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Virology > V6 > Flashcards

V6 Flashcards

1
Q

What is active immunisation?

A

When viral antigens are used to stimulate immunity, results in active immunity, takes some time to fully develop.

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2
Q

What are the types of active immunisation?

A
  • live attenuated vaccine
  • inactivated (killed) vaccine
  • defined viral antigens/subunit/split vaccine
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3
Q

How does the live attenuated vaccine work?

A
  • Replication-competent

- The virus looses its pathogenicity (becomes attenuated) but is still able to replicate in the vaccinee’s body.

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4
Q

What are the advantages of a live attenuated vaccine?

A
  • relatively small dose needed
  • relatively cheap
  • long-lasting immunity
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5
Q

What are the disadvantages of the live attenuated vaccine?

A
  • 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.
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6
Q

How does the inactivated vaccine work?

A
  • Replication-incompetent
  • Chemical agents such as formalin to inactivate the
    virus, so it cannot replicate in the vaccinee’s body.
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7
Q

How does the defined viral antigens / subunit / split vaccine work?

A
  • Replication-incompetent
  • Only parts of the virus that are relevant
    to elicit immunity are used
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8
Q

What are the advantages of inactivated and defined viral antigens / subunit / split vaccines?

A
  • 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
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9
Q

What are the disadvantages of inactivated and defined viral antigens / subunit / split vaccines?

A
  • Relatively more antigen needed.
  • Therefore relatively more expensive.
  • Immunity often not very long-lasting, therefore booster doses necessary.
  • Do not cause herd immunity
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10
Q

List examples of live attenuated vaccines

A

measles, rotavirus, previously oral polio, rubella, mumps, yellow fever, varicella roster

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11
Q

List examples of the inactivated vaccine

A

injectable polio, hepatitis A, rabies

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12
Q

List examples of the subunit vaccine

A

hepatitis B and influenza

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13
Q

What is passive immunisation?

A

Injection of human immunoglobulins prepared from donated blood that contains antibodies against particular viruses

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14
Q

What are the advantages of passive immunisation?

A

provides moderate protection

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15
Q

What are the disadvantages of passive immunisation?

A
  • must be given ASAP after exposure
  • short-lived protection
  • expensive
  • used for emergencies, not method of choice
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16
Q

List examples of passive immunity

A

Hepatitis A, B, varicella-roster, rabies (when non-immune person is exposed)

17
Q

What are the main challenges of antiviral treatment and how can they be overcome?

A
  • 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.
18
Q

What are the main antiviral drugs?

A
  • Acyclovir
  • Reverse Transcriptase Inhibitors
  • Protease inhibitors
  • Antiretroviral therapy
19
Q

What is the mode of action of Acyclovir?

A
  • Inhibition of viral DNA polymerase
20
Q

What is the mode of action of Nucleoside RTIs?

A
  • 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.
21
Q

What is the mode of action of Non-nucleoside RTI?

A
  • Inhibit HIV’s reverse transcriptase (RT)
    enzyme
  • Bind allosterically near, not at, active centre of enzyme. Do not require activation.
22
Q

What is the mode of action of Protease inhibitors?

A
  • 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.
23
Q

What is the mode of action of Antiretroviral therapy?

A
  • Combination therapy.
  • Maximal reduction (suppression) of viral replication activity.
  • Emergence of resistance slowed or halted.

Virology (8 decks)

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