T1 L8: Vaccines

Question 1

What is variola?

Answer 1

The virus that caused small pox before it was eradicated

Question 2

What are some examples where passive immunisation is used?

Answer 2

• Immunoglobulin replacement in antibody deficiency
• VZV prophylaxis eg. during exposure during pregnancy
• Anti-toxin therapies after a snake bite

Question 3

Which type of immunisation is temporary?

Answer 3

Passive immunisation because the antibodies will be metabolised

Question 4

What is VZV?

Answer 4

Chicken pox

Question 5

What is the effect if chicken pox during pregnancy?

Answer 5

Can cause foetal complications

Question 6

What is active immunisation?

Answer 6

It stimulates an adaptive immune response without any apparent infection because the pathogen is inactive

Question 7

What are some infections that the body can’t produce long-lasting protective immunity against?

Answer 7

TB
HIV
Malaria

Question 8

What are the possible components of a vaccine?

Answer 8

Antigen
-Stimulates an antigen-specific T and B-cell responses

Adjuvants
-Immune potentiators to increase the immunogenicity of the vaccine

Excipients
-Various diluents and additives required for vaccine integrity

Question 9

What does attenuated mean?

Answer 9

Weakened

Question 10

What are some examples of live-attenuated vaccines?

Answer 10

Measles
Mumps
Rubella
Polio (Sabin)
BCG
Cholera
Zoster
VZV
Live influenza

Question 11

How can organisms be attenuated?

Answer 11

-Prolonged culture ex vivo in non-physiological conditions

Question 12

What are the positives of a live vaccine?

Answer 12

• They replicate within the host to create highly effective and durable responses
• Good CD8 response
• Repeated booting not required

Question 13

What are some negatives of using live vaccines?

Answer 13

• Hard to store because they have a short half-life
• May revert to wild type Eg. vaccine associated poliomyelitis
• Immunocompromised people may develop clinical disease

Question 14

What is Poliomyelitis?

Answer 14

An enterovirus that establishes infections in the oropharynx and Gi tract but then spreads via lymphatics and then through the blood

1% of patients develop neurological symptoms leading to denervation and flaccid paralysis because the virus replicated in the NS

Question 15

What is the Sabin oral polio vaccine (OPV)?

Answer 15

• A live-attenuated vaccine
• Highly effective
• 1 in 750,000 develop vaccine associated paralytic polio

Viable virus can be recovered from stool after immunisation so it establishes some protection in non-immunised people

Question 16

What is the Salk injected polio vaccine (IPV)?

Answer 16

An inactivated vaccine

Better suited for endemic area where benefits of higher efficacy outweigh risks of vaccine-associated paralysis

UK switched to IPV in 2004

Question 17

What is a Ghon focus?

Answer 17

The calcified TB lesion visible in a chest X-ray

Question 18

What does BCG stand for?

Answer 18

Bacille Calmett-Guerin

Question 19

How does the BCG vaccine work?

Answer 19

It increases IFN-gamma cell responses to mycobacterium bovis therefore creating protection against mycobacterium tuberculosis

It 80% prevents dissemination but has little to no effect on pulmonary TB

Question 20

How are pathogens in vaccines inactivated?

Answer 20

The entire organism is used but physical or chemical methods are used to destroyed viability
Eg. Formaldehyde

Question 21

What effect does an inactivated vaccine have on B-cells and T-cells?

Answer 21

The inactivated organism stimulates B-cells and is taken up by antigen-presenting cells to stimulate antigen-specific CD4 T-cells

Minimal CD-8 response

Responses are less robust compared to live-attenuated vaccines

Question 22

What are some advantages of killed vaccines?

Answer 22

• No potential for reversion
• Safe for the immunocompromised
• Stable in storage

Question 23

What is pathogen reversion?

Answer 23

When it turns back to it’s original active virulent form

Question 24

What are some disadvantages of killed vaccines?

Answer 24

• Response is weaker compared to live vaccines

- No CD8 response so responses are less durable and boosters are needed

Question 25

What is antigenic drift?

Answer 25

Slow accumulation of mutations

Question 26

What is antigenic shift?

Answer 26

When major antigens combine Eg. Spanish flu

Question 27

What are toxoids?

Answer 27

Toxins that have been chemically detoxified to toxoids

Question 28

What is the function of polysaccharide capsules?

Answer 28

They make the pathogen immune to phagocytosis

Question 29

What are subunit vaccines with polysaccharide capsules?

Answer 29

Vaccines for organisms formed of purified polysaccharide capsules which aim to improve opsonisation

Question 30

What is vaccine conjugation?

Answer 30

Combines a strong antigen with a weak one to boost response

Eg. protein carrier attached to polysaccharide antigen

Question 31

What are some positives of subunit vaccines?

Answer 31

• Extremely safe
• Works well where primary infection can be prevented by an antibody response
• Works well where virus cannot be easily cultured Eg. HPV and Hep B

Question 32

What are some negatives of subunit vaccines?

Answer 32

• Development requires detailed knowledge of virology, pathogenesis, and immunology
• Specialised and expensive production
• Weaker immune responses so boosting is often needed

Question 33

What are some novel adjuncts?

Answer 33

Toll-like receptor ligands (CPG repeats)

Question 34

How do mRNA vaccines work?

Answer 34

A genetic sequence is delivered and then the host cells produce encoded antigens which stimulates an immune response

Question 35

How is a viral vector used in vaccines?

Answer 35

Viral vector vaccines use a modified version of a virus that is different from the virus being targeted to deliver important instructions to our cells