Viral Vaccines Flashcards
(26 cards)
What are the 4 main vaccine types?
- Inactivated
- Live-attenuated
- Sub-unit
- Vectored
What are inactivated vaccines?
Virus is chemically/physically inactivated
What are live attenuated vaccines?
Weakened version of the virus
What are sub-unit/acellular vaccines?
Specific viral proteins only (e.g. spike protein)
What are vectored vaccines?
Viral gene inserted into another harmless virus
Advantages of inactivated vaccines
- Very safe; no risk of disease or reversion to virulence
- Induces broad immunity
- Largely inexpensive
Disadvantages of inactivated vaccines
- Inactivation may destroy epitopes
- Usually requires adjuvant
- Often requires boosters
- Cold chain needed for storage and transport
What are the advantages of live attenuated vaccines?
- Strong immune response (both cellular and humoral)
- Antigen persists = longer immunity
- Can be multivalent
- Mucosal delivery possible (e.g. taken orally rather than requiring needle)
What does multivalent mean?
Contains antigens from multiple strains or types of a virus, or even from multiple different pathogens
What is an example of a multivalent vaccine?
MMR (measles, mumps and rubella)
What are the disadvantages of live attenuated vaccines?
- Risk of reversion to virulence (esp in immunocompromised)
- May cause mild disease
- Cold chain dependency
What does cold chain dependent mean?
Must be stored and transported at controlled low temperatures (to maintain effectiveness)
What are the advantages of vaccines that can be delivered mucosally?
- No needles; easier administration
- Mimics natural infection route
- Can induce both local mucosal and system immunity
What is an example of an inactivated vaccine?
The influenza vaccine which is updated annually to match circulating strains relies on inactivated viruses grown in chicken eggs or cell cultures
What is an example of how an attenuated vaccine is made?
Mumps vaccine:
- Involves serial passage of virus through non-human cells
- Forces virus to adapt to new environment and accumulate mutations that reduce its virulence in humans
- Virus is still immunogenic, but not virulent
What are the advantages of sub-unit vaccines?
- Pure antigen = no risk of infection
- Focused immune response
- Compatible with DIVA
What is DIVA?
Stands for Differentiating Infected from Vaccinated Animals.
Vaccinated animals lack one or more viral proteins present in naturally infected animals.
Allow diagnostic tests to distinguish between infected and vaccinated animals (important in outbreak control & veterinary medicine)
What are the disadvantages of sub-unit vaccines?
- May lose important conformational epitopes
- Low immunogenicity; needs strong adjuvants
- Cold chain necessary
- Multiple doses usually required
What are conformational epitopes?
Epitopes (immunogens) can depend on the native 3D shape of the protein (not just the amino acid sequence).
Subunit vaccines lack the 3D conformational structure of an actual pathogen, therefore may not present the same epitopes
What are the advantages of vectored vaccines?
- Endogenous and exogenous presentation induces cellular and humoral immunity
- Can be delivered mucosally
- Compatible with DIVA
What are the disadvantages of vectored vaccines?
- May not preserve tertiary structure of antigen
- Vector immunity may limit response to booster doses
- Weaker immune response compared to live-attenuated
What is the purpose of adjuvants?
Enhance the response of subunit/inactivated antigens by mimicking danger signals
What are the mechanisms through which adjuvants work?
- Enhance antigen uptake by APCs
- Stimulate inflammation
- Induce cytokines for T/B cell activation
What are some examples of adjuvants?
Aluminium hydroxide
