scholarly journals Characterization of a new influenza virus type D

2016 ◽  
Vol 72 (9) ◽  
pp. 531-535
Author(s):  
Iwona Markowska-Daniel ◽  
Marcin Mickiewicz ◽  
Lucjan Witkowski ◽  
Jerzy Kita
Keyword(s):  
Influenza Virus ◽  
Receptor Binding ◽  
Influenza A ◽  
Evolutionary Relationship ◽  
Influenza Viruses ◽  
Virus Protein ◽  
Cell Tropism ◽  
Receptor Binding Site ◽  
Antigenic Properties

Influenza is caused by viruses belonging to the Orthomyxoviridae family. Currently three types of influenza virus are known: A (Influenza A virus, IAV), B (IBV) and C (ICV). Despite the fact that all these viruses are derived from a common ancestor they differ from each other by the number of segments, the size and sequence of RNA segments, antigenicity, pathogenicity and the spectrum of natural reservoirs. In 2011, a new influenza virus was isolated in the USA from pigs manifesting influenza-like symptoms. The virus was the most closely related to ICV. It was able to replicate in vitro in different cell cultures and displayed much broader cell tropism than human ICV. Moreover, in contrast to ICV, it was able to replicate at 370C. Electron microscopic studies demonstrated features characteristic of Orthomyxoviruses. Despite morphological and organizational similarities, the biological properties of the new virus, including biochemical activity, differ from that of other influenza viruses. Enzymatic assays revealed that the new virus had negligible neuraminidase but detectable O-acetyloesterase activity. Further studies evidenced that the new virus varied from ICV in receptor binding, despite its sharing a conserved array of functional domains in the viral RNA genome replication and viral entry machinery. Analysis conducted with the use of the model of crystal structure of the hemagglutinin-esterase fusion protein (HE) of the new virus and its receptor demonstrated that this protein was multifunctional. It catalyzes cellular receptor binding, receptor cleavage, as well as membrane fusion. Moreover, divergent receptor-binding sites than HE of ICV have been discovered in the new virus. These amino acid differences may alter the binding specificity and affinity of the HE protein to the receptor that in turn result in the observed differences in cellular tropism between the two viruses. It also possesses an open channel between the 230-helix and 270-loop in the receptor-binding site, which is a unique feature of this virus. This might explain why the new virus has a broad cell tropism. It is possible that the sequence variation in the fusion domain may influence the replication of this virus at a higher temperature when compared to ICV. Next-generation sequencing demonstrated that the genome of the new virus, similarly to ICV, had seven single-stranded negative-sense RNA segments coding 9 viral proteins. Deep RNA sequencing found a M1 protein expression strategy different from that of ICV. Studies aimed at evaluating of the evolutionary relationship of both viruses revealed that the new virus and ICV shared an approximately 69-72% mean pairwise identity in the PB1 gene, which is reported to be the most conserved influenza virus protein. Additionally, differences were detected at 5’ and 3’ends of noncoding regions, which are also highly conserved. They both may be responsible for the lack of in vitro reassortment between ICV of human origin and the new virus. In the study characterizing antigenic properties of the new virus, no cross-reactivity was observed using HI and AGID tests. This indicates the major differences in conserved proteins M1 and NP between both viruses. Summing up, despite the fact that new virus is the most closely related to human ICV, the number of important antigenic and genetic distinctions among them is the basis for suggesting that the International Committee of Virus Taxonomy classify it as a separate genus - D. There is no doubt that the discovery of a new influenza virus genus will have a great impact on influenza research and ecology.

scholarly journals Amino Acid 226 in the Hemagglutinin of H9N2 Influenza Viruses Determines Cell Tropism and Replication in Human Airway Epithelial Cells

2007 ◽  
Vol 81 (10) ◽  
pp. 5181-5191 ◽  
Author(s):  
Hongquan Wan ◽  
Daniel R. Perez
Keyword(s):  
Amino Acid ◽  
Influenza A ◽  
Airway Epithelial Cells ◽  
Influenza Viruses ◽  
Cell Tropism ◽  
Airway Epithelial ◽  
Receptor Binding Site ◽  
Human Virus ◽  
Human Airway

