New approaches to influenza chemotherapy. Neuraminidase inhibitors

Extracellular vesicles as novel assay tools to study cellular interactions of anti-infective compounds - A perspective

Sudden outbreaks of novel infectious diseases and the persistent evolution of antimicrobial resistant pathogens make it necessary to develop specific tools to quickly understand pathogen-cell interactions and to study appropriate drug delivery strategies. Extracellular vesicles (EVs) are cell-specific biogenic transport systems, which are gaining more and more popularity as either diagnostic markers or drug delivery systems. Apart from that, there are emerging possibilities for EVs as tools to study drug penetration, drug-membrane interactions as well as pathogen-membrane interactions. However, it appears that the potential of EVs for such applications has not been fully exploited yet. Considering the vast variety of cells that can be involved in an infection, vesicle-based analytical methods are just emerging and the number of reported applications is still relatively small. Aim of this review is to discuss the current state of the art of EV-based assays, especially in the context of antimicrobial research and therapy, and to present some new perspectives for a more exhaustive and creative exploration in the future.

Synthesis of Glycodendrimers with Antiviral and Antibacterial Activity

Glycodendrimers are an important class of synthetic macromolecules that can be used to mimic many structural and functional features of cell-surface glycoconjugates. Their carbohydrate moieties perform key important functions in bacterial and viral infections, often regulated by carbohydrate-protein interactions. Several studies have shown that the molecular structure, valency and spatial organisation of carbohydrate epitopes in glycoconjugates are key factors in the specificity and avidity of carbohydrate-protein interactions. Choosing the right glycodendrimers almost always helps to interfere with such interactions and blocks bacterial or viral adhesion and entry into host cells as an effective strategy to inhibit bacterial or viral infections. Herein, the state of the art in the design and synthesis of glycodendrimers employed for the development of anti-adhesion therapy against bacterial and viral infections is described.

An Intranasal Proteosome-Adjuvanted Trivalent Influenza Vaccine Is Safe, Immunogenic & Efficacious in the Human Viral Influenza Challenge Model. Serum IgG & Mucosal IgA Are Important Correlates of Protection against Illness Associated with Infection

INTRODUCTION

A Proteosome-adjuvanted trivalent inactivated influenza vaccine (P-TIV) administered intra-nasally was shown to be safe, well tolerated and immunogenic in both systemic and mucosal compartments, and effective at preventing illness associated with evidence of influenza infection.

METHODS

In two separate studies using the human viral challenge model, subjects were selected to be immunologically naive to A/Panama/2007/1999 (H3N2) virus and then dosed via nasal spray with one of three regimens of P-TIV or placebo. One or two doses, 15 μg or 30 μg, were given either once only or twice 14 days apart (1 x 30 μg, 2 x 30 μg, 2 x 15 μg) and subjects were challenged with A/Panama/2007/1999 (H3N2) virus. Immune responses to the vaccine antigens were measured by haemagglutination inhibition assay (HAI) and nasal wash secretory IgA (sIgA) antibodies.

RESULTS

Vaccine reactogenicity was mild, predictable and generally consistent with earlier Phase I studies with this vaccine. Seroconversion to A/Panama/2007/1999 (H3N2), following vaccination but prior to challenge, occurred in 57% to 77% of subjects in active dosing groups and 2% of placebo subjects. The greatest relative rise in sIgA, following vaccination but prior to challenge, was observed in groups that received 2 doses.

CONCLUSION

Intranasal vaccination significantly protected against influenza (as defined by influenza symptoms combined with A/Panama seroconversion) following challenge with A/Panama/2007/1999 (H3N2). When data were pooled from both studies, efficacy ranged from 58% to 82% in active dosing groups for any influenza symptoms with seroconversion, 67% to 85% for systemic or lower respiratory illness and seroconversion, and 65% to 100% for febrile illness and seroconversion. The two dose regimen was found to be superior to the single dose regimen. In this study, protection against illness associated with evidence of influenza infection (evidence determined by seroconversion) following challenge with virus, significantly correlated with pre-challenge HAI titres (p = 0.0003) and mucosal sIgA (p≤0.0001) individually, and HAI (p = 0.028) and sIgA (p = 0.0014) together. HAI and sIgA levels were inversely related to rates of illness.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02522754.

Antiviral activity of an aqueous extract derived from Aloe arborescens Mill. against a broad panel of viruses causing infections of the upper respiratory tract

BACKGROUND

A number of antiviral therapies have evolved that may be effectively administered to treat respiratory viral diseases. But these therapies are very often of limited efficacy or have severe side effects. Therefore there is great interest in developing new efficacious and safe antiviral compounds e.g. based on the identification of compounds of herbal origin.

HYPOTHESIS

Since an aqueous extract of Aloe arborescens Mill. shows antiviral activity against viruses causing infections of the upper respiratory tract in vitro we hypothesised that a product containing it such as Biaron C(®) could have an antiviral activity too.

STUDY DESIGN

Antiviral activity of Bioaron C(®), an herbal medicinal product consisting of an aqueous extract of Aloe arborescens Mill., Vitamin C, and Aronia melanocarpa Elliot. succus, added as an excipient, was tested in vitro against a broad panel of viruses involved in upper respiratory tract infections.

METHODS

These studies included human adenovirus and several RNA viruses and were performed either with plaque reduction assays or with tests for the detection of a virus-caused cytopathic effect.

RESULTS

Our studies demonstrated an impressive activity of Bioaron C(®) against members of the orthomyxoviridae - influenza A and influenza B viruses. Replication of both analysed influenza A virus strains - H1N1 and H3N2 - as well as replication of two analysed influenza B viruses - strains Yamagatal and Beiying - was significantly reduced after addition of Bioaron C(®) to the infected cell cultures. In contrast antiviral activity of Bioaron C(®) against other RNA viruses showed a heterogeneous pattern. Bioaron C(®) inhibited the replication of human rhinovirus and coxsackievirus, both viruses belonging to the family of picornaviridae and both representing non-enveloped RNA viruses. In vitro infections with respiratory syncytial virus and parainfluenza virus, both belonging to the paramyxoviridae, were only poorly blocked by the test substance. No antiviral activity of Bioaron C(®) was detected against adenovirus - a non-enveloped DNA virus.

