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Module 204, Theme 1: Immunology > Vaccines > Flashcards

Vaccines Flashcards

1
Q

Immunisation

A

Artificial process by which an individual is rendered immune

  • Passive
  • Active
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2
Q

Passive immunisation

A

Type of immunisation that produces no active immune response in the host.
- They are antibodies extracted from a hyper-immune donor (human or animal)

Protection is temporary
- Due to no memory cells

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3
Q

Passive immunisation examples

A

Antibody deficiency
- Immunoglobulin replacement

VZV (Varicella zoster virus) prophylaxis
- Esp. exposure during pregnancy

Anti-toxin therapies
- Snake anti-serum

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4
Q

VZV prophylaxis during pregnancy

A

VZV can cause fatal complications so exposure is treated immediately with vaccine.

When to vaccine
- No history/ unsure history about chickenpox AND VZV IgG negative/ equivocal

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5
Q

Active immunisation

A

Immune acquired by a host through the generation of an adaptive immune response.

The vaccine stimulates an immune response without causing the fully clinical infection.

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6
Q

Herd immunity

A

Vaccinating a sufficient amount of people in a population (i.e around 90%), so that unimmunised individuals are at low risk.

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7
Q

Principals of vaccinations

A

Must be given to cohort before exposure to pathogen.

Herd immunity can minimise those that contract disease.

Most generate a long-lasting high IgG antibody response

Most effective vaccine are for disease where natural exposure results in protective immunity.

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8
Q

Problem diseases to vaccinate

A

Problem disease are usually where the immune system cannot eliminate the infection or create a long-lasting protective immunity.

Examples

  • Common cold
  • Mycobacterium TB
  • HIV
  • Malaria
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9
Q

Components of a vaccine

A

Antigen

  • Whole organism (live-attenuated or inactive)
  • Subunit

Adjuvants
- increases immunogenicity of vaccine

Excipients
- increases vaccine integrity

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10
Q

Live-attenuated vaccines examples

A

Measles

Mumps

Rubella

Polio

BCG

Cholera

Zoster

VZV

Live influenza

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11
Q

Live-attenuated vaccines

A

Vaccinate containing pathogen that are viable in vivo but unable to cause disease.
- Pathogens that have adapted to live ex vivo in the non-physiological conditions in culture are selected

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12
Q

Pros of live vaccines

A

Pros
- The pathogens are alive, so are able to replicate in hose, hence more immunogenic.

  • Can stimulate good CD8 responses with viral vaccines as viruses can cause intracellular infections.
  • Does not required repeated boosting
  • Can get secondary protection of unvaccinated individuals, infected with live-attenuated vaccine strain in some disease
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13
Q

Cons of live vaccines

A

Short shelf live due to very specific culturing conditions.

Pathogens can revert to wild type
- Cause full blown disease

Can cause full blown disease in immunocompromised individuals.

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14
Q

VZV

A

Varicella Zoster virus

  • Primarily causes chickenpox
  • Can permanently infect the sensory ganglia even though cellular and humeral immunity provides life-long protection (becomes zoster when reactivated)
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15
Q

VZV vaccine

A

Live-attenuated
- Induces anti-VZV antibodies

95% effective in preventing varicella

3-5% post-vaccination varicella infection

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16
Q

Reasons why VZV vaccine is not scheduled in the UK

A

Fairly benign childhood infection

Safety concerns that it would cause a disease shift to unvaccinated adults where VZV is less tolerated.

Could increase zoster and reduce immune boosting in adults

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17
Q

Zoster vaccination

A

Similar to VZV vaccine but with a higher dose
- Boosts memory T cell response to VZV

Results (in >60)

  • Reduces zoster incidence
  • Reduces severity and complications
18
Q

Poliomyelitis (polio)

A

Enterovirus- GIT, oropharynx
- Spreads to Peter’s patch–> lymphatics–> haematogenous spread

Neurological phase (1%)
- Motor neurones
- Brain stem
- Motor cortex
= flaccid paralysis due to denervation
19
Q

Salk injected polio vaccine (IPV)

A

Inactivated vaccine

Effective but is herd immunity inferior to Sabin

  • Does not cause vaccine-associated polio paralysis
20
Q

Sabin oral polio vaccine

A

Live-attenuated vaccine

  • Can be recovered from stool after immunisation
  • Very effective, and establishes secondary protection
  • Better suited from endemic areas affected

BUT
- Vaccine-associated paralytic polio (1:750,000)

21
Q

TB infection

A

Bacteria infects macrophages and is presented to CD4 T cells

  • release of IFN-g
  • activates granulomas
22
Q

TB Vaccination

A

BCG (Bacille Calmette Guerin)
- Non-TB bacterium Myocobacterium bovis (bovine)

Aims
- Increases Th-1 cell response to M bovis (increase in IFN-g)= protection against MTB

Administration
- Intradermal injection

Effectiveness

  • 80% effective in preventing disseminated TB/ TB meningitis in children.
  • Little/ no effect on pulmonary TB
23
Q

Inactivated vaccines

A

Vaccine with unviable pathogen
- Usually killed by certain methods, i.e formaldehyde.

