Antiviral activity of Epimedium koreanum Nakai water extract against influenza viruses

Epimedium koreanum Nakai (EKN) is a popular plant in Korean and Chinese medicine for treating a variety of ailments. The aqueous extract of EKN has a significant inhibitory impact on influenza A virus (IAV) infection by directly blocking viral attachment and having a virucidal effect, according to this study. Using fluorescent microscopy and fluorescence-activated cell sorting (FACS) with a green fluorescent protein (GFP)-tagged Influenza A/PR/8/34 virus, we examined the effect of EKN on viral infection. By viral infection, EKN strongly suppresses GFP expression, and at a dosage of 100 µg/mL, EKN decreased GFP expression by up to 90% of the untreated infected control. Immunofluorescence and Western blot analyses against influenza viral proteins revealed that EKN decreased influenza viral protein expression in a dose-dependent manner. EKN inhibited the H1N1 influenza virus's hemagglutinin (HA) and neuraminidase (NA), preventing viral attachment to cells. Furthermore, EKN had a virucidal impact and inhibited the cytopathic effects of H1N1, H3N2 and influenza B virus infection. Finally, our findings show that EKN has the potential to be developed as a natural viral inhibitor against influenza virus infection.

Carvacrol inhibits the excessive immune response induced by influenza virus A via suppressing viral replication and TLR/RLR pattern recognition

ETHNOPHARMACOLOGICAL RELEVANCE

Carvacrol, a monoterpene phenol from Mosla chinensis Maxim, which is a commonly Chinese herbal medicine. The most important pharmacology of it is dispelling exogenous evils by increasing perspiration. And it is the gentleman medicine in the Chinese herbal compound prescription of Xin-Jia-Xiang-Ru-Yin, mainly for the treatment of summer colds with dampness including influenza virus A infection.

AIM OF THE STUDY

Our preliminary study verified that the Xin-Jia-Xiang-Ru-Yin could inhibit acute lung injury of mice with influenza virus A infection. And there have been some reports implicating the high antimicrobial activity of carvacrol for a wide range of product preservation, but little research including the effects of it on viral infection. The aim of this study was to reveal the antiviral effects of carvacrol, the main constituent in Mosla chinensis Maxim.

MATERIALS AND METHODS

Initially, C57BL/6 mice were grouped and intranasally administered FM1 virus to construct viral infection models. After treatment with ribavirin and carvacrol for 5 days, all mice were euthanized, and specimens were immediately obtained. Histology, flow cytometry and Meso Scale Discovery (MSD) analysis were used to analyze pathological changes in lung tissue, the expression levels of cytokines and the differentiation and proportion of CD4+ T cells subsets, while Western blot and qRT-PCR were used to detect the expression of related proteins and mRNA.

RESULTS

Carvacrol attenuated lung tissue damage, the proportions of Th1, Th2, Th17 and Treg in CD4+ T cells and the relative proportions of Th1/Th2 and Th17/Treg cells. Carvacrol inhibited the expression of inflammation-associated cytokines including IFN-γ, IL-2, IL-4, IL-5, IL-12 and TNF-ɑ, IL-1, IL-10, IL-6. Decreased levels of TLR7, MyD88, IRAK4, TRAK6, NF-κB, RIG-I, IPS-I and IRF mRNA in carvacrol-treated mice were observed comparing to the mice in VC group. Further, the total expression of RIG-I, MyD88 and NF-κB proteins had increased significantly in the VC group but reduced obviously in the group treated with ribavirin or carvacrol.

CONCLUSIONS

These results indicate that carvacrol is a potential alternative treatment for the excessive immune response induced by influenza virus A infection, the cold-fighting effect of Mosla chinensis Maxim may depend on the anti-virus of carvacrol.

Theacrine and strictinin, two major ingredients for the anti-influenza activity of Yunnan Kucha tea

ETHNOPHARMACOLOGICAL RELEVANCE

Kucha tea plant (Camellia assamica var. kucha Chang et Wang) is regarded as a mutant variety of wild Pu'er tea plant found in few mountain areas of Yunnan, China. Its fresh young leaves and shoots are picked by the indigenous aborigines in these local areas to prepare an herbal tea for the treatment of common cold empirically.

