Inhibition Of Influenza Virus Infection Research Articles

A novel film spray containing curcumin inhibits SARS-CoV-2 and influenza virus infection and enhances mucosal immunity

BackgroundInfection by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) and influenza virus is still a major worldwide health concern. Plants are a good source of bioactive compounds to be used as preventive measures for both inhibiting the virus binding and enhancing mucosal innate immunity. Curcumin has been shown to possess antiviral activity and modulate innate immunity. Therefore, the purpose of this study was to develop an oro-nasal film spray containing curcumin and determine its antiviral activity against SARS-CoV-2 and influenza virus infection, as well as its effects on mucosal innate immunity and inflammatory cytokines in vitro.MethodsThe antiviral activity of the film spray against SARS-CoV-2, influenza A/H1N1, A/H3N2, and influenza B was assessed in vitro by plaque reduction assay. Cytotoxicity of the film spray to oral keratinocytes and nasal epithelial cells was assessed by MTT assay, and cytotoxicity to Vero and MDCK cells was assessed by an MTS-based cytotoxicity assay. Oral and nasal innate immune markers in response to the film spray were determined by ELISA and by a commercial Milliplex Map Kit, respectively.ResultsOur data show that the film spray containing curcumin can inhibit both SARS-CoV-2 and influenza virus infections while maintaining cell viability. Results obtained among 4 viruses revealed that curcumin film spray demonstrated the highest inhibitory activity against SARS-CoV-2 with the lowest EC50 of 3.15 µg/ml and the highest SI value of 4.62, followed by influenza B (EC50 = 6.32 µg/ml, SI = 2.04), influenza A/H1N1 (EC50 = 7.24 µg/ml, SI = 1.78), and influenza A/H3N2 (EC50 > 12.5 µg/ml, SI < 1.03), respectively. Antimicrobial peptides LL-37 and HD-5, IL-6 and TNF-α produced by oral keratinocytes were significantly induced by the film spray, while hBD2 was significantly reduced.ConclusionFilm spray containing curcumin possesses multiple actions against SARS-CoV-2 infection by inhibiting ACE-2 binding in target cells and enhancing mucosal innate immunity. The film spray can also inhibit influenza virus infection. Therefore, the curcumin film spray may be effective in preventing the viral infection of both SARS-CoV-2 and influenza.

The Interferon-Induced Protein with Tetratricopeptide Repeats Repress Influenza Virus Infection by Inhibiting Viral RNA Synthesis.

Influenza A virus (IAV) is an eight-segment negative-sense RNA virus and is subjected to gene recombination between strains to form novel strains, which may lead to influenza pandemics. Seasonal influenza occurs annually and causes great losses in public healthcare. In this study, we examined the role of interferon-induced protein with tetratricopeptide repeats 1 and 2 (IFIT1 and IFIT2) in influenza virus infection. Knockdown of IFIT1 or IFIT2 using a lentiviral shRNA increased viral nucleoprotein (NP) and nonstructural protein 1 (NS1) protein levels, as well as progeny virus production in A/Puerto Rico/8/34 H1N1 (PR/8)-infected lung epithelial A549 cells. Overexpression of IFIT1 or IFIT2 reduced viral NP and NS1 RNA and protein levels in PR/8-infected HEK293 cells. Overexpression of IFIT1 or IFIT2 also inhibited influenza virus infection of various H1N1 strains, including PR/8, A/WSN/1933, A/California/07/2009 and A/Oklahoma/3052/2009, as determined by a viral reporter luciferase assay. Furthermore, knockdown of IFIT1 or IFIT2 increased while overexpression of IFIT1 or IFIT2 decreased viral RNA, complementary RNA, and mRNA levels of NP and NS1, as well as viral polymerase activities. Taken together, our results support that both IFIT1 and -2 have anti-influenza virus activities by inhibiting viral RNA synthesis.

