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Orthomyxoviruses

Orthomyxoviruses. Negative-sense RNA virus Segmented genome Enveloped Hemagglutinin glycoprotein: viral attachment protein and fusion protein-It elicits neutralizing, protective antibody responses. Orthomyxoviruses. Replicates in cell nucleus but assembles and buds from the plasma membrane

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Orthomyxoviruses

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  1. Orthomyxoviruses • Negative-sense RNA virus • Segmented genome • Enveloped • Hemagglutinin glycoprotein: viral attachment protein and fusion protein-It elicits neutralizing, protective antibody responses

  2. Orthomyxoviruses • Replicates in cell nucleus but assembles and buds from the plasma membrane • Segmented genome promotes genetic diversity caused by mutation and reassortment of segments on infection with two different strains • Influenza A, B and C • Influenza A infects humans, mammals, and birds (zoonosis)

  3. Orthomyxoviruses • Only influenza A and B viruses cause significant human disease • Annual epidemics (mutation:drift) • Periodic pandemics(reassortment:shift) 1918-19:20 million death 1947 1957 1968 1977 2009

  4. Orthomyxoviruses • Pleomorphic: spherical and tubular • Hemagglutinin(HA): Mutation derived changes in HA causes shift and drift. Shift occur only in influenza A and different HAs are formed (H1, H2...) • Neurominidase(NA): also undergoes antigenic changes

  5. Orthomyxoviruses • Hemagglutinin(HA): viral attachment protein, binds to sialic acid on epitelial cell surface receptors,hemagglutinates human, chicken and quinea pig red blood cells, elicits protective neutralizing antibody response • Neurominidase(NA):It facilitates the release of virion from infected cell

  6. Influenza virus • Matrix and nucleoprotein are type-specific: Influenza A, B and C virus Subtypes: according to HA and NA Strains of Influenza A: A/Bangkok/1/79 (H3N2): Type/place of original isolation,date of isolation/antigen

  7. Influenza virus • Virus likes cool,humidity (winter) • Spread by inhalation of small aerosols • Cell culture • Antigen • PCR

  8. Influenza virus • Rimantadine,Amandatine: inhibits uncoating of influenza A • Zanamavir and oseltamivir: NA inhibitors • Influenza vaccine: trivalent formalin inactivated, every year

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