V6 Flashcards
What is active immunisation?
When viral antigens are used to stimulate immunity, results in active immunity, takes some time to fully develop.
What are the types of active immunisation?
- live attenuated vaccine
- inactivated (killed) vaccine
- defined viral antigens/subunit/split vaccine
How does the live attenuated vaccine work?
- Replication-competent
- The virus looses its pathogenicity (becomes attenuated) but is still able to replicate in the vaccinee’s body.
What are the advantages of a live attenuated vaccine?
- relatively small dose needed
- relatively cheap
- long-lasting immunity
What are the disadvantages of the live attenuated vaccine?
- requires cold chain to remain active
- May cause some degree of illness, esp. in immunocompromised.
- May revert to wild-type (pathogenic) virus.
- May be passed on to others.
How does the inactivated vaccine work?
- Replication-incompetent
- Chemical agents such as formalin to inactivate the
virus, so it cannot replicate in the vaccinee’s body.
How does the defined viral antigens / subunit / split vaccine work?
- Replication-incompetent
- Only parts of the virus that are relevant
to elicit immunity are used
What are the advantages of inactivated and defined viral antigens / subunit / split vaccines?
- Will not cause disease (but may still cause allergic reactions etc.)
- Cannot revert to wild-type (pathogenic) virus.
- Safe in pregnancy and immunocompromised.
- Cannot be passed on to others
What are the disadvantages of inactivated and defined viral antigens / subunit / split vaccines?
- Relatively more antigen needed.
- Therefore relatively more expensive.
- Immunity often not very long-lasting, therefore booster doses necessary.
- Do not cause herd immunity
List examples of live attenuated vaccines
measles, rotavirus, previously oral polio, rubella, mumps, yellow fever, varicella roster
List examples of the inactivated vaccine
injectable polio, hepatitis A, rabies
List examples of the subunit vaccine
hepatitis B and influenza
What is passive immunisation?
Injection of human immunoglobulins prepared from donated blood that contains antibodies against particular viruses
What are the advantages of passive immunisation?
provides moderate protection
What are the disadvantages of passive immunisation?
- must be given ASAP after exposure
- short-lived protection
- expensive
- used for emergencies, not method of choice
List examples of passive immunity
Hepatitis A, B, varicella-roster, rabies (when non-immune person is exposed)
What are the main challenges of antiviral treatment and how can they be overcome?
- To inhibit the virus without damaging the host cell is very tricky
- Unsurprisingly, early antivirals were developed from cancer chemotherapy agents.
- With better knowledge of viral replication, viral enzymes etc. better and more specific agents have been developed.
What are the main antiviral drugs?
- Acyclovir
- Reverse Transcriptase Inhibitors
- Protease inhibitors
- Antiretroviral therapy
What is the mode of action of Acyclovir?
- Inhibition of viral DNA polymerase
What is the mode of action of Nucleoside RTIs?
- Inhibit HIV’s reverse transcriptase (RT)
enzyme - Require intracellular phosphorylation to triphosphates.
- Compete with physiological base at active centre = substrate binding site.
- Contains one phosphate group already.
What is the mode of action of Non-nucleoside RTI?
- Inhibit HIV’s reverse transcriptase (RT)
enzyme - Bind allosterically near, not at, active centre of enzyme. Do not require activation.
What is the mode of action of Protease inhibitors?
- Inhibit HIV’s protease enzyme: Required for maturation of newly formed viral particles in order to render them able to infect new cells.
- PI = peptidomimetic substances (not actual proteins) that bind to and thereby block the active centre of the protease.
What is the mode of action of Antiretroviral therapy?
- Combination therapy.
- Maximal reduction (suppression) of viral replication activity.
- Emergence of resistance slowed or halted.