ABSTRACT Influenza A viruses of the H9N2 subtype are endemic in poultry in many Eurasian countries and have occasionally caused clinical respiratory diseases in humans. While some avian H9N2 viruses have glutamine (Q) at amino acid position 226 of the hemagglutinin (HA) receptor-binding site, an increasing number of isolates have leucine (L) at this position, which has been associated with the establishment of stable lineages of the H2 and H3 subtypes of viruses in humans. Little is known about the importance of this molecular trait in the infection of H9N2 viruses in humans. We show here that during the course of a single cycle of infection in human airway epithelial (HAE) cells cultured in vitro, the L-226-containing H9N2 viruses displayed human virus-like cell tropisms (preferentially infecting nonciliated cells) different from the tropisms showed by Q-226-containing H9N2 isolates (which infect both ciliated and nonciliated cells at ratios of 1:1 to 3:2) or other waterfowl viruses (which preferentially infect ciliated cells). During multiple cycles of replication in HAE cultures, L-226-containing H9N2 isolates grew consistently more efficiently and reached approximately 100-fold-higher peak titers than those containing Q-226, although peak titers were significantly lower than those induced by human H3N2 viruses. Our results suggest that the variation in residue 226 in the HA affects both cell tropism and replication of H9N2 viruses in HAE cells and may have implications for the abilities of these viruses to infect humans.

scholarly journals The index influenza A virus subtype H5N1 isolated from a human in 1997 differs in its receptor-binding properties from a virulent avian influenza virus

2004 ◽  
Vol 85 (4) ◽  
pp. 1001-1005 ◽  
Author(s):  
Kiyoko Iwatsuki-Horimoto ◽  
Rie Kanazawa ◽  
Shunji Sugii ◽  
Yoshihiro Kawaoka ◽  
Taisuke Horimoto
Keyword(s):  
Influenza Virus ◽  
Avian Influenza ◽  
Avian Influenza Virus ◽  
Receptor Binding ◽  
Influenza A ◽  
Amino Acid Sequences ◽  
Influenza Viruses ◽  
Binding Properties ◽  
Receptor Binding Site ◽  
H5n1 Influenza

To gain insight into the events that occur when avian influenza viruses are transmitted to humans, the receptor-binding properties of the index H5N1 influenza virus isolated from a human in 1997 and the A/turkey/Ontario/7732/66 (H5N9) virus were compared, by using a haemadsorption assay. Cells expressing the haemagglutinin (HA) of the human isolate were adsorbed by both chicken red blood cells (RBCs) and human RBCs; those expressing the avian virus HA were only adsorbed by chicken RBCs. These results indicate that human and avian influenza virus H5 HAs differ in their recognition of sialyloligosaccharides on the RBCs of different animal species. Mutational analyses indicated that differences in both the oligosaccharide chains and in the amino acid sequences around the HA receptor-binding site were responsible for this difference in receptor binding. These data further support the concept that alteration in receptor recognition is important for replication of avian viruses in humans.

scholarly journals Plasticity of the Influenza Virus H5 HA Protein

mBio ◽  
2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Huihui Kong ◽  
David F. Burke ◽  
Tiago Jose da Silva Lopes ◽  
Kosuke Takada ◽  
Masaki Imai ◽  
...  
Keyword(s):  
Influenza Virus ◽  
Amino Acid ◽  
Mammalian Cells ◽  
Influenza A ◽  
Viral Antigen ◽  
Influenza Viruses ◽  
Influenza A Viruses ◽  
Highly Pathogenic ◽  
Antigenic Properties ◽  
Ha Protein

