Vaccines & immunlogical memory Flashcards
what is immunisation?
process through which an individual develops immunity/memory to a disease (Includes both deliberate and natural infection)
what is vaccination?
deliberate administration of antigenic material to produce immunity to a disease
what is active immunity?
- protection produced by person’s own immune system
- can be stimulated by vaccine or naturally acquired infection
- usually permanent
what is passive immunity?
- protection transferred from another person or animal
- temporary protection that wanes with time
what are examples of passive immunity?
- placental transfer of antibodies
- antibodies in breast milk/colostrum
- venom antidotes (antibodies)
why vaccinate?
- Vaccination is effective at reducing or preventing disease
- Certain pathogens cause life-threatening or life-altering disease
- After clean water, vaccination is the most effective public health intervention in the world
& in order to induce immunologically-mediated resistance to disease
how effective is vacccination?
= estimated to save 2-3 million lives a year
- life-threatening diseases that used to be common in young children in UK are now relatively rare
what is the goal of vaccination?
reduce herd immunity
what is herd immunity?
concept used for vaccination, in which a population can be protected from a certain virus if a threshold of vaccination is reached
does every person need to be vaccinated to reach herd immunity?
- with herd immunity, vast majority of population are vaccinated, lowering overall amount of virus able to spread in whole population
→as a result, it’s not that every person is vaccinated, it’s that enough people are vaccinated to protect vulnerable groups who cannot get vaccinated and are kept safe
what is vaccination?
deliberate exposure to pathogen or pathogen derived antigens
what does immunological memory require from primary adaptive immune response?
needs to be effective so generate cells that are useful in secondary response:
- memory B cells
- long lived plasma cells
- CD8+ T cells
- CD4+ T cells
what is small description of what happens with memory B & T cells?
- they’re generated in primary immune response
- memory T & B cells can survive in dormant state for many years after antigen has been eliminated
- memory T &B cells rapidly re-activate in response to a 2nd encounter with that specific antigen (secondary immune response)
why do memory B &T cells make more effective immune response?
-are present in greater numbers than the original parent lymphocytes
-are long-lived, persisting in the absence of antigen
- are less reliant on co-stimulation than naive T cells
- have already undergone Ig class switching and are programmed to make high affinity antibodies
- Some Memory T cells are already present in peripheral tissues
therefore, upon re-exposure, adaptive immune response to a pathogen is more rapid, more aggressive & more effective
what are the main types of vaccines?
- inactivated vaccines (whole killed pathogens, subunit vaccines, conjugate vaccines)
- weakened pathogens (live, attenuated)
- DNA/RNA vaccines
what are whole killed vaccines?
vaccine consisting of whole virus or whole virus particles that have been inactivated by heat or chemical treatment. they’re no longer capable of infecting host cells or replicating
what are whole killed vaccines examples?
- inactivated polo vaccine (IPV)
- some flu vaccines
- hepatitis A vaccine
- rabies vaccine
what are subunit vaccines?
- like whole killed vaccines, they don’t contain live components of the pathogen but differ in that they contain only specific antigen fragments of the pathogen
→these fragment can be isolated from the pathogens itself or they can be expressed artificially in a lab
what are examples of subunit vaccines?
- some flu vaccines
- Hepatitis B vaccine (contains virus surface antigen)
- PPV (adult pneumonia vaccine) - contains polysaccharides from surface of 23 types of bacteria that cause pneumococcal disease
- toxoid vaccines
what are conjugate vaccines?
- in comparison to plain polysaccharide vaccines, conjugate vaccines benefit from a technology that binds the polysaccharide to a carrier protein that can induce a long-term protective response even in infants
→ these are important in providing defence in encapsulated bacteria (capsule = composed of polysaccharides)
what are examples of conjugate vaccines?
- Hib vaccine
- MenC vaccine
- PCV (childrens pneumonia vaccine)
what are live attenuated vaccines (LAV’s)?
contain whole bacteria or viruses which have been “weakened” so that they create a protective immune response but do not cause disease in healthy people. Live vaccines tend to create a strong and lasting immune response and are some of our best vaccines. However, they are not suitable for people whose immune system does not work, either due to drug treatment or underlying illness.
how is attenuation achived?
achieved using principles of evolution via serial passages of virus through cells of a foreign host species. Through natural selection (mutation), the pathogen will become adapted to foreign host such that it is no longer harmful to humans
what are examples of live-attenuated vaccines?
- Tuberculosis (BCG) vaccine
- oral polio vaccine
- measles vaccine
- Rotavirus vaccine
what are DNA vaccines?
viral vectors (from unrelated harmless virus) can be used to deliver dsDNA that encodes for specific antigenic protein into human cells
what are RNA vaccines?
synthetic RNA (which when translated generates an antigenic protein) is delivered into human cells via a lipid-based delivery system
