Coronaviruses Flashcards
Genome
(+)ssRNA
Structure
Helical and enveloped
VAP
Spike (S)
Host receptor
ACE2
Fusion peptide
Exposed by cleavage of Spike protein by TMPRSS2
Envelope protein (E)
Assembly, membrane channel activity
Membrane glycoprotein (M)
Assembly
Nucleocapsid (N)
Coats the genome
What is a critical step for entry
Processing of Spike by TMPRSS2 to reveal fusion peptide
Life cycle
- Binding and fusion with Spike-ACE2 and fusion protein
- Initial translation of orf1 to make double membrane vesicles
- Transcription on virus induced membranes
- Transcription of mRNAs
- Translation of structural proteins
- Genome replication
- Budding of RNA/N into an ER vesicle
- Furin matures then it’s released
What does the -1 ribosomal Frameshift do?
Causes polymerase to fall off
PL2pro
Responsible for first few cleavages
3CLpro
Responsible for many last cleavages
RNA EXOnuclease
Lowers mutation rate by proofreading
Remdesivir
Inhibits RNAP by preventing elongation
Problem with Remdesivir
Resistance via nsp12 mutations
How are the genes arranged and translated?
They are nested but each RNA has its own 5’ leader, transcription regulating sequence (TRS), and orf
Where did they come from?
Zoonotic transmissions mainly via bats
SARS1 Pathogenesis
Infection of pneumocytes in alveolar epithelium followed by macrophages
Virus mainly in lower respiratory tract
Acute lung damage (partially immune-mediated)
Some virus replication in intestines
Viral load peaks 10 days after infection during symptomatic phase
Virus cleared within 2 weeks but kung damage is so severe many deaths happened after that
SARS2 Pathogenesis
Much lower fatality rate but much more transmissible = more death
Infection of pneumocytes in alveolar epithelium, macrophages, and nasal cilia
Acute lung damage (partially due to immune-mediated excess cytokines)
Some virus replication outside lungs in intestine and possibly the kidneys
Viral load peaks early in the course of infection and is present before symptoms
How is pathogenicity different between SARS1 and SARS2?
SARS1 - infectious AFTER symptomatic, virus cleared in about 2 weeks
SARS2 - Lower case fatality but more transmissible so more overall death, also infects nasal cilia, replicates also in kidneys likely, infectious BEFORE being symptomatic