Orthomyxoviridae Flashcards
why -myxo?
myxa = mucus
morphology
-ssRNA genome, segmenter (8), helical capsid, enveloped, big size
Resistance
Weak, but in aerosol (airdroplets) is can survive for hours
Replication
Baltimore V - viral transcriptase enzyme
Biological properties
-core, matrix, envelope
proteins (genes on separate segments):
- core: nucleoprotein (NP), polymerase (PA, PB1, PB2)
- matrix (M1) protein
- envelope: hemagglutinin (HA), neuraminidase (NA), matrix (M2)
Virulence
H5, H7 - basic amino acids at the protease cleavage site
Propagation
embryoneted eggs (allantoic- amniotic membrane)
Influenza A, B and C affect?
A - euryxen, zoonotic
B and C: mainly humans
Antigenic properties:
-core and matrix proteins
conservative genes - A, B and C genus
Antigenic properties:
-envelope proteins (HA and NA)
hypervariable genes
- HA: 15 serotypes
- NA: 9 serotypes
How is sntigenicity determined?
antigenicity is determined by the HA and NA combination!
Antigenic drift
mutations in the HA and NA antigens
Antigenic shift
recombination resulting in new HA-NA combinations
Diagnosis
- direct
- indirect
- Direct: isolation (embyonated eggs) + HA test
- Indirect: HAI
Genus
- Influenzavirus A
- Influenzavirus B and C
- Thogotoirus
- Isavirus
What does influenzavirus typr A cause?
fever, respiratory symptoms, muscle pain
Influenzavirus A:
Species adaptation?
Yes, relative species adaptation
- porchine influenza (H1N1, H3N2)
- equine influenza (H7N7, H3N8)
- avian influenza - all types, several combinations (H5N1!)
- human influenza (H1N1, H2N2, H3N2)
Influenzavirus B and C:
example
human influenza (B: seals, C: dogs, swine)
Thogotoirus:
example
Tick-borne orthomyxo-like viruses
-Dhori, Batken, Thogoto virus (Asia)
Isavirus:
example
Infectious salmon anemia virus (Norway)
