10B. Lecture

Question 1

Morphological changes in cells independently from virus infections

Answer 1

aka. non-specific CPEs
•aging of the cells
•alteration of the pH range of the medium
•alteration of the incubation’s temperature
•toxic components in the inoculum
•bacterial contamination

Question 2

how are non-specific CPEs differentiated?

Answer 2

• Compare with the uninfected control
• Passage the isolate
• Perform direct demonstration:
• PCR, IHC, ISH
• VN

Question 3

direct damage of viruses on cells

Answer 3

• toxic effect of adsorption
• virus proteins inhibit cellular translation
• early proteins inhibit cellular nucleic acid transcription and replication
• viral proteins or virions are deposited in the cells
• viral proteins damage the cytoplasmic membrane permeability - osmotic changes
• cytosceleton depolymerisation
• expression of fusion proteins

Question 4

CPEs are usually investigated how

Answer 4

• Usually investigated by light microscopy (100-400 × magnification)
• some of the CPEs are visible in unstained cells
• staining (HE, Giemsa, etc.) usually gives more detailed information

Question 5

non-CPE producing viral infections

Answer 5

•the cytopathic character of a virus strain may change due to mutations (i.e. BVDV)
•the CPE is not always connected to the pathogenicity of the virus
-CSF - no CPE but pathogen
-Spumaviruses- obvious CPE but orphan

Question 6

The appearance of the CPE is influenced by

Answer 6

multiplicity of
infections (MOI)
•the most characteristic CPE is seen by low MOI (<0.1)

Question 7

CPEs

Answer 7

•CPE may occur independently or jointly
•Different viruses may cause similar CPE
•CPE may vary according to the host cell
→ CPE alone is usually not pathognomic
→ CPE is important character for the identification of the virus

Question 8

Inclusion body formation

Answer 8

• at the site of assembly of nucleocapsid → virus deposition (in nucleus RNA sometimes too, cytoplasm both RNA and DNA in eosinophils usually)
• seen in stained cells (of cell cultures or organ sections)
• homogenous staining
• surrounded by halo - shrinkage after fixation

Question 9

negri bodies and guarnieri bodies

Answer 9

•pathognomic IC inclusion bodies

Negri bodies (rabies), Guarnieri bodies (pox)

Question 10

cell rounding

Answer 10

• one of the most frequent CPE
• cytosceleton depolymerisation
• loss of electrolytes
• unstained: double refraction, detachment, shrinkage
• stained: intensive staining

Question 11

Syncytium-formation

Answer 11

•caused exclusively by enveloped viruses
•fusion proteins (F) on the surface of the virus
•primarily for viral penetration
•expressed on the cytoplasmic membrane of the cell
•fusion of infected and non-infected cell membranes
→ membrane tunnels → intracellular spread
→ hidden from the antibodies
•giant cells with many nuclei: polykaryocytes, syncytia
•in tissue sections multinucleated giant cells may be seen
→usually lymphatic cells
→results of impaired cellular division

Question 12

Lumpy cell nucleus

Answer 12

• chromatin conglomeration, rearrangement
• changed refraction (parvo)
• nucleus lumpy disintegration

Question 13

Cell vacuolisation

Answer 13

•vacuoles are formed in the cells in cytoplasm or nucleus

Question 14

hemadsorption

Answer 14

•viral hemagglutinin is expressed on the surface of the
infected cells
•RBCs are added into the culturing medium, and after 30
minutes incubation unbound RBCs are washed away
•infected cells are capturing RBCs

Question 15

diffuse vs. local/focal CPEs

Answer 15

Diffuse: all around in the cell culture
Local / focal: plaques
•certain viruses more frequently appear in plaques
•in lower MOI more frequently plaques are formed
•syncytia are seen as plaques

Question 16

•facilitation of plaque formation:

Answer 16

•supplementing the maintenance fluid with agar,

carboxymethyl cellulose or metrizamide

Question 17

•advantages of plaques

Answer 17

•virus purification: subsequent passages of viruses taken
from singular plaques - establishment of virus strains
•virus quantification: plaque counting