Via ha, the virus binds sialic acid receptors of the host cell and, upon endocytic uptake, ha triggers fusion between the viral envelope bilayer and the endosomal membrane by a low phinduced conformational change leading to the release of the viral genome into the host cell. Introduction to molecular biology of influenza a viruses. The influenza viruses contain a segmented, singlestranded rna genome of negative polarity. By electron microscopy, influenza a and b viruses are virtually indistinguishable. This virus structure is a conventional icosahedral or helical structure that is surrounded by a lipid bilayer membrane, meaning the virus is encased or enveloped. Structure of influenza a polymerase bound to the viral rna. The viral genomic rna, which consists of eight separate strands see section 2. Links to pubmed are also available for selected references. Influenza virus is one of the pandemic diseases that causes economic destruction and causes.
There has not been any drug effective against all strains. With the constant threat of emergence of a novel influenza virus pandemic, there must be continued evaluation of the molecular mechanisms that contribute to virulence. We use your linkedin profile and activity data to personalize ads and to show you more relevant ads. Indonesias decision to withhold samples of avian influenza virus a h5n1 from the world health organization for much of 2007 caused a crisis in global health. The importance of rna structures has been demonstrated in the life cycle of rnacontaining viruses, including the influenza virus. The influenza virion as the infectious particle is called is roughly spherical. The influenza virus is the main culprit of respiratory infection more commonly known as the flu. Structural biochemistryinfluenza virus wikibooks, open. The world health assembly produced a resolution to try to address the crisis at its may 2007 meeting.
Recognition of influenza virus by the immune system. The first inhibitors of influenza virus neuraminidase na, developed by p meindl and h tuppy in 1969, inhibited viral replication but had low potency and specificity. The crystal structure of the batspecific influenza a polymerase in complex with the viral rna promoter is presented, revealing how binding of the 5. Influenza viruses are divided into three typesa, b, con the basis of antigenic structure differences of np and m proteins. Available formats pdf please select a format to send. Molecular basis of the structure and function of h1 hemagglutinin of influenza virus nongluk sriwilaijaroen, yasuo suzuki proc jpn acad ser b phys biol sci. In the 1980s p m colman and his colleagues reported the crystal structure of influenza virus na and of its complex with neuraminic acid. The hemagglutinin glycoprotein of most human h7n9 viruses carries leu226, a residue linked to adaptation of. Influenza virus, neuraminidase, structure, functions, neuraminidase inhibitors, structure activity relationship. In this work we use smallangle xray scattering to conduct a detailed study on the structure and interactions in m2lipid membrane complexes and use this information to explain how the amphipathic helix imparts m2 with the ability to generate the specific types of membrane curvature necessary for viral. Jul 10, 2019 there are two main types of influenza flu virus. Structure of influenza virion influenza virions fig. The viral genome consists of eight segmented singlestranded rna segments seven for influenza c virus encoding from 9 to 12 proteins. It is an enveloped virus that is, the outer layer is a lipid membrane.
Evidence of a role for ns1 in influenza virus host range restriction jyothi m. Inserted into the lipid membrane are spikes, about 10 nm long, which are glycoproteins, known as ha hemagglutinin, and na neuraminidase. This new edition has been completely revised and reflects the integration of disciplines concerning the emergence, evolution, pathogenesis and control of influenza. In june 2009, who declared an h1n1 pandemic as the virus had spread to more than 70 countries and territories. However, the exact threedimensional structure of influenza b virus ha is quite different. Influenza virus sequence feature variant type analysis. Supporting documents for uk influenza pandemic preparedness strategy supporting documents for uk influenza pandemic preparedness strategy na na na 0 15652 for information for recipients use routes of transmission of the influenza virus. Influenza diagnosis clinical and epidemiological characteristics increase of febrile respiratory illness lab isolation of influenza virus from clinical specimen e. These extracellular structures allow copies of the viral genome to be transferred to new hosts, and their. Structure of the influenza virus europe pmc article.
Influenza a viruses can be broken down into subtypes depending on the genes that make up the surface proteins. The structure of the influenza virus includes a nucleoprotein rna center enclosed in capsid, a lipid envelope, and spikes of two key. On 10 august 2010, the who declared that the h1n1 pandemic is over as the virus is now behaving as a seasonal influenza virus. Influenza virus a m2 protein generates negative gaussian membrane curvature necessary for budding and scission, j. The structure of the influenza virus neuraminidases, the spatial organization of their active site, the mechanism of carbohydrate chains desialylation by neuraminidase, and its role in the. Both methods had similar findings, which suggested that on average, about 8% of the u. This virus has a close genetic relationship with subtype h5n8 viruses circulating in europe. The relation between biological activity and chemical structure of virus fractions volume 50 issue 2 l.