Function

  • Stimulates B cells and APCs
  • Stimulates antigen specific CD4+ T cells

Less robust response that live-attenuated vaccines

24
Q

Examples of inactivated vaccines

A

Hep A

Influenza

25
Q

Pros of killed vaccines

A

No potential reversion

Safe for those immunocompromised

Stable in storage

26
Q

Cons of killed vaccines

A

Mainly CD4/ Ab responses
- Less stimulation of CD8 T cells, like live vaccines

Less durable response than live vaccines

Higher uptake to achieve herd immunity

27
Q

Influenza virus structure

A

External antigens: they are subtype and strain specific antigens of Influenza A virus

  • Hemagglutinin
  • Neuraminidase

Internal antigens: type-specific proteins, determines whether A, B or C virus.

  • Matrix
  • RNP
28
Q

Influenza vaccination

A

Mainly triggers antibody response that are directed against hemagglutinin and neuramidase (external antigens)

29
Q

Difficulties with Influenza vaccine

A

Targets antigen prone to mutation
- Seasonal variation, so new vaccine is produced annually.

Major changes occur when viral strains combine- e.g with animal strain= pandemic influenza

30
Q

Subunit vaccines

A

Live vaccine
- Uses only a critical part of the organism

Components obtained by:

  • Purifying from the organism
  • Generating via recombinant techniques

Mechanism
- Elicits CD4/ Ab response

31
Q

Toxoids

A

Subunit vaccine

Toxins are obtained usually from toxin-producing bacteria then detoxified.

This stimulates Ab response–> toxin is then neutralised by Ab.

32
Q

Tetanus vaccine

A

Toxoid vaccine

Stimulates high-affinity IgG Ab to neutralise tetanus toxin
- Immune complex then removed via spleen

33
Q

Polysaccharide capsules

A

Subunit vaccine

The polysaccharide coat of certain bacteria is administered to induce IgG antibodies

  • Improves opsonisation
  • Bacteria: S. pneumonia N. meningitides

Problem

  • No protein, no T cell response
  • Only stimulates T-independent B cells

Response can be boosted with vaccine conjugation
- Protein carrier is attached to polysaccharide antigen.

34
Q

Vaccine conjugation

A

Method of boosting immune response to polysaccharide antigens.

  1. Polys. antigen is conjugated with protein
    - This is taken in via B cells using IgM receptor.
  2. Class II MHC processes and presents peptides from conjugate to helper T cells
  3. Helper T cells stimulate affinity maturation
    - Ab produced is specific for polysaccharide and not protein conjugate.
35
Q

Recombinant protein subunit vaccine

- Include examples

A

Key immunogenic proteins are studied then stimulated to be produced in Lower organisms

The proteins are then purified to produce a vaccine

Examples

  • Hep B surface antigen
  • HPV vaccine
36
Q

HPV vaccine

A

Recombinant protein subunit vaccine
- Done as HPV is difficult to culture

The vaccine includes empty sub-unit HPV particles- prevents primary infection

Mainly covers strains that cause cervical carcinoma
- HPV 16, 18

Quadravalent vaccine covers other strains

37
Q

Pros of subunit vaccines

A

Very safe

Works well where the primary infection can be prevented by Ab
- + when the virus cannot easily be cultured (HPV, Hep B)

38
Q

Cons of subunit vaccines

A

Requires very detailed knowledge of virology for its development

Very specialised

Expensive production

Weaker immune response
- Often require boosting

39
Q

Adjuvants

A

Addition to vaccines to most immune response to antigen.

Includes: Alum, LPS

mechanism

  • Binds to PRR on APCs
  • Enhances co-stimulation and cytokine secretion= more robust T/ B cell response

Includes: novel adjuvants (TLR ligands)

40
Q

DNA vaccines

A

Novel vaccine

Mechanism

  • Plasmid DNA that codes vaccine antigen is administered and taken up by cells
  • The antigen is transcribed and translated–> host. response

Poorly immunogenic in humans atm

41
Q

Viral vector

A

Novel approach to vaccines

Benign virus is engineered to contain genes encoding immunogenic antigens
- and cultured

The engineered virus is then used as live-attenuated vaccine
- Only used to animals atm

Module 204, Theme 1: Immunology (22 decks)

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