MATERIALS AND METHODS

Two extra compounds of relative abundance were detected in Kucha tea in comparison with Pu'er tea, and their chemical structures were identified as chlorogenic acid and theacrine. These two compounds as well as two major compounds, strictinin and caffeine, in Kucha tea were evaluated for their cytotoxicity and inhibitory effects on human influenza virus A/Puerto Rico/8/34 by analyzing viral protein expression and progeny production.

RESULTS

No or low cytotoxicity was detected for the four Kucha compounds when their concentrations were below 100 μM. Expression of viral NS1 protein was significantly inhibited by chlorogenic acid, theacrine or strictinin, but not caffeine at a concentration of 100 μM. The relative inhibitory potency was detected as chlorogenic acid < theacrine < strictinin, and both theacrine and strictinin displayed significant inhibition at a concentration of 50 μM. According to a plaque assay, viral progeny production was significantly reduced by theacrine or strictinin, but not by chlorogenic acid or caffeine under the same concentration of 100 μM.

CONCLUSION

It is suggested that theacrine and strictinin are two major ingredients responsible for the anti-influenza activity of Yunnan Kucha tea traditionally used for the treatment of common cold.

Chemoenzymatic Total Synthesis of Sorbicatechol Structural Analogues and Evaluation of Their Antiviral Potential

Sorbicillinoids are fungal polyketides characterized by highly complex and diverse molecular structures, with considerable stereochemical intricacy combined with a high degree of oxygenation. Many sorbicillinoids possess promising biological activities. An interesting member of this natural product family is sorbicatechol A, which is reported to have antiviral activity, particularly against influenza A virus (H1N1). Through a straightforward, one-pot chemoenzymatic approach with recently developed oxidoreductase SorbC, the characteristic bicyclo[2.2.2]octane core of sorbicatechol is structurally diversified by variation of its natural 2-methoxyphenol substituent. This facilitates the preparation of a focused library of structural analogues bearing substituted aromatic systems, alkanes, heterocycles, and ethers. Fast access to this structural diversity provides an opportunity to explore the antiviral potential of the sorbicatechol family.

Design and synthesis of 2-((1H-indol-3-yl)thio)-N-phenyl-acetamides as novel dual inhibitors of respiratory syncytial virus and influenza virus A

Respiratory syncytial virus (RSV) and influenza A virus (IAV) are two of the most common viruses that cause substantial morbidity and mortality in infants, young children, elderly persons, and immunocompromised individuals worldwide. Currently, there are no licensed vaccines or selective antiviral drugs against RSV infections and most IAV strains become resistant to clinical anti-influenza drug. Here, we described the discovery of a series of 2-((1H-indol-3-yl)thio)-N-phenyl-acetamide as novel and potent RSV and IAV dual inhibitors. Thirty-five derivatives were designed, prepared, and evaluated for their anti-RSV and anti-IAV activities. Among the tested compounds, 14'c, 14'e, 14'f, 14'h, and 14'i exhibited excellent activity against both RSV and IAV, which showed low micromolar to sub-micromolar EC50 values. Further, compounds 14'c and 14'e were identified as the most promising dual inhibitors with lesser cytotoxicity than the clinical drug, ribavirin. These findings may contribute to the development of a lead compound for the treatment of RSV and/or IAV infections.

3-Trifluoromethylpyrazolones derived nucleosides: Synthesis and antiviral evaluation

Dengue (DENV) viral infection is a global public health problem that infrequently develops life threatening diseases such as dengue hemorrhagic fever (DFS) and dengue shock syndrome (DSS). Middle East respiratory syndrome coronavirus (MERS-CoV) is a highly pathogenic human corona virus with 38% fatality rate of infected patients. A series of 4-arylhydrazono-5-trifluoromethyl-pyrazolones, their ribofuranosyl, and 5'-deoxyribofuranosyl nucleosides were synthesized, geometry optimized using Density functional theory (DFT), and evaluated for their antiviral activity. 2-Nitrophenylhydrazonopyra-zolone derivative 5 showed significant activity against MERS-CoV (EC50 = 4.6 μM). The nucleoside analog 8 showed moderate activity against DENV-2 (EC50 = 10 μM), while the activity was abolished with the corresponding 5'-deoxyribonucleoside analogs. The identified hits in this study set this category of compounds for further future optimizations.

