Prevention and treatment of viral disease

Question 1

What is prophylaxis?

Answer 1

Preventing disease before the aetiologic agent is acquired, by vaccination or giving drug before infection

Question 2

What is therapy?

Answer 2

Treating the disease after the host has been infected

Question 3

TRUE OR FALSE:

Antivral drugs are prophylactic

Answer 3

FALSE

Antiviral drugs = therapeutic

Vaccines = prophylactic

Question 4

What are the different types of viral vaccines?

Answer 4

• Live attenuated
• Inactivated
• Fractionated (purified subunit)
• Cloned

Question 5

Why is it difficult to develop drugs which selectively act against viral infections?

Answer 5

Viruses use many of the same pathways as humans for protein production = hard to find something that is selectively toxic

Question 6

What is a common therapy for viral infections?

Answer 6

Antivral drugs

Question 7

What is attenuation?

Answer 7

Using an alternative form of the virus that is still alive but with no pathological effects

Question 8

Describe how a virus is attenuated to make a live virus vaccine

Answer 8

1. Pathogenic virus is isolated from a patient and grown in human cultured cells
2. The cultured virus is used to infect monkey cells
3. The virus acquires many mutations that allow it to grow well in monkey cells
4. The virus no longer grows in human cells and may be a candidate for a vaccine

Question 9

What are the advantages and disadvantages of live vaccine?

Answer 9

ADVANTAGES:

• Rapid broad, long-lived immunity
• Dose sparing
• Cellular immunity

DISADVANTAGES:

• Requires attenuation
• May revert

Question 10

What are the advantages and disadvantages of inactivated vaccine?

Answer 10

ADVANTAGES:

• Safe
• Can be made from wild type virus

DISADVANTAGES:

• Frequent boosting required
• High doses needed

Question 11

What types of vaccines are available for influenza?

Answer 11

• Inactivated virus or HA subunit
• Live attenuated vaccine

Question 12

What types of vaccines are available for poliovirus?

Answer 12

• Salk = inactivated vaccine
• Sabin = live attenuated vaccine

Question 13

TRUE OR FALSE:

There is a vaccine for rotavirus

Answer 13

TRUE

Rotarix = live attenuated rotavirus vaccine

Question 14

TRUE OR FALSE:

A vaccine for shingles has not yet been discovered

Answer 14

FALSE

Live attenuated vaccine similar but distinct from the chickenpox vaccine

Question 15

TRUE OR FALSE:

The HPV vaccine is so far the only anticancer vaccine available in the UK

Answer 15

FALSE

There are vaccines for Hep B and Papillomavirus

Question 16

How can people with viral infections be treated?

Answer 16

• Interferons - induce the host’s natural antiviral response
• Antiviral drug with specific antivral activity
• Treatment that alleviate symptoms but do not inhibit virus replication

Question 17

What do most antiviral drugs target?

Answer 17

• Viral enzymes (often act as substrate analogues)
• Nucleoside analogues for cancer-like drugs

Question 18

What type of antiviral drug is acyclovir?

Answer 18

Nucleoside analogue (inhibits viral replication by chain termination)

Question 19

Describe how nucleoside analogues (e.g. acyclovir) are used as antiviral drugs

Answer 19

• Modified nucleoside (lacks 3’ -OH) incorporated into DNA
  
  • Prevents phosphodiester bond formation = chain termination
• Highly specific
• Only activated inside virus infected cells
• High affinity for viral DNA polymerase than for host cell polymerase

Question 20

How do antivirals target influenza virus replication?

Answer 20

• Neuraminidase = enzyme on the outside of influenza virus
  
  • Substrate = sialic acid
• Drugs Relenza and Tamiflu competitively inhibits neuraminidase

Question 21

Name some stages in the life cycle of viruses which could potentially allow therapeutic intervention

Answer 21

• Virus entry
• Early stages of infection (e.g. transcription with reverse transcriptase)
• Integration of virus DNA into host cell’s DNA
• Processing of protein for virus