAV isolates and the genetic variations related to their proteins, which may aid in the prevention, treatment, and control of IAV infections in Bangladesh, and would serve as a basis for future investigations.

Early oseltamivir reduces risk for influenza-associated aspergillosis in a double-hit murine model

Invasive pulmonary aspergillosis (IPA) is a life-threatening fungal infection occurring mainly in immunocompromised patients. We recently identified IPA as an emerging co-infection with high mortality in critically ill, but otherwise immunocompetent influenza patients. The neuraminidase inhibitor oseltamivir is the current standard-of-care treatment in hospitalized influenza patients; however, its efficacy in influenza-associated pulmonary aspergillosis (IAPA) is not known. Therefore, we have established an imaging-supported double-hit mouse model to investigate the therapeutic effect of oseltamivir on the development of IAPA. Immunocompetent mice received intranasal instillation influenza A or PBS followed by orotracheal inoculation with Aspergillus fumigatus 4 days later. Oseltamivir treatment or placebo was started at day 0, day 2, or day 4. Daily monitoring included micro-computed tomography and bioluminescence imaging of pneumonia and fungal burden. Non-invasive biomarkers were complemented with imaging, molecular, immunological, and pathological analysis. Influenza virus-infected immunocompetent mice developed proven airway IPA upon co-infection with Aspergillus fumigatus, whereas non-influenza-infected mice fully cleared Aspergillus, confirming influenza as a risk factor for developing IPA. Longitudinal micro-CT showed pulmonary lesions after influenza infection worsening after Aspergillus co-infection, congruent with bioluminescence imaging and histology confirming Aspergillus pneumonia. Early oseltamivir treatment prevented severe influenza pneumonia and mitigated the development of IPA and associated mortality. A time-dependent treatment effect was consistently observed with imaging, molecular, and pathological analyses. Hence, our findings underscore the importance of initiating oseltamivir as soon as possible, to suppress influenza infection and mitigate the risk of potentially lethal IAPA disease.

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.

Gold nanoparticles show potential in vitro antiviral and anticancer activity

AIMS

Gold nanoparticles (AuNPs) have been attracted interests in the various areas of clinical therapeutics. In this study, we investigated the anticancer and antiviral potential activity of AuNPs against influenza A virus and human glioblastoma (GMB) U-87 and U-251 cell lines.

MAIN METHODS

Gold nanoparticles (AuNPs) were synthesized by citrate reduction method. Then, ultraviolet-visible spectrophotometry (UV-vis spectra) and electron microscopy analysis confirmed the type, size (mean diameter of 17 nm) and distribution of the particles. The AuNPs in vitro antiviral and anticancer effects was evaluated by hemagglutination inhibition (HAI), tissue culture infectious dose 50 (TCID₅₀), real-time PCR, MTT, flow cytometry, and scratch assays.

KEY FINDINGS

The AuNPs were synthesized in spherical with a mean diameter of 17 ± 2 nm and an absorbance peak at 520 nm. The AuNPs were well tolerable by MDCK cells at concentrations up to 0.5μg/ml and they significantly inhibited the hemagglutination and virus infectivity, particularly when added pre- or during virus infection. Furthermore, anticancer results indicated that AuNPs treatment caused the marked induction of apoptosis and reduced growth and migration capability of U-87 and U-251 cell lines in a time-dependent manner.

SIGNIFICANCE

The present results suggest that AuNPs provide promising antiviral and anticancer approaches. Further research is needed to fully elucidate the mode of antiviral and anticancer action of AuNPs against influenza virus infection and human glioblastoma cell lines.

