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Immunology (Den 303) > Immunisation > Flashcards

Immunisation Flashcards

1
Q

Passive immunisation including limitation

A

The administration of pre-formed “immunity” from one person or animal, to another person
Limitation: antibody mediated

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2
Q

Immunisation

A

Passive

Active or vaccine

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3
Q

Advantages of passive immunisation

A

Gives immediate protection

Effective in immunocompromised patients

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4
Q

Disadvantages of passive immunisation

A

Short-lived Possible transfer of pathogens “Serum sickness” on transfer of animal sera

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5
Q

Passive immunisation: specific immunoglobulin examples

A 
Human tetanus immunoglobulin (HTIG)
-rapid protection of exposed individuals
Human rabies specific Ig
-used after exposure to rabies to give 		protection until vaccine becomes effective
Human Hepatitis B Ig (HBIG)
Varicella Zoster Ig (VZIG)
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6
Q

Passive immunisation: normal immunoglobulin (HNIG)

A

Prepared from pools of at least 1000 donors, contains antibody against measles, mumps, varicella,
hepatitis A etc.

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7
Q

Active immunisation (vaccination) divided into

A

Non-living vaccines (whole killed and toxoids)

Live attenuated Vaccines

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8
Q

Non-living vaccines

A 
1st exposure (vaccination)
-antibody response (IgM and IgG)
-smaller
Memory immune response
-larger antibody response, mainly IgG
-extremely rapid
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9
Q

Whole killed vaccines

A

Bacteria/ viruses grown in vitro & inactivated using agent such as formaldehyde or b-propionolactone
Non living vaccine does not cause infection, but antigens contained in it induce immune response which protects against infection
Non-living vaccines can also be cell-free toxoids-inactivated toxins

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10
Q

Problems and limitations of whole killed vaccines

A

Organisms must be grown to high titre in vitro
Whole pathogens often cause excessive reactogencity
Immune responses not always close to normal response to infection, e.g no mucosal immunity, no CTL responses
Usually need at least 2 shots

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11
Q

Non-living vaccines

A

Bacterial or viral

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12
Q

Bacterial non-living vaccines examples

A

Diphtheria-cell free formaldehyde treated toxin- rendered non toxic “toxoid”
Tetanus, toxoid, as above
Pertussis- killed whole bacteria, given with the two above as DTP. 3-doses. UK now moved to acellular pertussis (aP)
Cholera- heat killed bacteria

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13
Q

Viral whole killed vaccine examples

A

Polio vaccine (Salk)-inactivated virus-IPV
Influenza vaccine-inactivated virus
Hepatitis A vaccine-inactivated virus
Rabies vaccine-inactivated virus

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14
Q

Live attenuated vaccines

A

The organisms replicate within the host, and induce an immune response which is protective against the wild-type organism

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15
Q

Advantages of live attenuated vaccines

A

Lower doses are required, so the scale of in vitro growth needed is lower
Immune response more closely mimics that following real infection
Route of administration may be more favourable
Fewer doses may be required

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16
Q

Problems and limitations of live attenuated vaccines

A

Often impossible to balance attenuation and Immunogenicity
Reversion to virulence?
Transmissibility?
Live vaccines may not be so attenuated in immunocompromised hosts

17
Q

Bacterial live attenuated vaccine examples

A

Only 2BCG- Bacille Calmette Guerin. Mycobacterium bovis grown over many passages in vitro. Gives some protection against TB
Salmonella typhi- temperature sensitive strain given orally.

18
Q

Viral live attenuated vaccine examples

A

Poliomyelitis (Sabin)-widely used to bring polio to the brink of eradication
Vaccinia virus- used in billions of doses to eradicate smallpox due to cross-reactivity between itself and the variola virus
Measles, mumps and Rubella- 3 given together

19
Q

Pathogens lacking vaccines

A

A lot, e.g.
HIV, malaria, Schistosomiasis, Leishmania spp, Herpes simplex Virus, CMV, RSV, Rhinoviruses, Group B streptococci, Meningococcus group B, M.leprae,

20
Q

Why are there so many pathogens lacking vaccines?

A

Various reasons

  • pathogen too hard to grow
  • killed pathogen not protective
  • impossible to obtain attenuated and suitably immunogenic strain
  • too many strains causing disease etc.
21
Q

Novel approaches

A 
Recombinant proteins
Synthetic peptides
Live attenuated vectors
DNA vaccines
Polysaccharide-protein conjugates
22
Q

Recombinant proteins

A

Produced from bacteria, yeast, insect or mammalian cells
•Avoid problem of having to grow pathogen in vitro
•Major difficulties finding a protein or proteins which are protective, and generating strong enough immune response.
•2 examples on market, Hep B surface antigen, and HPV vaccines Cervarix and Gardasil

23
Q

Synthetic peptides

A 
Avoid need for pathogen growth
•Identifying protective epitopes a problem
•Inducing strong response can be problem
•Inducing broad response can be problem
•No examples on market
24
Q

Live attenuated vectors

A

Express protein from the pathogen in a vector which is known to be attenuated and safe, e.g
• Vaccinia
• BCG
• Adenovirus
None on market
Potential problems in immunodeficient people

25
Q

Vaccinia virus

A 
-Progressive vaccinia
Occurred in about 1.6 people per million vaccinated 
during the smallpox eradication
campaign.
These were likely 
immunocompromised people
26
Q

Live attenuated vectors

A 
Attenuated, genetically stable vaccine
Vector able to take additional
Foreign DNA
Insert DNA encoding protective
Antigen of pathogen, e.g HIV
27
Q

DNA vaccines

A 
Express protein from pathogen in mammalian expression plasmid which is then injected, so protein is expressed
• Avoid need to grow pathogen
• No live organism involved
• DNA cheap to produce
• Problem is poor immunogenicity
• None on market
28
Q

Herd immunity

A

Around 80% vaccinated protects the other 20%

29
Q

T independent antigens

A

Bacterial capsular polysaccharides cannot be processed + presented on MHC class II
-no T cell help
Antibody response of low magnitude
Low affinity
Predominantly IgM
Little or no boosting on secondary exposure
Infants respond especially poorly and are major target group for these vaccines
-e.g. Haemophilus influenzae
-neisseria meningitidis
-streptococcus pneumoniae

30
Q

Conjugation of TI antigens to proteins

A 
Hib polysacc specific B cells bind polysaccharide and internalise whole conjugate, including protein
Polysaccharide cannot be processed, but protein is and peptides derived from it are expressed on cell-surface with MHC class II
Polysaccharide specific B cell receives help from DT specific T cell
Strong antibody response even in infants, including IgG
31
Q

Conjugate vaccines

A

Neisseria meningitidis type C - polysaccharide-protein conjugate vaccine
•Streptococcus pneumoniae-23-valent polysaccharide vaccine or 7-valent conjugate
•Haemophilus influenzae type B (HiB)- Polysaccharide protein conjugate vaccine

32
Q

Recent changes to the childhood immunisation programme

A

Addition of pneumococcal conjugate vaccine (PCV) at 2, 4 and 13 months of age;
A dose of MenC vaccine at 3 and 4 months;
Booster dose of Hib and MenC vaccine (given as a combined Hib/MenC vaccine) at 12 months
HPV vaccine for teenage girls
BCG no longer routinely given to teenagers. Targeted on at risk infants

33
Q

Do vaccines work

A

Yes, almost eradicated some disases

34
Q

Do vaccines work

A

Yes, almost eradicated some disases

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Immunology (Den 303) (4 decks)

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