Anti-influenza chemotherapies

The recent outbreaks of avian influenza A (H5N1) virus have called attention to the need for antiviral treatments to use in the event of pandemic influenza. The goal of antiviral treatments is also to reduce symptoms and complications associated with seasonal epidemics. Two classes of antiviral drugs, M2 proton channel inhibitors (amantadine, rimantadine) and neuraminidase inhibitors (zanamivir, oseltamivir), are effective for the chemoprophylaxis and treatment of influenza. Antiviral resistance is especially frequent with treatment with M2 inhibitors, and limits their clinical use. Resistance to oseltamivir during treatment has been described recently in several Vietnamese patients infected with H5N1. A close monitoring of antiviral resistance is needed, as is further research into the development of new agents, potentially targeting other viral proteins such as hemagglutinin or polymerase, and which could be used in combination chemotherapies.L'actuelle épizootie de grippe A (H5N1) souligne la nécessité de traitements antiviraux pour faire face à une éventuelle pandémie grippale. Les traitements anti-influenza ont aussi pour objectif de réduire les symptômes et complications survenant lors des épidémies saisonnières. Deux classes d'antiviraux, les inhibiteurs du canal à protons M2 (amantadine, rimantadine), et les inhibiteurs de neuraminidase (zanamivir, oseltamivir), ont une efficacité prophylactique et thérapeutique. L'émergence de virus résistants est particulièrement fréquente lors du traitement avec les inhibiteurs de M2, et limite leur utilisation. Le développement d'une résistance à l'oseltamivir a été décrit chez plusieurs patients infectés avec le virus H5N1. Une surveillance étroite de la résistance aux anti-viraux s'impose, ainsi que le développement de nouveaux composés, pouvant cibler éventuellement d'autres protéines virales telles que l'hémagglutinine ou la polymérase, et pouvant être utilisés en polychimiothérapies

Novel sialic acid derivatives lock open the 150-loop of an influenza A virus group-1 sialidase

This work was supported by the Medical Research Council and the Scottish Funding Council.Influenza virus sialidase has an essential role in the virus’ life cycle. Two distinct groups of influenza A virus sialidases have been established, that differ in the flexibility of the ‘150-loop’, providing a more open active site in the apo form of the group-1 compared to group-2 enzymes. In this study we show, through a multidisciplinary approach, that novel sialic acid-based derivatives can exploit this structural difference and selectively inhibit the activity of group-1 sialidases. We also demonstrate that group-1 sialidases from drug-resistant mutant influenza viruses are sensitive to these designed compounds. Moreover, we have determined, by protein X-ray crystallography, that these inhibitors lock open the group-1 sialidase flexible 150-loop, in agreement with our molecular modelling prediction. This is the first direct proof that compounds may be developed to selectively target the pandemic A/H1N1, avian A/H5N1 and other group-1 sialidase-containing viruses, based on an open 150-loop conformation of the enzyme.Publisher PDFPeer reviewe

Enhancement of the influenza A hemagglutinin (HA)-mediated cell-cell fusion and virus entry by the viral neuraminidase (NA).

International audienceBACKGROUND: The major role of the neuraminidase (NA) protein of influenza A virus is related to its sialidase activity, which disrupts the interaction between the envelope hemagglutinin (HA) protein and the sialic acid receptors expressed at the surface of infected cells. This enzymatic activity is known to promote the release and spread of progeny viral particles following their production by infected cells, but a potential role of NA in earlier steps of the viral life cycle has never been clearly demonstrated. In this study we have examined the impact of NA expression on influenza HA-mediated viral membrane fusion and virion infectivity. METHODOLOGY/PRINCIPAL FINDINGS: The role of NA in the early stages of influenza virus replication was examined using a cell-cell fusion assay that mimics HA-mediated membrane fusion, and a virion infectivity assay using HIV-based pseudoparticles expressing influenza HA and/or NA proteins. In the cell-cell fusion assay, which bypasses the endocytocytosis step that is characteristic of influenza virus entry, we found that in proper HA maturation conditions, NA clearly enhanced fusion in a dose-dependent manner. Similarly, expression of NA at the surface of pseudoparticles significantly enhanced virion infectivity. Further experiments using exogenous soluble NA revealed that the most likely mechanism for enhancement of fusion and infectivity by NA was related to desialylation of virion-expressed HA. CONCLUSION/SIGNIFICANCE: The NA protein of influenza A virus is not only required for virion release and spread but also plays a critical role in virion infectivity and HA-mediated membrane fusion

