SARS-CoV-2

• SAR-CoV-2 belongs to the coronavirus family
• alpha and beta coronaviruses are known to infect humans
• SARS 1 versus SARS 2

  • 1 was known (civet cats, remove to break chain), 2 reservoir unknown
  • 1 transmission mainly in hospitals, 2 widespread community transmission
  • 2 abundant asymptomatic cases
• SARS 2 originated in Wuhan
• SARS 2 is closely related to bats coronavirus
• SARS-CoV-2 is

  • single stranded
  • positive sense
  • non-segmented
  • approx. 30kb long
• SARS-CoV-2 encodes for 27 genes
• CoV undergo discontinuous transcription, leading to high recombination rates
• error rate for RNA replication is reduced by proof reading enzyme ExoN 


  NSP14
• SARS-CoV-2

  • 125 nm diameter
  • enveloped viruses
  • numerous surface projected club-like spikes
• S protein (spike) function

  • entry of SARS-CoV-2 into cells
  • protective immune response
  • virulence
  • host tropism
• N protein function

  • component of nucleocapsid
  • viral transcription efficiency
  • protective immune responses
• M protein function

  • most abundant amongst structural proteins
  • assembly of virus particles
• E protein function

  • smallest amongst structural proteins
  • viral assembly and release
• SARS-CoV-2

  labels

  A) spike

  B) nucleocapsid

  C) membrane

  D) envelope

  
• virus can enter through

  endocytosis or releasing genome into cell
• delta through genome entry only and omicron through endocytosis
• SARS-CoV-2 replication cycle

  • fusion
  • replication
  • assembly
  • release
• delta replicates deep in lungs, severe infection
• omicron transmissible due to replication in upper respiratory tract
• innate immunity

  • cytokines produced by WBCs
  • which attracts more WBCS
  • creating cycle of inflammation, damages lung cells
  • damage through formation of fibrin
  • weakened blood vessels, fluid seeps into lungs, causing respiratory failure
• adaptive immunity

  • COVID patients have antibodies 1-3 weeks after recovery
  • severe disease correlates with high levels of antibodies
  • CD4 T helper cells- critical for antibody response, cross reactive immunity
  • CD8 T killer cell- important for many viral infections, may prevent reinfection
• SARS-CoV-2 local immunity in

  lungs, nasal passage, oral cavity, salivary glands
• transmission of SARS-CoV-2


  droplets, aerosoles, smear infection
• monoclonal antibody 


  prevent virus entering host cell
• camostat mesylate 


  prevent SARS-CoV-2 into cell by acting on TMPRESS2
• lopinavir-ritonavir 


  inhibition of protease activity of SARS-CoV-2
• ribavirin 


  may inhibit mRNA capping
• RNA synthesis inhibitors


  inhibits SARS-CoV-2 RNA synthesis and replication
• Chloroquine group 


  interfere with the release of progeny from infected host cells