scholarly journals Characterization of Human Influenza Virus Variants Selected In Vitro in the Presence of the Neuraminidase Inhibitor GS 4071

1998 ◽  
Vol 42 (12) ◽  
pp. 3234-3241 ◽  
Author(s):  
Chun Y. Tai ◽  
Paul A. Escarpe ◽  
Robert W. Sidwell ◽  
Matthew A. Williams ◽  
Willard Lew ◽  
...  
Keyword(s):  
Influenza Virus ◽  
Neuraminidase Inhibitor ◽  
H3n2 Virus ◽  
Wild Type Virus ◽  
Type Virus ◽  
Human Influenza ◽  
Wild Type ◽  
Viral Virulence ◽  
High Level

ABSTRACT An oral prodrug of GS 4071, a potent and selective inhibitor of influenza neuraminidases, is currently under clinical development for the treatment and prophylaxis of influenza virus infections in humans. To investigate the potential development of resistance during the clinical use of this compound, variants of the human influenza A/Victoria/3/75 (H3N2) virus with reduced susceptibility to the neuraminidase inhibitor GS 4071 were selected in vitro by passaging the virus in MDCK cells in the presence of inhibitor. After eight passages, variants containing two amino acid substitutions in the hemagglutinin (A28T in HA1 and R124M in HA2) but no changes in the neuraminidase were isolated. These variants exhibited a 10-fold reduction in susceptibility to GS 4071 and zanamivir (GG167) in an in vitro plaque reduction assay. After 12 passages, a second variant containing these hemagglutinin mutations and a Lys substitution for the conserved Arg292 of the neuraminidase was isolated. The mutant neuraminidase enzyme exhibited high-level (30,000-fold) resistance to GS 4071, but only moderate (30-fold) resistance to zanamivir and 4-amino-Neu5Ac2en, the amino analog of zanamivir. The mutant enzyme had weaker affinity for the fluorogenic substrate 2′-(4-methylumbelliferyl)-α-d- N -acetylneuraminic acid and lower enzymatic activity compared to the wild-type enzyme. The viral variant containing the mutant neuraminidase did not replicate as well as the wild-type virus in culture and was 10,000-fold less infectious than the wild-type virus in a mouse model. These results suggest that although the R292K neuraminidase mutation confers high-level resistance to GS 4071 in vitro, its effect on viral virulence is likely to render this mutation of limited clinical significance.

scholarly journals The pH of Activation of the Hemagglutinin Protein Regulates H5N1 Influenza Virus Pathogenicity and Transmissibility in Ducks

2009 ◽  
Vol 84 (3) ◽  
pp. 1527-1535 ◽  
Author(s):  
Mark L. Reed ◽  
Olga A. Bridges ◽  
Patrick Seiler ◽  
Jeong-Ki Kim ◽  
Hui-Ling Yen ◽  
...  
Keyword(s):  
Weight Loss ◽  
Influenza Virus ◽  
Membrane Fusion ◽  
Influenza Viruses ◽  
Wild Type Virus ◽  
Type Virus ◽  
Wild Type ◽  
H5n1 Influenza ◽  
Ha Protein

ABSTRACT While the molecular mechanism of membrane fusion by the influenza virus hemagglutinin (HA) protein has been studied extensively in vitro, the role of acid-dependent HA protein activation in virus replication, pathogenesis, and transmission in vivo has not been characterized. To investigate the biological significance of the pH of activation of the HA protein, we compared the properties of four recombinant viruses with altered HA protein acid stability to those of wild-type influenza virus A/chicken/Vietnam/C58/04 (H5N1) in vitro and in mallards. Membrane fusion by wild-type virus was activated at pH 5.9. Wild-type virus had a calculated environmental persistence of 62 days and caused extensive morbidity, mortality, shedding, and transmission in mallards. An N114K mutation that increased the pH of HA activation by 0.5 unit resulted in decreased replication, genetic stability, and environmental stability. Changes of +0.4 and −0.5 unit in the pH of activation by Y23H and K58I mutations, respectively, reduced weight loss, mortality, shedding, and transmission in mallards. An H24Q mutation that decreased the pH of activation by 0.3 unit resulted in weight loss, mortality, clinical symptoms, and shedding similar to those of the wild type. However, the HA-H241Q virus was shed more extensively into drinking water and persisted longer in the environment. The pH of activation of the H5 HA protein plays a key role in the propagation of H5N1 influenza viruses in ducks and may be a novel molecular factor in the ecology of influenza viruses. The data also demonstrate that H5N1 neuraminidase activity increases the pH of activation of the HA protein in vitro.