The Anti-Viral and Anti-Inflammatory Properties of Edible Bird's Nest in Influenza and Coronavirus Infections: From Pre-Clinical to Potential Clinical Application

Edible bird's nest (BN) is a Chinese traditional medicine with innumerable health benefits, including anti-viral, anti-inflammatory, neuroprotective, and immunomodulatory effects. A small number of studies have reported the anti-viral effects of EBN against influenza infections using in vitro and in vivo models, highlighting the importance of sialic acid and thymol derivatives in their therapeutic effects. At present, studies have reported that EBN suppresses the replicated virus from exiting the host cells, reduces the viral replication, endosomal trafficking of the virus, intracellular viral autophagy process, secretion of pro-inflammatory cytokines, reorient the actin cytoskeleton of the infected cells, and increase the lysosomal degradation of viral materials. In other models of disease, EBN attenuates oxidative stress-induced cellular apoptosis, enhances proliferation and activation of B-cells and their antibody secretion. Given the sum of its therapeutic actions, EBN appears to be a candidate that is worth further exploring for its protective effects against diseases transmitted through air droplets. At present, anti-viral drugs are employed as the first-line defense against respiratory viral infections, unless vaccines are available for the specific pathogens. In patients with severe symptoms due to exacerbated cytokine secretion, anti-inflammatory agents are applied. Treatment efficacy varies across the patients, and in times of a pandemic like COVID-19, many of the drugs are still at the experimental stage. In this review, we present a comprehensive overview of anti-viral and anti-inflammatory effects of EBN, chemical constituents from various EBN preparation techniques, and drugs currently used to treat influenza and novel coronavirus infections. We also aim to review the pathogenesis of influenza A and coronavirus, and the potential of EBN in their clinical application. We also describe the current literature in human consumption of EBN, known allergenic or contaminant presence, and the focus of future direction on how these can be addressed to further improve EBN for potential clinical application.

Prophylaxis and treatment of influenza: options, antiviral susceptibility, and existing recommendations

Influenza viruses of types A and B attack 5-10% of adults and 20-30% of children, thereby causing millions of acute respiratory infections in Germany annually. A significant number of these infections are associated with complications such as pneumonia and bacterial superinfections that need hospitalization and might lead to death. In addition to vaccines, drugs were developed that might support influenza prevention and that can be used to treat influenza patients. The timely application of anti-influenza drugs can inhibit virus replication, help reduce and shorten the symptoms, and prevent death as well as virus transmission. This review concisely describes the mechanism of action, the potential for prophylactic and therapeutic use, and the knowledge on resistance of anti-influenza drugs approved today. However, the main aim is to give an overview on the recommendations available in Germany for the proper use of these drugs. In doing so, the recommendations published in statements and guidelines of medical societies as well as the German influenza pandemic preparedness plan are summarized with the consideration of specific circumstances and groups of patients.

Engineered influenza virions reveal the contributions of non-hemagglutinin structural proteins to vaccine mediated protection

The development of improved and universal anti-influenza vaccines would represent a major advance in the protection of human health. In order to facilitate the development of such vaccines, understanding how viral proteins can contribute to protection from disease is critical. Much of the previous work to address these questions relied on reductionist systems (i.e. vaccinating with individual proteins or VLPs that contain only a few viral proteins); thus we have an incomplete understanding of how immunity to different subsets of viral proteins contribute to protection. Here, we report the development of a platform in which a single viral protein can be deleted from an authentic viral particle that retains the remaining full complement of structural proteins and viral RNA. As a first study with this system, we chose to delete the major IAV antigen, the hemagglutinin protein, to evaluate how the other components of the viral particle contribute en masse to protection from influenza disease. Our results show that while anti-HA immunity plays a major role in protection from challenge with a vaccine-matched strain, the contributions from other structural proteins were the major drivers of protection against highly antigenically drifted, homosubtypic strains. This work highlights the importance of evaluating the inclusion of non-HA viral proteins in the development of broadly efficacious and long-lasting influenza vaccines.ImportanceInfluenza virus vaccines currently afford short-term protection from viruses that are closely related to the vaccine strains. There is currently much effort to develop improved, next-generation influenza vaccines that elicit broader and longer-lasting protection. While the hemagglutinin protein is the major viral antigen, in this work, we developed an approach with which to evaluate the contributions of the non-hemagglutinin proteins to vaccine mediated protection. Our results indicate that other structural proteins together may help to mediate broad antiviral protection and should be considered in the development of more universal influenza vaccines.

siRNAs and viruses: The good, the bad and the way forward

There are no available antivirals for many viruses or strains, while current antivirals are limited by toxicity and drug resistance. Therefore, alternative strategies, such as RNA interference (RNAi) are required. RNAi suppresses gene expression of any mRNA, making it an attractive candidate for antiviral therapeutics. Studies have evaluated siRNAs in a range of viruses, with some showing promising results. However, issues with stability and delivery of siRNAs remain. These may be minimized by modifying the siRNA structure, using an efficient delivery vector and targeting multiple regions of a virus's genome in a single dose. Finding these solutions could accelerate the progress of RNAi-based antivirals. This review highlights selected examples of antiviral siRNAs, limitations of RNAi and strategies to overcome these limitations.

