Lecture 20 - Vaccines A/B Flashcards
What kind of virus is smallpox?
Variola, ds DNA virus
How does small pox infect the host? Tissue tropism?
Inhalation, localizes in vessels of skin and in the mouth and throat
What are macropapular rashes
Large fluid-filled blisters characteristic of small pox. Loaded with viral particles - highly infectious.
What is the most deadly virus of all time?
Variola
What were old methods of vaccinating against smallpox?
Variolation, cowpox and horsepox (vaccinia virus) exposure
What is active immunization?
Prophylactic administration of a vaccine to prevent future infections. May or not be lifelong depending on the pathogen and vaccine.
How does active immunization achieve life-long protection ideally?
Production of memory B and T cells. Mostly Ab dependent, Thelper cells - Tc cells not as important
What is passive immunization?
Administration of antitoxins (Ab’s or lymphocytes) that provide protection post-exposure.
Why does passive immunization not provide protection against future infections?
Ab’s or lymphocytes directly injected therefore no production of memory B and T cells - not true immunization.
What occurs during primary exposure to a pathogen?
Clonal amplification of specific B and T cells, Abs, memory B and T cells; takes time.
How does secondary exposure elicit a rapid response compared to the primary response?
Circulating Abs, high levels of clonally amplified B and T cells specific for the pathogen
What is sterilizing immunity?
They prevent infection because the pathogen cannot
replicate; these are the most effective vaccines as
they prevent transmission; eg. measles vaccine
What is a protective immunity?
Vaccinee is protected from the disease but can still transmit it – these are still effective in controlling infection; eg. polio vaccine
What caused the Measles outbreak in 2014? How could it have been prevented?
Reduced vaccine uptake - Two students at a Christian school in Chilliwack contracted measles and
exposed hundreds more. Herd immunity - low
vaccination rate in the region – 50-
60% compared to the national rate
of 95%. Many in this “Bible Belt”
region oppose vaccines based on
religious grounds.
How do vaccines activate the immune system?
All vaccines today work by eliciting a humoral (B cell) response – specific B cells (and T-helper cells) are
stimulated, neutralizing Abs are produced that prevent the pathogen from infecting cells by neutralizing
them and/or targeting them for destruction by phagocytic cells and NK cells. Some vaccines likely also
mediate a cytotoxic T cell response to kill infected cells; not clear how much these contribute to protection
What are the main types of vaccines for SARS-Cov-2?
Viral vector vaccines and mRNA vaccines
What are the different types of viral vector vaccines? Give examples of each.
Weakened virus capable of infecting and replicating without causing illness, vesicular stomatitis virus used for Ebola virus vaccine. Non-replicating vaccine, requires a higher dose, non-replicating adenovirus used for COVID-19.
Which COVID-19 vaccines use non-replicating adenovirus (viral vector vaccines) and what is the virus?
J&J - human adenovirus vector (Ad26)
Astrazeneca - chimpanzee adenovirus vector (ChAd)
Sputnik V - Ad26 boosted with Ad5 in case there was a immune response against the first one, it would destroy the second one instead.
What is the drawback for the J&J, astrazeneca and sputnik v vaccines?
Human adenoviruses cause respiratory infections. People may have anti-Ad Abs (are “seropositive”) due to previous infections, which could
destroy the vector. Hence the use of a non-human primate adenovirus for AstraZeneca
What are mRNA vaccines delivered in?
Lipid nanoparticles
How do mRNA vaccines evade bring recognized as PAMPs?
Modified to prevent being recognized
as PAMPs by cellular RNA pattern recognition receptors
How are mRNA vaccines able to be translated by host cell machinery?
mRNA has a 5’ cap and a 3’ polyA tail so that they are
recognized
What are the benefits and disadvantages of mRNA vaccines?
RNA is easily synthesized, can modify the mRNA
sequence to introduce amino acid changes seen in newlyemerging variants. mRNA is not very stable cf. vectors – require storage at low temperatures