ABSTRACT Since the emergence of highly pathogenic avian influenza viruses of the H5 subtype, the major viral antigen, hemagglutinin (HA), has undergone constant evolution, resulting in numerous genetic and antigenic (sub)clades. To explore the consequences of amino acid changes at sites that may affect the antigenicity of H5 viruses, we simultaneously mutated 17 amino acid positions of an H5 HA by using a synthetic gene library that, theoretically, encodes all combinations of the 20 amino acids at the 17 positions. All 251 mutant viruses sequenced possessed ≥13 amino acid substitutions in HA, demonstrating that the targeted sites can accommodate a substantial number of mutations. Selection with ferret sera raised against H5 viruses of different clades resulted in the isolation of 39 genotypes. Further analysis of seven variants demonstrated that they were antigenically different from the parental virus and replicated efficiently in mammalian cells. Our data demonstrate the substantial plasticity of the influenza virus H5 HA protein, which may lead to novel antigenic variants. IMPORTANCE The HA protein of influenza A viruses is the major viral antigen. In this study, we simultaneously introduced mutations at 17 amino acid positions of an H5 HA expected to affect antigenicity. Viruses with ≥13 amino acid changes in HA were viable, and some had altered antigenic properties. H5 HA can therefore accommodate many mutations in regions that affect antigenicity. The substantial plasticity of H5 HA may facilitate the emergence of novel antigenic variants.

scholarly journals Bayesian inference of antigenic and non-antigenic variables from haemagglutination inhibition assays for influenza surveillance

2018 ◽  
Vol 5 (7) ◽  
pp. 180113
Author(s):  
Emmanuel S. Adabor ◽  
Wilfred Ndifon
Keyword(s):  
Influenza Virus ◽  
Influenza A ◽  
Bayesian Method ◽  
Haemagglutination Inhibition ◽  
Virus Evolution ◽  
Influenza Viruses ◽  
Influenza Surveillance ◽  
Antigenic Properties ◽  
Analytical Work

Haemagglutination inhibition (HI) assays are typically used for comparing and characterizing influenza viruses. Data obtained from the assays (titres) are used quantitatively to determine antigenic differences between influenza strains. However, the use of these titres has been criticized as they sometimes fail to capture accurate antigenic differences between strains. Our previous analytical work revealed how antigenic and non-antigenic variables contribute to the titres. Building on this previous work, we have developed a Bayesian method for decoupling antigenic and non-antigenic contributions to the titres in this paper. We apply this method to a compendium of HI titres of influenza A (H3N2) viruses curated from 1968 to 2016. Remarkably, the results of this fit indicate that the non-antigenic variable, which is inversely correlated with viral avidity for the red blood cells used in HI assays, oscillates during the course of influenza virus evolution, with a period that corresponds roughly to the timescale on which antigenic variants replace each other. Together, the results suggest that the new Bayesian method is applicable to the analysis of long-term dynamics of both antigenic and non-antigenic properties of influenza virus.

scholarly journals Divergent Human-Origin Influenza Viruses Detected in Australian Swine Populations

2018 ◽  
Vol 92 (16) ◽  
Author(s):  
Frank Y. K. Wong ◽  
Celeste Donato ◽  
Yi-Mo Deng ◽  
Don Teng ◽  
Naomi Komadina ◽  
...  
Keyword(s):  
Influenza Virus ◽  
Influenza A ◽  
Swine Influenza ◽  
Influenza Viruses ◽  
Antigenic Drift ◽  
Human Origin ◽  
Human Influenza ◽  
Influenza A Viruses ◽  
Data Set ◽  
Antigenic Properties