scholarly journals Eurasian Avian-like M1 Plays More Important Role than M2 in Pathogenicity of 2009 Pandemic H1N1 Influenza Virus in Mice

Viruses ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 2335
Author(s):  
Lixiang Xie ◽  
Guanlong Xu ◽  
Lingxiang Xin ◽  
Zhaofei Wang ◽  
Rujuan Wu ◽  
...  
Keyword(s):  
Influenza Virus ◽  
Inflammatory Cytokines ◽  
Swine Influenza ◽  
Influenza Viruses ◽  
Chimeric Virus ◽  
Wild Type Virus ◽  
Type Virus ◽  
Wild Type ◽  
M Gene

Reassortant variant viruses generated between 2009 H1N1 pandemic influenza virus [A(H1N1)pdm09] and endemic swine influenza viruses posed a potential risk to humans. Surprisingly, genetic analysis showed that almost all of these variant viruses contained the M segment from A(H1N1)pdm09, which originated from Eurasian avian-like swine influenza viruses. Studies have shown that the A(H1N1)pdm09 M gene is critical for the transmissibility and pathogenicity of the variant viruses. However, the M gene encodes two proteins, M1 and M2, and which of those plays a more important role in virus pathogenicity remains unknown. In this study, the M1 and M2 genes of A(H1N1)pdm09 were replaced with those of endemic H3N2 swine influenza virus, respectively. The chimeric viruses were rescued and evaluated in vitro and in mice. Both M1 and M2 of H3N2 affected the virus replication in vitro. In mice, the introduction of H3N2 M1 attenuated the chimeric virus, where all the mice survived from the infection, compared with the wild type virus that caused 100 % mortality. However, the chimeric virus containing H3N2 M2 was still virulent to mice, and caused 16.6% mortality, as well as similar body weight loss to the wild type virus infected group. Compared with the wild type virus, the chimeric virus containing H3N2 M1 induced lower levels of inflammatory cytokines and higher levels of anti-inflammatory cytokines, whereas the chimeric virus containing H3N2 M2 induced substantial pro-inflammatory responses, but higher levels of anti-inflammatory cytokines. The study demonstrated that Eurasian avian-like M1 played a more important role than M2 in the pathogenicity of A(H1N1)pdm09 in mice.

scholarly journals Combinatorial Effect of Two Framework Mutations (E119V and I222L) in the Neuraminidase Active Site of H3N2 Influenza Virus on Resistance to Oseltamivir

2011 ◽  
Vol 55 (6) ◽  
pp. 2942-2952 ◽  
Author(s):  
Mathilde Richard ◽  
Olivier Ferraris ◽  
Alexandra Erny ◽  
Mendy Barthélémy ◽  
Aurélien Traversier ◽  
...  
Keyword(s):  
Influenza Virus ◽  
Reverse Genetics ◽  
Mdck Cells ◽  
Resistance Mechanisms ◽  
Mutant Virus ◽  
Wild Type Virus ◽  
Type Virus ◽  
Wild Type ◽  
Oseltamivir Resistance ◽  
High Level