Oseltamivir-Resistant Influenza Viruses A (H1N1), Norway, 2007–08

Resistance was not associated with oseltamivir use or more severe disease

Modular cell-based platform for high throughput identification of compounds that inhibit a viral interferon antagonist of choice

The work was supported by the Medical Research Council, U.K. (University of St Andrews Doctoral Training Grant to AV and CSA), Deutsche Forschungsgemeinschaft (PA 815/2-1) to CP, Tenovus Scotland (T15/38) to MN and Wellcome Trust to CP, MN (ISSF) and RER (101788/Z/13/Z)Viral interferon (IFN) antagonists are a diverse class of viral proteins that counteract the host IFN response, which is important for controlling viral infections. Viral IFN antagonists are often multifunctional proteins that perform vital roles in virus replication beyond IFN antagonism. The critical importance of viral IFN antagonists is highlighted by the fact that almost all viruses encode one of these proteins. Inhibition of viral IFN antagonists has the potential to exert pleiotropic antiviral effects and thus this important protein class represents a diverse plethora of novel therapeutic targets. To exploit this, we have successfully developed and executed a novel modular cell-based platform that facilitates the safe and rapid screening for inhibitors of a viral IFN antagonist of choice. The platform is based on two reporter cell-lines that provide a simple method to detect activation of IFN induction or signaling via an eGFP gene placed under the control of the IFNβ or an ISRE-containing promoter, respectively. Expression of a target IFN antagonist in the appropriate reporter cell-line will block the IFN response and hence eGFP expression. We hypothesized that addition of a compound that inhibits IFN antagonist function will release the block imposed on the IFN response and hence restore eGFP expression, providing a measurable parameter for high throughput screening (HTS). We demonstrate assay proof-of-concept by (i) exploiting hepatitis C virus (HCV) protease inhibitors to inhibit NS3-4A's capacity to block IFN induction and (ii) successfully executing two HTS targeting viral IFN antagonists that block IFN signaling; NS2 and IE1 from human respiratory syncytial virus (RSV) and cytomegalovirus (CMV) respectively, two clinically important viruses for which vaccine development has thus far been unsuccessful and new antivirals are required. Both screens performed robustly and Z′ Factor scores of >0.6 were achieved. We identified (i) four hit compounds that specifically inhibit RSV NS2's ability to block IFN signaling by mediating STAT2 degradation and exhibit modest antiviral activity and (ii) two hit compounds that interfere with IE1 transcription and significantly impair CMV replication. Overall, we demonstrate assay proof-of-concept as we target viral IFN antagonists from unrelated viruses and demonstrate its suitability for HTS.Publisher PDFPeer reviewe

Disseminated gonococcal infection in a Japanese man with complement 7 deficiency with compound heterozygous variants A case report

