Mm2

Question 1

Explain the viral life-cycle steps

Answer 1

1. Attachment cell-surface specific receptor
2. Injection of the viral Gino with the cell and it’s transferred to cytoplasm
3. Transcription (makes mRNA)
   - Early regulatory proteins
   - late structural proteins – make the cell capsule later when the virus is assembled
4. Genome = replicated
5. Virus reassembled + exits cell

Question 2

What are RNA viruses called

Answer 2

Retroviruses – they use reverse transcriptase

Question 3

List for types of viruses when classified according to the type of their genetic material

Answer 3

Double-stranded DNA, single-stranded DNA, antisense strand RNA, sense strand RNA

Question 4

Define tropism

Answer 4

The preference of viruses to affect certain tissues not others

Question 5

What determines the tropism of a virus

Answer 5

Susceptibility – permissvity – accessibility

Question 6

List different outcomes of infection by viruses

Answer 6

Acute infection
Persistent infection
Latent reactivating infection
Slow infection
Oncogenesis

Question 7

Name and example of a virus which causes an acute infection

Answer 7

Infection followed by the response of the organism and quick and complete resolution of infection

Rhinovirus, rotavirus, influenza

Question 8

Name and example of a virus which causes a persistent infection

Answer 8

Persistent infection in a wide group which is not cleared from the organism completely

Papillomaviruses in warts
Chronic carriers Hep B and C

Question 9

Name and example of a virus which causes a latent reactivating infection

Answer 9

Persistent infection in a wide group which is not cleared from the organism completely

Herpes simplex virus
Chickenpox and shingles

Question 10

Name and example of a virus which causes a slow infection

Answer 10

Measles, human immuno deficiency virus

Question 11

Name and example of a virus which causes an oncogenesis infection

Answer 11

May encode oncogenes, interferes with the cell cycle in order to enhance their own replication

Hep B/C
HIV

Question 12

Define zoonosis

Answer 12

The process of transmission from animals and humans

Can be direct-> vectors such as air or reverse

Question 13

Define host range

Answer 13

Organisms that can be infected by a disease

Question 14

Explain how viruses emerge and re-emerge using named examples

Answer 14

Illegal animals, infected mosquitos

West Nile fever, Zika, Ebola, SARS, MERS

Question 15

Explain why it is difficult to develop drugs which selectively act against viral infections

Answer 15

Viruses use the cells own machinery so therapies can be harmful to the host as well as the virus

Question 16

Summarise the general strategy of designing drugs which target infectious agents but not the patient’s own cells

Answer 16

1. Identify elements of viral life-cycle that differ from the hosts
2. Identify the site of drug action
3. Design the drug to be highly specific for the site
4. Block spread/replication virus

Question 17

Identify four stages in their life cycle of viruses which could potentially allow therapeutic intervention

Answer 17

1. Viral binding and entry
2. Viral replication
   Transcription, reverse transcription, integration, replication
3. Viral assembly
4. Viral exit

Question 18

List six examples of classes of drugs which have been used successfully in anti-viral therapy

Answer 18

1. Interferons
2. Nucleoside analogues eg. Acyclovir
3. Fusion/entry inhibitors
4. Non-nucleoside reverse transcriptase inhibitors
5. Integrate inhibitors
6. Protease inhibitors

Question 19

Explain the specific strategy of using acyclovir as an antiviral drug

Answer 19

The strategy is-

Chain termination on the Viral thymidine kinase