Lecture 18. Viral Replication

Question 1

What can viruses recognise?

Answer 1

Recognise specific structures on the host cell called cellular receptors through their VAPs

Question 2

How do viruses attach to cells?

Answer 2

Through and interaction between the VAPs and specific cellular receptors

Question 3

What is viral tropism?

Answer 3

The specificity of a virus to a specific host

Question 4

What is an example of cellular tropism?

Answer 4

HIV normally infects CD4 T cell and macrophages but not neurons

Question 5

What is an example of tissue tropism?

Answer 5

Influenza viruses normally infect lung tissues but not brain tissues

Question 6

What are examples of host tropisms?

Answer 6

Myxoma virus infects rabbits
Polio virus infects humans
Rabies infects humans & animals

Question 7

How do enveloped viruses enter cells at a lower pH?

Answer 7

Enveloped viruses-fusion via endosomes
As the pH inside the endosomes drops, fusion of the viral envelope with the cell membrane can now occur and this results in delivery of the internal components of the virus to the cytoplasm of the cell

Question 8

How do most non-enveloped viruses enter the cells?

Answer 8

Non-enveloped viruses may be taken up into endosomes known as endocytosis, They then cross (or destroy) the endosomal membrane

Question 9

How do a few non-enveloped viruses enter the cells?

Answer 9

Crossing plasma membrane directly (e.g poliovirus)

Question 10

What does uncoating mean?

Answer 10

Removal of the plasmid coating

Question 11

What viruses do not need to have their DNA delivered into the nucleus?

Answer 11

Poxoviruses RNA must be delivered into the cytoplasm (except HIV and Influenza virus)

Question 12

What are Class I viruses using the Baltimore classification of viruses?

Answer 12

Viruses with double-stranded DNA genomes (Adenoviruses, Herpesviruses)

Question 13

What are Class II viruses using the Baltimore classification of viruses?

Answer 13

Viruses with single-stranded DNA genomes (Parvoviruses)

Question 14

What are Class III viruses using the Baltimore classification of viruses?

Answer 14

Viruses with double-stranded RNA genomes (Reoviruses, Rotavirus)

Question 15

What are Class IV viruses using the Baltimore classification of viruses?

Answer 15

Viruses with plus-sense single-stranded RNA genomes (Picornaviruses, poliovirus)

Question 16

What are Class V viruses using the Baltimore classification of viruses?

Answer 16

Viruses with negative-sense single-stranded RNA genomes (Influenza, Ebola)

Question 17

What are Class VI viruses using the Baltimore classification of viruses?

Answer 17

Viruses with positive-sense single-stranded RNA genomes (Retroviruses) - replicate through DNA intermediate (reverse transcribed)

Question 18

What are Class VII viruses using the Baltimore classification of viruses?

Answer 18

Viruses with double-stranded DNA genomes-incomplete, partial, gapped (Hepadnaviruses-Hepatitis B virus)