Proteomics analysis of methionine enkephalin upregulated macrophages against infection by the influenza-A virus

Macrophages have a vital role in phagocytosis and antiviral effect against invading influenza viruses. Previously, we found that methionine enkephalin (MENK) inhibited influenza virus infection by upregulating the “antiviral state” of macrophages. To investigate the immunoregulatory mechanism of action of MENK on macrophages, we employed proteomic analysis to identify differentially expressed proteins (DEPs) between macrophages infected with the influenza-A virus and cells infected with the influenza-A virus after pretreatment with MENK. A total of 215 DEPs were identified: 164 proteins had upregulated expression and 51 proteins had downregulated expression. Proteomics analysis showed that DEPs were highly enriched in “cytokine-cytokine receptor interaction”, “phagosome”, and “complement and coagulation cascades pathway”. Proteomics analysis revealed that MENK could be an immune modulator or prophylactic for the prevention and treatment of influenza. MENK promoted the polarization of M1 macrophages, activated inflammatory responses, and enhanced phagocytosis and killing function by upregulating opsonizing receptors.

Transmembrane domain of IFITM3 is responsible for its interaction with influenza virus HA2 subunit.

Interferon-inducible transmembrane protein 3 (IFITM3) inhibits influenza virus infection by blocking viral membrane fusion, but the exact mechanism remains elusive. Here, we investigated the function and key region of IFITM3 in blocking influenza virus entry mediated by hemagglutinin (HA). The restriction of IFITM3 on HA-mediated viral entry was confirmed by pseudovirus harboring HA protein from H5 and H7 influenza viruses. Subcellular co-localization and immunocoprecipitation analyses revealed that IFITM3 partially co-located with the full-length HA protein and could directly interact with HA2 subunit but not HA1 subunit of H5 and H7 virus. Truncated analyses showed that the transmembrane domain of the IFITM3 and HA2 subunit might play an important role in their interaction. Finally, this interaction of IFITM3 was also verified with HA2 subunits from other subtypes of influenza A virus and influenza B virus. Overall, our data demonstrate for the first time a direct interaction between IFITM3 and influenza HA protein via the transmembrane domain, providing a new perspective for further exploring the biological significance of IFITM3 restriction on influenza virus infection or HA-mediated antagonism or escape.

Host succinate inhibits influenza virus infection through succinylation and nuclear retention of the viral nucleoprotein.

Influenza virus infection causes considerable morbidity and mortality, but current therapies have limited efficacy. We hypothesized that investigating the metabolic signaling during infection may help to design innovative antiviral approaches. Using bronchoalveolar lavages of infected mice, we here demonstrate that influenza virus induces a major reprogramming of lung metabolism. We focused on mitochondria‐derived succinate that accumulated both in the respiratory fluids of virus‐challenged mice and of patients with influenza pneumonia. Notably, succinate displays a potent antiviral activity in vitro as it inhibits the multiplication of influenza A/H1N1 and A/H3N2 strains and strongly decreases virus‐triggered metabolic perturbations and inflammatory responses. Moreover, mice receiving succinate intranasally showed reduced viral loads in lungs and increased survival compared to control animals. The antiviral mechanism involves a succinate‐dependent posttranslational modification, that is, succinylation, of the viral nucleoprotein at the highly conserved K87 residue. Succinylation of viral nucleoprotein altered its electrostatic interactions with viral RNA and further impaired the trafficking of viral ribonucleoprotein complexes. The finding that succinate efficiently disrupts the influenza replication cycle opens up new avenues for improved treatment of influenza pneumonia.

Exopolysaccharides from Lactobacillus delbrueckii ssp. bulgaricus OLL1073R-1 prevent influenza virus infection and attenuate secondary bacterial infection risk.

The present study assessed the inhibitory action of exopolysaccharides (EPS) produced by Lactobacillus delbrueckii ssp. bulgaricus OLL1073R-1 against influenza virus infection followed by secondary bacterial infection. We found that the presence of 200 or 400 μg ml-1 of EPS significantly protected against influenza virus infection in a dose-dependent manner when A549 cells were treated with EPS before infection but not after it. The expression of carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM-1), an adhesion molecule for bacteria adherence, on A549 cells was significantly enhanced during influenza virus infection compared with viral-non-infected A549 cells. However, this upregulated CEACAM-1 expression was significantly decreased by EPS treatment before viral infection in association with the reduction in the virus titre in A549 cells. In a bacterial adhesion assay using Staphylococcus aureus, the bacterial adherence to viral-infected A549 cells was significantly greater than that to viral-non-infected A549 cells, and the increased bacterial adherence induced by influenza virus infection tended to be decreased by EPS treatment before the infection. Our findings show that EPS treatment before viral infection can inhibit influenza virus infection and alleviate secondary bacterial infection through decreased CEACAM-1 expression.

