Virus-cell interactions (CPEs)

Question 1

CPEs

Answer 1

Alterations in the morphology of cells due to virus infection

• Usually degenerative processes
• Mainly observed in cell cultures
• Direct damage of viruses on cells

Question 2

Give examples of direct damage of viruses on cells

Answer 2

• Toxic effect of adsorption
• Virus proteins inhibit translation
• Cytoplasmic damage
• Cytoskeleton depolymerisation
• Expression of fusion proteins

Question 3

Light microscopy of CPEs

Answer 3

• Some cells don’t need staining
• Staining gives more detail

Question 4

Tools for the detection of virus multiplications in vitro

Question 5

Why is it that not all virus infections result in CPEs?

Answer 5

• The cytopathic character of a virus may change due to mutation
• The CPE in question isn’t always found with the virus

Question 6

The appearance of the CPE is influenced by…

Answer 6

The multiplicity of infections (MOI)

• The most characteristic CPE is seen by a low MOI

Question 7

The host cell can cause a difference in the…

Answer 7

CPEs expressed in the cell

Question 8

List the types of CPE

Answer 8

• Inclusion body
• Cell Rounding
• Syncytium-formation
• Lumpy cell nucleus
• Cell vacuolisation
• Hemadsorption
• Plaques

Question 9

Inclusion bodies (General)

Answer 9

• Can be Intranuclear or intracytoplasmic
• Found at the site of nucleocapsid assembly → virus deposition
• Seen in stained cells
  
  • Surrounded by a halo

Question 10

Intranuclear inclusion bodies

Answer 10

• Caused by DNA/RNA virus replicating in the nucleus
• Cowdry-A/Cowdry-B types depend on state of synthesis of macromolecules
• Basophyl, amphophyl, eosinophyl

Question 11

Intracytoplasmic inclusion bodies

Answer 11

• Usually caused by RNA viruses
• DNA viruses replicating in the cytoplasm
• Eosinophyl, rarely basophyl
• Pathognomic: Negri bodies, Guarnieri bodies

Question 12

Cell Rounding

Answer 12

• One of the most common CPEs
• Cytoskeleton depolymerisation
• Loss of electrolytes

Question 13

Syncytium-formation

Answer 13

• Caused by enveloped viruses only
• Fusion proteins on the surface of the virus
  
  • Used for viral penetration
• Giant cells with many nuclei
  
  • Polykaryocytes
  • Syncitia

Question 14

Lumpy cell nucleus

Answer 14

• Chromatin conglomeration, rearrangement
• Changed refraction (parvo)
• Nucleus lumpy disintegration

Question 15

Cell vacuolisation

Answer 15

• Vacuoles formed in the cells
  
  • In the nucleus or
  • In the cytoplasm

Question 16

Hemadsorption

Answer 16

• Viral hemagglutinin is expressed on the surface of infected cells
• RBCs added into the culturing medium, then washed away 30 mins later
• Infected cells capture RBCs
• Diagnosis of:
  
  • Paramyxoviruses

Question 17

Plaques

Answer 17

Local/focal

• Certain viruses are more frequent in plaques
• Lower MOI = more freqeuntly plaques are formed
• Syncytia are seen as plaques

Question 18

Advantages of plaques

Answer 18

• Virus purification: Subsequent passages of viruses taken from singular plaques - establishment of virus strains
• Virus quantification: Plaque counting

Question 19

Non-specific CPEs: differentiation

Answer 19

• Compare with uninfected control
• Passage the isolate
• Perform direct demonstration