Impact of Oseltamivir Treatment on Influenza A and B Virus Dynamics in Human Volunteers

Influenza viruses infect millions of humans every year causing an estimated 400,000 deaths globally. Due to continuous virus evolution current vaccines provide only limited protection against the flu. Several antiviral drugs are available to treat influenza infection, and one of the most commonly used drugs is oseltamivir (Tamiflu). While the mechanism of action of oseltamivir as a neuraminidase inhibitor is well-understood, the impact of oseltamivir on influenza virus dynamics in humans has been controversial. Many clinical trials with oseltamivir have been done by pharmaceutical companies such as Roche but the results of these trials until recently have been provided as summary reports or papers. Typically, such reports included median virus shedding curves for placebo and drug-treated influenza virus infected volunteers often indicating high efficacy of the early treatment. However, median shedding curves may be not accurately representing drug impact in individual volunteers. Importantly, due to public pressure clinical trials data testing oseltamivir efficacy has been recently released in the form of redacted PDF documents. We digitized and re-analyzed experimental data on influenza virus shedding in human volunteers from three previously published trials: on influenza A (1 trial) or B viruses (2 trials). Given that not all volunteers exposed to influenza viruses actually start virus shedding we found that impact of oseltamivir on the virus shedding dynamics was dependent on (i) selection of volunteers that were infected with the virus, and (ii) the detection limit in the measurement assay; both of these details were not well-articulated in the published studies. By assuming that any non-zero viral measurement is above the limit of detection we could match previously published data on median influenza A virus (flu A study) shedding but not on influenza B virus shedding (flu B study B) in human volunteers. Additional analyses confirmed that oseltamivir had an impact on the duration of shedding and overall shedding (defined as area under the curve) but this result varied by the trial. Interestingly, treatment had no impact on the rates at which shedding increased or declined with time in individual volunteers. Additional analyses showed that oseltamivir impacted the kinetics of the end of viral shedding, and in about 20-40% of volunteers that shed the virus treatment had no impact on viral shedding duration. Our results suggest an unusual impact of oseltamivir on influenza viruses shedding kinetics and caution about the use of published median data or data from a few individuals for inferences. Furthermore, we call for the need to publish raw data from critical clinical trials that can be independently analyzed.

Understanding the Impact of Resistance to Influenza Antivirals

Influenza poses a significant burden on society and health care systems. Although antivirals are an integral tool in effective influenza management, the potential for the emergence of antiviral-resistant viruses can lead to uncertainty and hesitation among front-line prescribers and policy makers. Here, we provide an overview of influenza antiviral resistance in context, exploring the key concepts underlying its development and clinical impact. Due to the acute nature of influenza in immunocompetent patients, resistant viruses that develop during antiviral treatment of a single patient ("treatment-emergent resistance") are usually cleared in a relatively short time, with no impact on future antiviral efficacy. In addition, although available data are limited by small numbers of patients, they show that antiviral treatment still provides clinical benefit to the patient within whom resistance emerges. In contrast, the sustained community transmission of resistant variants in the absence of treatment ("acquired resistance") is of greater concern and can potentially render front-line antivirals ineffective. Importantly, however, resistant viruses are usually associated with reduced fitness such that their widespread transmission is relatively rare. Influenza antivirals are an essential part of effective influenza management due to their ability to reduce the risk of complications and death in infected patients. Although antiviral resistance should be taken seriously and requires continuous careful monitoring, it is not comparable to antibiotic resistance in bacteria, which can become permanent and widespread, with far-reaching medical consequences. The benefits of antiviral treatment far outweigh concerns of potential resistance, which in the vast majority of cases does not have a significant clinical impact.

