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Immunology > 3.3 Vaccines and vaccination > Flashcards

3.3 Vaccines and vaccination Flashcards

1
Q

Why do we vaccinate ?

A

To prevent infectious disease in the individual / herd where this has health and welfare implications
– Not a substitute for good biosecurity and husbandry practices

To improve economic benefits in production animals
– Reduce the impact of endemic infections in intensive livestock systems

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2
Q

POPULATION MEDICINE AND VETERINARY PUBLIC HEALTH reason?

A
  • To prevent the spread of a pathogen in a population
  • To eradicate infectious disease rom a population
    Ex: Emerging diseases (Rabies, BTV8, FMDV)
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3
Q

Principles of vaccination:

A
  • Expose the host to foreign antigens without causing disease
    – Educate the immune system what pathogens look like, without causing an infection or side effects
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4
Q

Short/ medium term

A

Antibody persists to neutralise pathogen

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5
Q

(long term)

A

Memory lymphocytes quick to react

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6
Q

What structural antigens are present for neutralizing antibody?

A

Surface expressed (surface spike proteins)

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7
Q

Passive immunisation (antibodies);

A
  • colostrum antibodies (natural)
  • antiserum (artificial)
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8
Q

Active immunisation (antigen)

A

-Toxoids
- Modified-live organisms
- Killed organisms
- Subunit antigens
- Recombinant DNA/RNA

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9
Q

What do we vaccinate with?

A
  • Passive immunisation (antibodies)
  • Active immunisation (antigen)
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10
Q

Passive immunisation: Colostrum antibodies

A
  • vaccinate mother
  • mother makes antibodies that are transferred via colostrum
  • Maternally-derived antibodies (MDA) transferred to offspring in colostrum
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11
Q

What age do vaccines begin in puppies?

A

6 weeks

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12
Q

LactovacTM / RotavecTM vaccines:

A
  • Contain rotavirus, coronavirus and E. coli (K99) antigen
  • Vaccinate cow 3-12 weeks before calving
  • Calves fed on colostrum / milk will be protected from enteric infection
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13
Q

Passive immunisation Antiserum

A
  • Tetanus antitoxin (= antibodies) derived from horses immunised against tetanus
  • Inject antibodies (antiserum) into horse at risk of developing tetanus. Should give immediate protection
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14
Q

Which immunization is Immediate but short duration of protection

A

Passive immunization

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15
Q

Active immunisation:

A
  • Vaccinate animal
  • Animal makes immune response
  • Animal’s own immunity protects against infection
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16
Q

Active immunisation (antigen): toxoid

A

Some bacteria (esp Clostridia spp) are pathogenic by virtue of the toxins they produce

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17
Q

C. tetani =

A

Tetanus

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18
Q

C. botulinum =

A

Botulism “Botox”

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19
Q

C. difficile =

A

enterotoxaemia / flesh-eatin’ bug

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20
Q

____ effectively prevent the harmful effects of the toxin in the body

A

Neutralizing antibodies

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21
Q

Toxoid:

A

Looks similar to toxin but doesn’t have harmful properties

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22
Q

Tetanus toxoid vaccine:

A
  • Administer tetanus toxoid to horse
  • Horse makes antibodies (IgG)
  • Antibodies neutralize toxin if animal subsequently injuries and the wound gets contaminated with C. tetani
23
Q

Killed (inactivated) vaccines:

A
  • Virulent organisms cannot be used as vaccines as they would cause disease.
  • The organism can be killed so that it no longer replicates, but still contains the antigens required to stimulate an immune response.
24
Q

Killed (inactivated) vaccines: chemicals

A
  • Formaldehyde - crosslinks proteins
  • Alkylating agents - crosslinks nucleic acids
25
Q

Killed (inactivated) vaccines: heat or radiation

A

Sterilizes organisms

26
Q

Modified live (attenuated) vaccines:

A
  • Virulent organisms cannot be used as vaccines as they would cause disease
  • Their virulence can be reduced (attenuated) so that the organism is still alive but grows so slowly that it does not cause disease.
  • low virulence mutant organisms identified to produce a ‘vaccine strain’
27
Q

Attenuation

A

Grow virus in lab under unusual conditions to drive natural selection of low virulence mutants:
- Temperature sensitive mutants adapted to 35oC rather than 37oC
- Grow in unusual cell line so that adapted strain is less able to replicate in target host species.