CONCLUSIONS

These results represent the first proof of a selective antiviral activity of Bioaron C(®) against influenza viruses and create basis for further analyses of type and molecular mechanisms of the antiviral activity of this herbal medicine.

Antiviral activity in vitro of two preparations of the herbal medicinal product Sinupret® against viruses causing respiratory infections

Sinupret(®), a herbal medicinal product made from Gentian root, Primula flower, Elder flower, Sorrel herb, and Verbena herb is frequently used in the treatment of acute and chronic rhinosinusitis and respiratory viral infections such as common cold. To date little is known about its potential antiviral activity. Therefore experiments have been performed to measure the antiviral activity of Sinupret(®) oral drops (hereinafter referred to as "oral drops") and Sinupret(®) dry extract (hereinafter referred to as "dry extract"), in vitro against a broad panel of both enveloped and non-enveloped human pathogenic RNA and DNA viruses known to cause infections of the upper respiratory tract: influenza A, Chile 1/83 (H1N1) virus (FluA), Porcine Influenza A/California/07/2009 (H1N1) virus (pFluA), parainfluenza type 3 virus (Para 3), respiratory syncytial virus, strain Long (RSV), human rhinovirus B subtype 14 (HRV 14), coxsackievirus subtype A9 (CA9), and adenovirus C subtype 5 (Adeno 5). Concentration-dependent antiviral activity (EC(50) between 13.8 and 124.8 μg/ml) of Sinupret(®) was observed against RNA as well as DNA viruses independent of a viral envelope. Remarkable antiviral activity was shown against Adeno 5, HRV 14 and RSV in which dry extract was significantly superior to oral drops. This could be ascertained with different assays as plaque-reduction assays in plaque forming units (PFU), the analyses of a cytopathogenic effect (CPE) and with enzyme immunoassays (ELISA) to determine the amount of newly synthesised virus. Our results demonstrate that Sinupret(®) shows a broad spectrum of antiviral activity in vitro against viruses commonly known to cause respiratory infections.

IFITM3 inhibits influenza A virus infection by preventing cytosolic entry

To replicate, viruses must gain access to the host cell's resources. Interferon (IFN) regulates the actions of a large complement of interferon effector genes (IEGs) that prevent viral replication. The interferon inducible transmembrane protein family members, IFITM1, 2 and 3, are IEGs required for inhibition of influenza A virus, dengue virus, and West Nile virus replication in vitro. Here we report that IFN prevents emergence of viral genomes from the endosomal pathway, and that IFITM3 is both necessary and sufficient for this function. Notably, viral pseudoparticles were inhibited from transferring their contents into the host cell cytosol by IFN, and IFITM3 was required and sufficient for this action. We further demonstrate that IFN expands Rab7 and LAMP1-containing structures, and that IFITM3 overexpression is sufficient for this phenotype. Moreover, IFITM3 partially resides in late endosomal and lysosomal structures, placing it in the path of invading viruses. Collectively our data are consistent with the prediction that viruses that fuse in the late endosomes or lysosomes are vulnerable to IFITM3's actions, while viruses that enter at the cell surface or in the early endosomes may avoid inhibition. Multiple viruses enter host cells through the late endocytic pathway, and many of these invaders are attenuated by IFN. Therefore these findings are likely to have significance for the intrinsic immune system's neutralization of a diverse array of threats.

Influenza epidemics exact a great toll on world health. Thus research to identify new anti-influenza virus strategies would be useful. Each of our cells contains antiviral factors that work to inhibit infection. A large component of this antiviral program is regulated by the interferon family of signaling molecules. Here, we seek to better understand how one of these antiviral factors, IFITM3, contributes to both baseline, as well as interferon-induced, antagonism of influenza A viral infection. We found that interferon prevents influenza A virus from entering our cells by blocking the virus' fusion with the cellular membrane. Furthermore, we learned that IFITM3 is required for this antiviral action of interferon, and that high levels of IFITM3 alone can produce a similar viral inhibition. Together, these results improve our understanding of how IFITM3 serves to defend us against viral invasion at a very early stage of infection.

Potential of carbohydrate-binding agents as therapeutics against enveloped viruses

Twenty‐seven years after the discovery of HIV as the cause of AIDS more than 25 drugs directed against four different viral targets (i.e. reverse transcriptase, protease, integrase, envelope gp41) and one cellular target (i.e. CCR5 co‐receptor) are available for treatment. However, the search for an efficient vaccine is still ongoing. One of the main problems is the presence of a continuously evolving dense carbohydrate shield, consisting of N‐linked glycans that surrounds the virion and protects it against efficient recognition and persistent neutralization by the immune system. However, several lectins from the innate immune system specifically bind to these glycans in an attempt to process the virus antigens to provoke an immune response. Across a wide variety of different species in nature lectins can be found that can interact with the glycosylated envelope of HIV‐1 and can block the infection of susceptible cells by the virus. In this review, we will give an overview of the lectins from non‐mammalian origin that are endowed with antiviral properties and discuss the complex interactions between lectins of the innate immune system and HIV‐1. Also, attention will be given to different carbohydrate‐related modalities that can be exploited for antiviral chemotherapy.  © 2010 Wiley Periodicals, Inc. Med Res Rev

Systematic syntheses of influenza neuraminidase inhibitors: a series of carbosilane dendrimers uniformly functionalized with thioglycoside-type sialic acid moieties

In order to develop novel influenza sialidase inhibitors, we constructed a library of glycoclusters composed of twelve types of sialylated dendrimers with thioglycosidic linkage that are resistant to hydrolysis by the sialidases. These sialodendrimers were synthesized by condensation reaction between a thiosialoside modified on the aglycon terminal end by a thioacetyl group and twelve types of carbosilane dendrimers having brominated terminal ends under deacetylation conditions, and temporal re-protection was performed for purification. Removal of all protection of the glycodendrimers was accomplished by transesterification and subsequent saponification to provide corresponding water-soluble glycodendrimers in good yields. For investigation of the structure-activity relationship, dendrimer scaffolds having differences in number of the sugar moieties, such as 3-, 4-, 6- and 12-functionalized dendrimers, and in linkage patterns, such as normal aliphatic linkage, ether- and amide-linkages. Biological evaluations of these glycodendrimers showed that all of the ether- and amide-elongated compounds had inhibitory potencies for the influenza sialidases in the mM range, while compounds having normal aliphatic linkage did not have any activities except for a 12-functionalized compound.

