The influenza viruses are members of the family orthomyxoviridae. The relation between biological activity and chemical structure of virus fractions volume 50 issue 2 l. Neuraminidase promotes influenza virus release from infected cells and facilitates virus spread within the respiratory tract. Birds, pigs, horses, ferrets, dogs, and cats can all be infected with various strains of the influenza virus. Structure of the influenza virus hemagglutinin springerlink. Structure of influenza viruses, connected with influenza. Assembly and release sixth and seventh steps process involves bringing together newly formed genomic nucleic acid and structural proteins to form the nucleocapsid of the virus nonenveloped viruses exhibit full maturation in the cytoplasm or nucleus with disintegration of cell steps in viral replication. 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. Type a influenza is carried by animals and causes epidemics.
Once the key enters the lock, the influenza virus is then able to enter and infect the cell. This infographic briefly summarises the natural history, replication cycle, and pathogenesis of influenza viruses, the cause of seasonal influenza and of influenza pandemics. Structural analysis of influenza vaccine viruslike. Subtypes are named by combining the h and n numbers e. There are 18 different ha subtypes and 11 different na subtypes. The section will also welcome the case reports of influenza outbreaks in both. Most are roughly spherical, but influenza virions can sometimes be filamentous. Dec 29, 2001 human influenza a h5n1 virus related to a highly pathogenic avian influenza virus.
Influenza d viruses are known to infect pigs and cattle. The membrane contains two types of surface proteins and a number of protein channels. The iav genome consists of eight rna segments contained in separate viral ribonucleoprotein complexes vrnps that are packaged together into a single virus particle11,22. The influenza b virus is the causative agent of the common flu, but over the past years, it has become more potent in causing. 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. Influenza a and b viruses the primary influenza viruses that infect people are rna viruses that have eight gene segments. Structure of influenza viruses, connected with influenza life. 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. 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 frequently affects a large proportion of the population irrespective of age or previous infection history and remains today a poorly controlled disease, despite the fact that the infectious agent, influenza virus, was first isolated 50 years. Of the four antigenic types, influenza a virus is the most severe, influenza b virus is less severe but can still cause outbreaks, and influenza c virus is usually only associated with minor symptoms. Crystal structure of the human class ii mhc protein hla.
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. Influenza in birds is often referred to as avian influenza, in pigs as swine influenza, in horses as equine influenza and so on. The crystal structure of the uncleaved precursor of the major surface antigen of the extinct 1918 virus was determined at 3. Iav from different host species can reassort their. Structure of influenza virus influenza virion are usually spherical diameter 80110 nm an enveloped virus, the outer layer is a lipid membrane which is taken from the host cell inserted into the lipid membrane are spikes, about 10 nm long, which are glycoproteins, known as ha hemagglutinin, and na neuraminidase. An enveloped virus, the outer layer is a lipid membrane which is taken from the host cell. Influenza d virus is a species in the virus genus influenzavirus d, in the family orthomyxoviridae, that causes influenza. 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 influenza virus function at different stages of the viral infectious cycle are considered in. An influenza virus peptide binds to hladr1 in an extended conformation with a pronounced twist. 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. Structure of the catalytic and antigenic sites in influenza virus neuraminidase. We show that the matrix layer adjacent to the membrane is an ordered helix of the m1. Sialic acids 9oacetylneraminic acid hostvirus interaction ecology and disease geography worldwide, more common in winter associated diseases.
During the 1918 pandemic the influenza virus killed 50 to 100 million people 1,2,3,4. Influenza in humans is often referred to as the seasonal flu. Structure of influenza virus influenza virion are usually spherical diameter 80110 nm. The influenza virus genome consists of eight segments of negative. Influenza virus affects the respiratory tract by direct viral infection or by damage from the immune system response. Inserted into the lipid membrane are spikes, about 10 nm long, which are glycoproteins, known as ha hemagglutinin, and na neuraminidase. Thirtyfive per cent of the peptide surface is accessible to solvent and potentially available for. Jun, 2018 this infographic briefly summarises the natural history, replication cycle, and pathogenesis of influenza viruses, the cause of seasonal influenza and of influenza pandemics. The viral genomic rna, which consists of eight separate strands see section 2. It frequently affects a large proportion of the population irrespective of age or previous infection history and remains today a poorly controlled disease, despite the fact that the infectious agent, influenza virus, was first isolated 50 years ago see. Influenza viruses are enveloped singlestranded rna viruses with a pleomorphic appearance, and an average diameter of 120 nm. Structural biochemistryinfluenza virus wikibooks, open.
Virus transmission occurs through a susceptible individuals contact with aerosols or respiratory. The influenza virion as the infectious particle is called is roughly spherical. Structural analysis of influenza vaccine viruslike particles. Influenza virus remains a threat because of its ability to evade vaccineinduced immune responses due to antigenic drift. Projections of haemagglutinin and neuraminidase cover the surface of the particle figure 1. Influenza a virus, influenza b virus, and influenza c virus, respectively table 10. Jun 08, 2010 influenza is a lipidenveloped, pleomorphic virus. The doublestranded rna genome of the virus is packed. Structural organization of a filamentous influenza a virus.
