Viral Chemotherapy L25

Question 1

Describe RSV-Ig (RespiGam).

Answer 1

• IgG from pooled adult human sera with high levels of anti-RSV antibodies
• Delivered intra-venously
• Approved by FDA in 1996 for use in specific at-risk infants

Question 2

Describe the risks of RSV-Ig (RespiGam).

Answer 2

• Admistering IV to very sick babies difficult and risky
• May make routine vaccinations (eg MMR) ineffective
• Risk of infection carried in blood

Question 3

Describe Respiratory Syncytial Virus (RSV).

Answer 3

• Infects upper respiratory tract (eg. common cold) and lower respiratory tract (eg. bronchiolitis)
• Almost all children infected by age of 2
• Accounts for ~20% of all infants hospitalised with respiratory tract infection
• Significant morbidity in infants, elderly and at risk groups eg cystic fibrosis
• Repeated infections through life – tend to become milder

Question 4

Describe Palivizumab.

What does it treat?

How does it work?

Answer 4

• Palivizumab is humanised monoclonal antibody to F protein of Respiratory Syncytial virus (RSV)

Palivizumab antibody binds to F protein:

• Inhibits fusion process and entry to cell
• Targets virus particles for complement mediated lysis & opsonisation

Question 5

Describe the mechanics of Palivizumab.

Answer 5

• Inhibits fusion process and entry to cell

- Targets virus particles for complement mediated lysis & opsonisation

Question 6

_____ are natural anti-virals.

Answer 6

Interferons

Question 7

What do Interferons do?

Answer 7

• Create anti-viral state in neighbouring cells
• Upregulate MHCI presentation of viral antigens on surface of infected cells

Which leads to —->

• Increased killing of infected cells by CD8- cytotoxic T Cells

Question 8

What are the drawbacks of using interferons in antiviral therapy?

Answer 8

• Side effects – IFN causes flu-like symptoms
• High doses needed
• Expensive

Question 9

Describe Rhinovirus.

Answer 9

• Rhinovirus is member of Picornoviridae family
• Major cause of common cold
• +ve ss RNA genome
• Non-enveloped

Question 10

What do Nucleoside analogues do?

2

Answer 10

• Inhibit nucleic acid synthesis

- Act as chain terminator in DNA synthesis - no 3’OH group to form a bond with the next nucleoside

Question 11

Describe Aciclovir.

Describe the mechanism.

Answer 11

• Aciclovir is a prodrug
• Conversion to active form (aciclovir triphosphate) requires viral enzyme
• Act as chain terminator in DNA synthesis - no 3’OH group to form a bond with the next nucleoside
• Aciclovir therefore inhibits DNA synthesis in virus infected cells but has little effect on non-infected cells

Question 12

_____ therapy is commonly used to combat acquired anti-viral drug resistance.

Answer 12

Combination.

Question 13

_____ immunotherapy exploits molecules of the natural immune response (antibodies, Interferons).

Answer 13

Passive.