T1 L8: Vaccines Flashcards
What is variola?
The virus that caused small pox before it was eradicated
What are some examples where passive immunisation is used?
- Immunoglobulin replacement in antibody deficiency
- VZV prophylaxis eg. during exposure during pregnancy
- Anti-toxin therapies after a snake bite
Which type of immunisation is temporary?
Passive immunisation because the antibodies will be metabolised
What is VZV?
Chicken pox
What is the effect if chicken pox during pregnancy?
Can cause foetal complications
What is active immunisation?
It stimulates an adaptive immune response without any apparent infection because the pathogen is inactive
What are some infections that the body can’t produce long-lasting protective immunity against?
TB
HIV
Malaria
What are the possible components of a vaccine?
Antigen
-Stimulates an antigen-specific T and B-cell responses
Adjuvants
-Immune potentiators to increase the immunogenicity of the vaccine
Excipients
-Various diluents and additives required for vaccine integrity
What does attenuated mean?
Weakened
What are some examples of live-attenuated vaccines?
Measles Mumps Rubella Polio (Sabin) BCG Cholera Zoster VZV Live influenza
How can organisms be attenuated?
-Prolonged culture ex vivo in non-physiological conditions
What are the positives of a live vaccine?
- They replicate within the host to create highly effective and durable responses
- Good CD8 response
- Repeated booting not required
What are some negatives of using live vaccines?
- Hard to store because they have a short half-life
- May revert to wild type Eg. vaccine associated poliomyelitis
- Immunocompromised people may develop clinical disease
What is Poliomyelitis?
An enterovirus that establishes infections in the oropharynx and Gi tract but then spreads via lymphatics and then through the blood
1% of patients develop neurological symptoms leading to denervation and flaccid paralysis because the virus replicated in the NS
What is the Sabin oral polio vaccine (OPV)?
- A live-attenuated vaccine
- Highly effective
- 1 in 750,000 develop vaccine associated paralytic polio
Viable virus can be recovered from stool after immunisation so it establishes some protection in non-immunised people
What is the Salk injected polio vaccine (IPV)?
An inactivated vaccine
Better suited for endemic area where benefits of higher efficacy outweigh risks of vaccine-associated paralysis
UK switched to IPV in 2004
What is a Ghon focus?
The calcified TB lesion visible in a chest X-ray
What does BCG stand for?
Bacille Calmett-Guerin
How does the BCG vaccine work?
It increases IFN-gamma cell responses to mycobacterium bovis therefore creating protection against mycobacterium tuberculosis
It 80% prevents dissemination but has little to no effect on pulmonary TB
How are pathogens in vaccines inactivated?
The entire organism is used but physical or chemical methods are used to destroyed viability
Eg. Formaldehyde
What effect does an inactivated vaccine have on B-cells and T-cells?
The inactivated organism stimulates B-cells and is taken up by antigen-presenting cells to stimulate antigen-specific CD4 T-cells
Minimal CD-8 response
Responses are less robust compared to live-attenuated vaccines
What are some advantages of killed vaccines?
- No potential for reversion
- Safe for the immunocompromised
- Stable in storage
What is pathogen reversion?
When it turns back to it’s original active virulent form
What are some disadvantages of killed vaccines?
- Response is weaker compared to live vaccines
- No CD8 response so responses are less durable and boosters are needed
What is antigenic drift?
Slow accumulation of mutations
What is antigenic shift?
When major antigens combine Eg. Spanish flu
What are toxoids?
Toxins that have been chemically detoxified to toxoids
What is the function of polysaccharide capsules?
They make the pathogen immune to phagocytosis
What are subunit vaccines with polysaccharide capsules?
Vaccines for organisms formed of purified polysaccharide capsules which aim to improve opsonisation
What is vaccine conjugation?
Combines a strong antigen with a weak one to boost response
Eg. protein carrier attached to polysaccharide antigen
What are some positives of subunit vaccines?
- Extremely safe
- Works well where primary infection can be prevented by an antibody response
- Works well where virus cannot be easily cultured Eg. HPV and Hep B
What are some negatives of subunit vaccines?
- Development requires detailed knowledge of virology, pathogenesis, and immunology
- Specialised and expensive production
- Weaker immune responses so boosting is often needed
What are some novel adjuncts?
Toll-like receptor ligands (CPG repeats)
How do mRNA vaccines work?
A genetic sequence is delivered and then the host cells produce encoded antigens which stimulates an immune response
How is a viral vector used in vaccines?
Viral vector vaccines use a modified version of a virus that is different from the virus being targeted to deliver important instructions to our cells