Biodistribution and metabolism of the anti-influenza drug [11C]oseltamivir and its active metabolite [11C]Ro 64-0802 in mice

INTRODUCTION

Oseltamivir phosphate (Tamiflu) is an orally active anti-influenza drug, which is hydrolyzed by esterase to its carboxylate metabolite Ro 64-0802 with potent activity to inhibit the influenza virus. The abnormal behavior and death associated with the use of oseltamivir have developed into a major problem in Japan where Tamiflu is often prescribed for seasonal influenza. It is critical to determine the amount of oseltamivir and Ro 64-0802 in the human brain and to elucidate the relationship between their amounts and neuropsychiatric side effects. The aim of this study was to evaluate [(11)C]oseltamivir and [(11)C]Ro 64-0802 in mice as promising positron emission tomography (PET) ligands for measuring their amounts in living brains.

METHODS

Whole-body biodistribution of [(11)C]oseltamivir and [(11)C]Ro 64-0802 was determined in mice using the dissection method and micro-PET. In vitro and in vivo metabolite assay was performed in the plasma and brain of mice.

RESULTS

Between 1 and 60 min after injection of [(11)C]oseltamivir and [(11)C]Ro 64-0802, 0.20-0.06% and 0.39-0.03% ID/g were detected in the mouse brains, respectively (dissection method). Radioactivity concentrations in the living brains between 0 and 90 min after injection were measured at standardized uptake values of 0.25-0.05 for [(11)C]oseltamivir and 0.38-0.02 for [(11)C]Ro 64-0802 (micro-PET). In vivo metabolite assay demonstrated the presence of [(11)C]oseltamivir and [(11)C]Ro 64-0802 in the brains after [(11)C]oseltamivir injection.

CONCLUSION

This study determined the distribution and metabolism of [(11)C]oseltamivir and [(11)C]Ro 64-0802 in mice. PET could be used to measure their amounts in the living brain and to elucidate the relationship between the amounts in the brain and the side effects of Tamiflu in the central nervous system.

Anti-influenza drugs: the development of sialidase inhibitors

Viruses, particularly those that are harmful to humans, are the 'silent terrorists' of the twenty-first century. Well over four million humans die per annum as a result of viral infections alone. The scourge of influenza virus has plagued mankind throughout the ages. The fact that new viral strains emerge on a regular basis, particularly out of Asia, establishes a continual socio-economic threat to mankind. The arrival of the highly pathogenic avian influenza H5N1 heightened the threat of a potential human pandemic to the point where many countries have put in place 'preparedness plans' to defend against such an outcome. The discovery of the first designer influenza virus sialidase inhibitor and anti-influenza drug Relenza, and subsequently Tamiflu, has now inspired a number of continuing efforts towards the discovery of next generation anti-influenza drugs. Such drugs may act as 'first-line-of-defence' against the spread of influenza infection and buy time for necessary vaccine development particularly in a human pandemic setting. Furthermore, the fact that influenza virus can develop resistance to therapeutics makes these continuing efforts extremely important. An overview of the role of the virus-associated glycoprotein sialidase (neuraminidase) and some of the most recent developments towards the discovery of anti-influenza drugs based on the inhibition of influenza virus sialidase is provided in this chapter.

In vitro evaluation of the antiviral effects of the homeopathic preparation Gripp-Heel on selected respiratory viruses

Gripp-Heel is a homeopathic preparation frequently used in the treatment of respiratory viral infections such as various types of influenza and the common cold. The antiviral activity of Gripp-Heel was studied in vitro on human pathogenic enveloped and nonenveloped RNA and DNA viruses. Before the antiviral assays, in vitro cytotoxicity of Gripp-Heel was determined with cells used for the infection experiments (HeLa, HEp-2, MDCK, BGM) as well as with mitogen-stimulated peripheral blood mononuclear leukocytes. A concentration of 0.5 of the commercially available product slightly reduced cell viability and proliferative capacity, and experiments on antiviral activity were determined starting with a dilution of 0.2 of the commercially available product. The antiviral activity was determined against a broad panel of enveloped and nonenveloped DNA and RNA viruses with plaque reduction assay, cytopathogenic assays, virus titrations, analysis of the viral proteins in virus-specific enzyme immunoassays, and haemagglutination tests. Control substances were acyclovir (10 microg/mL), ribavirin (6 microg/mL), and amantadine hydrochloride (5 microg/mL), depending on the virus type. Gripp-Heel demonstrated dose-dependent in vitro activity (significant reductions of infectivity by 20% to 40%) against Human herpesvirus 1, Human adenovirus C serotype 5, Influenza A virus, Human respiratory syncytial virus, Human parainfluenza virus 3, Human rhinovirus B serotype 14, and Human coxsackievirus serotype A9. The mechanisms of this antiviral activity are still unclear, but type I interferon induction might be a possible explanation. Further research on this homeopathic preparation seems warranted.

