Beginnings

Question 1

What is a virion?

Answer 1

A vision is a small extracellular infectious particle made of the genome in form of a nuclei acid and the capsid.

Question 2

What are the principles of the Kochsche postulate for the identification of a pathogen?

Answer 2

1. Pathogens must be detectable in all diseased animals, not in healthy ones
2. Cultivating pathogens in pure culture
3. Pathogens can reproduce disease in healthy individuals
4. Pathogens can be reisolated from newly diseased animals

Question 3

The characteristics of viruses

Answer 3

Very small, infectious, obligate intracellular parasites
Viral genome: DNA or RNA
In suitable host cell: replication of viral genome and determines synthesis through virus derived or cellular components
New viruses are generated with newly synthesised components within the cell „de novo“
They are vehicles for the transmission of the viral genome into new host cells where uncoating and the next replicative cycle takes place

Question 4

Criteria for classification of virus

Answer 4

1. type of nucleic acid for the genome (Baltiomore scheme)
   - DNA/RNA
   - Size
   - ss/ds
   - linear, circular, segmented a.o.
2. existence of (lipid-)envelope
3. Symmetry of capsid
4. Arrangement of the genes
5. Replication strategy (Baltimore scheme)

Question 5

What are Virusoids, viroids and prions? With example

Answer 5

Virusoids: Helper-dependent-virus, has Virusoids-nucleic-acid and encodes proteins (do not build capsid) -> needs helper virus for packaging. Example: Hepatitis Delta Virusoid, needs Hepatitis B Virus

Viroids: small infectious RNA molecules, NO proteins Example: Cadang-cadang viroids; leads to coco palm death

Prions: infectious proteins, NO nucleic acid Examples: Creutzfeldt-Jakob, Scrapie, BSE - pathogenic PrP enters nervous system over gut and is transported into CNS where the protein accumulates

Question 6

Methods to detect virus infection in cell culture

Answer 6

• cytopathic effect (CPE)
• development of inclusion bodies
• hemadsorption

Question 7

Steps of the viral replicative cycle

Answer 7

• adsorption
• penetration
• replication
• generation of new particles
• release by cell lysis „viral burst“

Question 8

Steps of „in situ“ detection of viral antigens

Answer 8

• sample preparation
• fixation
• permeabilisation
• immunolabeling
• detection via immunocytochemistry or immunoflourescence