Several potent and specific inhibitors of this enzyme have been developed, and two zanamivir and oseltamivir have been approved for human use. The genome of influenza viruses is a linear, segmented and formed by ssrna. Influenza viruses a, b, c, and d represent the four antigenic types of influenza viruses. Review on influenza virus and its prevention and control. The influenza virus is the main culprit of respiratory infection more commonly known as the flu. Influenza a viruses can be broken down into subtypes depending on the genes that make up the surface proteins. 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. Reference strain influenza c virus cann arbor150 sequence.
Many viruses with doublestranded dna genomes have basic histonelike molecules closely associated with the dna. Influenza audorn72 virions are capsuleshaped or filamentous particles of highly uniform diameter. The influenza viruses section of virology journal will publish articles on all aspects of influenza virus research, including molecular genetics, molecular biology, biochemistry, biophysics, structural biology, cell biology, immunology, morphology, and pathogenesis. Here, we describe the isolation, evolution, and structure of a broadspectrum human monoclonal antibody mab, medi8852, effectively reacting with all influenza a hemagglutinin ha subtypes.
Till 2001, eight genome segments influenza a and b. The hemagglutinin glycoprotein of most human h7n9 viruses carries leu226, a residue linked to adaptation of h2n2 and h3n2 pandemic viruses to human receptors. The influenza a and b viruses that routinely spread in people human influenza viruses are responsible for seasonal flu epidemics. Influenza virus genome sequencing and genetic characterization. Structure of influenza virion influenza virions fig. Influenza has plagued man for centuries and has been described as an unvarying disease caused by a varying virus kilbourne 1975. Aug 23, 2018 influenza virus is a common cause of human respiratory infection with a high rate of morbidity and mortality, particularly in the elderly and in infants. Crystal structure of the human class ii mhc protein hladr1.
In humans, the respiratory epithelium is the only site where the hemagglutinin ha molecule is effectively cleaved, generating infectious virus particles. The 1918 spanish influenza pandemic represents the largest recorded outbreak of any infectious disease. Influenza, commonly known as the flu, is an infectious disease caused by an influenza virus. The influenza virion measures about 80120 nm in diameter. We use your linkedin profile and activity data to personalize ads and to show you more relevant ads. 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. Influenza virus is a common cause of human respiratory infection with a high rate of morbidity and mortality, particularly in the elderly and in infants.
The influenza virus iv is still of great importance as it poses an immanent threat to humans and animals. Virus transmission occurs through a susceptible individuals contact with aerosols or respiratory fomites from an. Basic concepts replication cycle producesfunctional rnas and proteinsgenomic rna or dna and structural proteins 100s1,000s new particles produced by each cyclereferred to as burst sizemany are defectiveend of eclipse phase replication may be cytolytic or noncytolytic steps in viral replication. 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. Today well start with the basic structure of influenza virus, illustrated above. At a sequence identity of approximately 25% to influenza a virus has, bhk ha shares a similar overall structure and domain organization. Unlike amantadine and rimantadine that target the m2 protein of influenza a viruses, these drugs inhibit replication of both. Structure and function analysis of an antibody recognizing. Here we report the crystal structure of hemagglutinin ha from influenza bhong kong873 bhk virus determined to 2. Among the three ivtypes a, b, and c influenza a viruses are clinically the most. These genes contain instructions for making new viruses, and its these instructions that an influenza virus uses once it infects a human cell to trick the cell into producing more influenza viruses, thereby spreading infection. First isolated from pigs in 2011, the virus was categorized as a new genus of orthomyxoviridae in 2016. Sometimes filamentous forms of the virus occur as well, and are more common among some influenza strains than others. The flu season is coming, and the frigid temperatures make it worse.
Each segment is encapsidated by the viral nucleoprotein to form a ribonucleoprotein rnp particle and each rnp carries its own polymerase complex. Enveloped viruses, such as influenza, infect millions of people worldwide on an annual basis. Nov 18, 2019 this is a picture of an influenza virus. These symptoms typically begin two days after exposure to the virus and most last less than a week. Influenza virus neuraminidase inhibitors the lancet. The evolution of influenza viruses results in i recurrent annual epidemics of disease that are caused by progressive antigenic drift of influenza a and b viruses due to the mutability of the rna genome and ii infrequent but severe pandemics caused by the emergence of novel influenza a subtypes to which the population has little immunity. Structural organization of a filamentous influenza a virus pnas. Influenza viruses infect many vertebrates, with influenza a, b and c viruses iav, ibv, and icv infecting humans. Influenza diagnosis clinical and epidemiological characteristics increase of febrile respiratory illness lab isolation of influenza virus from clinical specimen e. Feb 04, 2020 the flu season is coming, and the frigid temperatures make it worse.
Dec 21, 2017 influenza a viruses iavs are segmented singlestranded negative sense rna viruses that constitute a major threat to human health. An eerin infectious disease is an infectious disease. 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. Rna1 rna2 rna3 rna4 rna5 rna6 rna7 genome proteome host host human cell tropism epithelial respiratory cells interactions cell receptors. 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 20 outbreak of avianorigin h7n9 influenza in eastern china has raised concerns about its ability to transmit in the human population. The virus s shape is determined by a layer of matrix protein underneath the influenza membrane. Mar 19, 2004 the 1918 spanish influenza pandemic represents the largest recorded outbreak of any infectious disease. This work is licensed under a creative commons attribution. Influenza a viruses are classified by subtypes based on the properties of their hemagglutinin h and neuraminidase n surface proteins.