Lotus (Nelumbo nucifera Gaertn.) leaf water extracts suppress influenza a viral infection via inhibition of neuraminidase and hemagglutinin

• Lotus ( Nelumbo nucifera Gaertn.) leaf inhibits influenza virus infection. • Lotus leaf directly blocks IAV binding onto the cells. • Lotus leaf suppresses neuraminidase and hemagglutinin of IAV. • Lotus leaf prevents cytopathic effect by H1N1 and H3N2 IAV. • Isoquercitrin in the lotus leaf is the main active component for an anti-IAV efficacy. Lotus ( Nelumbo nucifera Gaertn.) is a perennial aquatic plant, that has been used in folk to treat various diseases. Here, we first demonstrate the water extract of lotu s leaf (WLL) has a strong inhibitory effect on influenza A virus (IAV) infection by inhibiting neuraminidase (NA) and hemagglutinin (HA). To investigate the effect of WLL on IAV infection, we used green fluorescent protein (GFP)-tagged Influenza A/PR/8/34, fluorescence-activated cell sorting (FACS) analysis, and plaque reduction assay. WLL significantly repressed viral infection, dose-dependently. Immunofluorescence (IF) analysis confirmed that WLL reduces influenza HA, NA, M2, and NP viral proteins expression. WLL strongly inhibited HA and reduced NA activity of IAV. Among six components in WLL, isoquercitrin exerted potent antiviral efficacy. Additionally, WLL potently inhibited the cytopathic effect caused by H1N1 or H3N2 IAV. In conclusion, our results suggest that WLL could be used as a natural viral inhibitor for H1N1 and H3N2 influenza viral infection.

Anticoronaviral Activity of the Natural Phloroglucinols, Dryocrassin ABBA and Filixic Acid ABA from the Rhizome of Dryopteris crassirhizoma by Targeting the Main Protease of SARS-CoV-2.

The rhizome of Dryopteris crassirhizoma Nakai. (Dryopteridaceae) has been used in traditional medicine in East Asia and has recently been reported to have anticancer, anti-inflammation, and antibacterial activity as well as antiviral activity. Natural phloroglucinols from D. crassirhizoma, dryocrassin ABBA and filixic acid ABA were reported to inhibit influenza virus infection with an inhibitory activity on neuraminidase. In this study, we found that dryocrassin ABBA and filixic acid ABA have an inhibitory activity against the main protease of SARS-CoV-2. Therefore, dryocrassin ABBA and filixic acid ABA exhibited inhibitory activity against SARS-CoV-2 infection in Vero cells dose-dependently using the immunofluorescence-based antiviral assays. Moreover, these compounds inhibited SARS-CoV and MERS-CoV infection, suggesting their broad-spectrum anticoronaviral activity. In addition, a 5-day repeated-dose toxicity study of dryocrassin ABBA and filixic acid ABA suggested that an approximately lethal dose of these compounds in mice was >10 mg/kg. Pharmacokinetic studies of dryocrassin ABBA showed good microsomal stability, low hERG inhibition, and low CYP450 inhibition. In vivo pharmacokinetic properties of dryocrassin ABBA showed a long half-life (5.5–12.6 h) and high plasma exposure (AUC 19.3–65 μg·h/mL). Therefore, dryocrassin ABBA has therapeutic potential against emerging coronavirus infections, including COVID-19.

The Potential Role of Probiotics in Protection against Influenza a Virus Infection in Mice.