ABSTRACTNeuraminidase (NA) inhibitors (NIs) are the first line of defense against influenza virus. Reverse genetics experiments allow the study of resistance mechanisms by anticipating the impacts of mutations to the virus. To look at the possibility of an increased effect on the resistance phenotype of a combination of framework mutations, known to confer resistance to oseltamivir or zanamivir, with limited effect on virus fitness, we constructed 4 viruses by reverse genetics in the A/Moscow/10/99 H3N2 background containing double mutations in their neuraminidase genes: E119D+I222L, E119V+I222L, D198N+I222L, and H274Y+I222L (N2 numbering). Among the viruses produced, the E119D+I222L mutant virus was not able to grow without bacterial NA complementation and the D198N+I222L mutant and H274Y+I222L mutant were not stable after passages in MDCK cells. The E119V+I222L mutant was stable after five passages in MDCK cells. This E119V-and-I222L combination had a combinatorial effect on oseltamivir resistance. The total NA activity of the E119V+I222L mutant was low (5% compared to that of the wild-type virus). This drop in NA activity resulted from a decreased NA quantity in the virion in comparison to that of the wild-type virus (1.4% of that of the wild type). In MDCK-SIAT1 cells, the E119V+I222L mutant virus did not present a replicative advantage over the wild-type virus, even in the presence of oseltamivir. Double mutations combining two framework mutations in the NA gene still have to be monitored, as they could induce a high level of resistance to NIs, without impairing the NA affinity. Our study allows a better understanding of the diversity of the mechanisms of resistance to NIs.

scholarly journals Lack of transmission of a human influenza virus with avian receptor specificity between ferrets is not due to decreased virus shedding but rather a lower infectivity in vivo

2011 ◽  
Vol 92 (8) ◽  
pp. 1822-1831 ◽  
Author(s):  
Kim L. Roberts ◽  
Holly Shelton ◽  
Margaret Scull ◽  
Raymond Pickles ◽  
Wendy S. Barclay
Keyword(s):  
Influenza Virus ◽  
Influenza Viruses ◽  
Mutant Virus ◽  
Host Cells ◽  
Productive Infection ◽  
Wild Type Virus ◽  
Upper Respiratory Tract ◽  
Type Virus ◽  
Human Influenza ◽  
Wild Type

Influenza virus attaches to host cells by sialic acid (SA). Human influenza viruses show preferential affinity for α2,6-linked SA, whereas avian influenza viruses bind α2,3-linked SA. In this study, mutation of the haemagglutinin receptor-binding site of a human H3N2 influenza A virus to switch binding to α2,3-linked SA did not eliminate infection of ferrets but prevented transmission, even in a co-housed model. The mutant virus was shed from the noses of ferrets directly inoculated with virus in the same amounts and for the same length of time as wild-type virus. Mutant virus infection was localized to the same anatomical regions of the upper respiratory tract of directly inoculated animals. Interestingly, wild-type virus was more readily neutralized than the mutant virus in vitro by ferret nasal washes containing mucus. Moreover after inoculation of equal doses, the mutant virus grew poorly in ex vivo ferret nasal turbinate tissue compared with wild-type virus. The dose of mutant virus required to establish infection in the directly inoculated ferrets was 40-fold higher than for wild-type virus. It was concluded that minimum infectious dose is a predictor of virus transmissibility and it is suggested that, as virus passes from one host to another through stringent environmental conditions, viruses with a preference for α2,3-linked SA are unlikely to inoculate a new mammalian host in sufficient quantities to initiate a productive infection.