De Novo Design of α-Helical Lipopeptides Targeting Viral Fusion Proteins: A Promising Strategy for Relatively Broad-Spectrum Antiviral Drug Discovery

Class I enveloped viruses share similarities in their apparent use of a hexameric coiled-coil assembly to drive the merging of virus and host cell membranes. Inhibition of coiled coil-mediated interactions using bioactive peptides that replicate an α-helical chain from the viral fusion machinery has significant antiviral potential. Here, we present the construction of a series of lipopeptides composed of a de novo heptad repeat sequence-based α-helical peptide plus a hydrocarbon tail. Promisingly, the constructs adopted stable α-helical conformations and exhibited relatively broad-spectrum antiviral activities against Middle East respiratory syndrome coronavirus (MERS-CoV) and influenza A viruses (IAVs). Together, these findings reveal a new strategy for relatively broad-spectrum antiviral drug discovery by relying on the tunability of the α-helical coiled-coil domains present in all class I fusion proteins and the amphiphilic nature of the individual helices from this multihelix motif.

Susceptibility of influenza viruses circulating in Western Saudi Arabia to neuraminidase inhibitors

OBJECTIVES

To investigate the sensitivity of circulating influenza viruses in Western Saudi Arabia to neuraminidase inhibitors (NAIs); mainly, zanamivir and oseltamivir.

METHODS

Respiratory samples were collected from patients presenting with respiratory symptoms to King Abdulaziz University Hospital, Jeddah, Kingdom of Saudi Arabia (KSA) between September 2013 and October 2014. All samples were tested prospectively by real-time reverse-transcription polymerase chain reaction for influenza A and B viruses. Positive samples were then inoculated on Madin-Darby Canine Kidney (MDCK) cells and isolated viruses were examined for their sensitivity to NAIs using fluorescent neuraminidase inhibition assay.

RESULTS

Out of 406 tested samples, 25 samples (6.2%) were positive for influenza A/pdmH1N1 virus, one sample (0.25%) was positive for influenza A/H3N2 virus, and 7 samples (1.7%) were positive for influenza B Yamagata-like virus. Screening of isolated influenza A and B viruses (9 out of 33) for their sensitivity to NAIs showed no significant resistance to available NAIs.

CONCLUSION

Our results show that circulating influenza viruses in Jeddah are still sensitive to NAIs.

Human miR-3145 inhibits influenza A viruses replication by targeting and silencing viral PB1 gene

MicroRNAs (miRNAs) play an important role in the regulation of gene expression and are involved in many cellular processes including inhibition of viral replication in infected cells. In this study, three subtypes of influenza A viruses (pH1N1, H5N1 and H3N2) were analyzed to identify candidate human miRNAs targeting and silencing viral genes expression. Candidate human miRNAs were predicted by miRBase and RNAhybrid based on minimum free energy (MFE) and hybridization patterns between human miRNAs and viral target genes. In silico analysis presented 76 miRNAs targeting influenza A viruses, including 70 miRNAs that targeted specific subtypes (21 for pH1N1, 27 for H5N1 and 22 for H3N2) and 6 miRNAs (miR-216b, miR-3145, miR-3682, miR-4513, miR-4753 and miR-5693) that targeted multiple subtypes of influenza A viruses. Interestingly, miR-3145 is the only candidate miRNA targeting all three subtypes of influenza A viruses. The miR-3145 targets to PB1 encoding polymerase basic protein 1, which is the main component of the viral polymerase complex. The silencing effect of miR-3145 was validated by 3'-UTR reporter assay and inhibition of influenza viral replication in A549 cells. In 3'-UTR reporter assay, results revealed that miR-3145 triggered significant reduction of the luciferase activity. Moreover, expression of viral PB1 genes was also inhibited considerably (P value < 0.05) in viral infected cells expressing mimic miR-3145. In conclusion, this study demonstrated that human miR-3145 triggered silencing of viral PB1 genes and lead to inhibition of multiple subtypes of influenza viral replication. Therefore, hsa-miR-3145 might be useful for alternative treatment of influenza A viruses in the future.

The medicinal potential of natural products for the development of anti- influenza agents

Influenza neuraminidase (NA) is an important target for designing anti-influenza drugs. By now, three inhibitors, zanamivir, oseltamivir and peramivir have been approved. However, in recent years, the potential threat of influenza pandemics and constant emergence of new drug-resistant influenza virus strains have weaken the defensive role of the current anti-influenza drugs. From another point of view, in this review we focused on some novel NA inhibitors which were mainly derived from natural products that had a variety of structural scaffolds, such as flavonoids, xanthones and diarylheptanoids. Besides interfering the function of NA, some of these compounds also can potently inhibit the replication of influenza virus. It is hoped that these compounds could be the source of leads and provide a guide for discovering new potent anti-influenza virus agents.

