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

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

Filling two needs with one deed: a combinatory mucosal vaccine against influenza A virus and respiratory syncytial virus

Influenza A Virus (IAV) and Respiratory Syncytial Virus (RSV) are both responsible for millions of severe respiratory tract infections every year worldwide. Effective vaccines able to prevent transmission and severe disease, are important measures to reduce the burden for the global health system. Despite the strong systemic immune responses induced upon current parental immunizations, this vaccination strategy fails to promote a robust mucosal immune response. Here, we investigated the immunogenicity and efficacy of a mucosal adenoviral vector vaccine to tackle both pathogens simultaneously at their entry site. For this purpose, BALB/c mice were immunized intranasally with adenoviral vectors (Ad) encoding the influenza-derived proteins, hemagglutinin (HA) and nucleoprotein (NP), in combination with an Ad encoding for the RSV fusion (F) protein. The mucosal combinatory vaccine induced neutralizing antibodies as well as local IgA responses against both viruses. Moreover, the vaccine elicited pulmonary CD8+ and CD4+ tissue resident memory T cells (TRM) against the immunodominant epitopes of RSV-F and IAV-NP. Furthermore, the addition of Ad-TGFβ or Ad-CCL17 as mucosal adjuvant enhanced the formation of functional CD8+ TRM responses against the conserved IAV-NP. Consequently, the combinatory vaccine not only provided protection against subsequent infections with RSV, but also against heterosubtypic challenges with pH1N1 or H3N2 strains. In conclusion, we present here a potent combinatory vaccine for mucosal applications, which provides protection against two of the most relevant respiratory viruses

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

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

Influenza Virus Ribonucleoprotein Complexes Gain Preferential Access to Cellular Export Machinery through Chromatin Targeting

In contrast to most RNA viruses, influenza viruses replicate their genome in the nucleus of infected cells. As a result, newly-synthesized vRNA genomes, in the form of viral ribonucleoprotein complexes (vRNPs), must be exported to the cytoplasm for productive infection. To characterize the composition of vRNP export complexes and their interplay with the nucleus of infected cells, we affinity-purified tagged vRNPs from biochemically fractionated infected nuclei. After treatment of infected cells with leptomycin B, a potent inhibitor of Crm1-mediated export, we isolated vRNP export complexes which, unexpectedly, were tethered to the host-cell chromatin with very high affinity. At late time points of infection, the cellular export receptor Crm1 also accumulated at the same regions of the chromatin as vRNPs, which led to a decrease in the export of other nuclear Crm1 substrates from the nucleus. Interestingly, chromatin targeting of vRNP export complexes brought them into association with Rcc1, the Ran guanine exchange factor responsible for generating RanGTP and driving Crm1-dependent nuclear export. Thus, influenza viruses gain preferential access to newly-generated host cell export machinery by targeting vRNP export complexes at the sites of Ran regeneration

Experimental Meningococcal Sepsis in Congenic Transgenic Mice Expressing Human Transferrin

Severe meningococcal sepsis is still of high morbidity and mortality. Its management may be improved by an experimental model allowing better understanding of its pathophysiology. We developed an animal model of meningococcal sepsis in transgenic BALB/c mice expressing human transferrin. We studied experimental meningococcal sepsis in congenic transgenic BALB/c mice expressing human transferrin by transcriptional profiling using microarray analysis of blood and brain samples. Genes encoding acute phase proteins, chemokines and cytokines constituted the largest strongly regulated groups. Dynamic bioluminescence imaging further showed high blood bacterial loads that were further enhanced after a primary viral infection by influenza A virus. Moreover, IL-1 receptor–associated kinase–3 (IRAK-3) was induced in infected mice. IRAK-3 is a negative regulator of Toll-dependant signaling and its induction may impair innate immunity and hence result in an immunocompromised state allowing bacterial survival and systemic spread during sepsis. This new approach should enable detailed analysis of the pathophysiology of meningococcal sepsis and its relationships with flu infection

Vers une prévention généralisée des infections par le virus respiratoire syncytial (VRS) de l'enfant et du sujet âgé

International audienceRespiratory syncytial virus (RSV) is the most common cause of bronchiolitis in young children. It is the leading cause of severe lower respiratory tract infections in children worldwide. Since its discovery in the 1960s, many teams have tried to develop preventive treatments for RSV infection. Until recent years, however, vaccine trials have been unsuccessful. Prevention of severe infection has relied on a monoclonal antibody, which has been reserved for high-risk infants because of its poor cost-effectiveness. The RSV surface F protein is the target of most vaccine or monoclonal antibodies. In 2013, researchers obtained the structure of F in its conformation on the viral surface. By targeting this particular conformation of F, several teams have developed effective vaccines and monoclonal antibodies to prevent severe RSV infections. In 2022, a monoclonal antibody with a long half-life, nirsevimab, was approved for the prevention of severe infections in infants. In 2023, 2 vaccines will be licensed for the prevention of severe infection in the elderly, one of them in neonates. This means that 2 passive immunisation strategies are now available to prevent severe RSV infection in infants: a single injection of a monoclonal antibody before the first exposure to RSV, or maternal vaccination at the end of pregnancy, allowing transplacental transfer of antibodies. Questions remain about the strategy to be adopted in different countries, the place of prevention of infection in children after one year of age, or the evolution of RSV in the face of this new selection pressure.Le virus respiratoire syncytial (VRS) est le principal agent de la bronchiolite du nourrisson. Depuis sa découverte dans les années 1960, de nombreuses équipes ont cherché à développer des traitements préventifs de l’infection VRS. Jusqu’à récemment, les essais de vaccination sont toutefois restés infructueux. La prévention des infections sévères reposait sur un anticorps monoclonal réservé aux nourrissons à haut risque du fait d’un ratio coût/efficacité médiocre. La majorité des vaccins ou des anticorps monoclonaux ciblent la protéine de surface F du VRS. En 2013, des chercheurs ont obtenu la structure de la F dans la conformation qu’elle adopte à la surface des virions. En ciblant cette conformation particulière de F, différentes équipes ont développé des vaccins et des anticorps monoclonaux efficaces. Ainsi en 2022, un anticorps monoclonal à longue demi-vie, le nirsevimab, a été approuvé pour la prévention des infections sévères chez le nourrisson. En 2023, 2 vaccins ont été approuvés pour la prévention des infections sévères chez le sujet âgé et chez le nouveau-né pour l’un des 2. Ainsi 2 stratégies d’immunisation passive sont désormais disponibles pour la prévention des infections sévères du nourrisson par le VRS : injection unique d’un anticorps monoclonal avant la première exposition au VRS ou vaccination maternelle en fin de grossesse permettant un transfert transplacentaire des anticorps. Des questions demeurent quant à la stratégie qui sera appliquée dans les différents pays, la place d’une prévention des infections chez l’enfant après un an ou l’évolution du VRS face à cette nouvelle pression de sélection