Novel linear polymers bearing thiosialosides as pendant-type epitopes for influenza neuraminidase inhibitors

A conventional synthesis of alpha-thioglycoside of sialic acid as a glycomonomer was accomplished. Radical copolymerization of the glycomonomer with vinyl acetate proceeded smoothly to afford a new class of glycopolymers having thiosialoside residues, in which all protection was removed by a combination of transesterification and saponification to provide a water-soluble thiosialoside cluster. The results of a preliminary study on biological responses against influenza virus neuraminidases using the thiosialoside polymer as a candidate for a neuraminidase inhibitor showed that the glycopolymer has potent inhibitory activity against the neuraminidases.

Tracheobronchitis in the Intensive Care Unit

Tracheobronchitis can be broadly defined as inflammation of the airways between the larynx and the bronchioles. Clinically, this syndrome is recognized by an increase in the volume and purulence of the lower respiratory tract secretions and is frequently associated with signs of variable airflow obstruction. In the intensive care unit (ICU), tracheobronchitis is a relatively common problem with an incidence as high as 10.6% [1]. Although tracheobronchitis is associated with a significantly longer length of ICU stay and a prolonged need for mechanical ventilation, it has not been shown to increase mortality. These outcomes can be improved through the use of antimicrobial agents [1].

Lower clinical effectiveness of oseltamivir against influenza B contrasted with influenza A infection in children

BACKGROUND

Recently, many Japanese physicians have claimed that oseltamivir is less effective in children with influenza B virus infection. This study assesses the effectiveness of oseltamivir against influenza A (H3N2) and influenza B in children on the basis of the duration of febrile illness.

METHODS

We used oseltamivir to treat 127 children with influenza A (H3N2; mean age, 6.97 years [range, 1-15 years]) and 362 children with influenza B (mean age, 5.16 years [range, 1-15 years]) in outpatient clinics. The duration of fever after the start of oseltamivir therapy was compared in the influenza A group and the influenza B group.

RESULTS

The mean duration of fever after the start of oseltamivir therapy was significantly greater in the influenza B group than in the influenza A (H3N2) group (2.18 days vs. 1.31 days, respectively; P<.001). The difference was marked in young children (1-5 years old; 2.37 days for the influenza B group vs. 1.42 days for the influenza A group) but was not significant among older children (11-15 years old). The 50% inhibitory concentration of oseltamivir against influenza B virus was 75.4+/-41.7 nmol/L and was substantially higher than that for type A (H3N2) virus (0.3+/-0.1 nmol/L). Only 3 (1.6%) of 192 influenza B viruses were resistant to oseltamivir.

CONCLUSIONS

Oseltamivir is much less effective against influenza B virus infection in young children, probably because of the low sensitivity of influenza B viruses to oseltamivir. The effectiveness of oseltamivir against influenza B is influenced by age and host immunity. A few oseltamivir-resistant influenza B strains were isolated before the start of oseltamivir therapy.

Drugs, their targets and the nature and number of drug targets

What is a drug target? And how many such targets are there? Here, we consider the nature of drug targets, and by classifying known drug substances on the basis of the discussed principles we provide an estimation of the total number of current drug targets.

Thiosialoside clusters using carbosilane dendrimer core scaffolds as a new class of influenza neuraminidase inhibitors

An efficient synthesis of a series of carbosilane dendrimers uniformly functionalized with alpha-thioglycoside of sialic acid was accomplished. The results of a preliminary study on biological responses against influenza virus sialidases using thiosialoside clusters showed that some of the glycodendrimers have inhibitory potencies against the sialidases.

Efficacy and Tolerability of the Oral Neuraminidase Inhibitor Peramivir in Experimental Human Influenza: Randomized, Controlled Trials for Prophylaxis and Treatment

Objective

Oseltamivir is the only oral neuraminidase inhibitor currently available; we determined the tolerability and antiviral efficacy of oral peramivir for treatment and prophylaxis of experimental human influenza A and B.

Participants

288 susceptible, healthy volunteers (ages 18–45) were inoculated intranasally with A/Texas/36/ 91/H1N1 or B/Yamagata/16/88 virus in four randomized, double-blind, placebo-controlled trials. Interventions: For treatment dosing was initiated at 24 h after inoculation with peramivir doses ranging from 100–800 mg/day for 5 days. For prophylaxis dosing was initiated 24 h before inoculation and continued for 4 days with peramivir doses ranging from 50–800 mg/day.

Outcomes

The primary outcome measure for treatment was quantitative viral detection defined by the area under the curve (AUC) for nasal wash viral titres. For prophylaxis the primary outcome measure was the incidence of virus recovery.

Results

In influenza A treatment, peramivir 400 mg q24h and 200mg q12h, but not lower doses, resulted in significant reductions in viral titre AUC. In influenza B treatment, both 400 and 800/400 mg once daily dose groups reduced AUC values. In influenza A prophylaxis, the percentage of individuals with nasal viral shedding did not differ significantly in the placebo (58%), 50 mg (61%), 200 mg (37%) and 400 mg (31%) dose groups. In influenza B prophylaxis, shedding frequencies were similar in placebo (55%), 200 mg (41%), 400 mg (35%) and 800 mg (47%) dose groups. The drug was well tolerated in all four studies, with nausea and headache being the most common side effects. No drug-resistant variants were detected.

Conclusion

Early treatment with peramivir was associated with significant antiviral effects in experimentally induced influenza in humans. Prophylaxis did not significantly reduce viral shedding. The relatively low blood peramivir concentrations observed may explain the lack of more robust antiviral effects, and parenteral dosing should be studied.

Antiviral Activity of Engystol®: AnIn VitroAnalysis

OBJECTIVES

To study the effects of the homeopathic preparation Engystol (Biologische Heilmittel HEEL GmbH, Baden-Baden, Germany) on a panel [corrected] of human pathogenic viruses in vitro.

DESIGN

The effects of Engystol were studied using plaque-reduction assays and virus titration assays, and by quantification of newly synthesized viral proteins in virus-specific enzyme-linked immunoabsorbent assays (ELISAs).