Influenza A virus induces severe respiratory tract infection and results in a serious global health problem. Influenza infection disturbs the cross-talk connection between lung and gut. Probiotic treatment can inhibit influenza virus infection; however, the mechanism remains to be explored. The mice received Lactobacillus mucosae 1025, Bifidobacterium breve CCFM1026, and their mixture MIX for 19 days. Effects of probiotics on clinical symptoms, immune responses, and gut microbial alteration were evaluated. L. mucosae 1025 and MIX significantly reduced the loss of body weight, pathological symptoms, and viral loading. B. breve CCFM1026 significantly reduced the proportion of neutrophils and increased lymphocytes, the expressions of TLR7, MyD88, TRAF6, and TNF-α to restore the immune disorders. MIX increased the antiviral protein MxA expression, the relative abundances of Lactobacillus, Mucispirillum, Adlercreutzia, Bifidobacterium, and further regulated SCFA metabolism resulting in an enhancement of butyrate. The correlation analysis revealed that the butyrate was positively related to MxA expression (p < 0.001) but was negatively related to viral loading (p < 0.05). The results implied the possible antiviral mechanisms that MIX decreased viral loading and increased the antiviral protein MxA expression, which was closely associated with the increased butyrate production resulting from gut microbial alteration.

Edible Bird's Nest: The Functional Values of the Prized Animal-Based Bioproduct From Southeast Asia-A Review.

Edible Bird’s Nest (EBN) is the most prized health delicacy among the Chinese population in the world. Although some scientific characterization and its bioactivities have been studied and researched, no lights have been shed on its actual composition or mechanism. The aim of this review paper is to address the advances of EBN as a therapeutic animal bioproduct, challenges and future perspectives of research involving EBN. The methodology of this review primarily involved a thorough search from the literature undertaken on Web of Science (WoS) using the keyword “edible bird nest”. Other information were obtained from the field/market in Malaysia, one of the largest EBN-producing countries. This article collects and describes the publications related to EBN and its therapeutic with diverse functional values. EBN extracts display anti-aging effects, inhibition of influenza virus infection, alternative traditional medicine in athletes and cancer patients, corneal wound healing effects, stimulation of proliferation of human adipose-derived stem cells, potentiate of mitogenic response, epidermal growth factor-like activities, enhancement of bone strength and dermal thickness, eye care, neuroprotective and antioxidant effects. In-depth literature study based on scientific findings were carried out on EBN and its properties. More importantly, the future direction of EBN in research and development as health-promoting ingredients in food and the potential treatment of certain diseases have been outlined.

Anti-Influenza A Virus Activity of Rhamnan Sulfate from Green Algae Monostroma nitidum in Mice with Normal and Compromised Immunity.

Influenza viruses cause a significant public health burden each year despite the availability of anti-influenza drugs and vaccines. Therefore, new anti-influenza virus agents are needed. Rhamnan sulfate (RS) is a sulfated polysaccharide derived from the green alga Monostroma nitidum. Here, we aimed to demonstrate the antiviral activity of RS, especially against influenza A virus (IFV) infection, in vitro and in vivo. RS showed inhibitory effects on viral proliferation of enveloped viruses in vitro. Evaluation of the anti-IFV activity of RS in vitro showed that it inhibited both virus adsorption and entry steps. The oral administration of RS in IFV-infected immunocompetent and immunocompromised mice suppressed viral proliferation in both mouse types. The oral administration of RS also had stimulatory effects on neutralizing antibody production. Fluorescent analysis showed that RS colocalized with M cells in Peyer’s patches, suggesting that RS bound to the M cells and may be incorporated into the Peyer’s patches, which are essential to intestinal immunity. In summary, RS inhibits influenza virus infection and promotes antibody production, suggesting that RS is a potential candidate for the treatment of influenza virus infections.

Thiosialoside-decorated polymers use a two-step mechanism to inhibit both early and late stages of influenza virus infection

We describe the preparation of thiosialoside-modified poly (methyl vinyl ether-alt-maleic anhydride) as second-generation polymeric conjugates for the inhibition of influenza virus infection. These synthetic glycopolymers show significantly enhanced neuraminidase inhibitory and antiviral activity in enzyme and cellular levels, respectively. The polyvalent thiosialosides also exhibit comparable inhibitory activity to the first-line anti-influenza drugs Zanamivir® and Oseltamivir® against the PR8 influenza virus strain in virus growth inhibition assays, which may be attributed to multivalent binding to neuraminidase on the virion particles, leading to the virion aggregation and further inhibiting the attaching/fusion and releasing steps in the influenza virus life-cycle. These findings suggest that attaching monomeric sialoside with neuraminidase inhibitory activity to a polymeric scaffold will synergistically disturb both the early and late stages of influenza virus infection, and provides a basis for the development of efficacious anti-viral agents against both wild-type and drug-resistant mutant strains.

