vaccines Flashcards
what are the 3 types of traditional vaccines
whole killed
toxoid
live attentuated
2 types of immunisation
passive
active / vaccination
define passive immunisation
the administration of pre formed ‘immunity’ from one person or animal to another person
limitation of passive immunisation
only humoral (antibody) mediated
not work if cell mediated
advantages of passive immunisation
gives immediate protection
effective in immunocomproised patients
disadvantages of passive
short lived
possible transfer of pathogens
‘serum sickenss’ on transfer of animal ser
2 examples of passive immunisation
Human Normal Immunoglobulin (HNIG)
Convalescing serum eg SARS Co-V2
how is HNIG prepared
from pools of of at least 100 donors
contains antibody against measles, mumps, varicella, hepatitis A etc
how is convalescing serum prepared
pooled from people recovering from covid -19
but clinical trial result sugggests no overall increased efficiacy against virus using passive immunisation
what was he first ever vaccine against
small pox
3 main approaches to making a vaccine
- using a whole virus or bacterium
- using parts that trigger the immune system
- using just the genetic material
2 different types of vaccines
non living vaccines - whole killed and toxoids
l;i’ve attentuated vaccines
what is the whole microbe vaccine approach
inactivated vaccine
live attentuated vaccine
viral vector vaccine
how are bacteria and viruses inactivated
they are grown in vitro and inactivated using agents such as formaldehyde or B-proplonolactone
do non living vaccines cause infection
no but the antigens contained in it induce an immune response that protects against infection - by non self antigen recognition
non living vaccines can also be cell freee toxoids - inactivated toxins
problems and limitations of whole killed vaccines
The 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)
• Immune responses are not always close to the normal response to infection, e.g., no mucosal immunity, no CD8 Tc responses
• Usually need at least 2 shots
4 examples of bacterial whole killed vaccines
diptheria
tetanus
pertussis
cholera
examples of viral whole killed vaccines
polio vaccine
influenza vaccine
hepatitis A vaccine
rabies vaccine
SARS - COV 2
what are live attentuated vaccines
The organisms replicate within the host and induce an immune response which is protective against the wild-type organism but does not cause disease.
benefits of live attenuated vaccines
more real life and provides better protection
Immune response more closely mimics that following real infection because its not fixed – no shape change.
Better immune response so lower doses are required, so the scale of in vitro growth needed is lower.
Route of administration may be more favourable (oral).
Fewer doses may be required to provide protection.
what is attenuation
where an organism is cultured in such a way that it does not cause disease when inoculated ito humans
it has lost its pathogenicity but retains its antigenecity ie shape
problems and limitations of live attenuated vaccines
often impossible to balance attenuation and immunogenicity
reversion to virulence
transmissibility
live vaccines may not be attenuated in immunocompromised hosts
examples of bacterial live attenuated vaccines
- Bacille Calmette-Guérin (BCG) Mycobacterium bovis grown over many passages in vitro.
Gives some protection against TB (tuberculosis) - Salmonella typhi - temperature sensitive strain given orally.
examples of viral live attenuated vaccines
poliomyeletis (SABIN)- widely used to brain g polio to extinction
vaccinia virus - used in billions of doses to eradicate smallpox
measles, mumps, rubella - MMR
pathogens lacking vaccines
HIV, malaria, Schistosomiasis, Leishmania spp, Herpes Simplex Virus, CMV, RSV, Rhinoviruses, Group B streptococci, Meningococcus group B, M. leprae…….
why do so many pathogens not have vaccines
- pathogen too difficult to grow
- killed pathogen not protective (shape change)
- impossible to obtain attenuated and suitably imunogenic strain
- too many strains causing disease
what are 5 novel vaccine approaches
- recombinant proteins
- synthetic peptides
- live attenuated vectors
- mrna vaccines
- polysaccharide protein conjugates
what are recombinant proteins
genetically engineered and produced from bacteria, yeast, insect or mammalian cells
they avoid the problem of having to grow the pathogen in vitro
what is the issue with recombinant proteins
major difficulties - finding a protein or proteins that are protective and generate a strong enough immune response
examples of recombinant proteins on the market
- hepatitis B surface antigen
- HPV vaccines
- SARS -Co-V2
what are synthetic peptides
peptides synthesised directly using a machine - avoids the need for pathogen growth
3 problems with synthetic peptides
identifying protective epitopes
inducing a strong response
inducing a broad response
are there any examples of synthetic peptides on the market
NO
what are live attenuated vectors
composed of a safe living attenuated viruses that have inserted genes encoding foreign antigens, which are displayed to the immune system
when can live attenuated vectors cause problems
in immunodeficiency people
what are viral vectors
attenuated, genetically stable vaccine vector able to take additional foreign DNA encoding for the desired antigen/protein
what are DNA vaccines
a mammalian plasmid containing DNA that encodes for the foreign protein of interest is injected directly
this requires a lipid nano carrier to get the dna into a human cell.
the dna goes to the nucleus, gets transcribed and the foreign protein expressed with MHC to stimulate the immune response
advantages of dna vaccines
avoid the need to grow the pathogen, viral vector
no live organism involve
dna is cheap to produce
problem of dna vaccine
often poor immunogenicity
are there any examples of dna vaccines on the market
NO
what are mrna vaccines
mrna of the target foreign protein is synthesised in vitro
it is complexed with lipid nano particles that stabilise and protect the mrna from degradation and allow the mrna to cross the plasma membrane
the mrna is translated int he cytoplasm and the protein presented on the surface of the cell with MHC
stimulationg the immune response
benefits of mrna vaccines
avoid the need to grow the pathogen , viral vector
no live organism needed
mrna is relatively cheap to produce
quick to make new variations of vaccine
examples of mrna vaccine
sars - co v2:
pfizer biotech, moderna, bayer curevac
what are t indepdent antigens
bacterial capsular polysaccharides cannot be processesed and 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
recent changes to vaccination programme
- addition of pneumococcal conjugate virus at 2,4, and 13 months
- a dose of Menc VACCINE AT 3 AND 4 months
- a booster dose of Hib and MenC vacccine at 12 months
- HPV for teenage girls and boys
- BCG no linger routinely given to teenagers. targeted on at risk infants
are vaccines safe
currently no scientific evidence to link vaccination with any lo9g term disease
why don’t people trust vaccines
misinformation on internet
religion
studies linking immunisation with contraction of other diseases
stages of vaccinationm
- Engage the innate immune system
- Danger signals that activate the immune system, triggers such as molecular fingerprints of infection – PAMPs (pathogen associated molecular patterns)
- Engage TLR receptors
- Activate specialist APC
- Engage the adaptive immune system
a. Generate memory T and B cells
b. Activate T cell help