Influenza Viruses: Harnessing the Crucial Role of the M2 Ion-Channel and Neuraminidase toward Inhibitor Design

As a member of the Orthomyxoviridae family of viruses, influenza viruses (IVs) are known causative agents of respiratory infection in vertebrates. They remain a major global threat responsible for the most virulent diseases and global pandemics in humans. The virulence of IVs and the consequential high morbidity and mortality of IV infections are primarily attributed to the high mutation rates in the IVs' genome coupled with the numerous genomic segments, which give rise to antiviral resistant and vaccine evading strains. Current therapeutic options include vaccines and small molecule inhibitors, which therapeutically target various catalytic processes in IVs. However, the periodic emergence of new IV strains necessitates the continuous development of novel anti-influenza therapeutic options. The crux of this review highlights the recent studies on the biology of influenza viruses, focusing on the structure, function, and mechanism of action of the M2 channel and neuraminidase as therapeutic targets. We further provide an update on the development of new M2 channel and neuraminidase inhibitors as an alternative to existing anti-influenza therapy. We conclude by highlighting therapeutic strategies that could be explored further towards the design of novel anti-influenza inhibitors with the ability to inhibit resistant strains.

Evaluation of Baloxavir Marboxil and Peramivir for the Treatment of High Pathogenicity Avian Influenza in Chickens

Control measures in the case of high pathogenicity avian influenza (HPAI) outbreaks in poultry include culling, surveillance, and biosecurity; wild birds in captivity may also be culled, although some rare bird species should be rescued for conservation. In this study, two anti-influenza drugs, baloxavir marboxil (BXM) and peramivir (PR), used in humans, were examined in treating HPAI in birds, using chickens as a model. Chickens were infected with H5N6 HPAI virus and were treated immediately or 24 h from challenge with 20 mg/kg BXM or PR twice a day for five days. As per our findings, BXM significantly reduced virus replication in organs and provided full protection to chickens compared with that induced by PR. In the 24-h-delayed treatment, neither drug completely inhibited virus replication nor ensured the survival of infected chickens. A single administration of 2.5 mg/kg of BXM was determined as the minimum dose required to fully protect chickens from HPAI virus; the concentration of baloxavir acid, the active form of BXM, in chicken blood at this dose was sufficient for a 48 h antiviral effect post-administration. Thus, these data can be a starting point for the use of BXM and PR in treating captive wild birds infected with HPAI virus.

Current treatment of COVID-19 in renal patients: hope or hype?

To date the severe acute respiratory syndrome coronavirus 2 (SARS- CoV-2), known as COVID-19, is for clinicians the most difficult global therapeutic problem. In this landscape, the management of patients with chronic kidney disease, acute kidney injury or patients undergoing immunosuppressant therapies for kidney transplant or glomerular diseases, represent a clinical challenge for nephrologists, especially in patients with severe acute lung involvement. Therefore in this setting, due to the lack of anti-COVID treatment schedules, tailored management is mandatory to reduce the side effects, as consequence of impaired renal function and drugs interactions. We report the main treatment actually used against SARS-CoV-2, underlining its possible use in the nephropatic patients and the central role of nephrologists to improve the clinical outcome.

A Mutated PB1 Residue 319 Synergizes with the PB2 N265S Mutation of the Live Attenuated Influenza Vaccine to Convey Temperature Sensitivity

Current influenza vaccines have modest efficacy. This is especially true for current live attenuated influenza vaccines (LAIV), which have been inferior to the inactivated versions in recent years. Therefore, a new generation of live vaccines may be needed. We previously showed that a mutation at PB1 residue 319 confers enhanced temperature sensitivity and attenuation in an LAIV constructed in the genetic background of the mouse-adapted Influenza A Virus (IAV) strain A/PR/8/34 (PR8). Here, we describe the origin/discovery of this unique mutation and demonstrate that, when combined with the PB2 N265S mutation of LAIV, it conveys an even greater level of temperature sensitivity and attenuation on PR8 than the complete set of attenuating mutations from LAIV. Furthermore, we show that the combined PB1 L319Q and PB2 N265S mutations confer temperature sensitivity on IAV polymerase activity in two different genetic backgrounds, PR8 and A/Cal/04/09. Collectively, these findings show that the PB2 LAIV mutation synergizes with a mutation in PB1 and may have potential utility for improving LAIVs.

