Generation of a high yield vaccine backbone for influenza B virus in embryonated chicken eggs.

Influenza B virus (IBV) strains are one of the components of seasonal influenza vaccines in both trivalent and quadrivalent formulations. The vast majority of these vaccines are produced in embryonated chickens' eggs. While optimized backbones for vaccine production in eggs exist and are in use for influenza A viruses, no such backbones exist for IBVs, resulting in unpredictable production yields.

Coronavirus as the Possible Causative Agent of the 1889-1894 Pandemic.

Using new and original nineteenth-century sources, we analysed the epidemiology, clinical features and virology of the 1889 pandemic, which was referred to at the time as 'Russian flu' or 'Asiatic flu'. However, we rejected this identification of the disease as an 'influenza', which we believe to have been based on insufficient knowledge of the causative agent and instead posit that the pandemic was caused by a coronavirus. We provide a new account of the 1889-1893 pandemic, with a more detailed chronology that included at least four epidemiological waves.

Pre-existing Hemagglutinin Stalk Antibodies Correlate with Protection of Lower Respiratory Symptoms in Flu-Infected Transplant Patients.

Hemagglutination-inhibitory antibodies are usually highly strain specific with little effect on infection with drifted or shifted strains. The significance of broadly cross-reactive non-HAI anti-influenza antibodies against conserved domains of virus glycoproteins, such as the hemagglutinin (HA) stalk, is of great interest. We characterize a cohort of 40 H1N1pmd09 influenza-infected patients and identify lower respiratory symptoms (LRSs) as a predictor for development of pneumonia.

Activity of human serum antibodies in an influenza virus hemagglutinin stalk-based ADCC reporter assay correlates with activity in a CD107a degranulation assay.

The stalk of the influenza virus hemagglutinin (HA) is an attractive target for antibody-based universal influenza virus vaccine development. While antibodies that target this part of the virus can be neutralizing, it has been shown in recent years that Fc receptor-mediated effector functions are of significant importance for the protective effect of anti-stalk antibodies. Several assays to measure Fc-Fc receptor interaction-based effector functions like antibody-dependent cellular cytotoxicity and antibody-dependent cellular phagocytosis exist, but they suffer from limitations such as low throughput and high run-to-run variability.

Viral Fitness Landscapes in Diverse Host Species Reveal Multiple Evolutionary Lines for the NS1 Gene of Influenza A Viruses.

Influenza A viruses (IAVs) have a remarkable tropism in their ability to circulate in both mammalian and avian species. The IAV NS1 protein is a multifunctional virulence factor that inhibits the type I interferon host response through a myriad of mechanisms. How NS1 has evolved to enable this remarkable property across species and its specific impact in the overall replication, pathogenicity, and host preference remain unknown.

Broadly Cross-Reactive, Nonneutralizing Antibodies against Influenza B Virus Hemagglutinin Demonstrate Effector Function-Dependent Protection against Lethal Viral Challenge in Mice.

Protection from influenza virus infection is canonically associated with antibodies that neutralize the virus by blocking the interaction between the viral hemagglutinin and host cell receptors. However, protection can also be conferred by other mechanisms, including antibody-mediated effector functions. Here, we report the characterization of 22 broadly cross-reactive, nonneutralizing antibodies specific for influenza B virus hemagglutinin.

Influenza B virus reverse genetic backbones with improved growth properties in the EB66® cell line as basis for vaccine seed virus generation.

Vaccination remains the best available prophylaxis to prevent influenza virus infections, yet current inadequacies in influenza virus vaccine manufacturing often lead to vaccine shortages at times when the vaccine is most needed, as it was the case during the last influenza virus pandemic. Novel influenza virus vaccine production systems will be crucial to improve public health and safety. Here we report the optimization of influenza B virus growth in the proprietary EB66® cell line, currently in use for human vaccine production.

Specific Mutations in the PB2 Protein of Influenza A Virus Compensate for the Lack of Efficient Interferon Antagonism of the NS1 Protein of Bat Influenza A-Like Viruses.