Repurposing Papaverine as an Antiviral Agent against Influenza Viruses and Paramyxoviruses.

Influenza viruses are highly infectious and are the leading cause of human respiratory diseases and may trigger severe epidemics and occasional pandemics. Although antiviral drugs against influenza viruses have been developed, there is an urgent need to design new strategies to develop influenza virus inhibitors due to the increasing resistance of viruses toward currently available drugs. In this study, we examined the antiviral activity of natural compounds against the following influenza virus strains: A/WSN/33 (H1N1), A/Udorn/72 (H3N2), and B/Lee/40. Papaverine (a nonnarcotic alkaloid that has been used for the treatment of heart disease, impotency, and psychosis) was found to be an effective inhibitor of multiple strains of influenza virus. Kinetic studies demonstrated that papaverine inhibited influenza virus infection at a late stage in the virus life cycle. An alteration in influenza virus morphology and viral ribonucleoprotein (vRNP) localization was observed as an effect of papaverine treatment. Papaverine is a well-known phosphodiesterase inhibitor and also modifies the mitogen-activated protein kinase (MAPK) pathway by downregulating the phosphorylation of MEK and extracellular signal-regulated kinase (ERK). Thus, the modulation of host cell signaling pathways by papaverine may be associated with the nuclear retention of vRNPs and the reduction of influenza virus titers. Interestingly, papaverine also inhibited paramyxoviruses parainfluenza virus 5 (PIV5), human parainfluenza virus 3 (HPIV3), and respiratory syncytial virus (RSV) infections. We propose that papaverine can be a potential candidate to be used as an antiviral agent against a broad range of influenza viruses and paramyxoviruses.IMPORTANCE Influenza viruses are important human pathogens that are the causative agents of epidemics and pandemics. Despite the availability of an annual vaccine, a large number of cases occur every year globally. Here, we report that papaverine, a vasodilator, shows inhibitory action against various strains of influenza virus as well as the paramyxoviruses PIV5, HPIV3, and RSV. A significant effect of papaverine on the influenza virus morphology was observed. Papaverine treatment of influenza-virus-infected cells resulted in the inhibition of virus at a later time in the virus life cycle through the suppression of nuclear export of vRNP and also interfered with the host cellular cAMP and MEK/ERK cascade pathways. This study explores the use of papaverine as an effective inhibitor of both influenza viruses as well as paramyxoviruses.

Human microRNA-30 inhibits influenza virus infection by suppressing the expression of SOCS1, SOCS3, and NEDD4.

Influenza A virus (IAV) has evolved multiple mechanisms to compromise type I interferon (IFN) responses. The antiviral function of IFN is mainly exerted by activating the JAK/STAT signalling and subsequently inducing IFN‐stimulated gene (ISG) production. However, the mechanism by which IAV combat the type I IFN signalling pathway is not fully elucidated. In this study, we explored the roles of human microRNAs modulated by IAV infection in type I IFN responses. We demonstrated that microRNA‐30 (miR‐30) family members were downregulated by IAV infection. Our data showed that the forced expression of miR‐30 family members inhibited IAV proliferation, while miR‐30 family member inhibitors promoted IAV proliferation. Mechanistically, we found that miR‐30 family members targeted and reduced SOCS1 and SOCS3 expression, and thus relieved their inhibiting effects on IFN/JAK/STAT signalling pathway. In addition, miR‐30 family members inhibited the expression of NEDD4, a negative regulator of IFITM3, which is important for host defence against influenza viruses. Our findings suggest that IAV utilises a novel strategy to restrain host type I IFN‐mediated antiviral immune responses by decreasing the expression of miR‐30 family members, and add a new way to understand the mechanism of immune escape caused by influenza viruses.