Predictors and Outcomes of Hospitalization for Influenza: Real-World Evidence from the United States Medicare Population

INTRODUCTION

The purpose of this study was to identify predictors of initial hospitalization and describe the outcomes of high-risk patients hospitalized with influenza.

METHODS

Data were taken from the 5% national US Medicare database from 2012 to 2015. Patients (aged at least 13 years) were required to have at least one diagnosis for influenza and have continuous health plan enrollment for 6 months before (baseline) and 3 months (follow-up) after the date of influenza diagnosis. Patients who died during follow-up were included. Patients were categorized as initially hospitalized if hospitalized within 0-1 day of diagnosis. High-risk initially hospitalized patients were defined as patients aged at least 65 years or those that had a diagnostic code for chronic lung disease, cardiovascular or cerebrovascular disease, or weakened immune system during baseline period. Logistic regression models were developed to determine predictors of initial hospitalization.

RESULTS

The study population included 8127 high-risk patients who were initially hospitalized and 16,784 who were not hospitalized. Among high-risk patients, 89.3% were diagnosed in the emergency room, whereas 7.5% and 3.2% were diagnosed in a physician's office or other Medicare settings, respectively. Chronic obstructive pulmonary disorder, congestive heart failure, chronic kidney disease, older age, being male, other comorbidities, number of comorbidities, and baseline healthcare resource use were the predictors of hospitalization. Median length of stay for the hospitalization was 5.0 days, and the 30-day readmission rate was 14%. All-cause mortality rate was 5.1% during the inpatient stay and 9.2% within 30 days of diagnosis. Hospitalized patients with influenza incurred an increase of $16,568 per patient in total all-cause healthcare costs from pre-influenza to post-influenza diagnosis.

CONCLUSION

The study characterized the burden of hospitalization for influenza and found that hospitalized high-risk patients experience greater comorbidity burden, higher likelihood of multiple inpatient admissions, and costly medical interventions compared to patients who were not hospitalized.

Semisynthetic Cardenolides Acting as Antiviral Inhibitors of Influenza A Virus Replication by Preventing Polymerase Complex Formation

Influenza virus infections represent a major public health issue by causing annual epidemics and occasional pandemics that affect thousands of people worldwide. Vaccination is the main prophylaxis to prevent these epidemics/pandemics, although the effectiveness of licensed vaccines is rather limited due to the constant mutations of influenza virus antigenic characteristics. The available anti-influenza drugs are still restricted and there is an increasing viral resistance to these compounds, thus highlighting the need for research and development of new antiviral drugs. In this work, two semisynthetic derivatives of digitoxigenin, namely C10 (3β-((N-(2-hydroxyethyl)aminoacetyl)amino-3-deoxydigitoxigenin) and C11 (3β-(hydroxyacetyl)amino-3-deoxydigitoxigenin), showed anti-influenza A virus activity by affecting the expression of viral proteins at the early and late stages of replication cycle, and altering the transcription and synthesis of new viral proteins, thereby inhibiting the formation of new virions. Such antiviral action occurred due to the interference in the assembly of viral polymerase, resulting in an impaired polymerase activity and, therefore, reducing viral replication. Confirming the in vitro results, a clinically relevant ex vivo model of influenza virus infection of human tumor-free lung tissues corroborated the potential of these compounds, especially C10, to completely abrogate influenza A virus replication at the highest concentration tested (2.0 µM). Taken together, these promising results demonstrated that C10 and C11 can be considered as potential new anti-influenza drug candidates.

