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Infection & Immunology > vaccine > Flashcards

vaccine Flashcards

1
Q

What is an ideal vaccine?

A
  • to produce the same immune protection which usually follows natural infection but w/o causing disease
  • to generate long-lasting immunity
  • to interrupt spread of infection
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2
Q

Immunization: the deliberate provocation of an 1._______ immune response by introducing 2. _______ in the body.
It’s a procedure designed to increase concentrations of 3. _______ and/or 4.________ which are reactive against infection.

A
  1. adaptive
  2. antigen
  3. antibodies
  4. effector T cells
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3
Q

Describe the 2 types of immunization

A

Passive immunity: protection is immediate

Active immunity: takes time (usually several weeks) to develop.

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4
Q

Describe passive immunity:

  1. Natural
  2. Artificial
A
  1. Natural: transplacental (mother to child) lg G

2. Artificial: injection of preformed antibodies

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5
Q

Advantages & disadvantages of passive immunity

A

Adv:

  • immediate protection
  • can be used in immunosuppressed

Disadv:

  • short period of protection
  • potential allergic response if foreign antibodies given
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6
Q

Desc. active immunity:

  1. Natural:
  2. Artificial:
A
  1. Natural: following infections (immune to re-infection)

2. Artificial: vaccination– ensure large no. of antibodies & lymphocytes are avail before exposure to pathogen

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7
Q

Does smallpox only occur in humans?

A

Yes

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8
Q

Does smallpox cause a latent or persistent infection?

A

No

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9
Q

How was the eradication of smallpox possible?

A
  • smallpox vaccine was effective against all strains of variola virus
  • high fidelity DNA polymerase, variola viruses were unable to undergo antigenic variation to escape immunity
  • CD4 T cell-dependent neutralising antibodies to vaccinia antigens (pox virus family) are cross-reactive with smallpox antigens
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10
Q

Features of effective vaccines

A
  • safe
  • protective
  • gives sustained protection (must last for several years)
  • induces neutralising antibody (prevent infection)
  • induced protective t cells
  • practical considerations: low cost per dose, few side effects, etc
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11
Q

Selective vaccination for those at increased risk of disease:

A
  • hep B
  • influenza
  • yellow fever
  • rabies
  • meningitis
  • hep A
  • measles
  • strep. pneumonae
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12
Q

What is herd immunity?

A

Herd immunity occurs when a large portion of a community (the herd) becomes immune to a disease, making the spread of disease from person to person unlikely. As a result, the whole community becomes protected — not just those who are immune.

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13
Q

To achieve herd immunity, the % of individuals who need to be vaccinated depends on _____________________

A

the disease and the vaccines used.

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14
Q

Herd immunity is only valid for _____________

A

transmissible infectious diseases eg. flu

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15
Q

Why is herd immunity important?

A
  • no vaccine is 100% effective

- immunocompromised people are unable to receive live vaccines

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16
Q

What do vaccines generally contain?

And describe them.

A
  1. Antigen(s) : any protein, peptide, substance, etc that stimulates an immune response (SPECIFIC to the pathogen of interest)
  2. Adjuvant : a substance that enhances the immune response to a weakly immunogenic antigen (non-specific). It can also allow slow release of antigen to allow time for memory response to form
17
Q

Desc inactivated (killed) vaccines

A
  • inactivation through heat or chemical fixation
  • need multiple injections in initial course
  • usually need boosters
  • may be toxic
  • need for adjuvant
  • poor cell mediated immunity
18
Q

Examples of inactivated (killed) vaccines

A 
cholera
plague
influenza
rabies
polio (salk)
19
Q

Desc live (attenuated) vaccines

A

They contain virulent human viruses that has been weakened.

20
Q

Examples of live (attenuated) vaccines

A 
polio (oral vaccine)
mumps
measles
rubella
yellow fever
chickenpox
typhoid
21
Q

Advantages of live (attenuated) vaccines

A
  • mimic natural infection
  • produce large antigenic stimulus (organism can still replicate)
  • generally induce T & B lymphocytes responses
  • provide long-lasting protection
22
Q

Disadvantages of live (attenuated) vaccines

A
  • may retain some pathogenicity
  • may revert to virulence
  • may not be safe to vaccinate the immunocompromised
  • require a good cold chain
23
Q

Desc inactivated exotoxins (toxoid)

A
  • inactivated by heat or chemicals

- intended to build immunity against the toxins & not the bacteria that produce the toxins

24
Q

Examples of inactivated exotoxins (toxoid)

A

tetanus toxoid

diphtheria toxoid

25
Q

What vaccine is most effective for those <2y.o. particularly vulnerable to bacterial meningitis?

A

conjugate vaccine

26
Q

Examples of conjugate vaccine

A

polysaccharides from Pneumococcus & meningococcal capsules

27
Q

Do polysaccharides from Pneumococcus have low levels of lg M?

A

Yes

28
Q

Do polysaccharides from Pneumococcus have memory?

A

No

29
Q

Desc subunit vaccines

A
  • they present 1 or more antigens to the immune system w/o introducing pathogen particles
  • “subunit”: antigen is a fragment of the pathogen
30
Q

The 2 methods of subunit vaccines

A
  1. Present an antigen to the immune system using a specific, isolated protein from the pathogen
  2. Put an antigen’s gene from the targeted virus into another virus, to make a recombinant virus. The recombinant vector will express the antigen which is extracted.
31
Q

Example of a subunit vaccine

A

hep. B vaccine (yeast vector)

32
Q

Advantages of subunit vaccine

A
  • cannot revert back to virulence
  • safe for the immunocompromised
  • can withstand changes in conditions (eg. temp., light exposure, humidity)
33
Q

Disadvantages of subunit vaccine

A
  • reduced immunogenicity compared to attenuated vaccines
  • require adjuvants to improve immunogenicity
  • often require multiple doses/ boosters to provide long-term immunity
  • q costly
  • can be difficult to isolate the specific antigen
34
Q

RNA vaccine:

A

uses a copy of the mRNA that codes for the antigen of interest to produce an immune response

35
Q

3 types of RNA vaccine

A
  1. non-replicating mRNA (mRNA encoding antigen + liposome)
  2. in VIVO self-replicating mRNA (mRNA encoding antigen + the viral RNA replication machinery)
  3. in VITRO dendritic cell non-replication mRNA
36
Q

Advantages of RNA vaccine

A
  1. Safety
    - RNA vaccines are not made with pathogen particles of inactivated pathogen, so are non-infectious
    - RNA does not integrate itself into the host genome
    - RNA strand in the vaccine is degraded once the protein is made
  2. Production: vaccines can be produced more rapidly in the lab
37
Q

Disadvantages of RNA vaccine + strategies to tackle them

A
  1. May elicit an unintended immune rxn
    - strategy: to minimise, the mRNA vaccine sequences are designed to mimic those produced by mammalian cells
  2. Delivery: free RNA in the body is quickly degraded
    - strategy: the RNA strand is incorporated into a larger molecule to help stabilise it or package into particles/lipsomes
  3. Storage: need to be frozen or refridgerated

Infection & Immunology (8 decks)

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