SUBJECTS

The DNA viruses Adeno 5 and herpes simplex type 1 (HSV-1), the RNA virus respiratory syncytial virus (RSV), and human rhinovirus (HRV).

RESULTS

A 73% reduction of Adeno 5 specific proteins and an 80% reduction in HSV-1 specific proteins were observed in ELISAs of virus-infected cells treated with Engystol after infection. The effects appeared to be dose-dependent. With these viruses, similar results were observed in titration assays of viral offspring from cells treated with Engystol. Pretreatment of adenovirus with Engystol did not inhibit the infectivity of the virus suspension and no Engystol-induced stimulation of interferon-alpha could be observed. Plaque-reduction assays with the RNA viruses, RSV and HRV, showed reductions in infectivity by 37% (RSV) and 20% (HRV), respectively.

CONCLUSIONS

The results indicate antiviral activity of Engystol independent of the activation of the cellular interferon system.

[Anti-virals for influenza virus infection]

Dramatic advances in the diagnosis and treatment of influenza in Japan has been made in recent years. Rapid diagnosis tests for influenza are routinely performed in Japanese hospitals. Both zanamivir and oseltamivir have been approved for the treatment of influenza since 2001, in addition to amantadine. Japan has the highest figure of neuraminidase inhibitor-use in the world because the treatment of influenza with neuraminidase inhibitors is covered by Japan's National Health Insurance program. Therefore, we should carefully observe the appearance of resistance strains and side effects to neuraminidase inhibitors.

Production and characterization of a human recombinant monoclonal Fab fragment specific for influenza A viruses

A human recombinant monoclonal Fab fragment that specifically recognizes all the influenza A virus strains tested was produced in transformed Escherichia coli using the phage display technique. No strain of influenza B virus reacted with it. It was purified after four cycles of panning and by a single passage through an immunoaffinity column. About 1 mg of pure monoclonal antibody was obtained from 1 liter of culture medium in 3 working days. The Fab fragment reacted with a viral 27-kDa protein, which could reasonably be a matrix protein. Indirect immunofluorescence tests performed on virus-infected MDCK cells showed that this Fab fragment was at least equally efficient as other commercial monoclonal antibody-based systems in detecting influenza A viral infections. The potential advantages of human recombinant Fabs on murine monoclonal antibodies are discussed.

[Influenza]

Influenza (flu) is an acute contagious viral infection characterized by inflammation of the respiratory tract that every winter affects more than 100 million people in Europe, Japan and the United States of America, also being responsible for several thousand of excess deaths (data from the United States reveal between 20,000 to 40,000 excess deaths annually). The Mixovirus influenzae is the agent that causes influenza, commonly called flu. There are 3 types of influenza virus: A, B, C, and only types A and B are perceived to be clinically relevant in humans. Due to the segmented nature of its genetic material, the influenza virus is highly mutagenic, causing frequent insertion of new antigenic strains into the community, against which the population presents no immunity. Presently, there are few options for the control of influenza and annual immunization is the most effective means to prevent disease and its complications. In Brazil, according to data collected by the VigiGripe's Project - linked to the Federal University of Sao Paulo -, circulation of the influenza virus also has a seasonal pattern, with peak activity occurring between May and September. Yearly vaccination is, therefore, best indicated on March and April. Currently, there are four medications available for the treatment of influenza viruses: amantadine and rimantadine, and two second generation pharmaceutical products, the neuraminidase inhibitors, oseltamivir and zanamivir. The latter two drugs have set the stage for a new approach to the management and control of influenza infections.

Population analysis of the pharmacokinetics and pharmacodynamics of RWJ-270201 (BCX-1812) in treating experimental influenza A and B virus in healthy volunteers

OBJECTIVE

Our objective was to assess the pharmacokinetics and pharmacodynamics of RWJ-270201 (BCX-1812), an oral neuraminidase inhibitor for the treatment of influenza A and B virus in healthy volunteers.

METHODS

This was a double-blind, randomized, placebo-controlled, parallel group study. A total of 80 adult male and female subjects were enrolled for the influenza A challenge study. This was a 5-arm study (100 mg/qd, 200 mg/qd, 200 mg/bid, 400 mg/qd, and placebo). In the challenge B virus model, 60 subjects were enrolled for a 3-arm study (800 mg on Day 1 followed by 400 mg on Days 2-5; 800 mg on Days 1-5; and placebo). The pharmacokinetics of RWJ-270201 (BCX-1812) were characterized with the use of a population approach and were described by a 2-compartmental model with first-order absorption and elimination. The pharmacodynamic data, mean log viral titers, were described with the use of an empirical equation relating the viral growth and the effect of drug on changes in viral titers.

RESULTS

Pharmacokinetic analyses show that weight was the most significant covariate for all estimated pharmacokinetic parameters. The pharmacodynamic data, mean log viral titers showed a decrease in viral titers with increase in plasma exposure. The decrease in viral titer started to occur 12 hours following the drug dosing, and viral suppression lasted 72 hours to 96 hours. The exposures associated with a 50% decrease in viral titers were 1089 ng-h/mL and 1898 ng-h/mL, respectively.

CONCLUSIONS

A PK/PD model was well utilized to characterize the effect of RWJ-270201 (BCX-1812) on the influenza A and B virus. The results from this model showed that both the loading dose and the standard dose regimens are efficacious against A and B virus. RWJ-270201 (BCX-1812) is under clinical development for the treatment of influenza A and B infections in adult and high-risk populations. It is a potent and selective inhibitor of both influenza A and B virus neuraminidases and inhibits the viral cleavage of sialic acid from cell surface glycoproteins and glycolipids. Consequently, RWJ-270201 (BCX-1812) prevents infection by stopping the release of newly formed virus from the surface of infected cells and preventing viral spread across the mucous lining of the respiratory tract. It therefore represents an attractive agent for antiviral therapy.