Synthesis and characterization of 1,2,4-triazolo[1,5-a]pyrimidine-2-carboxamide-based compounds targeting the PA-PB1 interface of influenza A virus polymerase

Influenza viruses (Flu) are responsible for seasonal epidemics causing high rates of morbidity, which can dramatically increase during severe pandemic outbreaks. Antiviral drugs are an indispensable weapon to treat infected people and reduce the impact on human health, nevertheless anti-Flu armamentarium still remains inadequate. In search for new anti-Flu drugs, our group has focused on viral RNA-dependent RNA polymerase (RdRP) developing disruptors of PA-PB1 subunits interface with the best compounds characterized by cycloheptathiophene-3-carboxamide and 1,2,4-triazolo[1,5-a]pyrimidine-2-carboxamide scaffolds. By merging these moieties, two very interesting hybrid compounds were recently identified, starting from which, in this paper, a series of analogues were designed and synthesized. In particular, a thorough exploration of the cycloheptathiophene-3-carboxamide moiety led to acquire important SAR insight and identify new active compounds showing both the ability to inhibit PA-PB1 interaction and viral replication in the micromolar range and at non-toxic concentrations. For few compounds, the ability to efficiently inhibit PA-PB1 subunits interaction did not translate into anti-Flu activity. Chemical/physical properties were investigated for a couple of compounds suggesting that the low solubility of compound 14, due to a strong crystal lattice, may have impaired its antiviral activity. Finally, computational studies performed on compound 23, in which the phenyl ring suitably replaced the cycloheptathiophene, suggested that, in addition to hydrophobic interactions, H-bonds enhanced its binding within the PA_C cavity.

Differentiation of COVID-19 from seasonal influenza: A multicenter comparative study

As coronavirus disease 2019 (COVID‐19) crashed into the influenza season, clinical characteristics of both infectious diseases were compared to make a difference. We reported 211 COVID‐19 patients and 115 influenza patients as two separate cohorts at different locations. Demographic data, medical history, laboratory findings, and radiological characters were summarized and compared between two cohorts, as well as between patients at the intensive care unit (ICU) andnon‐ICU within the COVID‐19 cohort. For all 326 patients, the median age was 57.0 (interquartile range: 45.0–69.0) and 48.2% was male, while 43.9% had comorbidities that included hypertension, diabetes, bronchitis, and heart diseases. Patients had cough (75.5%), fever (69.3%), expectoration (41.1%), dyspnea (19.3%), chest pain (18.7%), and fatigue (16.0%), etc. Both viral infections caused substantial blood abnormality, whereas the COVID‐19 cohort showed a lower frequency of leukocytosis, neutrophilia, or lymphocytopenia, but a higher chance of creatine kinase elevation. A total of 7.7% of all patients possessed no abnormal sign in chest computed tomography (CT) scans. For both infections, pulmonary lesions in radiological findings did not show any difference in their location or distribution. Nevertheless, compared to the influenza cohort, the COVID‐19 cohort presented more diversity in CT features, where certain specific CT patterns showed significantly more frequency, including consolidation, crazy paving pattern, rounded opacities, air bronchogram, tree‐in‐bud sign, interlobular septal thickening, and bronchiolar wall thickening. Differentiable clinical manifestations and CT patterns may help diagnose COVID‐19 from influenza and gain a better understanding of both contagious respiratory illnesses.

Therapeutic strategies against COVID-19

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a novel coronavirus that mainly affects the upper and lower respiratory tract and is responsible for extremely different degrees of disease, ranging from flu-like symptoms to atypical pneumonia that may evolve to acute respiratory distress syndrome and, ultimately, death. No specific therapy for SARS-CoV-2 has yet been identified, but since the beginning of the outbreak, several pre-existing therapeutics have been reconsidered for the treatment of infected patients. The aim of this article is to discuss current therapeutics against SARS-CoV-2. A literature review was performed using PubMed, collecting data from English-language articles published until June 20th, 2020. Literature analysis showed that with the acquisition of more in-depth knowledge on the characteristics of SARS-CoV-2 and the pathogenesis of the different clinical manifestations, a more rationale use of available drugs has become possible. However, the road to defining which drugs are effective and which schedules of administration must be used to maximize efficacy and minimize adverse events is still very long. To date, it is only clear that no drug can alone cope with all the problems posed by SARS-CoV-2 infection and effective antivirals and inflammatory drugs must be given together to reduce COVID-19 clinical manifestations. Moreover, choice of therapy must always be tailored on clinical manifestations and, when they occur, drugs able to fight coagulopathy and venous thromboembolism that may contribute to respiratory deterioration must be prescribed.