The structure of the influenza virus includes a nucleoprotein rna center enclosed in capsid, a lipid envelope, and spikes of two key proteins on its surface. Structural analysis of the roles of influenza a virus membrane. This work is licensed under a creative commons attribution. The influenza a and b viruses that routinely spread in people human influenza viruses are responsible for seasonal flu epidemics. Port influenza virus as shown in figure 173, influenza virus is an enveloped virus with its negative single stranded rna segmented genome encased in a lipid bilayer membrane that is taken up as the virus buds out of the. The 195758 influenza pandemic, also known as asian flu, was a global pandemic of influenza a virus subtype h2n2 which originated in guizhou, china and killed at least 1 million people worldwide. Some strains of h1n1 are endemic in humans and cause a small fraction of all influenza like illness and a small fraction of all seasonal influenza. The genome of the influenza a virus is segmented into eight rna molecules, each folded into a rod. Influenza virus structure and pathways introduction influenza virus is responsible for the greatest pandemic in human history causing 20 40 million deaths worldwide during the 1918 flu season.
Review on influenza virus and its prevention and control. The strain of virus that caused the pandemic, influenza a virus subtype h2n2, was a recombination of avian influenza probably from geese and human influenza viruses. Type a influenza is carried by animals and causes epidemics. Semicontinuous cells human embryonic kidney and skin fibroblasts continuous cells hela, vero, hep2, llcmk2, mdck. The structure of the hemagglutinin ha of a mutant influenza virus that escapes neutralization by a monoclonal antibody shows that the mutation causes changes in ha structure which avoid an energetically less favorable conformation. The envelope of the virus is formed when the virus is exiting the cell via budding, and the infectivity of these viruses is mostly dependent on the envelope. The 20 outbreak of avianorigin h7n9 influenza in eastern china has raised concerns about its ability to transmit in the human population. In this article we will discuss about the morphology and replication of influenza virus.
These statistical estimations are based on cdcmeasured flu hospitalization rates that are adjusted to produce an estimate of the total number of influenza infections in the united states for a given flu season. Structure of influenza virus influenza virion are usually spherical diameter 80110 nm. Replication of each iav genome segment occurs in the nucleus independently of each other 1,2. The doublestranded rna genome of the virus is packed. Structure of influenza viruses, connected with influenza life. Jan 29, 2019 with the constant threat of emergence of a novel influenza virus pandemic, there must be continued evaluation of the molecular mechanisms that contribute to virulence. Transcription and replication of influenza virus rna. The single serotype of influenza b virus ha has a similar overall structure as that of influenza a virus ha. Influenza a virus strains adopt different host specificities mainly depending on their hemagglutinin ha protein.
I thought it might be useful to explain how the virus multiplies, how it infects us, and how we combat infection. Molecular basis of the structure and function of h1 hemagglutinin of influenza virus. Dec 27, 2011 animation of the mechanism of an influenza virus and how crucells antibodies target the ha1 proteins on the virus and prevent further spread of influenza. Influenza a viruses, the causative agents of both epidemic and pandemic flu, are enveloped, singlestranded, negativesense rna viruses. Animation of the mechanism of an influenza virus and how crucells antibodies target the ha1 proteins on the virus and prevent further spread of influenza. The relation between biological activity and chemical structure of virus fractions. The hemagglutinin glycoprotein of most human h7n9 viruses carries leu226, a residue linked to adaptation of h2n2 and h3n2 pandemic viruses to human receptors. Apr 30, 2009 today well start with the basic structure of influenza virus, illustrated above. The ha1 molecule in influenza b virus also forms a crown structure on top of the trimeric ha2 molecules. The structure of influenza a is shown schematically in figure 4. Changes in rna secondary structure affect ns1 protein.
The structure of the influenza virus see figure 1 is somewhat variable, but the virion particles are usually spherical or ovoid in shape and 80 to 120 nanometers in diameter. It is an enveloped virus possessing genome segmented into eight linear single stranded molecules ranging in size from 890 to 2341 nucleotides. Once the key enters the lock, the influenza virus is then able to enter and infect the cell. Mar 15, 2012 influenza a h1n1 influenza a h1n1 virus is a subtype of influenza a virus and was the most common cause of human influenza flu in 2009. The first cases were reported in guizhou in late 1956 or february 1957, and were reported in the neighboring province of yunnan. Influenza virus samples, international law, and global. Pdf on jan 1, 2005, elspeth garman and others published the structure, function, and inhibition of influenza virus neuraminidase find, read and cite all the.