RWJ-270201 (BCX-1812): a novel neuraminidase inhibitor for influenza

The influenza virus neuraminidase (NA) is important in the pathogenesis of infection and, thus, is an attractive target for agents used in the treatment and prophylaxis of influenza. This article describes preclinical and early clinical data related to RWJ-270201 (BCX-1812), a novel, orally active NA inhibitor that was rationally designed for having potent and selective activity against influenza A and B viruses. RWJ-270201 is a unique NA inhibitor with a cyclopentane ring structure and high selectivity for the influenza NA. RWJ-270201 has efficacy comparable to or better than earlier NA inhibitors against a wide range of influenza A and B isolates, including recently emerged and avian strains, both in vitro and in a lethal murine model of influenza. Based on the high selectivity and efficacy of RWJ-270201 against both type A and B influenza strains in preclinical studies as well as murine pharmacodynamic studies supporting the potential for once-daily administration, clinical trials were initiated in order to determine the tolerability and antiviral activity of RWJ-270201 in humans. To date, clinical studies have indicated that RWJ-270201 is well tolerated and has antiviral activity in human experimental influenza models when administered orally once daily.

Antiviral activity of an extract derived from roots of Eleutherococcus senticosus

A liquid extract from Eleutherococcus senticosus roots inhibited the productive replication of human rhinovirus (HRV), respiratory syncytial virus (RSV) and influenza A virus in cell cultures infected with these viruses, all of which belong to the RNA type viruses. Analysis of virus production after treatment of the infected cells using plaque-reduction assays showed a strong antiviral activity of the Eleutherococcus extract. In contrast, no effect was detected using the same protocol for cells infected with the DNA viruses, adenovirus (Adeno 5) or herpes simplex type 1 virus (HSV 1). Pre-treatment of cells did not inhibit either virus adsorption or virus replication. The results of the study demonstrate that the Eleutherococcus extract inhibited the replication of all RNA viruses studied so far. This antiviral activity remained stable under the conditions used for drug preparation and storage.

Oseltamivir: a review of its use in influenza

Oseltamivir is a prodrug of oseltamivir carboxylate (Ro 64-0802, GS4071), a potent and selective inhibitor of the neuraminidase glycoprotein essential for replication of influenza A and B viruses. Studies in volunteers with experimental human influenza A or B showed that administration of oral oseltamivir 20 to 200 mg twice daily for 5 days reduced both the quantity and duration of viral shedding compared with placebo. Subsequent assessment of the drug at a dosage of 75 mg twice daily for 5 days in otherwise healthy adults with naturally acquired febrile influenza showed that oseltamivir reduced the duration of the disease by up to 1.5 days and the severity of illness by up to 38% compared with placebo when initiated within 36 hours of symptom onset (earlier initiation of therapy was associated with faster resolution). The incidence of secondary complications and the use of antibacterials were also reduced significantly in oseltamivir recipients. A liquid formulation of oseltamivir (2 mg/kg twice daily for 5 days) has been shown to be effective in the treatment of children with influenza, and data presented in abstracts suggest that the drug may also be of use in high-risk populations such as the elderly or those with chronic cardiac or respiratory disease. In addition to treatment efficacy, the drug has demonstrated efficacy when used for seasonal or household prophylaxis. Oral oseltamivir (75 mg once or twice daily for 6 weeks) during a period of local influenza activity significantly prevented the development of naturally acquired influenza by >70% compared with placebo in unvaccinated otherwise healthy adults. The drug also demonstrated efficacy when used adjunctively in previously vaccinated high-risk elderly patients (92% protective efficacy). Short term administration of oseltamivir (75 mg once daily for 7 days) may significantly reduce the risk of illness in household contacts of infected persons when administered within 48 hours of symptom onset in the infected person. Oseltamivir 75 mg twice daily for 5 days was well tolerated in clinical trials in healthy adults and high-risk patients, with nausea and vomiting being the most commonly reported events. Gastrointestinal events were mild and transient and both nausea and vomiting were less likely when oseltamivir was taken with food.

CONCLUSIONS

Oseltamivir is a well tolerated orally active neuraminidase inhibitor which significantly reduces the duration of symptomatic illness and hastens the return to normal levels of activity when initiated promptly in patients with naturally acquired influenza. It therefore represents a useful therapeutic alternative to zanamivir (especially in patients who prefer oral administration or who have an underlying respiratory disorder) and the M2 inhibitors amantadine and rimantadine (because of its broader spectrum of anti-influenza activity and lower likelihood of resistance) in patients with influenza. In addition, although annual vaccination remains the best means of influenza prevention, there may be a place for oseltamivir in providing household prophylaxis or adjunctive prophylaxis in high-risk vaccinated patients during an outbreak of the disease or for use in patients in whom vaccination is unsuitable or ineffective.

Comparative binding energy (COMBINE) analysis of influenza neuraminidase-inhibitor complexes

Neuraminidase is a surface glycoprotein of influenza viruses that cleaves terminal sialic acids from carbohydrates. It is critical for viral release from infected cells and facilitates viral spread in the respiratory tract. The catalytic active site of neuraminidase is highly conserved in all type A and B influenza viruses, making it an excellent target for antiinfluenza drug design. Indeed, neuraminidase inhibitors have recently become available in the clinic for the treatment of influenza. Here, we describe the use of 3D structures of neuraminidase-inhibitor complexes to derive quantitative structure-activity relationships (QSARs) to aid understanding of the mechanism of inhibition and the discovery of new inhibitors. Crystal structures of neuraminidase-inhibitor complexes were used alongside modeled complexes to derive QSAR models by COMparative BINding Energy (COMBINE) analysis (Ortiz, A. R.; Pisabarro, M. T.; Gago, F.; Wade, R. C. J. Med. Chem. 1995, 38, 2681-2691). The neuraminidase proteins studied include type A subtypes N2 and N9 (which have ca. 50% sequence identity) and an active site mutant of the N9 subtype. The inhibitors include sialic acid and benzoic acid analogues with diverse frameworks and substitution groups. By considering the contributions of the protein residues and a key water molecule to the electrostatic and van der Waals intermolecular interaction energies, a predictive and robust QSAR model for binding to type A neuraminidase was obtained. In this QSAR model, 12 protein residues and 1 bound water molecule are highlighted as particularly important for inhibitory activity. This QSAR model provides guidelines for structural modification of current inhibitors and the design of novel inhibitors in order to optimize inhibitory activity.

