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TW12 – Principles of Vaccines – 12th December 2016

Vaccination (injection): artificial induction of actively-acquired immunity – nonpathogenic, which is critically otherwise it would be disastrous
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Aim is to prevent disease
Vaccine (preparation): A form of a pathogenic agent modified to make it nonpathogenic and suitable for use in a vaccination
Prophylactic: Preventive immunisation (e
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prophylactic measures)
Toxoid: Chemically modified toxin from pathogenic organism, no longer toxic but is
still an antigen, used in vaccines
Adjuvant: substance that enhances body’s immune response to an antigen
Variolation: make wound and infect it with pathogens from another infected
person/wound (to provide immunity)
In order of rising:
IgA: Infection at mucosal surface
IgM: Early immune response
IgG: B-cells being educated after being in contact with IgA and IgM
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g
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g
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, can be prep in a variety of different ways – which means it
can withstand extremes in temperature etc
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Difficult and expensive
because need to prove that its non-pathogenic
Examples include polio vaccine and BCG tb vaccine

Killed (inactive) microbe vaccines: - wild type or similar treated to make them ‘nonviable’
Killed by heat (no residue) or chemicals (residue)
When immunogenic molecule is polysaccharide heat is good method
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Chemicals (formaldehyde and beta-propio-lacone) don’t affect proteins but can
leave toxic residue, preserves immunogenic specificity
Advantages
Can produce new vaccine quickly – you just have to prove that they’re dead
You don’t have to keep going back and testing like you do with attenuated vaccines,
because you’ve seen that nothing grows in there
Easy and cheap to produce
Low risk of change in immunogenic specificity
Disadvantages

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Large quantity required to induce immunity (short lived and relatively weak)
Examples: typhoid vaccine or whooping cough (pertussis) vaccine

Inactivated toxin vaccines – vaccine created from a toxin, created into toxoid –
rather than the microbe itself
Made by purifying toxin from microbial culture fluids
Formaldehyde cause minor chance to shape of toxin protein, retains immunogenic
specificity
Can be done by growing on agar plate, spun up and layer at top is toxic substrate
Advantages
Not biochemically active, yet still immunogenic and immunospecific
Produced easily
Purity is high – minimum adverse reactions
Immunity highly specific
Disadvantages
Only applicable to disease caused by toxigenic bacteria where main symptoms are
caused by toxin
Must get toxin level to something that won’t infect the person
Addition of adjuvant, e
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aluminium hydroxide
Examples: tetanus, and diphtheria vaccines

Purified sub-unit vaccines:
Significant molecules (in the disease) are extracted from the microbial cells and
purified (could be microbial attachment molecules or microbial anti-phagocytic
molecules)
Advantages
High purity - adverse reactions are rare
High levels of immunospecificity
Protein sub unit may be made in non-pathogenic microbes, use genetic engineering
– production safer
Disadvantages
Immunogenicity of protein sub unit: addition of adjuvant or conjugation with
phospholipid membrane fragments
Immunogenicity of polysaccharides: addition of adjuvant or conjugation with a
harmless protein
Example: flu vaccine (viral surface molecule), haemophilus meningitis vaccine
(capsular polysaccharide molecule)

Future vaccines:
Multiple genetically engineered vaccines – strain of microbe containing cloned gene
coding
Anti-idiotype vaccines



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