vaccines Flashcards
what are the two types of immunisation?
passive
active
describe passive immunisation
The administration of pre-formed “immunity” from one person or animal to another person
what are the limitations of passive immunisation?
Only humoral (antibody) mediated
(not work if cell mediated!)
what are the advantages for passive immunisation?
Gives immediate protection
Effective in immunocompromised patients
what are the disadvantages for passive immunisation?
Short-lived
Possible transfer of pathogens
“Serum sickness” on transfer of animal sera
2 examples of passive immunisation
- Human Normal Immunoglobulin (HNIG)
- Convalescing Serum ( SARS CO-V2
What are the three approaches to making a vaccine?
- inactivated vaccine
- Live attenuated vaccine
- Viral vector vaccines
how do non living vaccines work?
Non-living vaccines do not cause infection, 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-free toxoids - inactivated toxins
problems and limitations with 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
examples of bacteria used in vaccines
diphtheria -formaldehyde treated toxin - rendered a non-toxic “toxoid
tetanus - texoid as above
pertuissis- whooping cough
cholera- heat killed bacteria
examples of viruses used in vaccines
Polio vaccine (Salk) - inactivated virus-IPV
Influenza vaccine - inactivated virus
Hepatitis A vaccine - inactivated virus
Rabies vaccine - inactivated virus
SARS-Co-V2 (Valneva) - inactivated virus
what are live attenuated 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.
This is more real-life and provides better protection
define attenuation
Where an organism is cultured in such a way that it does not cause disease when inoculated into humans.
It has lost its pathogenicity but retains its antigenicity – (i.e., shape).
advantages to live attenuated vaccines
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.
problems and limitations with live attenuated vaccines
- Often impossible to balance attenuation and immunogenicity
- Reversion to virulence
- Transmissibility
- Live vaccines may not be so attenuated in immunocompromised host
2 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
- Poliomyelitis (Sabin) - widely used to bring polio to the brink of eradication
- Vaccinia virus - used in billions of doses to eradicate smallpox due to cross-reactivity between itself and the variola virus
- Measles, Mumps and Rubella - 3 given together as MMR
give examples of pathogens lacking vaccines
HIV, malaria, Schistosomiasis, Leishmania spp, Herpes Simplex Virus, CMV, RSV, Rhinoviruses, Group B streptococci, Meningococcus group B, M. leprae…….
why are there so many pathogen lacking vaccines?
-Pathogen too difficult to grow
-Killed pathogen not protective (shape change)
-Impossible to obtain attenuated and suitably immunogenic strain
-Too many strains causing disease etc.
what are the 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
advantages of recombinant proteins
Avoid the problem of having to grow pathogen in vitro
disadvantages of recombinant proteins
Major difficulties are finding a protein or proteins that are protective and generate a strong enough immune response
examples of recombinant proteins
Hepatitis B Surface Antigen
HPV vaccines Cervarix and Gardasil (HPV16 and 18)
SARS-Co-V2 – Novavax (recombinant spike protein produced by moth cells in culture, these are purified, assembled into a synthetic nanoparticle for injection – 14 spike proteins per particle)
