L21

Question 1

are vaccines effective and how do they work

Answer 1

no vaccine 100% effective, but the attempt to break chain of transmission by building a immune response

• if no vaccine, high powered infection, passed on easily
  If vaccinated, some of the infection will be destroyed, so wont be strong enough to be passed on to someone else- so really its helping others
• virus spread stops when probability of infection drops below critical threshold (Ro)
• e.g. small pox, need 80-85% of pop. to be vaccinated to be effective (HERD IMMUNITY)
• oral vaccines more effective then injected
• made based on vector, proteins, virus, or nucleic acid

Question 2

features essential for eradication

Answer 2

• replication in only 1 host
  -vaccination induces lifelong immunity
• ## e.g. small pox + polio meet these conditions

Question 3

what are antiviral drugs and why are there so few

Answer 3

• 2nd attempt at defense after vaccines
• help treat HIV
• not many options
• because compounds interfer with virus growth,a ffecting host cell
• side effects common, which is unacceptable
• every step in viral lfie cycle engages host function
• some cant be propagated
• have no animal model

Question 4

explain resistance to antiviral drugs

Answer 4

• occurs because viruses replicate efficiently, and high mutation frequency

Question 5

bacteria vs viruses

Answer 5

bacteria
- grow on non-living surfaces
- multiple by binary fission
- killed by antibiotics
- some good, used therapeutically

viruses
- smallest life form
- need a living host
-needs antiviral drugs
- e.g. bacteriophages

Question 6

process for developing phage therapy

Answer 6

-identify problem- significance + impact
- pathogen known + identified
- sample collection for phage isolation
- isolation of phage + determination of host range
- purification of phage- lytic only (using soft top agar techniques, triple plaque purification methods, transmission electron microscopy)
- redetermination of host range
- development of therapy