Vaccination

Question 1

Outline how vaccines work

Answer 1

• First encounter with organism as relatively harmless vaccine stimulates primary response-> memory lymphocytes. Secondary response is then much stronger
- Vaccine delivery- uptake and processing by APC (B and DCs)
-> B cell activation and proliferation and presentation to T cells
-> B and T cell memory
• Herd immunity- less spread

Question 2

What are the types of vaccine?

Answer 2

• Live attenuated- avirulent form (MMR)
• Killed/inactivated- chemical inactivated form of agent (Polio)
• Sub-unit- isolated components of agent (HepB) /conjugate (Hib)
• Peptide- Under development

Question 3

Outline attenuated vaccines

Answer 3

1.

• Pathogenic virus isolated and grown in human cultured cells
• virus used to infect monkey cells- mutations mean it no longer grows well in human cells-> attenuated

2.

• Isolate pathogenic virus then isolate virulence gene
• mutate or delete virulence gene
• > avirulence

Question 4

Outline conjugate vaccines

Answer 4

• Polysaccharide antigens can’t be presented on MHC molecules on APCs but protein can
- polysaccharides are T independent antigen-> no memory generation
• Conjugate vaccine is where a protein carrier is combined with the polysaccharide leading to CD4 T cell help

Question 5

Outline peptide immunotherapy

Answer 5

Recognition of MHC II in absence of costimulation induces tolerance:

• > cause T cell death, switching off, or converting to Treg which will prevent an aggressive immune response
• under development for MS and T1D

Question 6

Outline the difficulties of Flu vaccine development

Answer 6

• Antigenic drift- neutralising antibodies against haemagglutinin block binding to cells, but mutations alter epitopes
• Antigenic shift- occurs when RNA segments are exchanged between viral strains in a host- no cross-protective immunity to virus expressing a novel haemagglutinin. Eg H1N1 (avian/swine)

Question 7

How is flu vaccine made?

Answer 7

• Inactivated for adults, attenuated for children
• Candidate viruses injected into fertilised hens eggs and incubated to allow the virus to replicate
• Influenza virus isolated and killed and virus antigen is purified

Question 8

Outline vaccines for older people

Answer 8

• Vaccination results in lower antibody titre and reduced antibody efficacy. Memory T cells not as effective
• Vaccines for people 60+ -> Flu, pneumococcal, tetanus, shingles
• protective immunity often not achieved, can reduce disease severity