Ways to fight virus

Question 1

What are some strategies to control infectious diseases?

Answer 1

• vaccine (but not effective if person is already infected)

- antivirals (can stop infection once it has started)

Question 2

What does the best antiviral drug target?

Answer 2

• Inhibits a specific step in viral replication or pathogenesis (must be potent- block virus replication completely)
• must be safe

Question 3

What is the current treatment for HIV?

Answer 3

• Highly active antiretroviral therapy (HAART)

- it is a combination of several (3-4) antiretroviral drugs

Question 4

What is the purpose of a vaccine?

Answer 4

• To elicit an immune response that will prevent or limit disease upon first encounter with the target organism/antigen,
• Prevent disease, transmission and eradicate disease

Question 5

What are some successful vaccines?

Answer 5

• smallpox
• polio (salk- inactivated virus, sabin- attenuated virus)
• diphtheria (toxoid- inactivates toxin)

Question 6

What is passive immunisation?

Answer 6

• transfer of immune sera/cells to provide protection
• immediate protection but short term
  eg. rabies immune globulin, maternal antibodies transferred to newborn

Question 7

What is active immunisation?

Answer 7

• Introduction of foreign material into a host to stimulate an adaptive immune response
• Typically involves preparation containing one or more microbial agents or a vector that directly express one or more microbial antigens

Question 8

What does a good vaccine typically need?

Answer 8

• Something to stimulate the innate immune system (infection- live attenuated or adjuvant)
• T cell epitopes (peptides that can bind to MHC proteins)
• B cell epitopes (relevant site that can neutralise pathogen or toxin

Question 9

What are the benefits of live attenuated vaccines?

Answer 9

• pathogen replication creates strong innate immune signals
• diverse range of antigens expressed
• prolonged antigen expression
• higher antigen loads
• better t cell response

Question 10

What are 2 ways attenuation of pathogen can be achieved?

Answer 10

• Through in vitro passage so it no longer grows well in human cells (can;t revert quickly back to wildtype)
• By targeted deletion of virulence genes/determinants

Question 11

What is subunit vaccine?

Answer 11

• Contains component(s) of pathogen rather than the complete organism. eg. hepatitis B vaccine

Question 12

What is toxoid vaccine?

Answer 12

• Immunisation with inactive forms of toxins. eg. tetanus/diphtheria
• antibodies bind to native toxin and block activity

Question 13

What is conjugate vaccine?

Answer 13

• Consist of an antigen coupled to a carrier
• antigen is typically carbohydrate
• can’t stimulate a T cell response so need to be coupled with carrier
• haemophilus influenza B, streptococcus pneumoniae

Question 14

What are DNA vaccine?

Answer 14

• Plasmids (bacterial DNA) provide ‘stranger’ stimuli to immune system
• elicit weak immune response, used for ‘priming’

Question 15

What are adjuvants?

Answer 15

• delivery of signals 1,2 and 3 for T cells

- right type of help for B cells

Question 16

What is a rotavirus?

Answer 16

• major cause of severe diarrhoea in young children

Question 17

What are the key elements of an expression vector?

Answer 17

• promoter
• multiple cloning site
• origin replication
• antibiotic resistance gene
• epitope tag/reporter gene
• selectable marker (used for eukaryotic cells)

Question 18

What are features of shuttle plasmids? What are they used for?

Answer 18

• generally quite small and have a greater range of restriction sites
• used in sub-cloning

Question 19

Which plasmid is commonly used for protein expression in bacteria? What are it’s features?

Answer 19

• pGEX
• encodes for the epitope GST, used for purification
• has tac promoter, Ori, stop codon, amp resistance gene, Lac repressor gene, cleavable epitope (factor Xa)

Question 20

What are the pros of prokaryotic expression?

Answer 20

• Convenient/easy
• produce and purify protein using the least expensive and easiest reagents and equipment
• best for large scale production of protein

Question 21

What are the cons of prokaryotic expression?

Answer 21

• lack many of the immunogenic properties
• 3D native conformation
• lack PTMs (post translational modifications) needed for specific activity