Coronaviruses

Question 1

Morphology

Answer 1

• core, lipid membrane, envelope
• enveloped +ssRNA virus
• core has nucleoprotein surrounding RNA in helical arrangement
• virion particle has no polymerase but genome does
• spike glycoprotein trimer

Question 2

Genome

Answer 2

• huge genome compared to other RNA viruses

- extra gene with proofreading enzyme allows low mutation rate

Question 3

Genome Organisation of SARS1

Answer 3

• monopartite and linear
• capped and tailed
• virion RNA infectious
• complex genome with many accessory proteins
• 5’ end has viral polymerase complex
• Spike protein binds to other cellular receptors
• accessory genes involved in preventing host immune response

Question 4

Life Cycle

Answer 4

• non strucutral gene impact pathogenicity
  1. entry via endosome
  2. membrane fusion causes viral RNA release
  3. translation of genome and proteolysis into replicase
  4. replicase synthesizes negative sense RNA for transcription and translation
  5. assembly and budding of proteins
  6. replication of negative sense to form positive sense for virion particle formation

Question 5

Spike mutations

Answer 5

• infects H2 receptor in humans
• low mutation rate but lots of virus infections raises changes
• mutations with better H2 access or affinity would proliferate
• variants can arise rapidly in individuals with long term infections
• immunosuppressed patients have chronic infections where the virus persists and mutates