Orthomyxoviruses Flashcards
Which genome type?
(-)ssRNA with 8 segments
VRNP
Viral ribonucleoprotein structure - the 8 gene segments coated in NucleoProteins and polymerase proteins
What is the VAP?
Hemagglutinin
Neuraminidase
Envelope glycoprotein essential for replication.
Cleaves sialic acid to free hemagglutinin so it can bind an actual receptor not a dummy one in mucus as well as free budding viruses.
What category is this virus?
Enveloped and helical
(all helical animal viruses are enveloped)
What’s an example of an orthomyxovirus?
Influenza A-D
Influenza A
Seasonal, the only one to cause pandemics because of its large host range
Host range: birds, bats, humans, other mammals
Influenza B
Seasonal
Host range: humans, seals
Life cycle
- Attachment - VAP hemagglutanin & host sialic acid
- Penetration - endocytosis with acidification to cause endosomal membrane fusion
- Uncoating - full uncoating occurs in the nucleus
- Expression - vRNP goes to the nucleus and there’s primary transcription via virion associated polymerase. Splicing and translation occurs in the cytoplasm
- Replication - goes (-)ssRNA to (+)ssRNA back to (-)ssRNA. Includes secondary transcription and progeny nucleocapsid is transported out of the nucleus
- Assembly
- Maturation
- Release - budding
How can an 8 segment genome make 10 proteins?
(+)ssRNA splicing in the cytoplasm
What is the avian sialic acid receptor linkage?
alpha2,3
What is the human sialic acid receptor linkage?
Alpha2,6
Why is sialic acid receptor linkage important?
Determines host range which is a big barrier to spillover
How are (-)ssRNA genes expressed?
Packaged RNA dependent RNAP converts (-)ssRNA to (+)ssRNA which = mRNA
Host translates (+)ssRNA
New (+)ssRNA converted to (-)ssRNA to replicate the genome
How does IAV know what is vRNP, vRNA, or mRNA?
vRNA - uncapped (-) sense
mRNA - 5’ cap stolen from host and (+) sense
vRNP - is the prepackaged structure of genome segment and (-) sense