Defence and vaccination against bacteria

Question 1

Which type of acquired immunity is important for preventing septicaemia?

Answer 1

Humoral immunity

Question 2

Which type of acquired immunity is important for preventing intracellular infections?

Answer 2

Cell mediated immunity

Question 3

3 roles of antibodies

Answer 3

Toxin neutralisation
Focus complement binding
Opsonin

Question 4

Why is cell-mediated immunity important?

Answer 4

For eliminating intracellular bacteria

Interaction between T lymphocytes and macrophage is key to clearance

Question 5

Name 7 properties of a good vaccine

Answer 5

Stimulates effective immune response
Safe
No adverse reactions
Inexpensive
Stable
Easy administration
Simple to control

Question 6

2 methods of vaccine protection

Answer 6

Direct

Indirect (Herd)

Question 7

Direct protection

Answer 7

Give individual immunity

Stops colonisation that leads to infection

Question 8

Herd immunity

Answer 8

Transmission cycle broken
Prevents spread
Indirectly protects those who are still susceptible (not immune)

Question 9

Clinical trials

Answer 9

Phase 1: Safety/ immunogenicity, small no of adults
Phase 2: Assesses immune response/ expands safety database, includes all groups likely to use
Phase 3: Protection studies- placebo controlled double blind, need good disease surveillance, vaccine efficacy determined

Question 10

Vaccine efficacy equation

Answer 10

1 - (Attack rate in vaccinated / Attack rate in unvaccinated)

Question 11

Herd effect is a relationship between

Answer 11

Basic reproduction number R0,
vaccine effectiveness,
coverage needed to reduce or eliminate disease

Question 12

When can herd effect be calculated

Answer 12

Post vaccine introduction

Question 13

Herd effect equation

Answer 13

1 - (attack rate unvaccinated post-introduction / attack rate unvaccinated pre-introduction)

Question 14

Vaccine coverage needed equation

Answer 14

( 1 - 1/R0) / Effectiveness

Question 15

3 components of a vaccine

Answer 15

Antigen: stimulate immune response to target disease
Adjuvant: enhance and modulate immune response
Excipients: maintain pH/ stability, preservative

Question 16

Types of vaccine antigen

Answer 16

Live attenuated organisms
Killed whole organisms
Purified component vaccines
Toxoids
Polysaccharide conjugates

Question 17

Childhood immunisation programme UK

Answer 17

Pre-primary: DTaP-IPV booster, MMR booster
Live attenuated influenza
Girls 12-13: HPV
Secondary ed: dTaP-IPV booster, MenACYW

Question 18

What antigens are in the paediatric combined vaccine DTaP-Hib-IPV?

Answer 18

Tetanus toxoid 
Diphtheria toxoid
Pertussis components
Haemophilus influenza type b
Inactivated polio types. 1,2 and 3

Question 19

What is the adjuvant in DTaP-Hib-IPV?

Answer 19

Aluminium phosphate

Question 20

Examples of DTaP-Hib-IPV

Answer 20

Pediacel (Sanofi)

Infanrix (GSK)

Question 21

Polysaccharides as antigens

Answer 21

T cell independent
Large and linear
Not readily degraded
Highly repetitive

Question 22

Immune response to polysaccharides

Answer 22

Predominantly IgM
Poor memory effect
Low avidity antibody

Question 23

Conjugate vaccines

Answer 23

Polysaccharide chemically linked to immunogenic protein e.g. Tetanus toxoid

Question 24

Why are conjugate vaccines expensive?

Answer 24

Sophisticated technology is required to produce

Question 25

Why do conjugate vaccines have highly purified components?

Answer 25

purified saccharide and carrier proteins such as tetanus toxoid Makes them safe and simple for licensure and control

Question 26

When are conjugate vaccines very effective?

Answer 26

When humoral immunity is required Long-lived, boost-able immunity Reduce carriage i.e. offer herd immunity

Question 27

T cell dependent antigens

Answer 27

Naive T cells primed by interaction with APCs, requires antigenic stimulation via MHCII-TCR pathway T cells interact with B cells: Saccharide specific B cells take up conjugate and present the carrier peptides to T cells via MHCII Activated B cells differentiate into antibody secreting plasma cells and memory B cells

Question 28

Mode of action of T cell dependent antigens

Answer 28

Stimulates T cells so when vacinee encounters organism again, B cells that are stimulated get T cell help where they wouldn’t have got T cell help if the polysaccharide hadn’t been conjugated

Question 29

List 3 licensed conjugate vaccines

Answer 29

Hib Pneumococcal MenC

Question 30

What is the problem with MenC?

Answer 30

Need a booster later on (MenACYW)

Question 31

What is the problem with using 13 serotypes in a pneumococcal vaccine?

Answer 31

Potentially 100 infection causing serotypes | Concerns about serotype replacement: replacement disease being caused by serotypes not in vaccine

Question 32

Meningococcal Outer Membrane Vesicle Vaccines

Answer 32

OMVs from gram negative bacteria released by meningococci in vivo and culture Contain all protein antigens associated with OM Vaccine produced by detergent extraction to make them less reactogenic

Question 33

What is the Reverse vaccinology approach?

Answer 33

genome sequence data used to identify candidate antigens Produce recombinant antigens Test in mice to see if good immune response Develop into vaccine for clinical trials and use in people

Question 34

Describe Tuberculosis BCG vaccine

Answer 34

Attenuated strain of Mycobacterium bovis | Efficacy uncertain as instituted at time of social, economic and public health improvements

Question 35

Types of typhoid vaccine

Answer 35

Vivotif live attenuated vaccine | Vi polysaccharide- capsule from typhoid, not suitable in very young

Question 36

2 types of Cholera vaccine

Answer 36

Killed whole cell parenteral vaccine | Killed whole cell oral vaccine

Question 37

What are the 2 ways in which adjuvants potentiate the immune response?

Answer 37

Delivery systems | Immune potentiators

Question 38

How do adjuvants work as delivery systems?

Answer 38

Usually a depot of antigen which is slowly released. Way of getting antigen to where you want in the body e.g. mineral salts, surface active agents, liposomes

Question 39

How do adjuvants work as immune potentiators?

Answer 39

molecules that alter immune response to make it different/ better e.g. Toxins, lipids, Nucleic acids (CpG), Peptidoglycan

Question 40

How do adjuvants relate to PAMPs?

Answer 40

they stimulate an innate immune response

Question 41

Risk benefit analysis of vaccinating the immunocompromised

Answer 41

Need to protect vulnerable patient Public health perspective (herd immunity) Protect patient by immunising close contacts Live vaccines need particular consideration Decision on whether to vaccinate depends on the nature of immunodeficiency and the vaccine