34 - Orthomyxoviridae

Question 1

Orthomyxoviridae

Answer 1

• Etymologi: muxa: mucus
• Morphology:
  
  • ​-ssRNA genome
  • Segmented
  • Helical capsid
  • Enveloped
• Resistance: weak (but in aerosol survives for hours)
• Biological properties:
  
  • Baltimore V. – viral transcriptase enzyme
  • Proteins (genes on separate segments):
    
    • Core:
      
      • Nucleoprotein (NP)
      • Polymerase (PA, PB1, PB2)
    • Matrix: (M1) protein
    • Proteins in envelope:
      
      • Hemagglutinin (where the virus binds to the host cell)
      • Neuraminidase (for release and spread the virus)
      • Matrix M2 protein (ion channel)
    • Virulence (H5, H7) ~ basic aa. at the protease cleavage site
  • Propagation: embryonated eggs (allantoic-, amniotic membrane)
  • Influenza A – euryxen, zoonotic; B, C and D: mainly humans
• Antigenic properties:
  
  • Core and matrix proteins: conservative genes – A, B, C, D genus
  • Envelope proteins (HA and NA): hypervariable genes
    
    • ​HA: 16 serotypes
    • NA: 9 serotypes
    • → Antigenecity is determined by the HA and NA combination!
  • Antigenic drift: mutations in the HA and NA antigens
  • Antigenic shift: recombination resulting new HA-NA combination
• Diagnosis:
  
  • Isolation (embryonated eggs) + HA test
  • Indirect: HAI

Question 2

Orthomyxoviridae

List the different genera

Answer 2

• Influenzavirus A genus
• Influenzavirus B genus
• Influenzavirus C genus
• Influenzavirus D genus
• Thogotovirus genus
• Quaranjavirus genus
• Isavirus genus

Question 3

Orthomyxoviridae

Influnzavirus A genus

Answer 3

• Influenzavirus type A
  
  • Fever, respiratory symptoms, muscle pains
  • Relative species adaptation
    
    • Porcine influenza
    • Equine influenza
    • Avian influenza (all types, several combinations, manily the avian influenza that adapt to other hosts)
      
      • H5N1 (wild birds → chickens → wild birds → humans)
      • H7N9
    • Human influenza (H1N1, H2N2, H3N2) (orginally from water fowl)

Question 4

Orthomyxoviridae

Influnzavirus B, C, D genus

Answer 4

Human influenza

Question 5

Orthomyxoviridae

Thogotovirus genus

Answer 5

• Arboviruses, tick vectors
• Asia, Africal, Mediterranen basin
• Dhori, Batken, Thogoto virus

Question 6

Orthomyxoviridae

Isavirus genus

Answer 6

Infectious salmon anemia virus (Norway)