ABSTRACTGlobal swine populations infected with influenza A viruses pose a persistent pandemic risk. With the exception of a few countries, our understanding of the genetic diversity of swine influenza viruses is limited, hampering control measures and pandemic risk assessment. Here we report the genomic characteristics and evolutionary history of influenza A viruses isolated in Australia from 2012 to 2016 from two geographically isolated swine populations in the states of Queensland and Western Australia. Phylogenetic analysis with an expansive human and swine influenza virus data set comprising >40,000 sequences sampled globally revealed evidence of the pervasive introduction and long-term establishment of gene segments derived from several human influenza viruses of past seasons, including the H1N1/1977, H1N1/1995, H3N2/1968, and H3N2/2003, and the H1N1 2009 pandemic (H1N1pdm09) influenza A viruses, and a genotype that contained gene segments derived from the past three pandemics (1968, reemerged 1977, and 2009). Of the six human-derived gene lineages, only one, comprising two viruses isolated in Queensland during 2012, was closely related to swine viruses detected from other regions, indicating a previously undetected circulation of Australian swine lineages for approximately 3 to 44 years. Although the date of introduction of these lineages into Australian swine populations could not be accurately ascertained, we found evidence of sustained transmission of two lineages in swine from 2012 to 2016. The continued detection of human-origin influenza virus lineages in swine over several decades with little or unpredictable antigenic drift indicates that isolated swine populations can act as antigenic archives of human influenza viruses, raising the risk of reemergence in humans when sufficient susceptible populations arise.IMPORTANCEWe describe the evolutionary origins and antigenic properties of influenza A viruses isolated from two separate Australian swine populations from 2012 to 2016, showing that these viruses are distinct from each other and from those isolated from swine globally. Whole-genome sequencing of virus isolates revealed a high genotypic diversity that had been generated exclusively through the introduction and establishment of human influenza viruses that circulated in past seasons. We detected six reassortants with gene segments derived from human H1N1/H1N1pdm09 and various human H3N2 viruses that circulated during various periods since 1968. We also found that these swine viruses were not related to swine viruses collected elsewhere, indicating independent circulation. The detection of unique lineages and genotypes in Australia suggests that isolated swine populations that are sufficiently large can sustain influenza virus for extensive periods; we show direct evidence of a sustained transmission for at least 4 years between 2012 and 2016.

scholarly journals Generation and characterization of variants of NWS/G70C influenza virus after in vitro passage in 4-amino-Neu5Ac2en and 4-guanidino-Neu5Ac2en.

1996 ◽  
Vol 40 (1) ◽  
pp. 40-46 ◽  
Author(s):  
J L McKimm-Breschkin ◽  
T J Blick ◽  
A Sahasrabudhe ◽  
T Tiong ◽  
D Marshall ◽  
...  
Keyword(s):  
Amino Acids ◽  
Influenza Virus ◽  
Receptor Binding ◽  
Liquid Culture ◽  
Plaque Assay ◽  
Enoic Acid ◽  
Cross Resistance ◽  
Receptor Binding Site ◽  
Significant Difference

The compounds 4-amino-Neu5Ac2en (5-acetylamino-2,6-anhydro-4-amino-3,4,5- trideoxy-D-glycerol-D-galacto-non-2-enoic acid) and 4-guanidino-Neu5Ac2en (5-acetylamino-2,6-anhydro-4-guanidino-3,4,5- trideoxy-D-glycerol-D-galacto-non-2-enoic acid), which selectively inhibit the influenza virus neuraminidase, have been tested in vitro for their ability to generate drug-resistant variants. NWS/G70C virus (H1N9) was cultured in each drug by limiting-dilution passaging. After five or six passages in either compound, there emerged viruses which had a reduced sensitivity to the inhibitors in cell culture. Variant viruses were up to 1,000-fold less sensitive in plaque assays, liquid culture, and a hemagglutination-elution assay. In addition, cross-resistance to both compounds was seen in all three assays. Some isolates demonstrated drug dependence with an increase in both size and number of plaques in a plaque assay and an increase in virus yield in liquid culture in the presence of inhibitors. No significant difference in neuraminidase enzyme activity was detected in vitro, and no sequence changes in the conserved sites of the neuraminidase were found. However, changes in conserved amino acids in the hemagglutinin were detected. These amino acids were associated with either the hemagglutinin receptor binding site, Thr-155, or the left edge of the receptor binding pocket, Val-223 and Arg-229. Hence, mutations at these sites could be expected to affect the affinity or specificity of the hemagglutinin binding. Compensating mutations resulting in a weakly binding hemagglutinin thus seem to be circumventing the inhibition of the neuraminidase by allowing the virus to be released from cells with less dependence on the neuraminidase.

scholarly journals Antiviral Activity of Aspalathus linearis against Human Influenza Virus

