Vaccines 2 Flashcards
Describe antigenic variation in terms of drift and shift
- Drift: Point mutation in DNA lead to coding change in the Aa. Results in changes in the structure of the protein
- Shift: Reassortment of segments in the genome between different strains of the same pathogen, leading to dramatic changes in the expressed protein.
Which version of antigenic variation results in the immune response being totally non protective?
-Antigenic shift (reassortment of genome segments)
(In shift the protein completely changes so no Ab bind to it, whereas in drift, some protein remains unchanged so some Ab can bind giving it partial protection)
Which virus is a good example for using both types of antigenic variation?
Influenza
What impact does variation, drift and shift have on clinical disease?
-Clinical disease is more severe due to: Antigens are altered so IR no longer recognises it
For which pathogens is variation, drift and shift more important?
- Extracellular pathogens (e.g. flu) and their surface antigens. Antibodies are the primary defence against these pathogens.
Describe the impact of variation on vaccination
-Leads to multiple infections with the same pathogen, the vaccine must contain all strains to be effective which is difficult
Describe the impact of shift on vaccination
-Population has NO immunity so pandemic occurs, vaccine not protective anymore so clinical signs are severe and individuals shed pathogens.
Describe the impact of drift on vaccination
-Mild epidemic occurs due to small degree of immunological protection existing. Mild clinical disease and shed, even in vaccinated animals
What strategies can be used to try and overcome variation, drift and shift?
- Continuous surveillance or circulating strains
- Repeated updating on strains in vaccines
What are the requirements for commercial vaccines?
- Licensed
- Target species
- Safe
- Efficacious(needs to stimulate protective IR)
- Route of immunisation stated
- Pregnancy status may also be included
Who is the regulatory authority for vaccinations in the UK?
Vet Medicines Directorate (work for DEFRA)
List some ways that vaccine safety can be shown
- Experimental/ field trials
- Multiple immunisations in target species
- 5 to 10 x antigenic payload (ensure deviation won’t result in adverse effects)
- Shedding of vaccine virus to cohorts
What are the reasons why vaccines may not be so effective in neonates/ aged animals?
- Neonates: maternal Ab interferes with vaccine response/ Immature immune systems
- Ages: immune senescence or compromised immunity
Who would you report an adverse vaccine reaction to?
Vet medicine directorate
-They monitor any problems
Who monitors vaccines in the field?
MAVIS (marketing authorisations veterinary information service)- a part of VMD
