6 - SARS-CoV-2 Flashcards
when was the first coronavirus discovered?
1931
when was reverse genetics discovered?
2000
what family doe the Sars-CoV-2 virus belong to?
Coronaviridae
which members of the coronavirinae subfamily are known to cause infections in humans
alphacoronavirus and betacoronavirus
SARS-CoV-1
- Spill-over reservoir unknown: civet cats -cull to break the chain
- Most transmission occurred in hospital setting (hubs)
- No transmission until 24-36h after symptoms, lack of asymptomatic cases -contract tracing effective
SARS-CoV-2
- Spill-over reservoir unknown
- Widespread community transmission
- Possible abundant asymptomatic/mild cases
SARS-COV-2 Genome
- Single-stranded
- non-segmented
- positive sense
- ~30 kb long genome. - encodes for 27 genes which are either structutral, non-structural, accessory proteins
structural proteins
- Constitute the virion
* Include S, E, M, N
non- structural proteins
- Not structural components of virion
* Include NSP1, NSP2, NSP3, NSP14 etc
What is the role of non-structural proteins in SARS-COV-2?
They form a large compound that replicates RNA
accessory proteins
- Produced only in infected cells
* Includes ORF3b, ORF6, ORF7a etc
coronavirus virion and viral proteins
- ~125 nm diameter
- enveloped viruses
- Numerous surface-projected club-like spikes
Functions of S protein
- Entry of SARS-COV-2 into cells
- Host tropism
- Protective immune responses (vaccines)
- Virulence – severity of the disease
Functions of N protein
- Component of nucleocapsid
- Virus transcription efficiency
- Protective immune responses (vaccines)
Functions of M protein
- Most abundant amongst structural proteins
* Assembly of virus particles
Functions of E protein
- Smallest amongst all the structural proteins
* Virus assembly, and release
What are the 4 stages of the SARS-COV-2 replication cycle
Fusion, replication, assembly and release
What are the two ways in which SARS-COV-2 can enter the host cell?
- the virus will bind to the ACE-2 receptor and then the receptor is cleaved by TMPRSS2 and then the plasma membrane fuses with the virus
- the virus binds to ACE-2 and is endocytosed into the cell
Why is omicron less severe than delta?
Omicron replicates in the upper respiratory tract meaning that the lungs do not experience the damage that they would with delta which replicates in the lungs
Which types of immunity is important for long term protection against COVID?
Antibodies, CD4+ T cells and CD8+ T cells
How is SARS-CoV-2 transmitted?
Droplets (e.g. coughing), aerosols (e.g. talking) or smear infection (e.g. on surfaces such as door handles)