Rationale: Complement deficiency are known to be predisposed to disseminated gonococcal infection (DGI). We herein present a case of DGI involving a Japanese man who latently had a complement 7 deficiency with compound heterozygous variants. Patient concerns: A previously healthy 51-year-old Japanese man complained of sudden-onset high fever. Physical examination revealed various skin lesions including red papules on his trunk and extremities, an impetigo-like pustule on left forearm, and tendinitis of his right forefinger. Diagnosis: Blood culture testing detected gram-negative cocci, which was confirmed to be Neisseria gonorrhoeae based on mass spectrometry and a pathogen-specific PCR test. Interventions: Screening tests for underlying immunocompromised factors uncovered that complement activities (CH50) was undetectable. With a suspicion of a congenital complement deficiency, genetic analysis revealed rare single nucleotide variants in complement 7 (C7), including c.281-1G>T and a novel variant c.1454C>T (p.A485V). CH50 was normally recovered by adding purified human C7 to the patient's serum, supporting that the patient has C7 deficiency with compound heterozygous variants. Outcomes: Under a diagnosis of DGI, the patient underwent an antibiotic treatment with cefotaxime for a week and was discharged without any sequela. Lessons: DGI is a rare sexually-transmitted infection that potentially induces systemic complications. Complement immunity usually defeats N. gonorrhoeae and prevents the organism from causing DGI. This case highlighted the importance of suspecting a complement deficiency when a person develops DGI

Five years of monitoring for the emergence of oseltamivir resistance in patients with influenza A infections in the Influenza Resistance Information Study (IRIS)

Background and Objectives: The Influenza Resistance Information Study (IRIS) was initiated in 2008 to study the emergence of neuraminidase inhibitor (NAI) resistance and the clinical course of influenza in immunocompetent treated and untreated patients. Methods: Patients had throat/nose swabs collected on Days 1, 3, 6 and 10 for analyses of influenza type, subtype and virus susceptibility to NAIs. RT-PCR Positive samples were cultured, and tested for NAI resistance by specific RT-PCR and phenotypic testing. Scores for influenza symptoms were recorded on diary cards (Days 1–10). This study focuses on Influenza A infected cases only. Results: Among 3230 RT-PCR-positive patients, 2316 had influenza A of whom 1216 received oseltamivir monotherapy within 2 days of symptom onset (9 seasonal H1N1; 662 H3N2; 545 H1N1pdm2009). Except for 9 patients with naturally resistant seasonal H1N1 (2008/9), no resistance was detected in Day 1 samples. Emergence of resistance (post-Day 1) was detected in 43/1207 (3.56%) oseltamivir-treated influenza A infected patients, with a higher frequency in 1 to 5-year-old (11.8%) versus >5-year-old (1.4%). All N1 and N2 resistant viruses had H275Y (n=27) or R292K (n=16) substitutions, respectively. For 43 patients, virus clearance was significantly delayed versus treated patients with susceptible viruses (8.1 vs 10.9 days; p<0.0001), and 11 (23.2%) remained RT-PCR positive for influenza at Day 10. However their symptoms resolved by Day 6 or earlier. Conclusions: Oseltamivir resistance was only detected during antiviral treatment, with the highest incidence occurring among 1–5-year-olds. Resistance delayed viral clearance, but had no impact on symptom resolution

Mutations in components of complement influence the outcome of Factor I-associated atypical hemolytic uremic syndrome

Genetic studies have shown that mutations of complement inhibitors such as membrane cofactor protein, Factors H, I, or B and C3 predispose patients to atypical hemolytic uremic syndrome (aHUS). Factor I is a circulating serine protease that inhibits complement by degrading C3b and up to now only a few mutations in the CFI gene have been characterized. In a large cohort of 202 patients with aHUS, we identified 23 patients carrying exonic mutations in CFI. Their overall clinical outcome was unfavorable, as half died or developed end-stage renal disease after their first syndrome episode. Eight patients with CFI mutations carried at least one additional known genetic risk factor for aHUS, such as a mutation in MCP, CFH, C3 or CFB; a compound heterozygous second mutation in CFI; or mutations in both the MCP and CFH genes. Five patients exhibited homozygous deletion of the Factor H-related protein 1 (CFHR-1) gene. Ten patients with aHUS had one mutation in their CFI gene (Factor I-aHUS), resulting in a quantitative or functional Factor I deficiency. Patients with a complete deletion of the CFHR-1 gene had a significantly higher risk of a bad prognosis compared with those with one Factor I mutation as their unique vulnerability feature. Our results emphasize the necessity of genetic screening for all susceptibility factors in patients with aHUS