Recently, two new influenza A-like viruses have been discovered in bats, A/little yellow-shouldered bat/Guatemala/060/2010 (HL17NL10) and A/flat-faced bat/Peru/033/2010 (HL18NL11). The hemagglutinin (HA)-like (HL) and neuraminidase (NA)-like (NL) proteins of these viruses lack hemagglutination and neuraminidase activities, despite their sequence and structural homologies with the HA and NA proteins of conventional influenza A viruses. We have now investigated whether the NS1 proteins of the HL17NL10 and HL18NL11 viruses can functionally replace the NS1 protein of a conventional influenza A virus.

Novel Bat Influenza Virus NS1 Proteins Bind Double-Stranded RNA and Antagonize Host Innate Immunity.

We demonstrate that novel bat HL17NL10 and HL18NL11 influenza virus NS1 proteins are effective interferon antagonists but do not block general host gene expression. Solving the RNA-binding domain structures revealed the canonical NS1 symmetrical homodimer, and RNA binding required conserved basic residues in this domain. Interferon antagonism was strictly dependent on RNA binding, and chimeric bat influenza viruses expressing NS1s defective in this activity were highly attenuated in interferon-competent cells but not in cells unable to establish antiviral immunity.

Enhancement of the proapoptotic properties of newcastle disease virus promotes tumor remission in syngeneic murine cancer models.

Newcastle disease virus (NDV) is considered a promising agent for cancer therapy due to its oncolytic properties. These include preferential replication in transformed cells, induction of innate and adaptive immune responses within tumors, and cytopathic effects in infected tumor cells due to the activation of apoptosis. To enhance the latter and thus possibly enhance the overall oncolytic activity of NDV, we generated a recombinant NDV encoding the human TNF receptor Fas (rNDV-B1/Fas).

The interferon signaling antagonist function of yellow fever virus NS5 protein is activated by type I interferon.

To successfully establish infection, flaviviruses have to overcome the antiviral state induced by type I interferon (IFN-I). The nonstructural NS5 proteins of several flaviviruses antagonize IFN-I signaling. Here we show that yellow fever virus (YFV) inhibits IFN-I signaling through a unique mechanism that involves binding of YFV NS5 to the IFN-activated transcription factor STAT2 only in cells that have been stimulated with IFN-I.

A single amino acid substitution in the novel H7N9 influenza A virus NS1 protein increases CPSF30 binding and virulence.

Although an effective interferon antagonist in human and avian cells, the novel H7N9 influenza virus NS1 protein is defective at inhibiting CPSF30. An I106M substitution in H7N9 NS1 can restore CPSF30 binding together with the ability to block host gene expression. Furthermore, a recombinant virus expressing H7N9 NS1-I106M replicates to higher titers in vivo, and is subtly more virulent, than the parental virus.

The NS1 protein: a multitasking virulence factor.

The non-structural protein 1 of influenza virus (NS1) is a relatively small polypeptide with an outstanding number of ascribed functions. NS1 is the main viral antagonist of the innate immune response during influenza virus infection, chiefly by inhibiting the type I interferon system at multiple steps. As such, its role is critical to overcome the first barrier the host presents to halt the viral infection.

HIV-1 interacts with human endogenous retrovirus K (HML-2) envelopes derived from human primary lymphocytes.

Unlabelled: Human endogenous retroviruses (HERVs) are viruses that have colonized the germ line and spread through vertical passage. Only the more recently acquired HERVs, such as the HERV-K (HML-2) group, maintain coding open reading frames. Expression of HERV-Ks has been linked to different pathological conditions, including HIV infection, but our knowledge on which specific HERV-Ks are expressed in primary lymphocytes currently is very limited.

Rescue of recombinant Newcastle disease virus from cDNA.

Newcastle disease virus (NDV), the prototype member of the Avulavirus genus of the family Paramyxoviridae(1), is a non-segmented, negative-sense, single-stranded, enveloped RNA virus (Figure 1) with potential applications as a vector for vaccination and treatment of human diseases. In-depth exploration of these applications has only become possible after the establishment of reverse genetics techniques to rescue recombinant viruses from plasmids encoding their complete genomes as cDNA(2-5). Viral cDNA can be conveniently modified in vitro by using standard cloning procedures to alter the genotype of the virus and/or to include new transcriptional units.

