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MIIM2002 - 2 > Streptococcus Pneumoniae Prevention And Vaccination > Flashcards

Streptococcus Pneumoniae Prevention And Vaccination Flashcards

0
Q

Immune complexes involved in killing of S pneumoniae

A

MAC1
FcgammaR
NADPH oxidase complex
Neutrophil extracellular traps

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1
Q

MAC1

A

C3b receptor on macrophages

Initiates phagocytosis

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2
Q

FcgammaR

A

On macrophages

For IgG-opsonised bacteria

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3
Q

NADPH oxidase complex

A

Generates reactive oxygen and nitrogen radicals

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4
Q

Neutrophil extra cellular traps

A

Nets extruded by neutrophils

DNA, cathelicidins

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5
Q

Location of asymptomatic S pneumoniae replication

A

Nasopharynx

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6
Q

Removal of C3b opsonised bacteria

A

Red blood cells express C3bR
Bind C3b opsonised bacteria
Splenic macrophages remove aged red blood cells, with bound antigen-C3b complexes

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7
Q

T cell independent antigen

A

Polysaccharide

Eg: bacterial capsule

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8
Q

Cells that detect polysaccharide capsule

A

CD5+ B1 B cells

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9
Q

Why is there little memory response to S pneumoniae?

A

Only B1 B cells detect capsular antigen (no T cell response)
B cell secretes IgM, limited isotype switching to IgG (no Th response)
No memory

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10
Q

Effective S pneumoniae vaccine design

A

Need conjugation, so that B cells make antibodies against polysaccharides, T cell receptors against protein epitopes

Results in isotype switching

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11
Q

Issues with conjugates vaccines

A

Expensive

Around 50 tests on vaccine required before ready

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13
Q

Serotype replacement

A

Non-vaccine serotype replaces serotype vaccinated against

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14
Q

Features of the ideal prophylactic S pneumoniae vaccine

A

IgG secretion in blood, meninges

IgA secretion on mucosal surfaces

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15
Q

Features of the ideal therapeutic S pneumoniae vaccine

A

Effective phagocytosis in spleen, tissues

Production of antibodies against capsular antigens

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16
Q

First pneumococcal vaccine

A

1911

Whole cell killed vaccine

17
Q

Second pneumococcal vaccine

A

1983
Pneumococcal polysaccharide vaccine
Polysaccharide from 23 most common serotypes
– Protects against >80% of pneumococcal disease worldwide

18
Q

Efficacy of polysaccharide pneumococcal vaccine

A

Limited
Short-lived protection, as no memory response stimulated
~80% reduction in disease among immunocompetent adults

19
Q

Reason for lack of memory response from polysaccharide vaccine

A

No Th cell induction for isotype switching

20
Q

How do Th cells help B cells in antibody production?
1)
2)

A

1) Costimulation - CD40, CD40L

2) Providing a cytokine environment to stimulate isotype switching

21
Q

Th cell activation

A 
APC presents antigen on MHC class II
CD80, CD86 (APC) interacts with CD28 (Th cell)
APC secretes cytokines
22
Q 
T cell dependent antigen response
1)
2)
3)
4)
5)
6)
A

1) Protein antigens
2) No repeating epitopes
3) Response in infants
4) Isotype switching
5) High affinity antibodies produced
6) Memory cells produced

23
Q 
T cell independent antigen response
1)
2)
3)
4)
5)
6)
A

1) Polysaccharide antigens
2) Repeating epitopes
3) No response in infants
4) No/limited isotype switching
5) Low affinity antibodies
6) No memory cells

24
Q

How to generate a T-cell response from a polysaccharide vaccine

A

Conjugate a protein epitope onto the relevant polysaccharide

25
Q

How do conjugated vaccines work?

A

Polysaccharide and connected protein are phagocytosed by B cell
B cell presents protein epitope on MHCII
T cells recognise protein epitope on MHCII, generate response

26
Q

A major viral cause of childhood meningitis

A

Haemophilus influenzae, type B

27
Q

Type of vaccine produced against Haemophilus influenzae type B

A

Conjugated

28
Q

Contents of Haemophilus influenzae type B conjugated vaccine
1)
2)

A

1) H. influenzae type B polysaccharide capsular antigen

2) Tetanus toxoid protein or diptheria toxoid protein

29
Q

Polysaccharide making up H. influenzae type B capsule

A

Polyribosylribitol phosphate (PRP)

30
Q

How many different serotypes make up H. influenzae vaccine?

A

Seven - heptavalent

31
Q

Efficacy of conjugated S. pneumoniae vaccine

A

94% efficacy against vaccine serotypes

32
Q

Emerging pathogenic serotype of S. pneumoniae among vaccinated children

A

Serotype 19A

33
Q

PCV

A

Polysaccharide conjugated vaccine

34
Q

Most current PCV for streptococci

A

13v PCV

Contains serotype 19A

MIIM2002 - 2 (12 decks)

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