Type of immunity & vaccines

• Biology
• Further Education (Key Stage 5)

Type of immunity & vaccines

Maternal antibodies pass to fetus across placenta or to baby in breast milk.
Immunity lasts for a few months.

1. Natural passive
2. Natural active
3. Artificial passive
4. Artificial active

Immune response to infection with pathogen.
Person may become ill and develop symptoms. Long-term immunity.

1. Natural passive
2. Natural active
3. Artificial passive
4. Artificial active

Immune response to a vaccine containing dead or weakened pathogen or a preparation of antigens.
Long-term immunity but boosters may be required.

1. Natural passive
2. Natural active
3. Artificial passive
4. Artificial active

Injection of antibodies from another source (e.g. in serum).
Provides temporary immunity but the antibodies are eventually broken down.

1. Natural passive
2. Natural active
3. Artificial passive
4. Artificial active

Explain why vaccination produces artificial active immunity

• Artificial – because antibodies are made in response to a vaccine rather than a pathogen
• Active – because antibodies are produced by the body’s own plasma cells
  
• Immunity – because memory cells are retained
  

Explain why an individual who has been vaccinated does not develop the disease symptoms if they encounter the pathogen at a later date 

When the vaccine was given the antigens present did not cause disease symptoms

Did stimulate a primary immune response

Memory cells were produced

Therefore when the individual was infected with the pathogen at a later date

A much larger and more rapid secondary immune response was stimulated

This eliminated the pathogen before it could multiply and cause disease symptoms

• When the vaccine was given the antigens present did not cause disease symptoms
• Did stimulate a primary immune response 
• Memory cells were produced
• Therefore when the individual was infected with the pathogen at a later date 
• A much larger and more rapid secondary immune response was stimulated 
• This eliminated the pathogen before it could multiply and cause disease symptoms

Type of vaccine: match the name to the image

Live attenuated

Chimeric live attenuated

Inactivated

Subunit

Nucleic acid-based

Live (Attenuated) Vaccine 

• Modified strains (bacteria or viruses) that reproduce slowly and are not pathogenic
  
• May be achieved through genetic modification of pathogen

• Pathogen reproduces slowly so antigen present for longer
  
• Gives strongest immune response and long-lasting immunity (less need for boosters)

MMR

BCG

(for TB)

Oral polio vaccine

Who are live attenuated vaccines unsuitable for?

Live (Attenuated) Vaccine 

• Cannot be given to anyone with weakened immune system (e.g. after chemotherapy or HIV patients)
  
• Strain may revert and become pathogenic
  

Chimeric Live Vaccine 

• Gene for specific antigen from pathogen introduced into a harmless viral vector
  
• Vector delivers gene to target cells that then synthesise antigen
• Safer
  
• Provides immunity for pathogens that cannot easily be attenuated or inactivated without destroying antigen activity
  

Ebola

Technical difference between chimeric live attenuated vaccine and recombinant vector vaccine.

Live --> can replicate but not harmful

Recombinant --> cannot replicate

Inactivated Vaccine 

• Pathogen is killed or inactivated by heat or chemical treatment (e.g. formaldehyde) so it does not cause disease
  
• Antigens are still intact and can provoke immune response

Typhoid

Cholera

What are the advantages & disadvantages of inactivated vaccines?

Inactivated Vaccine 

• More stable and safer than live vaccines
  
• Does not need refrigeration so travels better
  
• Gives a weaker immune response (if antigens altered by heat) so boosters are necessary

Toxoid

• Harmless version of toxin obtained by heating or chemical treatment
  
• Can trigger the production of antitoxin antibodies in an immune response
• Safe to use where the toxins produced by the pathogen are the cause of symptoms
  
• Gives a weaker immune response so boosters necessary

Diphtheria

Tetanus

Which of the following is NOT an advantage of a toxoid vaccine?

1. Provokes a stronger immune response
2. Safe
3. Causes production of anti-toxin antibodies

Subunit Vaccines

• Harmless version of toxin obtained by heating or chemical treatment
  
• Can trigger the production of antitoxin antibodies in an immune response
• Safe to use where the toxins produced by the pathogen are the cause of symptoms
  
• Gives a weaker immune response so boosters necessary

HPV

HepB

Subunit Vaccines

Subunit vaccine

• Preparation of antigens extracted from pathogen
  

Conjugated vaccine

• Antigens joined to a protein
  
• Safe to use since no whole bacteria / virus
  
• Can construct vaccines to several different strains
  
• Humoral and cellular immune response are stimulated when antigen is joined to protein
  

Recombinant subunit vaccine

• Gene from pathogen inserted into a bacterium / yeast to produce the specific antigen
  

Ag in subunit & conjugate vaccine can be a polysaccharide (e.g. from bacteria coat) instead of a protein.

HepB = recombinant

Which type of vaccine is safer?

1. Live attenuated vaccine
2. Subunit vaccine

Nucleic Acid Vaccine

• Contain mRNA that direct host cells to produce a specific antigen
  
• Safe to use
  
• mRNA broken down within a few days
  
• Cannot combine with human genomic DNA

What are the only mRNA vaccines currently licensed?

Suggest why a vaccine against HIV has not been developed

• Many strains of HIV
• High mutation rate that changes the antigens, so memory cells do not recognise them
  
• Currently three mRNA HIV vaccines are in stage 1 clinical trial
  

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