Influenza A virus Flashcards
1
Q
Family
A
Orthomyxoviridae
2
Q
Genus
A
Influenzavirus A
3
Q
HA spike
A
- hemagglutinin
- binds to sialic acid
- glues together red blood cells
4
Q
NA spike
A
- neuraminidase
- cleaves sialic acid from glycoprotein
- inhibited by Tamiflu
5
Q
antigen drift
A
- mutations in HA and NA spike
- Flu A and Flu B
- enough mutations create new subtype
6
Q
antigenic shift
A
- reassortment of segmented genome
- Flu A only
7
Q
nuclear import/export
A
- vRNP without NP imported into nucleus, transcribed, and exported to cytoplasm and translated
- NP imported into nucleus for genome replication and synthesis of new vRNPs.
- newly synthesized M1 imported into nucleus, binds to vRNP, covers NLS on both
- newly synthesized NS2 imported into nucleus, binds to M1 (NES still exposed) and exported out of nucleus. NS2 recycled. M1 prevents reimport into nucleus
8
Q
Stages
A
Attachment
Penetration
Uncoating
Gene Expression
Genome Replication
Prep For Release
Assembly
Release
Maturation
9
Q
Attachment
A
- receptor mediated (sialic acid)
- attachment protein is HA spike
10
Q
Penetration
A
Clathrin mediated endocytosis
11
Q
Uncoating
A
- acidification of endosome by H+-ATPase
- Two steps in parallel:
1) conformational change in HA spike causes fusion of viral envelope with endosomal membrane
2) dissociation of M1 protein from nucleocapsid M2 ion channels allow protons to pass through - release of nucleocapsids into cytoplasm
- nucleocapsid has NLS on it so will be imported into nucleus
12
Q
Gene Expression
A
- transcription of vRNp by viral RdRp without free NP
- the mature mRNA is 5’ capped by cap snatching, 3’ polyadenylated by transcription of oligoU sequence, and naked (not covered by NP) -
mRNA is not a complete copy of vRNA - exported to the cytoplasm for translation
- differential splicing of segments 7 (M1+M2) and 8 (NS1+NS2) may occur
13
Q
Genome replication
A
- only in prescence of NP
- cap independent initiation of RNA synthesis by viral RdRp
- vRNPs copied to make cRNP (+)
- cRNP copied to make vRNP (-)
- absence of 5’ cap on cRNA causes RdRp to ignore transcription termination signals so cRNA are full length copies of vRNA
14
Q
Prep for release
A
- HA0 (immature form of HA), NA, M2 translated in RER and shuttled through golgi to plasma membrane
- NA cleaves sialic acid from host and viral glycoproteins to prevent clumping
- M1 coated nucleocapids exported from nucleus to plasma membrane
15
Q
Assembly
A
M1 coated vRNPs associate in 7+1 bundle
