L17 - GL Smith - Influenza and Hepatitis viruses Flashcards
(73 cards)
describe influenza’s genome
-ve sense ssRNA genome with 8 RNA segments.
does influenza hace a lipid ,membrane?
yep
which ion channel does flu have?
M2
which glyocoproteins does influenza express on its surface?
haemagglutinin (HA), neuraminidase (NA)
influenza:
Beneath the virus envelope is the ____(_) protein and within the nucleocapsid the _______ (NP) is associated with the RNA genome.
Beneath the virus envelope is the matrix (M1) protein and within the nucleocapsid the nucleoprotein (NP) is associated with the RNA genome.
describe influenzas polymerase
Virion core also has PB1, PB2 and PA that make up the virus RNA-dependent RNA polymerase (RdRp). The RdRp must be packaged within the virion to transcribe the –ve sense ssRNA genome into the virus mRNAs to initiate the infectious cycle
is influenza spherical?
yes, roughly, if grown in cell culture
However, fresh clinical isolates can have a filamentous morphology.
where does influenza replicate?
is this special
Unlike most –ve sense ssRNA viruses, influenza virus replicates in the nucleus.
flu:
There are __ HA types and _ NA types.
There are 18 HA types and 11 NA types.
Most HA sub-types have been found in _ that are the natural reservoirs of most influenza viruses.
Most HA sub-types have been found in birds that are the natural reservoirs of most influenza viruses.
describe influenza transmission characteristics
transmitted via aerosol and inhaled virions initiate infection in the respiratory tract.\
Influenza transmission is highly seasonal with epidemics occurring during winter months when people are closer together inside.
label
how does flu enter the cell?
HA binds sialic acid
endocytosis
acidification in endosome causes 2 changes
- a conformational change in the HA that promotes fusion of the virus and endosomal membrane.
- enabled by low pH is the import of protons into the virus core via the M2 ion channel. This destabilises the core and promotes un-coating.
label
is HA a dimer or trimer?
trimer
describe HA structure
trimer and each monomer is composed of HA1 and HA2 subunits that are derived by proteolytic cleavage from a precursor called HA0
HA:
The HA2 subunit provides ….
The HA2 subunit provides the stalk between the globular head and the virus membrane, in which it is anchored.
describe how acidification enables HA to cause fusion of virus and endosome
HA2 contains fusogenic peptide buried in trimer. Acidification causes conformational change, exposure of fusion peptide and its insertion into host membrane
just FYI
in flu’s entry to the cell - what channel enables the import of H+ ions
M2 channel
how do they drugs amantadine and rimantidine work?
block M2 pore
prevent protonation of the core and virion uncoating
describe the process of protein replication for flu
nucleocapsid transported to nucleus
RdRp transcribes each –ve sense ssRNA segment into a mRNA
each segment codes for one protein, but for RNA segments 7 and 8, the mRNA may be spliced to produce different proteins (M1 and M2 from segment 7, and NS1 and NS2 from segment 8).
describe cap snatching in flu
The 5’ end is derived by cap-snatching from host mRNAs. That is why host DNA-dependent RNA polymerase II activity is needed for influenza replication – to provide the supply of caps that influenza virus RdRp steals to synthesise virus mRNAs.
ngl im not all thta sure
how does influenza leave teh cell?
budding