Zanamivir and oseltamivir: two new options for the treatment and prevention of influenza

BACKGROUND

Influenza infection is responsible for thousands of hospitalizations and deaths in the United States each year. Until recently, management options were limited to vaccination or use of the antiviral agents amantadine and rimantadine. Two antiviral drugs, zanamivir and oseltamivir, have recently been approved by the US Food and Drug Administration for the treatment of influenza A and influenza B.

OBJECTIVE

This article reviews the published data on the pharmacology and clinical utility of zanamivir and oseltamivir in the treatment and prevention of influenza A and influenza B illness.

METHODS

To identify relevant literature, a search of MEDLINE, International Pharmaceutical Abstracts, and the Iowa Drug Information Service was conducted for the period from 1969 to 2000. The search terms used were influenza, neuraminidase, zanamivir, oseltamivir; amantadine, and rimantadine. The reference lists of the articles so obtained were used to identify additional publications.

RESULTS

Zanamivir and oseltamivir inactivate viral neuraminidase, an enzyme responsible for cleaving sialic acid residues on newly formed virions as they bud off from the host cell. This inhibition results in aggregation of virions on the surface of the host cell, which limits the extent of infection and speeds recovery from illness. Clinical studies have shown that neuraminidase inhibitors can decrease the median duration of influenza-related symptoms by approximately 1 day if initiated within 48 hours of the onset of symptoms of influenza.

CONCLUSIONS

Evidence supports the use of zanamivir and oseltamivir in the treatment of influenza; however, additional studies are needed to clarify their utility and tolerability in pediatric and high-risk patients, as well as their utility in the prevention of influenza.

Pandemic threat posed by avian influenza A viruses

Influenza pandemics, defined as global outbreaks of the disease due to viruses with new antigenic subtypes, have exacted high death tolls from human populations. The last two pandemics were caused by hybrid viruses, or reassortants, that harbored a combination of avian and human viral genes. Avian influenza viruses are therefore key contributors to the emergence of human influenza pandemics. In 1997, an H5N1 influenza virus was directly transmitted from birds in live poultry markets in Hong Kong to humans. Eighteen people were infected in this outbreak, six of whom died. This avian virus exhibited high virulence in both avian and mammalian species, causing systemic infection in both chickens and mice. Subsequently, another avian virus with the H9N2 subtype was directly transmitted from birds to humans in Hong Kong. Interestingly, the genes encoding the internal proteins of the H9N2 virus are genetically highly related to those of the H5N1 virus, suggesting a unique property of these gene products. The identification of avian viruses in humans underscores the potential of these and similar strains to produce devastating influenza outbreaks in major population centers. Although highly pathogenic avian influenza viruses had been identified before the 1997 outbreak in Hong Kong, their devastating effects had been confined to poultry. With the Hong Kong outbreak, it became clear that the virulence potential of these viruses extended to humans.

Planning for the next pandemic of influenza

Worldwide influenza pandemics have occurred at irregular and unpredictable intervals throughout history and it is confidently expected that they will continue to occur in the future. It is now recognised that these pandemics result when avian influenza A viruses succeed in adaptation to and transmission between humans. The impact of pandemic influenza is substantial in terms of morbidity, mortality and economic cost and there is the potential for serious social disruption. Influenza vaccines remain the most effective defence against influenza but will be in short supply during a pandemic, as will the new specific anti-influenza drugs, due to the lead-time required for production and rapid spread of the virus. To minimise the impact of pandemics it is imperative to maximise the availability of both vaccines and antivirals and to ensure that they are used optimally. This requires planning at both the international and national levels. The World Health Organization has, therefore, developed a staged plan for responding to a pandemic threat which is based principally on its surveillance program. It has also prepared guidelines to assist national agencies in their planning. However, there may be further options for increasing our preparedness which should also be considered.

Predicting influenza infections during epidemics with use of a clinical case definition

Combined pharyngeal and nasal swab specimens were collected from 100 subjects who presented with a flu-like illness (fever >37.8 degrees C plus 2 of 4 symptoms: cough, myalgia, sore throat, and headache) of <72 hours' duration at 3 different clinics in the province of Quebec, Canada, during the 1998-1999 flu season. The rate of laboratory-confirmed influenza infection was 72% according to cell culture findings and 79% according to the results of multiplex reverse-transcription polymerase chain reaction (RT-PCR) analysis (85%, influenza AH3; 15%, influenza B). All subjects for whom these results were discordant (negative culture and positive PCR) presented with a temperature > or =38.2 degrees C as well as 3 or 4 of the symptoms in the clinical case definition. Stepwise logistic regression showed that cough (odds ratio [OR], 6.7; 95% confidence interval [CI], 1.4-34.1; P=.02) and fever (OR, 3.1; 95% CI, 1.4-8.0; P=.01) were the only factors significantly associated with a positive PCR test for influenza. The positive predictive value, negative predictive value, sensitivity, and the specificity of a case definition including fever (temperature of >38 degrees C) and cough for the diagnosis of influenza infection during this flu season were 86.8%, 39.3%, 77.6%, and 55.0%, respectively.