Development of oseltamivir phosphonate congeners as anti-influenza agents

Oseltamivir phosphonic acid (tamiphosphor, 3a), its monoethyl ester (3c), guanidino-tamiphosphor (4a), and its monoethyl ester (4c) are potent inhibitors of influenza neuraminidases. They inhibit the replication of influenza viruses, including the oseltamivir-resistant H275Y strain, at low nanomolar to picomolar levels, and significantly protect mice from infection with lethal doses of influenza viruses when orally administered with 1 mg/kg or higher doses. These compounds are stable in simulated gastric fluid, liver microsomes, and human blood and are largely free from binding to plasma proteins. Pharmacokinetic properties of these inhibitors are thoroughly studied in dogs, rats, and mice. The absolute oral bioavailability of these compounds was lower than 12%. No conversion of monoester 4c to phosphonic acid 4a was observed in rats after intravenous administration, but partial conversion of 4c was observed with oral administration. Advanced formulation may be investigated to develop these new anti-influenza agents for better therapeutic use.

Utility of Maoto in an influenza season where reduced effectiveness of oseltamivir was observed - a clinical, non-randomized study in children

BACKGROUND

In an influenza season where reduced effectiveness of oseltamivir was observed, we investigated the effectiveness of Maoto for influenza infection in children.

METHODS

Patients diagnosed with influenza by rapid diagnostic kit underwent treatment in one of the following groups: Maoto-treated group (group 1 (M)); oseltamivir-treated group (group 2 (O)); Maoto+oseltamivir-treated group (group 3 (M+O)); zanamivir-treated group (group 4 (Z)); and Maoto+zanamivir-treated group (group 5 (M+Z)).

RESULTS

In influenza A patients who completed the study (n = 150), the mean duration of fever after administration (DFA) was significantly shorter in group 3 (M+O) (31.1 h, p < 0.01) and in group 4 (Z) (35.2 h, p < 0.05), as compared to group 2 (O) (56.0 h). Among these, in patients aged ≤5 years (n = 54), DFA was significantly shorter in group 1 (M) (33.2 h, p < 0.05) and in group 3 (M+O) (34.6 h, p < 0.05), as compared to group 2 (O) (61.4 h). In influenza B patients who completed the study (n = 70), no significant differences in DFA were observed among the groups.

CONCLUSION

Maoto may be useful, particularly in cases of influenza with low sensitivity to oseltamivir and in patients aged ≤5 years for whom the use of zanamivir is difficult.

Influenza nucleoprotein: promising target for antiviral chemotherapy

In the search for new anti-influenza agents, the viral polymerase has often been targeted due to the involvement of multiple conserved proteins and their distinct activities. Polymerase associates with each of the eight singled-stranded negative-sense viral RNA segments. These transcriptionally competent segments are coated with multiple copies of nucleoprotein (NP) to form the ribonucleoprotein. NP is an abundant essential protein, possessing operative and structural functions, and participating in genome organization, nuclear trafficking and RNA transcription and replication. This review examines the NP structure and function, and explores NP as an emerging target for anti-influenza drug development, focusing on recently discovered aryl piperazine amide inhibitor chemotypes.

[New antiviral agents of influenza]

Influenza is a serious health threat for people all over the world and the new and more effective antiviral drugs such as peramivir, laninamivir, and favipiravir have been developed. In this article we review new drugs and drug candidates of newer compounds, which are currently undergoing testing, against influenza with an emphasis on the recent progress of targeting of pathogen replication system, as well as a comprehensive, state-of-the-art picture of drug therapy.

