Ch3 Flashcards
1
Q
What is vaccine and how does it work?
A
- killed or weakened version or a subunit of a pathogen
- trick the immune system as if the body was attacked by pathogens –> generation of memory B and T cells –> secondary immune response –> rapid elimination of pathogens
2
Q
What are the characteristics of a successful vaccine?
A
- safety
=> no risk of causing disease => few side effects - efficacy
=> stimulates helper T cells –> maximise the activity of immune cells through the release of cytokines –> development of memory B and T cells and eliminate pathogens by antibody and cytotoxic T cells - pathogenicity
=> only cause mild disease symptoms
=> targeted pathogens only undergo little mutation
=> no latency
=> no attack on self-immune cells
3
Q
How to prepare live attenuated vaccine?
A
- prepared by weakened pathogens through attenuation
4
Q
How can attenuation be done?
A
- growing pathogens under abnormal culture conditions –> pathogens mutate to adapt –> lose their pathogenicity
- mutating virulent genes by recombinant DNA technology
5
Q
What are the pros and cons of live attenuated vaccines?
A
- pros
=> retain their ability to replicate in the host –> act as intracellular Ag –> form peptide-MHC I complex –> increase both humoral and cell-mediated immune response –> lower the chance of having boosters - cons
=> requires refrigeration –> high production cost –> high selling price
=> pathogens may mutate back to pathogenic form through reversion as they are still active and living pathogens
=> more side-effects as they mimic real pathogens –> too effective
6
Q
What are inactivated vaccines?
A
- whole pathogens are killed by heat, gamma irradiation or chemicals –> protect epitopes but remove pathogen’s virulence
7
Q
What are the pros and cons of inactivated vaccines?
A
- pros
=> no possibility of reversion –> safer to use
=> more stable than live vaccines - cons
=> dead microbes cannot act as intracellular Ag –> Ag not presented on MHC I –> mainly B cell response but no cytotoxic T cell response –> boosters and adjuvants are often required
8
Q
How are protein subunit vaccines produced?
A
- produced by recombinant DNA technology
- DNA encoding the protein subunit antigen is introduced into E. coli –> expression of large amount of protein Ag –> direct inject protein as vaccine
9
Q
What are the pros and cons of protein subunit vaccines?
A
- pros
=> contains only the protein Ag –> safer as there is no risk of reversion - cons
=> no cytotoxic T cell activation as Ab response predominates
10
Q
How do polysaccharide subunit vaccine works?
A
- stimulate immune response against polysaccharide molecules in bacterial capsule
11
Q
What are the pros and cons of polysaccharide subunit vaccine?
A
- pros
=> no need to use the whole bacterial pathogen –> safe - cons
=> only T-independent antigens involved –> B cells response only –> as there is no helper T cells response –> no memory cells
12
Q
How can polysaccharide subunit be improved?
A
- improved by chemically linking a carbohydrate antigen to a carrier protein –> conjugate vaccine –> act as T-dependent antigen –> activation of both B and helper T cells response –> production of Ab and memory cells
13
Q
What are recombinant vector vaccines?
A
- transfer a gene encoding a protein Ag of a pathogen into an attenuated viral vector –> form a recombinant vector –> infect host muscle cells –> present protein Ag both intracellularly and extracellularly
14
Q
What are the pros and cons of recombinant vector vaccines?
A
- pros
=> strong humoral and cell-mediated response
=> low risk of reversion as most of the pathogen genome is eliminated - cons
=> side effects due to host immune response to the recombinant vector- vector may be damaged –> vaccine becomes useless
- may be life-threatening as the vector may still cause death
=> low stability as refrigeration is required
15
Q
What are DNA and RNA vaccines?
A
- plasmid DNA or RNA coding for a protein Ag of a pathogen is injected into the muscle –> host muscle cells take up DNA or RNA and express the protein Ag intracellularly and extracellularly –> present Ag via MHC I and MHCII –> increase humoral and T cells response