New-generation screening assays for the detection of anti-influenza compounds targeting viral and host functions.

Current options for influenza antiviral therapy are limited to the neuraminidase inhibitors, and knowledge that high levels of oseltamivir resistance have been seen among previously circulating H1N1 viruses increases the urgency to find new influenza therapeutics. To feed this pipeline, assays that are appropriate for use in high-throughput screens are being developed and are discussed in this review. Particular emphasis is placed on cell-based assays that capture both inhibitors of viral functions as well as the host functions that facilitate optimal influenza virus replication.

Identification of small molecules with type I interferon inducing properties by high-throughput screening.

The continuous emergence of virus that are resistant to current anti-viral drugs, combined with the introduction of new viral pathogens for which no therapeutics are available, creates an urgent need for the development of novel broad spectrum antivirals. Type I interferon (IFN) can, by modulating the cellular expression profile, stimulate a non-specific antiviral state. The antiviral and adjuvant properties of IFN have been extensively demonstrated; however, its clinical application has been so far limited.

Contribution of NS1 effector domain dimerization to influenza A virus replication and virulence.

Conserved tryptophan-187 facilitates homodimerization of the influenza A virus NS1 protein effector domain. We generated a mutant influenza virus strain expressing NS1-W187R to destabilize this self-interaction. NS1-W187R protein exhibited lower double-stranded RNA (dsRNA)-binding activity, showed a temporal redistribution during infection, and was minimally compromised for interferon antagonism.

A novel small molecule inhibitor of influenza A viruses that targets polymerase function and indirectly induces interferon.

Influenza viruses continue to pose a major public health threat worldwide and options for antiviral therapy are limited by the emergence of drug-resistant virus strains. The antiviral cytokine, interferon (IFN) is an essential mediator of the innate immune response and influenza viruses, like many viruses, have evolved strategies to evade this response, resulting in increased replication and enhanced pathogenicity. A cell-based assay that monitors IFN production was developed and applied in a high-throughput compound screen to identify molecules that restore the IFN response to influenza virus infected cells.

Strain-specific contribution of NS1-activated phosphoinositide 3-kinase signaling to influenza A virus replication and virulence.

We generated influenza A viruses expressing mutant NS1 proteins unable to activate phosphoinositide 3-kinase (PI3K) in two mouse-lethal strains. The recombinant A/Puerto Rico/8/34 (rPR8) mutant virus strain was attenuated and caused reduced morbidity/mortality. For the recombinant A/WSN/33 (rWSN) virus strain, the inability to stimulate PI3K had minimal impact on replication or morbidity/mortality.

Characterization of chicken endoglin, a member of the zona pellucida family of proteins, and its tissue expression.

Endoglin is a TGF-β co-receptor expressed in endothelial cells, where it plays a crucial role in angiogenesis, cardiovascular development and vascular remodeling. In humans, mutations in the endoglin gene give rise to Hereditary Hemorrhagic Telangiectasia type 1 (HHT1), an autosomal dominant disorder associated with vascular lesions in skin, mucosa and internal organs. So far, endoglin cDNA has been sequenced in several species from mammals, amphibians and birds.

A transient homotypic interaction model for the influenza A virus NS1 protein effector domain.

Influenza A virus NS1 protein is a multifunctional virulence factor consisting of an RNA binding domain (RBD), a short linker, an effector domain (ED), and a C-terminal 'tail'. Although poorly understood, NS1 multimerization may autoregulate its actions. While RBD dimerization seems functionally conserved, two possible apo ED dimers have been proposed (helix-helix and strand-strand).

Inhibition of the type I interferon response in human dendritic cells by dengue virus infection requires a catalytically active NS2B3 complex.

Dengue virus (DENV) is the most prevalent arthropod-borne human virus, able to infect and replicate in human dendritic cells (DCs), inducing their activation and the production of proinflammatory cytokines. However, DENV can successfully evade the immune response in order to produce disease in humans. Several mechanisms of immune evasion have been suggested for DENV, most of them involving interference with type I interferon (IFN) signaling.