The URNA Genes of Herpesvirus Saimiri (Strain C488) Are Dispensable for Transformation of Human T Cells In Vitro

1999 ◽  
Vol 73 (12) ◽  
pp. 10551-10555 ◽  
Author(s):  
Armin Ensser ◽  
André Pfinder ◽  
Ingrid Müller-Fleckenstein ◽  
Bernhard Fleckenstein
Keyword(s):  
Cell Culture ◽  
Herpesvirus Saimiri ◽  
Wild Type Virus ◽  
Type Virus ◽  
Wild Type ◽  
Human T Cell ◽  
Human T Cells ◽  
Small Nuclear Rnas ◽  
T Cell Lines

ABSTRACT The herpesvirus saimiri strain C488 genome contains five genes for small nuclear RNAs, termed herpesvirus saimiri URNAs (or HSURs). Using a cosmid-based approach, all HSURs were precisely deleted from the genome. The mutant virus replicated at levels that were similar to those of wild-type viruses in OMK cells. Although the HSURs are expressed in wild-type virus-transformed human T-cell lines, the deletion does not affect viral transformation in cell culture.

scholarly journals Vaccinia Virus Envelope H3L Protein Binds to Cell Surface Heparan Sulfate and Is Important for Intracellular Mature Virion Morphogenesis and Virus Infection In Vitro and In Vivo

2000 ◽  
Vol 74 (7) ◽  
pp. 3353-3365 ◽  
Author(s):  
Chi-Long Lin ◽  
Che-Sheng Chung ◽  
Hans G. Heine ◽  
Wen Chang
Keyword(s):  
Cell Surface ◽  
Vaccinia Virus ◽  
Heparan Sulfate ◽  
Mutant Virus ◽  
Wild Type Virus ◽  
Type Virus ◽  
Wild Type ◽  
Virion Morphogenesis

ABSTRACT An immunodominant antigen, p35, is expressed on the envelope of intracellular mature virions (IMV) of vaccinia virus. p35 is encoded by the viral late gene H3L, but its role in the virus life cycle is not known. This report demonstrates that soluble H3L protein binds to heparan sulfate on the cell surface and competes with the binding of vaccinia virus, indicating a role for H3L protein in IMV adsorption to mammalian cells. A mutant virus defective in expression of H3L (H3L−) was constructed; the mutant virus has a small plaque phenotype and 10-fold lower IMV and extracellular enveloped virion titers than the wild-type virus. Virion morphogenesis is severely blocked and intermediate viral structures such as viral factories and crescents accumulate in cells infected with the H3L− mutant virus. IMV from the H3L− mutant virus are somewhat altered and less infectious than wild-type virions. However, cells infected by the mutant virus form multinucleated syncytia after low pH treatment, suggesting that H3L protein is not required for cell fusion. Mice inoculated intranasally with wild-type virus show high mortality and severe weight loss, whereas mice infected with H3L− mutant virus survive and recover faster, indicating that inactivation of the H3L gene attenuates virus virulence in vivo. In summary, these data indicate that H3L protein mediates vaccinia virus adsorption to cell surface heparan sulfate and is important for vaccinia virus infection in vitro and in vivo. In addition, H3L protein plays a role in virion assembly.

scholarly journals Mutations in the Vaccinia Virus A33R and B5R Envelope Proteins That Enhance Release of Extracellular Virions and Eliminate Formation of Actin-Containing Microvilli without Preventing Tyrosine Phosphorylation of the A36R Protein

2003 ◽  
Vol 77 (22) ◽  
pp. 12266-12275 ◽  
Author(s):  
Ehud Katz ◽  
Brian M. Ward ◽  
Andrea S. Weisberg ◽  
Bernard Moss
Keyword(s):  
Vaccinia Virus ◽  
Envelope Protein ◽  
Actin Polymerization ◽  
Single Amino Acid ◽  
Wild Type Virus ◽  
Virus Release ◽  
Type Virus ◽  
Wild Type ◽  
Extracellular Virus

