Immunisation

Question 1

Name the types of vaccines used

Answer 1

Whole killed, toxoids, live attenuated

Question 2

Name the types of immunisation

Answer 2

Passive immunisation

active immunisation or vaccination

Question 3

Define passive immunisation

Answer 3

The administration of pre-formed immunity from one person or animal to another person

Question 4

Passive immunisation advantages, limitations and disadvantages?

Answer 4

Advantages - gives immediate protection, effective in immunocompromised pts

Disadvantages - short lived, possible transfer of pathogens, serum sickness on transfer of animal sera

Limitation - antibody mediated

Question 5

Examples of passive immunisation?

Answer 5

Specific immunoglobulin;

• Human tetanus immunoglobulin = rapid protection
• Human rabies specific Ig = after rabies exposure to give protection until vaccine effective
• Human hepatitis B Ig

Question 6

Passive immunisation backup - Normal immunoglobulin?

Answer 6

From pools of at least 1000 donors, contains antibody against measles, mumps, hepatitis A
Done in emergencies

Question 7

What is active immunisation?

Answer 7

Vaccination - divided into:

• Non-living vaccines
• Live attenuated vaccines

Question 8

What are non-living vaccines?

Answer 8

The memory immune response
1st response = IgM
2nd exposure to antigen = larger immune response as memory B cells work = mainly IgG

Question 9

What are whole killed vaccines?

Answer 9

Bac or viruses grow in vitro and inactivated using an agent e.g. formaldehyde

• Non-living vaccine does not cause infec, but antigens cause an immune response that protects against infection
• Can also be cell-free toxoids-inactivated toxins

Question 10

Limitations of whole killed vaccines?

Answer 10

• Organism must be growth to high titre in vitro
• Whole pathogens often cause excessive reactogencity
• Immune response are not always close to normal response to infec
• Need at least 2 shots

Question 11

Examples of non-living vaccines?

Answer 11

Bacterial;

• Diptheria-cell free formaldehyde treated toxin = rendered non-toxic
• Tetanus, toxoid
• Cholera - heat killed bac

Viral;

• Polio vaccine - inactivated virus - IPV
• Influenza vaccine - inactivated virus
• Hepatitis A vaccine - inactivated virus
• Rabies vaccine - inactivated virus

Question 12

What are live attenuated vaccines?

Define attenuation?

Answer 12

Organisms replicate within the host
Induce immune response = protective against the wild-type organism
More protective

Attenuation = Organism is cultured in such a way that it does not cause disease when inoculated into humans

Question 13

Advantages of live attenuated vaccines?

Answer 13

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

Question 14

Limitations of live attenuated vaccines?

Answer 14

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

Question 15

Examples of live attenuated vaccines?

Answer 15

Bacterial;

• BCG - Myobacterium bovis grown over many passages in vitro - gives some protection against TB
• Salmonella typhi - temp sensitive strain given orally

Viral;

• Poliomyelitis - bring polio to brink of eradication
• Measles, mumps and rubella - 3 given together
• Vaccina virus - eradicate smallpox

Question 16

Examples of pathogens lacking vaccines?

Answer 16

HIV, malaria, Herpes simplex virus, CMV

Question 17

Why do so many pathogens lack vaccines?

Answer 17

• Pathogen too hard to grow
• Killed pathogen not protective
• Impossible to obtain attenuated and suitability immunogenic strain
• Too many strains causing disease

Question 18

Novel approaches?

Answer 18

Recombinant proteins, synthetic peptides, live attenuated vectors, DNA vaccines

Question 19

How are recombinant proteins formed?

Examples of recombinant proteins?

Answer 19

Produced from bac, yeast, inset or mammalian cells

- Hep B surface antigen, HPV vaccines cervarix

Question 20

Recombinant protein benefits and negatives?

Answer 20

Benefit = Avoid problem of having to grow pathogen in vitro
Neg = Major difficulties are finding protective protein(s) and generating a strong immune response

Question 21

Synthetic peptides pos and negs?

Answer 21

• Avoid need to pathogen growth

Negs;
- Identifying protective epitopes and inducing a strong and broad response is a problem

Question 22

Live attenuated vectors?

Answer 22

Express protein from the pathogen in a vector which is know to be attenuated and safe
e.g. Vaccina, BCG
Potential problems in immunodeficient people

Question 23

How do live attenuated vectors work?

Answer 23

= Attenuated, genetically stable vaccine

• Vector able to take additional foreign DNA
• Insert DNA encoding protective antigen of pathogen e.g. HIV

Question 24

How do DNA vaccines work?

Answer 24

Express protein from the pathogen in a mammalian expression plasmid which is then injected = protein is expressed

Question 25

Pros and cons of DNA vaccines?

Answer 25

• Avoid need to grow pathogen
• No live organisms involved
• Cheap

Neg = poor immunogenicity

Question 26

T independent antigens?

Answer 26

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

Question 27

Conjugation of TI antigens to proteins?

Answer 27

• 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

Question 28

Examples of conjugate vaccines?

Answer 28

• 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

Question 29

Recent changes to childhood immunisation programme?

Answer 29

The addition of a pneumococcal conjugate vaccine (PCV) at 2, 4 and 13 months of age;

A dose of MenC vaccine at 3 and 4 months;

A booster dose of Hib and MenC vaccine (given as a combined Hib/MenC vaccine) at 12 months of age.

HPV vaccine for teenage girls

BCG no longer routinely given to teenagers. Targeted on at risk infants.

Question 30

Do vaccines work?

Answer 30

Diptheria - 5 died since vaccine = 99.99% change

Polio - 0 died since vaccine = 99.98% change