In vitro inhibition of influenza virus infection by a crude extract from Isatis indigotica root resulting in the prevention of viral attachment

Isatis indigotica root (IIR) has been widely used as a Chinese medicinal herb to treat regular seasonal influenza over the long history of traditional Chinese medicinal practice. However, its inhibitory activities against influenza virus infections along with the associated mechanisms have not been investigated comprehensively. In this study, the chemical nature, mode of action and in vitro anti-influenza activities of a crude extract (G2) of IIR were characterized. The extract was found to inhibit different subtypes of human or avian influenza viruses at various magnitudes of activity (IC50 0.39‑4.3 mg/ml) in vitro, including A/PR/8/34 (H1N1), A/FM/1/47 (H1N1), A/Aichi/2/68 (H3N2), seasonal influenza (A/Guangzhou/GIRD/02/09 H1N1, B/Guangzhou/GIRD/08/09), novel swine-originating influenza (A/Guangzhou/GIRD/07/09, H1N1), A/Duck/Guangdong/09 (H6N2), A/Duck/Guangdong/94 (H7N3) and A/Chicken/Guangdong/96 (H9N2), while G2 was inactive against respiratory syncytial virus (RSV), adenovirus 3 (ADV3), parainfluenza virus 3 (PIV3) and enterovirus 71 (EV71). An apparent virus titer reduction was detected when the influenza viruses were pretreated with G2, and it was also shown that G2 exhibited inhibitory effects on influenza virus hemagglutination. In addition, G2 played a role in the early stages of infection, which did not easily result in the emergence of virus drug resistance. Thus, G2 may affect the attachment of influenza virus by interfering with the viral particles, thereby preventing the binding of influenza virus to the host cell surface.

[The origin of the genetic variability of influenza viruses]

To better understand the significant variability displayed by influenza viruses, we need to be aware not only of its genetic characteristics, but also of the effect this genetic makeup has on proteins associated with viral replication and antigenicity. The origin of such diversity is due first and foremost to its segmented genome that allows segment reassortment (antigenic shift) and second to the error prone viral polymerase (antigenic drift) responsible of copying the genes enclosed in these segments. These two combined mechanisms confer a genetic plasticity that often leads to the emergence of new influenza viruses in nature.

Molecular design of spacer-N-linked sialoglycopolypeptide as polymeric inhibitors against influenza virus infection

A series of spacer-N-linked glycopolymers carrying long/short α2,3/6 sialylated glycan were designed as polymeric inhibitors of influenza virus. Lactose (Lac) and N-acetyllactosamine (LN: Galβ1,4GlcNAc) were first converted to spacer-N-linked disaccharide glycosides, followed by consecutive enzymatic addition of GlcNAc and Gal residues to the glycosides. The resulting spacer-N-linked glycosides with di-, tetra-, and hexasaccharides carrying a Lac, LN, lacto-N-neotetraose (LNnT: Galβ1,4GlcNAcβ1,3Galβ1,4Glc), and LNβ1,3LNnT were coupled to the carboxy group of γ-polyglutamic acid (γ-PGA) and enzymatically converted to glycopolypeptides carrying α2,3/6 sialylated glycans. The interactions of a series of sialoglycopolypeptides with avian and human influenza virus strains were investigated using a hemagglutination inhibition assay. The avian virus A/Duck/HongKong/313/4/78 (H5N3) bound specifically, regardless of the structure of the asialo portion. In contrast, human virus A/Aichi/2/68 (H3N2) bound preferentially to long α2,6sialylated glycans with penta- or heptasaccharides in a glycan length-dependent manner. Furthermore, the Sambucus sieboldiana (SNA) lectin was also useful as a model of human virus hemagglutinin (HA) for understanding the carbohydrate binding properties, because the recognition motifs of the inner sugar in the receptor were very similar.

Synthesis and in vivo influenza virus-inhibitory effect of ester prodrug of 4-guanidino-7-O-methyl-Neu5Ac2en

A series of ester prodrugs of 7-O-methyl derivative of Zanamivir (compound 3) was synthesized and their efficacy was evaluated in an influenza infected mice model by intranasal administration. Compound 7c (CS-8958), octanoyl ester prodrug of the C-9 alcohol of compound 3, was found to be much longer-acting than Zanamivir. Furthermore, the in vivo efficacies of compounds 12a, 12b, and 12c, the linear alkyl ester prodrug of the carboxylic acid, were comparable to that exerted by compound 7c.