ABSTRACT The spread of vaccinia virus in cell cultures is mediated by virions that adhere to the tips of specialized actin-containing microvilli and also by virions that are released into the medium. The use of a small plaque-forming A36R gene deletion mutant to select spontaneous second-site mutants exhibiting enhanced virus release was described previously. Two types of mutations were found: C-terminal truncations of the A33R envelope protein and a single amino acid substitution of the B5R envelope protein. In the present study, we transferred each type of mutation into a wild-type virus background in order to study their effects in vitro and in vivo. The two new mutants conserved the enhanced virus release properties of the original isolates; the A33R mutant produced considerably more extracellular virus than the B5R mutant. The extracellular virus particles contained the truncated A33R protein in one case and the mutated B5R protein in the other. Remarkably, both mutants failed to form actin tails and specialized microvilli, despite the presence of an intact A36R gene. The synthesis of the A36R protein as well as its physical association with the mutated or wild-type A33R protein was demonstrated. Moreover, the A36R protein was tyrosine phosphorylated, a step mediated by a membrane-associated Src kinase that regulates the nucleation of actin polymerization. The presence of large numbers of adherent virions on the cell surface argued against rapid dissociation as having a key role in preventing actin tail formation. Thus, the A33R and B5R proteins may be more directly involved in the formation or stabilization of actin tails than had been previously thought. When mice were inoculated intranasally, the A33R mutant was highly attenuated and the B5R mutant was mildly attenuated compared to wild-type virus. Enhanced virus release, therefore, did not compensate for the loss of actin tails and specialized microvilli.

scholarly journals Inhibition of Cellular Proteasome Activities Enhances Hepadnavirus Replication in an HBX-Dependent Manner

2004 ◽  
Vol 78 (9) ◽  
pp. 4566-4572 ◽  
Author(s):  
Zhensheng Zhang ◽  
Ulrike Protzer ◽  
Zongyi Hu ◽  
James Jacob ◽  
T. Jake Liang
Keyword(s):  
Recombinant Adenovirus ◽  
Hepatitis Virus ◽  
Proteasome Inhibitors ◽  
Productive Infection ◽  
Wild Type Virus ◽  
Dependent Manner ◽  
Type Virus ◽  
Wild Type

ABSTRACT The X protein (HBX) of the hepatitis B virus (HBV) is not essential for the HBV life cycle in vitro but is important for productive infection in vivo. Our previous study suggests that interaction of HBX with the proteasome complex may underlie the pleiotropic functions of HBX. With the woodchuck model, we demonstrated that the X-deficient mutants of woodchuck hepatitis virus (WHV) are not completely replication defective, possibly behaving like attenuated viruses. In the present study, we analyzed the effects of the proteasome inhibitors on the replication of wild-type and X-negative HBV and WHV. Recombinant adenoviruses or baculoviruses expressing replicating HBV or WHV genomes have been developed as a robust and convenient system to study viral replication in tissue culture. In cells infected with either the recombinant adenovirus-HBV or baculovirus-WHV, the replication level of the X-negative construct was about 10% of that of the wild-type virus. In the presence of proteasome inhibitors, the replication of the wild-type virus was not affected, while the replication of the X-negative virus of either HBV or WHV was enhanced and restored to the wild-type level. Our data suggest that HBX affects hepadnavirus replication through a proteasome-dependent pathway.

scholarly journals Codon Deletions in the Influenza A Virus PA Gene Generate Temperature-Sensitive Viruses

2016 ◽  
Vol 90 (7) ◽  
pp. 3684-3693 ◽  
Author(s):  
Léa Meyer ◽  
Alix Sausset ◽  
Laura Sedano ◽  
Bruno Da Costa ◽  
Ronan Le Goffic ◽  
...  
Keyword(s):  
Influenza Virus ◽  
Rna Polymerase ◽  
Influenza A Virus ◽  
Influenza A ◽  
Wild Type Virus ◽  
Deletion Mutants ◽  
Temperature Sensitive ◽  
Restrictive Temperature ◽  
Wild Type