Catalytic Asymmetric Hetero-Diels-Alder Reactions of Carbonyl Compounds and Imines

Asymmetric catalysis is a challenge for chemists: How can we design catalysts to achieve the goal of forming optically active compounds? This review provides the reader with an overview of the development of catalytic asymmetric hetero-Diels-Alder reactions of carbonyl compounds and imines. Since its discovery, the Diels-Alder reaction has undergone intensive development and is of fundamental importance for synthetic, physical, and theoretical chemists. The Diels-Alder reaction has been through different stages of development, and at the beginning of the 21st century catalytic Diels-Alder reactions are one of the main areas of focus. The preparation of numerous compounds of importance for our society is based on cycloaddition reactions to carbonyl compounds and imines. There are several parallels between the reactions of carbonyl compounds and those of imines, which, however, begin to vanish on entering the field of catalytic reactions. Why? From a mechanistic point of view some similarities can be drawn, but the synthetic development of catalytic enantioselective hetero-Diels-Alder reactions of imines are several years behind those of the carbonyl compounds. For hetero-Diels-Alder reactions of carbonyl compounds there a number of different chiral catalysts, and great progress has been achieved in developing enantioselective reactions for unactivated and activated carbonyl compounds. In contrast the development of catalytic enantioselective hetero-Diels-Alder reactions of imines is in its infancy and only few catalytic reactions have been published. This review will focus on the most important developments, and discuss the synthetic and mechanistic aspects of enantioselective hetero-Diels-Alder reactions of carbonyl compounds catalyzed by chiral Lewis acids. For the hetero-Diels-Alder reactions of imines, the diastereoselective reactions of optically substrates catalyzed by Lewis acids will be presented first, followed by the catalytic enantioselective reactions.

Evaluation of BioStar FLU OIA assay for rapid detection of influenza A and B viruses in respiratory specimens

BACKGROUND

Demand for the rapid diagnosis of influenza infections has increased with the advent of the availability of neuraminidase antiviral therapy for influenza A and B. Several rapid assays that detect both influenza A and B are now available.

OBJECTIVES

In this study we compared the performance of the BioStar FLU OIA assay to Bartels Viral Respiratory Screening and Identification Kit (Bartels Inc., Issaquah, WA), and cell culture.

STUDY DESIGN

A total of 145 patient specimens for influenza virus detection submitted in either viral transport medium or in sterile containers were evaluated by the three methods. Specimen types included nasal washings, nasal swabs, sputum, throat swabs, and bronchial alveolar lavage (BAL) fluids.

RESULTS

Fifty six positive specimens were identified based on culture and/or DFA. Of these, 30 specimens were positive by the OIA assay for an overall sensitivity of 54%. The OIA assay detected 48% (n = 21) of the 44 culture positive specimens and 81% (n = 29) of the 36 DFA positive specimens. Eighty six of the 89 culture/DFA negative samples were negative by the OIA assay (97% specificity). Analysis of the OIA assay sensitivity from samples submitted in M4 transport medium or in sterile containers revealed that M4 transport medium does not reduce the sensitivity of the OIA assay. Fifteen of the 27 positive samples submitted in M4 transport medium were positive by the OIA assay (56% sensitivity) compared to 15 of 29 positive samples transported in sterile containers (52% sensitivity). Twelve specimens were either culture and/or DFA positive for viruses other than influenza, but negative by the OIA assay, suggesting that there was no cross reactivity of the OIA assay with the other virus types recovered in this study.

CONCLUSIONS

The overall excellent specificity of the BioStar FLU OIA allows for treatment of positive patients for influenza, however, a negative result should be confirmed by DFA and culture.

Direct measurement of the anti-influenza agent zanamivir in the respiratory tract following inhalation

In a single-center, randomized study, zanamivir (Relenza) concentrations in induced sputum samples and nasal washings of healthy adults following oral inhalation were measured. Concentrations in sputum exceeded the median viral neuraminidase 50% inhibitory concentration at 6, 12, and 24 h, and those in nasal washings did so at 6 and 12 h. There were no zanamivir-related adverse events or laboratory abnormalities.

Influenza vaccine, anti-influenza drugs, and rapid diagnosis in Japan

The percentage of individuals receiving influenza vaccine is markedly lower in Japan than in many other economically advanced countries. To increase the rate of coverage, the current practice of giving people two inoculations instead of one needs to be changed. In addition, free vaccination services for the elderly and high-risk patients need to be offered. Amantadine is available for the treatment of influenza type A infection in Japan. Moreover, zanamivir, a neuraminidase inhibitor effective against both influenza type A and B viruses, has been approved in Japan. A rapid diagnosis kit for influenza type A virus is available in Japan. With the current threat of new pandemic influenza viruses emerging, it is necessary to actively confront influenza in Japan by increasing the vaccine coverage rate, by employing amantadine and neuraminidase inhibitors for influenza virus infection, and by providing rapid diagnosis of influenza.

Inhibition of neuraminidase with neuraminic acid C-glycosides

Neuraminic (sialic) acid based alpha-C-glycosides have been synthesized and their inhibitory activity towards bacterial neuraminidase (sialidase) was examined. While some C-glycosides were found to be potent inhibitors (Ki 15-30 microM) of this neuraminidase, others afforded no measurable activity. The structure-activity relationship of these C-glycosides is discussed in the context of other previously reported sialidase inhibitors.

Influenza virus genetics

Significant progress has been made in understanding the process of influenza A virus replication in cell culture; however, much less is known about the genetic control of virus-host interactions in disease. This review provides an overview of the genetic analysis of influenza virus biology. The functional map of the individual genes of influenza A virus is presented as well as the status of our current understanding of pathogenesis. Influenza has a segmented genome so it is possible to obtain reassortants that contain novel combinations of genome segments derived from different viruses. This is a very useful genetic tool and is also an important aspect of influenza evolution and biology. Human influenza viruses originate from avian strains of influenza virus so that influenza infection is at its basis a zoonosis. Influenza virus strains are host-restricted, however, and avian strains must be adapted to the human host. So questions of host-range and interaction with host factors are important determinants of the ability of influenza virus to cause disease in humans. Host-range is restricted primarily due to host-specific interactions of the ribonucleocapsid and the viral receptor. There are two classes of drugs for inhibiting influenza infection, amantadine HCl and neuraminidase inhibitors. The mode of action and basis for resistance to these drugs are presented. Prospective targets for antiviral therapy are also discussed.