2017 ◽  
Vol 12 (4) ◽  
pp. 1934578X1701200 ◽  
Author(s):  
Ratika Rahmasari ◽  
Takahiro Haruyama ◽  
Siriwan Charyasriwong ◽  
Tomoki Nishida ◽  
Nobuyuki Kobayashi
Keyword(s):  
Influenza Virus ◽  
Influenza A Virus ◽  
Influenza A ◽  
Time Course ◽  
Influenza Viruses ◽  
Replication Process ◽  
Human Influenza Virus ◽  
Alkaline Extract ◽  
Aspalathus Linearis

Influenza A viruses are responsible for annual epidemics and occasional pandemics, which cause significant morbidity and mortality. The limited protection offered by influenza vaccination, and the emergence of drug-resistant influenza strains, highlight the urgent need for the development of novel anti-influenza drugs. However, the search for antiviral substances from the library of low molecular weight chemical compounds is limited. Thus, because of their natural diversity and accessibility, plants or plant-derived materials are rapidly becoming valuable sources for the discovery and development of new antiviral drugs. In this study, crude extracts of Aspalathus linearis, a plant reported to have anti-HIV activity, were evaluated in vitro for their activity against the influenza A virus. Of the extracts tested, an alkaline extract of Aspalathus linearis demonstrated the strongest inhibition against influenza A virus and could also inhibit different types of influenza viruses, including Oseltamivir-resistant influenza viruses A and B. Our time course of addition studies indicated that the alkaline extract of Aspalathus linearis exerts its antiviral effect predominantly during the late stages of the influenza virus replication process.

scholarly journals A Novel Neuraminidase-Dependent Hemagglutinin Cleavage Mechanism Enables the Systemic Spread of an H7N6 Avian Influenza Virus

mBio ◽  
2019 ◽  
Vol 10 (6) ◽  
Author(s):  
Hyeok-il Kwon ◽  
Young-Il Kim ◽  
Su-Jin Park ◽  
Eun-Ha Kim ◽  
Semi Kim ◽  
...  
Keyword(s):  
Influenza Virus ◽  
Avian Influenza ◽  
Influenza A ◽  
Systemic Infection ◽  
Influenza Viruses ◽  
Mallard Duck ◽  
Virulence Markers ◽  
Systemic Spread ◽  
Cleavage Motif

ABSTRACT In this study, we demonstrate a novel mechanism for hemagglutinin (HA) activation in a naturally occurring H7N6 avian influenza A virus strain, A/mallard duck/Korea/6L/2007 (A/Mdk/6L/07). This novel mechanism allows for systemic infection of chickens, ducks, and mice, and A/Mdk/6L/07 can replicate in vitro without exogenous trypsin and exhibits broad tissue tropism in animals despite the presence of a monobasic HA cleavage motif (PEIPKGR/G). The trypsin-independent growth phenotype requires the N6 neuraminidase and the specific recognition of glycine at the P2 position of the HA cleavage motif by a thrombin-like protease. Correspondingly, viral growth is significantly attenuated by the addition of a thrombin-like protease inhibitor (argatroban). These data provide evidence for a previously unrecognized virus replication mechanism and support the hypothesis that thrombin-mediated HA cleavage is an important virulence marker and potential therapeutic target for H7 influenza viruses. IMPORTANCE The identification of virulence markers in influenza viruses underpins risk assessment programs and the development of novel therapeutics. The cleavage of the influenza virus HA is a required step in the viral life cycle, and phenotypic differences in viruses can be caused by changes in this process. Here, we describe a novel mechanism for HA cleavage in an H7N6 influenza virus isolated from a mallard duck. The mechanism requires the N6 protein and full activity of thrombin-like proteases and allows the virus to cause systemic infection in chickens, ducks, and mice. The thrombin-mediated cleavage of HA is thus a novel virulence determinant of avian influenza viruses.

scholarly journals Ethanol Extract of Caesalpinia decapetala Inhibits Influenza Virus Infection In Vitro and In Vivo

Viruses ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 557 ◽  
Author(s):  
Li Zhang ◽  
Jungang Chen ◽  
Chang Ke ◽  
Haiwei Zhang ◽  
Shoujun Zhang ◽  
...  
Keyword(s):  
Influenza Virus ◽  
Influenza A ◽  
Antiviral Agents ◽  
Influenza Virus Infection ◽  
Virus Titer ◽  
Ethanol Extract ◽  
Influenza Viruses ◽  
Virus Infections

