Vaccines

Question 1

define R0 (“r nought”)

Answer 1

pf people an infected person in a community can presumably infect

ie. how contagious

Question 2

define herd immunity

Answer 2

state where pop is sufficiently immune that the infection will not spread

Question 3

define Re

Answer 3

the effective reproduction number
# of people in pop who can be infected by an individual at any specific time

CHANGES as pop becomes increasingly immunised (or death)

Question 4

Equation relating Re to R0, using population immunised Pi

Answer 4

Re = Ro * (1-Pi)

where Pi is proportion of pop immunised at that time

Question 5

what is an antigen?

Answer 5

a particle that enters the body and triggers an immune / antibody response

antibodies recognise antigens
eg. the spike protein on surface of a virus

Question 6

define protective antigen

Answer 6

molecules that when recognised by the immune system trigger a response that provides protection against a specific pathogen

crucial for developing vaccines - induce immunity without causing the disease

Question 7

define epitope

Answer 7

the specific region on the antigen that an immune system component (T-cell or antibody) recognises and binds to

Question 8

what are APCs? give examples

Answer 8

Antigen-presenting cells
a type of immune cell that engulfs the antigens and displays them on their surface to T-cells to initiate immune response

usually dendritic cells and macrophages

Question 9

what is MHC? what is its main purpose?

Answer 9

Major Histocompatibility Complex – helps immune system distinguish between self and non-self cells

a set of genes that encodes cell surface proteins

all nucleated cells have MHC Class I
MHC Class II primarily on APCs

Question 10

what is the role of helper T cells in immune response

Answer 10

CD4+ T cells are white BCs, required in almost all ADAPTIVE immune response

Recognises the MHC-Antigen complex on APCs through their T-cell receptor

Then activate both cell-mediated and antibody-mediated immunity pathways

Question 11

name the two main adaptive immunity pathways

Answer 11

1. Cell-mediated immunity: through cytotoxic (“killer”) T-cells
2. Antibody-mediated: B-cells produce abs to neutralise virus

Question 12

name four main classes of vaccines

Answer 12

1. Jennerian (whole pathogen)
2. Vector vaccines (harmless virus + pathogen)
3. Protein-based vaccines (subunit, VLPs)
4. Nucleic-acid based vaccines

Question 13

Name the two types of Jennerian vaccines (Edward Jenner - the guy that came up with the “first vaccine” for smallpox)

Answer 13

1. Live-attenuated vaccines (LAVs)
2. Inactivated vaccines

Question 14

how do live attenuated vaccines (LAVs) work?

Answer 14

LAVs contain a weakened (“attenuated”) version of a pathogen, stimulating the immune system to produce antibodies.

Question 15

how are LAVs produced (how is attenuation achieved)?

Answer 15

attenuation is achieved using forward and reverse genetic approaches (eg. passaging through rabbits / chickens to introduce mutations)

long production process

Question 16

what are inactivated vaccines (Jennerian)?

Answer 16

virus is KILLED by crosslinking agents but it keeps its 3D shape

Question 17

pros and cons of LAVs vs Inactivated vaccines

Answer 17

LAVs: highly immunogenic (potent) but cannot be administered to immunocompromised

Inactivated: safer but less immunogenic

Question 18

what are vector vaccines?

Answer 18

combines a pathogenic virus and a harmless virus (eg. adenovirus) as a “carrier” or “vector”
carries DNA that codes for pathogenic antigens

Question 19

what is a replicating vaccine?

Answer 19

contain live agents that can replicate inside the host, more closely mimics a natural infection

a description that can apply to vector vaccines (ie. replicating vector vaccine), or live-attenuated vaccines

Question 20

what is a non-replicating vaccine?

Answer 20

contains inactive agents or vectors that do not replicate inside the host. generally safer for the immunocompromised, but less immunogenic

describes a type of vector vaccines, or inactivated Jennerian vaccines

Question 21

What viruses are commonly used as the “vector” for vector vaccines?

Answer 21

Adenovirus –> adenovirus-based vaccines

usually chimpanzee adenovirus, not a human one, to avoid pre-existing immunity
vector is replication-deficient
key genes (eg. E1) deleted

Question 22

what is a reverse genetics approach to producing vector vaccines?

Answer 22

rather than starting with a virus and weakening it, start with the virus’s genetic sequence and engineer it in the lab

assemble full viral genome from DNA fragments (this is the “reverse” part)

Question 23

what are VLP vaccines?

Answer 23

Vaccine-Like Particles
artificial, non-infectious self-assembling structures that lack genetic material causing disease (like empty houses)

Question 24

give two examples of VLP vaccines

Answer 24

Hepatitis B vaccine (HBV)
HPV vaccine (human papillomavirus vaccine)

Question 25

why are VLPs usually easy to separate / purify?

Answer 25

distinct physical characteristics: regular size, usually large / icosahedral structure often high density

Question 26

what are subunit vaccines? name pros and cons

Answer 26

contains purified components of pathogens (fragments) - selected protective antigens only very safe as there is no genetic material but requires multiple doses and adjuvants

Question 27

what are adjuvants?

Answer 27

molecules that increase immune response (improve strength and longevity of response) (usually made of aluminium salts, LPS or oil-in-water emulsions...)

Question 28

what are some mechanisms by which adjuvants work to enhance immune response for subunit vaccines?

Answer 28

improve antigen presentation stimulate APCs / other immune system components slowing down antigen release to prolong immune response

Question 29

name an example of a subunit vaccine

Answer 29

Influenza A virus ie. the seasonal flu - need to update for different strains each season recommended for ppl over 65, pregnant women etc

Question 30

what are the two protective antigens in influenza A virus?

Answer 30

HA and NA: Hemagglutinin and Neuraminidase

Question 31

give examples of administration technologies for vaccines

Answer 31

common: intramuscular or intradermaal injection (vary in depth) novel: micro needles, or nanopatch (better for children)

Question 32

a novel production and delivery platform is edible vaccines. what are some expression systems?

Answer 32

plants like potatoes, bananas, legumes etc generally simple genetics, non-perishable and can be eaten RAW

Question 33

what are nucleic-acid based vaccines? name the two types

Answer 33

a newer category of vaccine - uses genetic material to instruct host cells to make antigens. DNA or mRNA vaccines