Identification of the Components in a Vaccinium oldhamii Extract Showing Inhibitory Activity against Influenza Virus Adsorption.

We previously reported that extracts from plants of the Ericaceae genus Vaccinium, commonly known as the kind of blueberry, inhibited the early steps of influenza virus (IFV) infection to host cells, and that the activity was correlated with the total polyphenol content. Particularly potent inhibitory activity was observed for Vaccinium oldhamii. In this study, we identified the active components in Vaccinium oldhamii involved in the inhibition of IFV infection. We sequentially fractionated the Vaccinium oldhamii extract using a synthetic adsorbent resin column. High inhibitory activity was observed for the fractions eluted with 30%, 40%, and 50% ethanol, and three peaks (peak A, B, and C) considered to represent polyphenols were identified in the fractions by HPLC analysis. Among these peaks, high inhibitory activity was detected for peak A and B, but not for peak C. These peaks were analyzed by LC/MS, which revealed that peak A contained procyanidin B2 and ferulic acid derivatives, whereas peak B contained two ferulic acid O-hexosides, and peak C contained quercetin-3-O-rhamnoside and quercetin-O-pentoside-O-rhamnoside. It is already known that these polyphenols have anti-IFV activity, but we speculate that ferulic acid derivatives are the major contributors to the inhibition of the early steps of IFV replication, such as either adsorption or entry, observed for Vaccinium oldhamii.

Enhanced inhibition of influenza virus infection by peptide-noble-metal nanoparticle conjugates.

The influenza (“flu”) type-A virus is a major medical and veterinary health concern and causes global pandemics. The peptide “FluPep” is an established inhibitor of influenza virus infectivity in model systems. We have explored the potential for noble-metal nanoparticle conjugates of FluPep to enhance its antiviral activity and to determine their potential as a delivery platform for FluPep. FluPep ligand is FluPep extended at its N-terminus with the sequence CVVVTAAA, to allow for its incorporation into a mixed-matrix ligand shell of a peptidol and an alkanethiol ethylene glycol consisting of 70% CVVVTol and 30% HS(CH2)11(OC2H4)4OH (mol/mol). Gold and silver nanoparticles (ca. 10 nm diameter) with up to 5% (mol/mol) FluPep ligand remained as stable as the control of mixed-matrix-passivated nanoparticles in a variety of tests, including ligand exchange with dithiothreitol. The free FluPep ligand peptide was found to inhibit viral plaque formation in canine MDCK cells (IC50 = 2.1 nM), but was less potent than FluPep itself (IC50 = 140 pM). Nanoparticles functionalised with FluPep ligand showed enhanced antiviral activity compared to the free peptides. The IC50 value of the FluPep-functionalised nanoparticles decreased as the grafting density of FluPep ligand increased from 0.03% to 5% (both mol/mol), with IC50 values down to about 10% of that of the corresponding free peptide. The data demonstrate that conjugation of FluPep to gold and silver nanoparticles enhances its antiviral potency; the antimicrobial activity of silver ions may enable the design of even more potent antimicrobial inhibitors, capable of targeting both influenza and bacterial co-infections.

Virucidal nano-perforator of viral membrane trapping viral RNAs in the endosome

Membrane-disrupting agents that selectively target virus versus host membranes could potentially inhibit a broad-spectrum of enveloped viruses, but currently such antivirals are lacking. Here, we develop a nanodisc incorporated with a decoy virus receptor that inhibits virus infection. Mechanistically, nanodiscs carrying the viral receptor sialic acid bind to influenza virions and are co-endocytosed into host cells. At low pH in the endosome, the nanodiscs rupture the viral envelope, trapping viral RNAs inside the endolysosome for enzymatic decomposition. In contrast, liposomes containing a decoy receptor show weak antiviral activity due to the lack of membrane disruption. The nanodiscs inhibit influenza virus infection and reduce morbidity and mortality in a mouse model. Our results suggest a new class of antivirals applicable to other enveloped viruses that cause irreversible physical damage specifically to virus envelope by viruses’ own fusion machine. In conclusion, the lipid nanostructure provides another dimension for antiviral activity of decoy molecules.

