SEVERE ACUTE RESPIRATORY SYNDROME (SARS)

MOLECULAR MECHANISMS OF ACTION

SARS-CoV is an enveloped, positive stranded RNA virus

Viral Life Cycle

1. Attachment and Penetration

• Enveloped viruses infect cells that express specific virus receptors by fusion of the viral envelope with host cell membranes.
• SARS-CoV spike glycoprotein recognizes the host cell receptor angiotensin – converting enzyme 2 (ACE2)
• Membrane fusion is mediated by spike glycoproteins on the viral envelope.
• Coronavirus entry is mediated by a single large spike glycoprotein, S, that undergoes conformational changes when bound to its specific cellular receptor.
  

2. Uncoating

• Nucleic acid of RNA viruses is released into the cytoplasm of the host cell
• How the envelope is removed is poorly understood
  

3. Translation and Replication

• Since coronaviruses are positive stranded RNA viruses, the viral genome is the same sense as host cell mRNA
• Therefore, the viral genome can immediately load onto ribosomes and start translation
• The virus is replicated using a polymerase that was encoded in the viral genome

4. Assembly

• Viral RNA is assembled into new virion particles

5. Release

• The host cell is lysed and new SARS-CoV particles are released
  

http://www.time.com/time/asia/covers/501030407/virus1.html

http://www.time.com/time/asia/covers/501030407/virus2.html

http://www.time.com/time/asia/covers/501030407/virus3.html

Goldsby, Richard A. et al. Kuby Immunology. New York: W.H. Freeman and Company, 2000.

Murray, Patrick R. et al. Medical Microbiology. Mosby, 1998.

Li, Wenhui et al Angiotensin-converting enzyme 2 is a functional receptor for the SARS coronavirus Nature 2003 426: 450-454