Effectiveness of oseltamivir treatment among children with influenza A or B virus infections during four successive winters in Niigata City, Japan

Oseltamivir has been used for treatment of influenza A and B infections, but recent reports documented that it was less active against the latter. We compared the effectiveness of oseltamivir in children between laboratory confirmed influenza A and B over 4 influenza seasons from 2001 to 2005 in a pediatric clinic in Japan. Among 1,848 patients screened, 299 influenza A and 209 influenza B patients were administered oseltamivir (treated groups), and 28 influenza A and 66 influenza B patients were assigned as non-treated groups. The duration of fever, defined as period when patients had the maximum temperature higher than 37.5 degrees C in three-time measurements in a day after the clinic visit, was evaluated among the four groups. In uni-variate analysis, the duration of fever was shorter for treated group than non-treated for influenza A (1.8 +/- 0.9 days vs 2.6 +/- 1.3 days, p < 0.01), but it was not significant for influenza B (2.4 +/- 1.3 days vs 2.8 +/- 1.2 days, p = 0.9). The fever duration was longer in treated influenza B than A patients (p < 0.01). Multi-variate analysis indicated younger age (< 6 years old) and higher body temperature at the clinic visit prolonged the duration of fever. Adjusted average duration of fever indicated that oseltamivir was effective for both types, but more effective on influenza A, and the benefit increased for younger children. Our data provide evidence that oseltamivir is beneficial for influenza infections, but the effectiveness is differed by type and age.

[Synthesis and antiviral activity of lupane triterpenoids with modified cycle E]

A reductive transformation of the peroxide products of ozonolysis of derivatives of 3beta-O-acetyl-22(17-->28)-abeo-lupa-17(28),20(29)-diene and the subsequent intramolecular ketalization led to a compound with a trioxane fragment. This is a new approach to a skeletal modification of triterpenoid cycle E. An activity of the synthesized compounds was found toward the viruses of type A influenza and herpes simplex.

Concise synthesis of dideoxy-epigallocatechin gallate (DO-EGCG) and evaluation of its anti-influenza virus activity

Dideoxy-epigallocatechin gallate (DO-EGCG) (2), a simplified analog of naturally occurring EGCG (1), was efficiently prepared by directly introducing a ketone group at C3 and successive reduction to the sec-alcohol with 2,3-cis stereochemistry. Compound 2 showed potent anti-influenza virus activity, indicating that the hydroxyl substituents on the A-ring are not crucial for anti-influenza virus activity.

Amantadine resistance among porcine H1N1, H1N2, and H3N2 influenza A viruses isolated in Germany between 1981 and 2001

This study was designed to gain insight into amantadine susceptibility of porcine influenza A viruses isolated in Germany between 1981 and 2001. The 12 studied H1N1, H1N2, and H3N2 porcine influenza virus strains were isolated in chicken eggs and passaged once in MDCK cells. Plaque reduction assays were applied to examine virus susceptibility to amantadine. Genotyping was used to confirm drug resistance. In the results of these antiviral studies, only 3 of the 12 isolates were shown to be amantadine-susceptible. All resistant strains contained the AA substitutions G16E, S31N, and R77Q in the membrane protein 2 (M2). Additionally, L27A was detected in two H1N1 strains. S31N and/or L27A are well-known amino acid substitutions in M2 that confer amantadine resistance. The role of the pig as an intermediate host of avian and human influenza A viruses, the possible involvement of genetic reassortment, and the high incidence of naturally amantadine-resistant porcine influenza A viruses suggest a real risk of emergence of amantadine resistant human viruses. Therefore, drug susceptibility monitoring appears to be warranted for effective application of those drugs.

Synthesis and biological evaluation of novel bisheterocycle-containing compounds as potential anti-influenza virus agents

A series of novel 4,2-bisheterocycle tandem derivatives consisting of a methyloxazole and thiazole subunit were synthesized. Many compounds were found to inhibit human influenza A virus. Several analogues exhibited moderate biological activity and could serve as leads for further optimizations for antivirus research.

[Antiviral and anti-stress activity of the gamma-L-glutamyl-histamine and its derivatives]

Effect of gamma-L-glutamylhistamine gamma-L-Glu-HA and some of its derivatives on the state of nonspecific resistance and antiviral activity was studied using experimental models of influenza virus and herpes simplex virus infections. Activities of natural killer (NK) cells and interferon (IFN) system were measured. The model of physical-emotional stress in mice was used. It was shown that the gamma-L-Glu-HA derivative II can prevent totally or substantially a decrease in the NK activity. This agent also prevents inhibition of synthesis of alpha- and gamma-IFN during the post-stress period. The gamma-L-Glu-HA derivatives II, III, and VII increased the mice resistance to influenza virus type A/Aichi at low infection dose (10LD50). The derivative II showed its protective effect even at high dose of pathogen (100LD50). However, this gamma-L-Glu-HA derivative was virtually ineffective under harsh experimental conditions. Thus, a number of gamma-L-Glu-HA derivatives tested in this work demonstrated immunomodulation activity. These agents were able to normalize parameters of nonspecific immunity. They exerted a pronounced antiviral effect against influenza virus but were virtually ineffective against encephalitis in mice caused by herpes simplex virus, type 1. Of all tested agents, gamma-L-Glu-HA derivative II was found to be the most promising.

