Immunisation Flashcards
types of immunisation
passive
active/vaccination
passive immunisation
administration of pre formed immunity from one person/animal to another persoon
limitations of passive immunity
only antibody mediated (will not work if cell mediated)
ad/dis of passive immunisation
dvantages
- gives immediate protection
- effective in immunocompromised patients
Disadvantages
- short lived
- possible transfer of pathogens
- ‘serum sickness’ on transfer of animal sera
how are the antibodies made for passive immunisation
1) Human normal immunoglobulin
- prepared from pools of at least 1000 donors
- serum contains antibodies against diseases
types of vaccines for active immunisation
non living vaccinces
live attenuated vaccines
non living vaccines
whole killed and toxids
herpes virus
SARS -CoV-2
humoral antibody repsocne
1) Antigen presenting cell takes in antigen via phagocytosis
2) presents on the APC surface with MHC II
3) T cell receptor correct shape detects antigen
4) TCR of niave T cell binds to Ag
5) signalling
6) Niave T cell becomes activated and turns into primed Th2 cell
T and B cell cooperation and AB production
1) B cells can internalise and present the same antigen with MHC class 2 – primed to the Th2 cells
2) Th2 cells secrete cytokines (which interact with the B cells) Il4/5/10/13
3) These cause B cells to divide, clonal expansion and differentiate into plasma cells and memory B cells
4) Plasma cells secrete antibody that have high specific to the antigen
Antibodes made are specific to the antigen
primary vs secondary immune repsocne
Primary immune response
- low antibody production
- memory B cells made
Secondary immune response
- larger and quicker response
latent perido
where the cells are making the antibodies and recognising the antibodies
how can bacteria or viruses be inactivated
formaldehyde or B-propioactone
- cross links but retains shape
problems and limitations of whole kills vaccines
- organisms must be grown to high titre in vitro (viruses and some bacteria difficult/expensive to grow in the lab)
- whole pathogens can cause excessive reactogenicity (i.e. adverse reactions, excessive immunological responses, can cause disease in itself)
- immune responses are not always close to the normal response to infection eg no mucosal immunity - no CD8 Tc response
- usually need at least 2 shots and regular boosters
what is attenuation
where an organisms is cultured in such a way it does not cause disease when inoculated into humans
advantages of live attenuated vaccines
1) immune response more closely mimics that following real infection because its not mixed no shape change
2) better immune response so lower doses are required so scale of in vitro growth needed is lower
3) route of administration more favourable (oral
4) fewer doses may need to be given for immunisation
problems and limitations of of live attenuated vaccines
- often impossible to balance attenuation and immunogenicity (attenuation may mean Ab will not recognise the real thing)
- reversion to virulence (pathogenic form)
- transmissibility
- live vaccines may not be so attenuated in immunocompromised host
why is it hard to develop vaccines
- pathogen too difficult to grow in culture
- killed pathogen not protective (shape change)
- impossible to obtain attenuated and suitability immunogenic strain
- too many strains causing disease
- cost
novel vaccine approaches
1) recombinant proteins
2) synthetic peptides
3) live attenuated vectors
4) mRNA vaccines
5) polysaccharide- protein conjugates
reconbinant protein uses
protein from the bacteria/vruses used
- just need the DNA to make the protein
- difficult to find proton that are protective and genaerate a strong immune response
synthetic peptides and problems
peptides synthesised directly using a machine - avoids the need for pathogen growth Problems - identifying protective epitopes - inducing a strong or broad response
live attenuated vectors - viral vectors
+ how does it work
Composed of a safe living attenuated viruses that have inserted genes encoding forgein antigens, which are displayed to the immune system
Attenuated genetically stable vaccine vector able to take additional forgein DNA
- this encodes the desired antigen/protein
When injected the virus is taken up by APC, the viral DNA is released and enters the nuclear
- viral DNA is transcribed into mRNA and translated to a protein
- some of this spike protein is presented with MHC II on the cell surface as a forgein antigen
- this is recognised by T cells and initiates an immune response to the spike protein
- the virus is replication deficient and cannot replicate in human cells replicating its spread
T independent antigens
Bacterial capsular polysaccharides cannot be processed and presented on MHC class II - however low antibody repsonce, usually IgM
no T cells required for the immune repsonce