Influenza virus infections can lead to viral pneumonia and acute respiratory distress syndrome in severe cases, causing significant morbidity and mortality and posing a great threat to human health. Because of the diversity of influenza virus strains and drug resistance to the current direct antiviral agents, there have been no effective drugs as yet to cure all patients infected by influenza viruses. Natural products from plants contain compounds with diverse structures that have the potential to interact with multiple host and virus factors. In this study, we identified the ethanol extract of Caesalpinia decapetala (Roth) Alston (EEC) as an inhibitor against the replication of a panel of influenza A and B viruses both on human pulmonary epithelial A549 and human monocytic U937 cells. The animal study revealed that EEC administration reduces the weight loss and improves the survival rate of mice infected with lethal influenza virus. Also, EEC treatment attenuated lung injury and reduced virus titer significantly. In conclusion, we showed that EEC has antiviral activity both in vitro and in vivo, suggesting that the plant C. decapetala has the potential to be further developed as a resource of new anti-influenza drugs.

scholarly journals Kallikrein-Related Peptidase 5 Contributes to H3N2 Influenza Virus Infection in Human Lungs

2017 ◽  
Vol 91 (16) ◽  
Author(s):  
Mélia Magnen ◽  
Fabien Gueugnon ◽  
Antoine Guillon ◽  
Thomas Baranek ◽  
Virginie C. Thibault ◽  
...  
Keyword(s):  
Influenza Virus ◽  
Respiratory Tract ◽  
Serine Proteases ◽  
Lower Respiratory Tract ◽  
Influenza A ◽  
Seasonal Influenza ◽  
Influenza Viruses ◽  
H3n2 Virus ◽  
Influenza A Viruses

ABSTRACT Hemagglutinin (HA) of influenza virus must be activated by proteolysis before the virus can become infectious. Previous studies indicated that HA cleavage is driven by membrane-bound or extracellular serine proteases in the respiratory tract. However, there is still uncertainty as to which proteases are critical for activating HAs of seasonal influenza A viruses (IAVs) in humans. This study focuses on human KLK1 and KLK5, 2 of the 15 serine proteases known as the kallikrein-related peptidases (KLKs). We find that their mRNA expression in primary human bronchial cells is stimulated by IAV infection. Both enzymes cleaved recombinant HA from several strains of the H1 and/or H3 virus subtype in vitro, but only KLK5 promoted the infectivity of A/Puerto Rico/8/34 (H1N1) and A/Scotland/20/74 (H3N2) virions in MDCK cells. We assessed the ability of treated viruses to initiate influenza in mice. The nasal instillation of only the KLK5-treated virus resulted in weight loss and lethal outcomes. The secretion of this protease in the human lower respiratory tract is enhanced during influenza. Moreover, we show that pretreatment of airway secretions with a KLK5-selective inhibitor significantly reduced the activation of influenza A/Scotland/20/74 virions, providing further evidence of its importance. Differently, increased KLK1 secretion appeared to be associated with the recruitment of inflammatory cells in human airways regardless of the origin of inflammation. Thus, our findings point to the involvement of KLK5 in the proteolytic activation and spread of seasonal influenza viruses in humans. IMPORTANCE Influenza A viruses (IAVs) cause acute infection of the respiratory tract that affects millions of people during seasonal outbreaks every year. Cleavage of the hemagglutinin precursor by host proteases is a critical step in the life cycle of these viruses. Consequently, host proteases that activate HA can be considered promising targets for the development of new antivirals. However, the specific proteases that activate seasonal influenza viruses, especially H3N2 viruses, in the human respiratory tract have remain undefined despite many years of work. Here we demonstrate that the secreted, extracellular protease KLK5 (kallikrein-related peptidase 5) is efficient in promoting the infectivity of H3N2 IAV in vitro and in vivo. Furthermore, we found that its secretion was selectively enhanced in the human lower respiratory tract during a seasonal outbreak dominated by an H3N2 virus. Collectively, our data support the clinical relevance of this protease in human influenza pathogenesis.

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