V - Vaccination Flashcards
Describe the physiology of generation of immunological memory.
Long lived memory B cells are generated during primary humoral immune responses.
Memory B cells can survive in a dormant state for many years after the antigen has been eliminated.
Memory B cells rapidly re-activate in response to a second encounter with that specific antigen - clonal expansion , differentiation into plasma cells, antibody production.
Describe how T memory can be generated through vaccination.
Vaccination stimulates rare naïve T cells, inducing a strong T cell response in 14-21 days.
Some become effector T cells, which mostly die by apoptosis, but a small number become memory cells.
Describe some characteristics of memory T cells.
Primed CD4+ cells - able to produce cytokines immediately.
Primed CD8+ cells - able to kill immediately.
Can be maintained for long time without antigen.
Define: Immunisation Vaccination Active immunity Passive immunity
Immunisation - is the process through which an individual develops immunity/memory to a disease (includes both deliberate and natural infection).
Vaccination - is the deliberate administration of antigenic material to produce immunity to a disease
Active immunity - protection produced by the person’s own immune system (can be stimulated or naturally acquired).
Passive immunity - protection transferred from another person, or animal.
Describe the four methods of generating immunological memory.
- Exposure of an individual to the infectious organism itself. E.g. variolation - the same organism is being administered as the one that causes disease, but the route of administration is different.
- Exposure to similar but less virulent pathogen - e.g. cowpox protect against smallpox. One disease is being induced to generate cross-reactive immunity against another disease.
- Exposure to an inactivated pathogen e.g. attenuated vaccines.
- Exposure to a less virulent version of the same pathogen e.g. live attenuated vaccines.
What is an adjuvant and how does it work?
A mixture of inflammatory substances which stimulates an immune response to coadministered peptides, proteins or carbohydrates.
It binds to macrophages and signals the unequivocal presence of a microbial invader.
Give examples of inactivated whole cell vaccines (i.e. whole organism is used)
- Polio (Salk, inactivated)
- Hepatitis A
- Rabies
- Cholera
- Plague
Give examples of inactivated fractional cell vaccines (i.e. only part of the organism is used)
Subunit vaccines • Hepatitis B • Influenza • Acellular pertussis • HPV • Anthrax Toxoid • Diphtheria • Tetanus Pure polysaccharide vaccines
What is a polysaccharide vaccine?
What are their limitations?
Polysaccharide sugars from the outer capsule of some bacteria determines pathogenicity and antigenicity. However, polysaccharides are not good at stimulating response:
- Generates antibody with less functional activity
- especially in immature immune system
What is a live attenuated vaccine?
How is it made?
Examples?
A weakened form of the “wild” virus or bacterium.
It is made by:
1. Pathogenic virus is isolated from humans and used to infect monkey cells.
2. After repeated culture, it acquires mutations that allow it to grow well in monkey cells.
3. Virus no longer grows well in human cells and can be used as a vaccine.
Examples - MMR, chickenpox, yellow fever, BCG, oral typhoid.
Sabin or salk polio vaccine?
Give pros and cons of both.
Sabin (live attenuated): cheap; easy to administer; but SAFETY - risk of reversion to virulent form.
Salk (inactivated): safe; but needs two or more doses; more expensive; requires injection.
Describe two types of sources of passive immunity, and give examples of both.
- Naturally acquired - e.g. maternal antibody (IgG in third trimester; breastmilk contains IgA).
- Therapeutic:
a) Pooled normal human immunoglobulin - transfor of antibody from an unrelated individual.
b) Monoclonal antibody - monthly intramuscular injection for RSV virus.
