BM424 - Block E (vaccination)

summarise the differences between active and passive immunity and immunisation?

immunity

active = body making own antibodies

passive = obtained antibodies from mother at birth/during infancy

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immunisation

active = giving antigen - getting body to make antibodies

passive = giving antibody

what is the purpose of a vaccine?

to exploit a body's natural immune defence system

what requirements exist of a vaccine?

must not cause disease

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must evoke a proper/sufficient immune response

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must be cost-effective/safe

what is a notable achievement of vaccination?

eradication of small pox

what is herd immunity?

achieved when sufficient % of a population is vaccinated against a disease so that spread is limited and disease eventually eradicated

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= 1 - 1/R0

what differences exist between vaccine development normally vs under pandemic?

normal = long

pandemic = short

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not short because less thorough but because trials are done on larger scale/with more investment

what two types of vaccine are currently in use?

component and whole virus

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component can be protein subunit/mRNA/VLP

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whole virus can be inactivated or live-attenuated

what do mRNA vaccines require?

liponanoparticles (for transport around body/entry into cells)

summarise the moderna/pfizer vaccine?

= mRNA in liponanoparticle (LNP)

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delivers mRNA to host cell for translation to spike protein

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cell displays spike protein on surface + is targeted for immune response (antibody production)

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vaccine not stable - requires freezing

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fast acting

what is the difference between the pfizer and moderna covid vaccines?

largely the same but each has a different lipid nanoparticle component (i.e., different overall composition of lipid nanoparticle)

summarise the composition of an mRNA vaccine liponanoparticle?

DPSC = structural/stabilises structure

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cholesterol = fluidity/fusion

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ionising lipid = holds mRNA and released in cell

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PEGylated lipid = protects from immune response

summarise the astrazeneca vaccine? (ChAdOx1)

DNA in viral vector

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spike protein gene introduced to weakened adenovirus (vector)

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introduce to host (provokes immune response due to presence of foreign pathogen/antigen)

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delivers DNA to host cell

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host cell machinery transcribes and translates spike protein for surface display

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targeted by immune system

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slower than pfizer/moderna becauser requires transcription and translation

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evokes an immune response earlier

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can be stored in fridge because more stable

summarise the immune response to a vaccine that would be desireable?

APCs recognise spike protein + engulf/digest to display to T cells in lymph nodes

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T cells become CD4 or CD8

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CD4 stimulate B cells to produce specific antibodies against antigen

(memory B cells remember antibody/antigen for next encounter)

why do covid vaccines target the spike protein?

spike protein = how virus gains entry into host cell

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preventing entry preventing reproduction preventing spread

summarise the immunological aspects important regarding vaccines?

adaptive/acquired immunity

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primary response = low antibody concentration with lag

secondary response = high antibody concentration with decreased/no lag

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MHC I and II for CD8 and CD4

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TH1 for inflammation, TH2 for B cell stimulation

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antibodies neutralise/activate complement/tag

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memory cells (= reason for acquired immunity)

in what sense do malaria, HIV, and TB present an ongoing challenge for vaccination?

for a disease to be vaccinatable:

- immune defence must involve antibodies

- antigen must be stable

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neither of these are true for malaria/HIV/TB (T cell-mediated immune response + unstable antigen presentation)

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TB has stable antigen but difficult to access

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all = intracellular

what link exists between viruses and cancer?

oncogenic viruses

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retroviruses can inactivate tumour suppressor genes

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examples = HPV (cervical cancer)