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Molecular Immunology > Lecture 11 > Flashcards

Lecture 11 Flashcards

1
Q

What is active immunisation

A

Manipulating the immune system to generate a persistent protective response against pathogens.

Immunisation with a vaccine can trigger an immune response and safely mimic natural infection

Mobilise the appropriate arms of the immune system and generate immunological memory

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2
Q

What’s natural passive immunity and what does it provide protection against

A

Occurs naturally by the transfer of maternal antibodies across the placenta to the developing foetus.

Diptheria, tetanus, streptococcus, rubella, mumps, poliovirus

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3
Q

What’s the major hazard with passive immunity

A

Not the primary infection itself (can be eliminated by innate immunity) but the effects of potent toxins released by bacteria e.g. teanus and botulinum

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4
Q

What’s the most commonly used deactivated toxin derivative (toxoid)

A

Tetanus toxoid

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5
Q

Advantages of passive immunisation

A
  • Use of the preformed antibodies can quickly neutralise toxins and venoms
  • A conventional immune response may be too slow
  • In the case of highly virulent pathogens, pre formed antibodies isolated or engineered from immunised animals may be the only means of treatment
  • In some cases, antibodies from surviving patients can be used
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6
Q

What are the drawbacks of passive immunisation

A
  • Does not activate immunological memory
    -No long term protection
    -Possibility of reaction to anti-sera
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7
Q

What are the different vaccines

A

-Whole organism (live attenuated pathogen or killed inactive pathogen)
-Subunit toxoids (antigenic extracts, recombinant proteins, conjugate vaccines)
-Peptides
-DNA vaccines
-Engineered virus

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8
Q

Features of a live attenuated vaccine (whole organism)

A

The pathogen is altered/ treated to reduce virulence ( for example by adaptation after prolonged cultivation in special medium)

The organism is used in a weakened form

It’s stable to replicate but at a reduced rate

Can produce a short-lived infection but can be cleared by the host without harmful outcome

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9
Q

Features of an inactivated organism (whole organism) vaccine

A
  • The organism is rendered inactive and non-viable by heat, chemical or other treatments.
  • Cannot replicate
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10
Q

Advantages of live attenuated vaccines

A
  • Attenuated pathogens sets up a transient infection
    -Activation of full natural immune response
    -Prolonged contact with the immune system
    -Stimulation of a memory response in the T and B cell compartments results in prolonged comprehensive protection

Often only a single immunization is required which is advantageous for third world countries

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11
Q

Disadvantages of live attenuated vaccines

A

Immunocompromised patients may become infected as a result of immunization.

Complications such as the live measles vaccines

The attenuated organism can revert to a virulent form for example polio sabio - could leads to a serious outbreak in poor areas

Live organisms need to be refrigerated for stable storage- issue for remote areas

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12
Q

Advantages of inactivated pathogens

A
  • No risk of infection
  • storage is less critical
    -Wide range of different antigenic components are present so good immune response is possible
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13
Q

Disadvantages of inactivated pathogens

A
  • Tend to just activate humoral responses
    -Lack of T cell involvement
    -Without transient infection, the immune response can be weak
    -Repeated booster vaccinations required
    -Adjuvents can be used to increase the immune response
    -Patient compliance can be an issue
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14
Q

Examples of inactivated vaccines

A

Bacterial: anthrax, cholera, pertussis, plague

Viruses: Hepatitis A, influenza, polio, rabies, rubella

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15
Q

What are the 3 major types of subunit vaccines

A

Inactivated exotoxins (toxoids)

Capsular polysaccharides

Recombinant microbial antigens

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16
Q

What are capsular polysaccharides

A

Capsular PSs are highly polar, hydrophilic cell surface polymers consisting of oligosaccharide repeating units. These molecules are the main antigens involved in the protective immunity to encapsulated bacteria

17
Q

What do capsular polysaccharides interfere with

A

Bacterial interactions with phagocytes by blocking opsonization

18
Q

What’s opsonisation

A

The coating of the organisms by specific antibodies and complement which enables host phagocytes to inject and destroy invading bacteria

19
Q

Advantages of synthetic peptides as antigens

A

-Safety
-Only portions of pathogen are used
- No risk of infection
- May be easier to store and preserve

20
Q

Disadvantages of synthetic peptides as antigens

A
  • Immune response is less powerful than to live attenuated vaccines
    -Repeat vaccinations needed and adjuvants
21
Q

What is an adjuvant

A

Any substance added to stimulate the immune response

22
Q

What can adjuvants include

A
  • Whole killed organisms
    -Toxoids
    -Proteins (Conjugate vaccines)
    -Chemicals
    -Aluminium salts
    -Oil emulsions
23
Q

What can aluminium salts do

A

Extend the half life of immunoglobulin in the site of injection (depot effect)

Chemicals can cause irritation and inflammation

24
Q

What do toxoids trigger and do

A

They trigger out the immune system and send out danger signals, acting as delivery systems and immune stimulators

25
Q

Examples of adjuvants used in humans

A

Alum (dominant)
Oil/ water emulsions
Detoxified bacterial lipopolysaccharide
Cytokines
Toll-like receptor agonists

26
Q

What safety hazards can be accompanied from high efficiency

A
  • Risk of autoimmunity
  • Chronic inflammation
27
Q

What’s the aim of DNA vaccines

A

To transiently express genes from pathogens in host cells and generate immune responses similar to natural infection leading to T and B cell memory responses

28
Q

Advantages of DNA vaccines

A

They do not require complex storage and transportation.

Delivery can be simple and adaptable to widespread vaccination programs “DNA gun”

29
Q

Disadvantages of DNA vaccines

A
  • No transient infection
    -DNA vaccination is likely to produce a mild immune response and require subsequent boosting
    -
30
Q

What are RNA vaccines

A
  • Similar to DNA vaccines
  • Can be designed to encode speciifc antigens

-Injection into cells leads to transient expression of antigen.

31
Q

What’s the aim of recombinant vector vaccines

A
  • Imitates the effects of transient infections with pathogens but using a non-pathogenic organism

Genes for major pathogens are introduced into a non-pathogenic or attenuated microorganism and introduced into the host

32
Q

Advantages of recombinant viral vaccines

A

Creates ideal stimulus to immune system

Produces immunological memory

Flexible (different components can be engineered)

Safe (relative to live attenuated pathogen)

33
Q

Drawbacks of recombinant viral vaccines

A
  • Requrie refrigeration for transport

-Can cause illness in compromised individuals

  • Immune response to virus in subjects can negate effectiveness
34
Q

What is an ideal vaccine

A
  • Safe
    -Should induce a suitable response (for example, mucosal)
    -High antibody titer
    -Generates T and B cell memory
  • Is stable and easy to transport
    -Should not require repeated boosting
    -Patient compliance
35
Q
A

Molecular Immunology (15 decks)

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