Next Generation Influenza Vaccines: Looking into the Crystal Ball

Influenza infections are responsible for significant number of deaths and overwhelming costs worldwide every year. Vaccination represents the only cost-efficient alternative to address this major problem in human health. However, current vaccines are fraught by many limitations, being far from optimal. Among them, the need to upgrade vaccines every year through a time-consuming process open to different caveats, and the critical fact that they exhibit poorer efficacy in individuals who are at high risk for severe infections. Where are we? How can knowledge and technologies contribute towards removing current roadblocks? What does the future offer in terms of next generation vaccines?

How does one choose the appropriate pharmacotherapy for children with lower respiratory tract infections?

INTRODUCTION

The definition of acute lower respiratory tract infection (LRTI) includes any infection involving the respiratory tract below the level of the larynx. In children, the most common acute LRTIs, and those with the greatest clinical relevance, are community-acquired pneumonia (CAP), bronchiolitis, bronchitis and tuberculosis (TB). The clinical relevance of LRTIs implies that they must be addressed with the most effective therapy. Antibiotics and antivirals play an essential role in this regard.

AREAS COVERED

In this paper, the most recent advances in the drug treatment of LRTIs in children are discussed.

EXPERT OPINION

Although LRTIs are extremely common and one of the most important causes of hospitalization and death in children, anti-infective therapy for these diseases remains unsatisfactory. For CAP and BR, the most important problem is the overuse and misuse of antibiotics; for BCL, the lack of drugs with demonstrated efficacy, safety and tolerability; for TB, the poor knowledge on the true efficacy and safety of the new drugs specifically planned to overcome the problem of MDR M. tuberculosis strains. There is still a long way to go for the therapy of pediatric LRTIs to be considered satisfactory.

Next-generation direct-acting influenza therapeutics

Influenza viruses are a major threat to human health globally. In addition to further improving vaccine prophylaxis, disease management through antiviral therapeutics constitutes an important component of the current intervention strategy to prevent advance to complicated disease and reduce case-fatality rates. Standard-of-care is treatment with neuraminidase inhibitors that prevent viral dissemination. In 2018, the first mechanistically new influenza drug class for the treatment of uncomplicated seasonal influenza in 2 decades was approved for human use. Targeting the PA endonuclease subunit of the viral polymerase complex, this class suppresses viral replication. However, the genetic barrier against viral resistance to both drug classes is low, pre-existing resistance is observed in circulating strains, and resistant viruses are pathogenic and transmit efficiently. Addressing the resistance problem has emerged as an important objective for the development of next-generation influenza virus therapeutics. This review will discuss the status of influenza therapeutics including the endonuclease inhibitor baloxavir marboxil after its first year of clinical use and evaluate a subset of direct-acting antiviral candidates in different stages of preclinical and clinical development.

Influenza in dialysis patients: an opportunity to decrease mortality?

PURPOSE OF REVIEW

Influenza is a major cause of morbidity in dialysis patients.

RECENT FINDINGS

A recent meta-analysis finds reduced influenza infections, hospitalizations and deaths with use of high dose as compared with standard-dose vaccine in the elderly. There remain no randomized clinical trials of vaccine efficacy in dialysis patients. One observational study finds reduced all-cause hospitalization with high-dose as compared with standard-dose vaccine but another study finds no difference in influenza related events. A simulation study, in which the timing of vaccination and antibody waning rates are varied, finds vaccine efficacy among populations prone to premature waning, to be greater if the vaccine is administered later, as long as the opportunity to vaccinate does not decline. In a phase 3 trial involving low-risk patients with uncomplicated influenza, baloxavir (which is of a novel class of antiinfluenza treatment), was associated with a faster decline in virus titers and no difference in resolution of symptoms as compared with oseltamivir.

SUMMARY

By extension of high-quality evidence in the elderly, we recommend using the high dose vaccine in all dialysis patients. Vaccine efficacy may be enhanced in dialysis patients if vaccination is delayed until late October to mid-November. It is premature to use baloxavir over oseltamivir or the combination to treat influenza in dialysis patients though trials are forthcoming.