The Antihistamine Drugs Carbinoxamine Maleate and Chlorpheniramine Maleate Exhibit Potent Antiviral Activity Against a Broad Spectrum of Influenza Viruses.

Influenza A viruses (IAV) comprise some of the most common infectious pathogens in humans, and they cause significant mortality and morbidity in immunocompromised people as well as children and the elderly. After screening an FDA-approved drug library containing 1280 compounds by cytopathic effect (CPE) reduction assay using the Cell Counting Kit-8, we found two antihistamines, carbinoxamine maleate (CAM) and S-(+)-chlorpheniramine maleate (SCM) with potent antiviral activity against A/Shanghai/4664T/2013(H7N9) infection with IC50 (half-maximal inhibitory concentration) of 3.56 and 11.84 μM, respectively. Further studies showed that CAM and SCM could also inhibit infection by other influenza A viruses, including A/Shanghai/37T/2009(H1N1), A/Puerto Rico/8/1934(H1N1), A/Guizhou/54/1989(H3N2), and one influenza B virus, B/Shanghai/2017(BY). Mice were challenged intranasally with A/H7N9/4664T/2013 (H7N9) virus and intraperitoneally injected with CAM (10 mg/kg per day) or SCM (1 mg/kg per day) for 5 days. CAM or SCM (10 mg/kg per day) were fully protected against challenge with A/Shanghai/4664T/2013(H7N9). The results from mechanistic studies indicate that both could inhibit influenza virus infection by blocking viral entry into the target cell, the early stage of virus life cycle. However, CAM and SCM neither blocked virus attachment, characteristic of HA activity, nor virus release, characteristic of NA activity. Such data suggest that these two compounds may interfere with the endocytosis process. Thus, we have identified two FDA-approved antihistamine drugs, CAM and SCM, which can be repurposed for inhibiting infection by divergent influenza A strains and one influenza B strain with potential to be used for treatment and prevention of influenza virus infection.

Inhibition of Influenza Virus Infection by Lentinus edodes Mycelia Extract Through Its Direct Action and Immunopotentiating Activity.

Lentinula edodes mycelia (LEM) solid culture extracts contain many bioactive compounds with diverse pharmacological activities such as antitumor, antiviral, and immunopotentiating effects. In this study, we examined the anti-influenza virus activity of LEM in vitro and in vivo. LEM directly inhibited influenza virus growth in vitro at early phases of infection, possibly at the entry process of viral particles to host cells. We also found that the nasal administration of LEM increased the survival rate of infected mice, and this was likely due to the direct action of LEM on the viral growth. The oral administration of LEM showed prolonged median survival time of infected mice. Histological analysis revealed that the moderate bronchiolitis was observed in infected mice by the oral administration with LEM, and the extent of alveolitis was dramatically reduced. The orally LEM-administered mice showed a rapid activation of IFN-β gene expression upon influenza virus infection. These results suggest that the immunopotentiation activity of LEM on type I IFN pathway represses the virus spread to distal alveolar regions from peribronchiolar regions which are primary infection sites in the mouse model. We propose that LEM has anti-influenza virus activities through the direct action on viral growth and stimulatory activity of innate immunity.

Synergic effect of curcumin and its structural analogue (Monoacetylcurcumin) on anti-influenza virus infection

Curcumin (Cur), a polyphenolic compound extracted from spice and common food colourant turmeric, contains versatile bio-activities. Monoacetylcurcumin (MAC), a structural analogue of Cur, differs from Cur by acetyl modification, but retains enone groups. Comparative analysis revealed MAC effectively inhibited influenza virus infection (IAV) to a similar extent as, if not superior to, curcumin. Both compounds mildly reduced viral NA activity. Surprisingly, unlike Cur, the MAC inhibition of IAV did not occur through the blocking of HA activity. However, MAC strongly dampened Akt phosphorylation, the prerequisite signalling for efficient IAV propagation. A much stronger inhibition effect on IAV infection was observed when MAC treatment was in combination with Cur. Collectively, MAC demonstrated clear antiviral activity, and likely inhibited IAV via multiple mechanisms that were not identical to Cur. Importantly, Cur and MAC in combination synergistically inhibited IAV infection.