Structural studies of the resistance of influenza virus neuramindase to inhibitors

Zanamivir and oseltamivir, specific inhibitors of influenza virus neuraminidase, have significantly different characteristics in resistance studies. In both cases resistance is known to arise through mutations in either the hemagglutinin or neuraminidase surface proteins. A new inhibitor under development by Biocryst Pharmaceuticals, BCX-1812, has both a guanidino group, as in zanamivir, and a bulky hydrophobic group, as in oseltamivir. Using influenza A/NWS/Tern/Australia/G70C/75 (H1N9), neuraminidase variants E119G and R292K have previously been selected by different inhibitors. The sensitivity of these variants to BCX-1812 has now been measured and found in both cases to be intermediate between those of zanamivir and oseltamivir. In addition, the X-ray crystal structures of the complexes of BCX-1812 with the wild type and the two mutant neuraminidases were determined. The ligand is bound in an identical manner in each structure, with a rearrangement of the side chain of E276 from its ligand-free position. A structural explanation of the mechanism of resistance of BCX-1812, relative to zanamivir and oseltamivir in particular, is provided.

Combination treatment of influenza A virus infections in cell culture and in mice with the cyclopentane neuraminidase inhibitor RWJ-270201 and ribavirin

Treatment of virus infections with compounds acting by different mechanisms may lead to more potent effects when these agents are used in combination. Under this premise, two known active influenza virus inhibitors, ribavirin and the novel cyclopentane influenza virus neuraminidase inhibitor (1S,2S,3R,4R)-3-[(1S)-(acetylamino)-2-ethylbutyl]-4-[(aminoiminomethyl)amino]-2-hydroxy-cyclopentanecarboxylic acid (RWJ-270201, BCX-1812) were studied. Experiments in cell culture demonstrated that RWJ-270201 plus ribavirin synergistically reduced extracellular influenza A/NWS/33 (H1N1) virus yields at low concentrations of each inhibitor. Mice were treated with ribavirin at 20 and 6.25 mg/kg/day combined with RWJ-270201 at 1, 0.32, or 0.1 mg/kg/day, or used alone. Treatments were twice daily for 5 days starting 4 h before exposure to influenza A/NWS virus. Only RWJ-270201 alone at 1 mg/kg/day significantly prevented mortality. In contrast, most drug combinations increased survival significantly compared to the placebo group. Doses of the two compounds used in combination delayed the mean day of death, and improved arterial oxygen saturation levels, as measured on day 11 of the infection. The combination of the two inhibitors produced additive to synergistic interactions in these mouse experiments with no enhancement of host toxicity. Treatment of influenza infections in the clinical setting may benefit by these two agents in combination.

Absence of SP-A modulates innate and adaptive defense responses to pulmonary influenza infection

Mice lacking surfactant protein SP-A [SP-A(-/-)] and wild type SP-A(+/+) mice were infected with influenza A virus (IAV) by intranasal instillation. Decreased clearance of IAV was observed in SP-A(-/-) mice and was associated with increased pulmonary inflammation. Treatment of SP-A(-/-) mice with exogenous SP-A enhanced viral clearance and decreased lung inflammation. Uptake of IAV by alveolar macrophages was similar in SP-A(-/-) and SP-A(+/+) mice. Myeloperoxidase activity was reduced in isolated bronchoalveolar lavage neutrophils from SP-A(-/-) mice. B lymphocytes and activated T lymphocytes were increased in the lung and spleen, whereas T helper (Th) 1 responses were increased [interferon-gamma, interleukin (IL)-2, and IgG(2a)] and Th2 responses were decreased (IL-4, and IL-10, and IgG(1)) in the lungs of SP-A(-/-) mice 7 days after IAV infection. In the absence of SP-A, impaired viral clearance was associated with increased lung inflammation, decreased neutrophil myeloperoxidase activity, and increased Th1 responses. Because the airway is the usual portal of entry for IAV and other respiratory pathogens, SP-A is likely to play a role in innate defense and adaptive immune responses to IAV.