Influenza, commonly known as the flu, is an infectious disease caused by an influenza virus. Structure and function of influenza virus hemagglutinin ha by gary c. Influenza virus infection is so common that the number of people infected each season can only be estimated. These are an internal protein asso ciated with the viral ribonucleic acid rna which is responsible for the group specific antigen of the virion, and two surface pro. Conserved and hostspecific features of influenza virion. Although the influenza a virus surface glycoprotein neuraminidase na has been studied mainly in the context of its role in viral release from cells, accumulating evidence suggests it plays an important, multifunctional role in. Enhanced surveillance to detect newly emerging viruses is warranted. Again, the types are divided into subtypes on the basis of antigenic variation of ha and na. The textbook of influenza is a comprehensive resource covering all aspects of influenza, from the genetic and molecular biology of the virus through to clinical aspects of the disease and the latest drug developments and treatments. There are three main strains of the influenza virus, types a, b and c. In 1997 fears of a future pandemic arose with the discovery of a new strain of h5n1 avian influenza. Type a and b viruses are the most common causes of influenza disease symptoms and epidemic outbreaks, whilst type c has a milder disease phenotype and predominantly affects children. Interaction of ha with sialic acid receptor leads to virus entry into the host cell, release of viral rna and viral replication. Galloway, toru takimoto, mirco schmolke, victoria hunt, edward klem, adolfo garciasastre, monnie mcgee, richard h.
Influenza a h1n1 influenza a h1n1 virus is a subtype of influenza a virus and was the most common cause of human influenza flu in 2009. The structure of the influenza virus s ha surface proteins is designed to fit the sialic acid receptors of the human cell, like a key to a lock. Quantitative live cell imaging reveals influenza virus. The structure of a biologically active influenza virus. I examine how the parties to this controversy used international law in framing and negotiating the dispute. Mar 09, 2018 there are two main types of influenza flu virus. Highly pathogenic avian influenza virus h5n8 clade 2. Frontiers influenza virus neuraminidase structure and. They are spherical or filamentous in shape, with the spherical forms on the order of 100 nm in diameter and the filamentous forms often in excess of 300 nm in length.
It is highly contagious disease that considered as emerging. Influenza virus neuraminidase inhibitors the lancet. Some strains of h1n1 are endemic in humans and cause a small fraction of all influenzalike illness and a small fraction of all seasonal influenza. A 2018 cdc study published in clinical infectious diseases external icon looked at the percentage of the u. Get a printable copy pdf file of the complete article 2. The influenza virus belongs to the family orthomyxoviridae and is found in types a, b and c. The genome of influenza viruses is a linear, segmented and formed by ssrna. As it was a novel strain of the virus, there was minimal immunity in the population.
An enveloped virus, the outer layer is a lipid membrane which is taken from the host cell. It is an enveloped virus that is, the outer layer is a lipid membrane which is taken from the host cell in which the virus multiplies. The genome of the influenza a virus is segmented into eight rna molecules, each folded into a rodshaped, doublehelical ribonucleoprotein complex rnp. Till 2001, eight genome segments influenza a and b. Unicef s response to the h1n1 pandemic is covered under pandemic influenza. Influenza virus, neuraminidase, structure, functions, neuraminidase inhibitors, structureactivity relationship. Structure and function of the influenza virus genome. Receptor binding and ph stability how influenza a virus. Secondary structure model of the naked segment 7 influenza a virus genomic rna biochem j november, 2016 mov10 sequesters the rnp of influenza a virus in the cytoplasm and is antagonized by viral ns1 protein. The envelope of the virus is formed when the virus is exiting the cell via budding, and the infectivity of these viruses is. Oct 09, 2008 we use your linkedin profile and activity data to personalize ads and to show you more relevant ads. The structure of the influenza a virus genome biorxiv. Structure of influenza viruses, connected with influenza.
We isolated highly pathogenic avian influenza virus h5n8 of clade 2. Influenza is a disease that deeply affects millions of people every year. Structure of the influenza virus pubmed central pmc. Pdf the structure, function, and inhibition of influenza virus. Electron micrographs of subviral particles of the wsn strain of influenza virus a are presented. Therefore i have made a list of these articles, with links, to make it easier for everyone to take influenza 101. The assembly of influenza a virus at the plasma membrane of infected cells leads to. After removal of the glycoprotein spike layer, the internal structure. The influenza a and b viruses that routinely spread in people human influenza viruses are responsible for seasonal flu epidemics each year. Inserted into the lipid membrane are spikes, about 10 nm long, which are glycoproteins. Sometimes filamentous forms of the virus occur as well, and are more common among some influenza strains than others.
1513 491 1302 416 1458 185 157 55 888 1089 532 127 1115 673 1125 1209 558 42 41 227 1358 921 447 1341 491 290 818 1261 1211 1051 1018 311 1435 880 1322 1110