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Orthomyxovirus

Orthomyxovirus. INTRODUCTION. Cause RTI Genetic variation (shift and drift). Estimated 40-50 million deaths worldwide in pandemic of 1918-1919. PROPERTIES. Classification : - Family : Orthomyxoviridae - Genus : Three genera according to matrix

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Orthomyxovirus

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  1. Orthomyxovirus

  2. INTRODUCTION • Cause RTI • Genetic variation (shift and drift) • Estimated 40-50 million deaths worldwide in pandemic of • 1918-1919

  3. PROPERTIES • Classification: - Family:Orthomyxoviridae - Genus:Three genera according to matrix protein and nucleoprotein: . Influenza A, & B A (Human & animal; moderate to severe illness, shift and drift) B ( Human, milder illness, only drift) . Influenza C (Animal, rarely human) . ‘thogoto-like-viruses’ (Animal)

  4. ORTHOMYXOVIRUSES HA- hemagglutinin NA - neuraminidase helical nucleocapsid (RNA plus NP protein) lipid bilayer membrane polymerase complex M protein

  5. Morphology • Helical, 100-200 nm. • Enveloped • Proteins: - Hemagglutinin (HA, 80%, 15 subtypes; H1-H15): Agglutinate RBC, Attachment - Neuraminidase (NA, 20%, 9 subtypes; N1-N9): Destroy neuraminic (Sialic) acid from the receptor protein (Release the virus) - M2 protein: Ion channels, protons entry - Matrix protein (M): Assembly

  6. The HA and NA antigens of influenza

  7. Genome: 8 fragments of –ss RNA Replication: Endocytosis Nucleus Budding

  8. Cellular replication of influenza virus

  9. Genetic variation Antigenic shift: Pandamics • Decade (10 years) • Inf. A • Human strain + Animal strain Infect same cell Genetic reassortment • Complete change

  10. Antigenic ShiftGenetic reassortment

  11. Genetic reassortment with influenza A

  12. Antigenic drift: Epidemics • Annual • Inf. A & B • Mutation (Deletion and insertion • Incomplete change

  13. Antigenic Drift(Mutation)

  14. Antigenic shift and drift

  15. Pandemics and Pandemic Threats of the 20th Century • 1918-19 “Spanish flu” H1N1 • 1957 “Asian flu” H2N2 • 1968 “Hong Kong flu” H3N2 • 1976 “Swine flu” episode H1N1 • 1977 “Russian flu” H1N1 • 1997 “Bird flu” in HK H5N1 • 1999 “Bird flu” in HK H9N2 • 2003 “Bird flu” in Netherlands H7N7 • 2004 “Bird flu” in SE Asia H5N1

  16. CLINICAL ASPECTS • Incubation period:2-3 days • Symptoms:Shivering, malaise, headache, aching, rise T

  17. PATHOGENESIS Droplets URT Multiply in epith. cells Destroy cilia • Decreased clearance • Risk bacterial infection • Viremia rare

  18. Secondary bacterial infection: • - S. aureus • - S. pneumonia, H. influenza, and hemolytic streptococcus • Complication ( Rey`s syndrome): Often type B: • - Encephalitis • - Liver & Viscera • FATAL

  19. IMMUNE RESPONSE • Humoral: Is not important • Cellular: TC cells & Macrophages

  20. Vaccines: • Killed or inactivated (Inf. A & B): - Whole virus: Local reaction - Split: Less local reaction - Subunit or surface antigen: Save • Live attenuated: Adapted to grow at less Temp. e,g., 25o C • Reassortment genes: Under test

  21. Subunit influenza vaccine

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