ABSTRACTThe influenza virus RNA-dependent RNA polymerase, which is composed of three subunits, PB1, PB2, and PA, catalyzes genome replication and transcription within the cell nucleus. The PA linker (residues 197 to 256) can be altered by nucleotide substitutions to engineer temperature-sensitive (ts), attenuated mutants that display a defect in the transport of the PA–PB1 complex to the nucleus at a restrictive temperature. In this study, we investigated the ability of the PA linker to tolerate deletion mutations for furtherin vitroandin vivocharacterization. Four viable mutants with single-codon deletions were generated; all of them exhibited atsphenotype that was associated with the reduced efficiency of replication/transcription of a pseudoviral reporter RNA in a minireplicon assay. Using fluorescently tagged PB1, we observed that the deletion mutants did not efficiently recruit PB1 to reach the nucleus at a restrictive temperature (39.5°C). Mouse infections showed that the four mutants were attenuated and induced antibodies that were able to protect mice from challenge with a lethal homologous wild-type virus. Serialin vitropassages of two deletion mutants at 39.5°C and 37°C did not allow the restoration of a wild-type phenotype among virus progeny. Thus, our results identify codons that can be deleted in the PA gene to engineer genetically stabletsmutants that could be used to design novel attenuated vaccines.IMPORTANCEIn order to generate genetically stable live influenza A virus vaccines, we constructed viruses with single-codon deletions in a discrete domain of the RNA polymerase PA gene. The four rescued viruses exhibited a temperature-sensitive phenotype that we found was associated with a defect in the transport of the PA–PB1 dimer to the nucleus, where viral replication occurs. Thesetsdeletion mutants were shown to be attenuated and to be able to produce antibodies in mice and to protect them from a lethal challenge. Assays to select revertants that were able to grow efficiently at a restrictive temperature failed, showing that these deletion mutants are genetically more stable than conventional substitution mutants. These results are of interest for the design of genetically stable live influenza virus vaccines.

scholarly journals Ultrapotent bispecific antibodies neutralize emerging SARS-CoV-2 variants

2021 ◽  
Author(s):  
Hyeseon Cho ◽  
Kristina Kay Gonzales-Wartz ◽  
Deli Huang ◽  
Meng Yuan ◽  
Mary Peterson ◽  
...  
Keyword(s):  
Bispecific Antibody ◽  
Complete Loss ◽  
Memory B Cells ◽  
Spike Protein ◽  
Bispecific Antibodies ◽  
Wild Type Virus ◽  
Type Virus ◽  
Wild Type ◽  
Hamster Model

The emergence of SARS-CoV-2 variants that threaten the efficacy of existing vaccines and therapeutic antibodies underscores the urgent need for new antibody-based tools that potently neutralize variants by targeting multiple sites of the spike protein. We isolated 216 monoclonal antibodies targeting SARS-CoV-2 from plasmablasts and memory B cells of COVID-19 patients. The three most potent antibodies targeted distinct regions of the RBD, and all three neutralized the SARS-CoV-2 variants B.1.1.7 and B.1.351. The crystal structure of the most potent antibody, CV503, revealed that it binds to the ridge region of SARS-CoV-2 RBD, competes with the ACE2 receptor, and has limited contact with key variant residues K417, E484 and N501. We designed bispecific antibodies by combining non-overlapping specificities and identified five ultrapotent bispecific antibodies that inhibit authentic SARS-CoV-2 infection at concentrations of <1 ng/mL. Through a novel mode of action three bispecific antibodies cross-linked adjacent spike proteins using dual NTD/RBD specificities. One bispecific antibody was >100-fold more potent than a cocktail of its parent monoclonals in vitro and prevented clinical disease in a hamster model at a 2.5 mg/kg dose. Notably, six of nine bispecific antibodies neutralized B.1.1.7, B.1.351 and the wild-type virus with comparable potency, despite partial or complete loss of activity of at least one parent monoclonal antibody against B.1.351. Furthermore, a bispecific antibody that neutralized B.1.351 protected against SARS-CoV-2 expressing the crucial E484K mutation in the hamster model. Thus, bispecific antibodies represent a promising next-generation countermeasure against SARS-CoV-2 variants of concern.

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