III - A. Virology | 2. Cultivation of viruses. Replication of viruses. The productive virus infection

Question 1

I. Replication of viruses
1A. What is the infective cycle of virus

Answer 1

Question 2

I. Replication of viruses
1B. In the infective cycle, what happen in step 1: attachment?

Answer 2

attachment: interaction of virion with the host cell via receptor-ligand interactions

Question 3

I. Replication of viruses
1C. In the infective cycle, what happen in step 2: penetration?

Answer 3

penetration: virus is taken up inside the cell (attachment initiates receptor-mediated endocytosis)

Question 4

I. Replication of viruses
1D. In the infective cycle, what happen in step 3: uncoating?

Answer 4

uncoating: physical separation of the nucleic acid from the outer components of the virion

Question 5

I. Replication of viruses
1E. In the infective cycle, what happen in step 3: „eclipse”?

Answer 5

„eclipse”: virion „disappeares”, time of viral genome replication and protein synthesis
- transcription of early genes, then translation into proteins
- replication of nucleic acid
- transcription of late genes, then translation into proteins

Question 6

I. Replication of viruses
1F. In the infective cycle, what happen in step 5: release?

Answer 6

Release
* through lysis of host cell
* through budding
* througn exocytosis

Question 7

I. Replication of viruses - Types of infection
2A. What are the 4 types of viral infection?

Answer 7

1. productive infection
2. abortive infection
3. restrictive infection
4. latent infection

Question 8

I. Replication of viruses - Types of infection
2B. What is productive infection?

Answer 8

the virus replicates inside a susceptible cell (or permissive cell)

Question 9

I. Replication of viruses - Types of infection
2C. What is abortive infection?

Answer 9

Abortive infection: cell were infected by the virus but can not produce any progeny virus as a result of the infection

Question 10

I. Replication of viruses - Types of infection
2D. What is restrictive infection?

Answer 10

restrictive infection: the complete repertoire of virus genes necessary for virus replication is not transcribed and translated into functional products
=> the infection is referred to as restrictive

Question 11

I. Replication of viruses - Types of infection
2F. What is latent infection?

Answer 11

latent infection: the residence in the body of a specific infectious agent without any manifest symptoms

Question 12

I. Replication of viruses
3A. What are the infection types based on clinical symptoms?

Answer 12

• acute
• chronic (or persistent)
• latent-reactivating
• slow virus infection

Question 13

I. Replication of viruses
3B. Give examples of viruses causing acute infection

Answer 13

• Rhinovirus
• Rotavirus
• Influenza virus

Question 14

I. Replication of viruses
3C. Give examples of viruses causing persistent infection

Answer 14

Lymphocytic choriomeningitis virus

Question 15

I. Replication of viruses
3D. Give examples of virus causing latent infection

Answer 15

Herpes simplex virus

Question 16

I. Replication of viruses
3E. Give examples of slow virus infection

Answer 16

• Measles SSPE
• Human immunodeficiency virus

Question 17

II. Cultivation of viruses
1. What are the issues with cultivation of viruses?

Answer 17

• obligate parasites (lack of metabolism)
• have to find the susceptible (permissive) host cell

Question 18

II. Cultivation of viruses
2. What are the 3 cultivation methods?

Answer 18

1. Inoculation of laboratory animals
2. Cultivation of viruses in embryonated egg
3. In vitro cell or tissue cultures

Question 19

II. Cultivation of viruses
3. What are the features of cultivation of viruses in embryonated egg?

Answer 19

• 8-12 days old, embryonated egg
• inoculation of different layers of the egg
• detection of changes / cytopathic effects
• Used in influenza vaccine production
• Cheaper, easier compared to use of lab animals

Question 20

II. Cultivation of viruses
4. What are the features of Inoculation of laboratory animals?

Answer 20

• Not used in diagnostics anymore, only for research (for studies of pathogenesis)
• inoculation of susceptible tissue
• eg. newborn mice were used to differentiate Coxsackie A and B viruses

Question 21

II. Cultivation of viruses
5A. What are the features of cultivation in vitro cell or tissue cultures

Answer 21

• primary, secondary and continous cell lines
• Mostly used method for virus propagation
• Cells of human or animal origin are cultivated in the lab in flask / Petri dish
• Flasks for cell culturing → monolayer cultures
• Bottles→ suspension cultures
• Cell culture media with liquid, serum, antibiotics, amino acids, vitamins, growth factors

Question 22

II. Cultivation of viruses
5B. How do we prepare cell culture? ( Tissue culture)

Answer 22

wash and centrifuge cells
→ cultivate cells in culture media
→ primary cells
→ transformed cells
→ continuous cell like (immortalized cells with abnormalities)

Question 23

II. Cultivation of viruses
6. How do we detect virus infected cells?

Answer 23

• detection of cytopathic effects
• detection of virus-encoded proteins (immunohistochemistry)
• detection of virus-specific nucleic acid
• haemadsorption

Question 24

II. Cultivation of viruses
7. How do we detect viruses based on Cytopathologic effects (CPE)?

Answer 24