General multiplication

Question 1

Give the steps of multiplication

Answer 1

1. Adsorption
2. Penetration
3. Decapsidation
4. Eclipse
5. Maturation
6. Release

Question 2

Adsorption

Answer 2

• Virus surface antireceptor → Cell surface receptor
• If both are negative = Repulsion
• Reversible connection → Cations neutralise electrostatic power
• Irreversible connection → Chemical bonds between proteins

Question 3

Penetration

Answer 3

• Energy-dependent 4x more energy needed than adsorption
• General forms:
  
  • Translocation
  • Endocytosis
  • Membrane fusion​​
• Alternative forms
  
  • Injection
  • Sexfimbria
  • Passive

Question 4

Translocation

Answer 4

• ‘Trapdoor’ mechanism
• Amporphous RNA-protein complex

Question 5

Endocytosis (during penetration)

Answer 5

Cell nutrition endosome → Phagolysosome → Decapsidation

Question 6

Membrane fusion (during penetration)

Answer 6

Virial fusion (F) protein induces:

• Vital envelope merges into the cytoplasmic membrane of the host
• Only nucleocapsid gets into the cytosol

Question 7

Injection

Answer 7

• In tailed bacteriophages
• Lysozyme enzyme + contractile proteins

Question 8

Sexfimbria

Answer 8

Lack of cell wall → Bacterial sexual disease

Question 9

Passive penetration

Answer 9

• Cellular wall injuries
• Arthropod bites

Question 10

Decapsidation

Answer 10

The release of nucleic acid from the capsid

Dangerous for the virus but necessary for transcription

Question 11

Strategies of decapsidation

Answer 11

• Use of cellular proteases
• Viral uncoating proteins
• Partial decapsidation
  
  • Hiding the nucleic acid until early virus protein production
• Sometimes simultaneous penetration + decapsidation

Question 12

Eclipse

Answer 12

Expression + copy of viral genetic information

• Transcription, translation + NA replication
• Different strategies according to the type of nucleic acid
  
  • Baltimore system

Question 13

Maturation

Answer 13

Polypeptide → Protein

• Glycosylation, dimer formation, antigen development
• in the ER/Golgi

Question 14

Virus assembly

Answer 14

• At the site of replication → protection
• Protein transport - may evolve inclusion bodies
• Nucleic acid signal → connects to the capsomers
• Scaffolding proteins regulate the assembly
• Envelope + matrix proteins required from cellular membranes

Question 15

Methods of virus assembly

Answer 15

Icosahederal

• Nucleic acid enters into the capsid

Helical

• Capsomers surround the nucleic acid

Question 16

Virus release

Answer 16

• Passive/active
• Non-enveloped viruses → Cytolysis
• Enveloped viruses:
  
  • Budding
• Cell-associated viruses - Release at cell death
• Cell fusion (syncytium) → Membrane tunnels

Question 17

Alternative forms of virus release

Answer 17

• Lysosome disintegration
• T-Bacteriophages : Lysozyme digests cell wall
• Plant cells firmly connected together
  
  • The virus spreads from cell to cell