Genetic modification
- targeted disruption of virulence genes

28
Q

Responsible for attachment ?

A

Spike protein

29
Q

Subunit vaccines: FeLV

A
  • Leukocell 2 (Zoetis): Purified gp70 envelope protein from virus-infected cells
    -Leukogen (Virbac): Recombinant (cloned) p45 envelope protein produced in E. coli
30
Q

Recombinant vaccines identify?

A

Encoding antigen:
Clone encoding sequence into
- plasmid DNA
- virus vector

31
Q

Recombinant vaccines: When injected into animal, recombinant protein is made in

A

vivo and stimulates an immune response

32
Q

Recombinant virus vaccine for FeLV

A

PureVax FeLV (Merial):recombinant canarypox vaccine expressing FeLV gp70
• Canarypox can infect mammalian cells but cannot complete its life-cycle.
• Protein antigen is produced by viruses attempt to replicate.
• Protein antigen stimulates immune response.

33
Q

Recombinant virus vaccine for Covid-19:

A

• Coronavirusspikeproteingeneidentified
• Cloned into a simian adenovirus

34
Q

How does the Covid-19 vaccine work?

A
35
Q

Adjuvants:

A
  • Oily substances – act as a depot of antigen to allow longer exposure of the immune system
  • Act like PAMPs to trigger innate immunity (viaPRRs) that influences adaptive immune responses
36
Q

Adjuvants quantitative effect:

A

Added to killed and subunit vaccines to enhance their immunogenicity and increase antibody response

37
Q

Adjuvants qualitative effect:

A

Can alter the antibody isotype produced
- IgG / IgA / IgE

Can alter the TH1 : TH2 balance influencing cell- mediated vs antibody-mediated response

38
Q

How do we deliver vaccines ?

A
  • Usually by subcutaneous (or intramuscular) injection for systemic protection (IgG usually)
  • Intranasal administration for good mucosal immune responses (i.e. IgA rather than IgG)
    e.g. Kennel cough vaccines
39
Q

Problem with killed / subunit vaccines?

A

Single antigen = short antibody response, need another dose for replication

40
Q

MLV / recombinant virus vaccines =

A

High titre and long plateau phase

41
Q

Vaccine protocols: When vaccinating animals >12 weeks of age

A
  • Killed / subunit vaccines generally require two doses given 2-4 weeks apart.
    – MLV / recombinant virus vaccines might only require a single dose.
42
Q

Vaccine protocols: when vaccinating young animals

A
  • Immune system is immature up to 6 weeks of age
    – Maternally-derived antibody (MDA) may interfere with vaccination up to 12 weeks of age
    – Generally administer a primary course of two doses given at 8 weeks and 12 weeks of age
43
Q

When are general boosters given?

A

one year after primary course

44
Q

When are subsequent boosters given?

A

Every 1-3 years
– Many modern MLV have a 3 year “duration of immunity”
Ex: rabies DA2PPL

45
Q

What happens if booster is missed?

A

No immunological reason to ‘start the primary course again’ if a booster is missed
– Memory lymphocytes are still there
– But this might be a regulatory requirement
(e.g. FEI regulations on equine influenza vaccination)

46
Q

How do we know that the vaccine has worked ?

A
  • The owner gets a signed vaccination certificate
    • Should perform serology post-vaccination but this is not commonly done in general practice
    • Some evidence that certain breeds (e.g. Rottweiler and Dobermann) have a higher prevalence of vaccine failures
47
Q

Pet Travel Scheme (PETS):

A
  • Rabies serology is recommended as part of PETS (NB change in EU regulations from Jan 2012)
  • Blood test 3-6 weeks post-vaccination
  • Must reach >0.5 IU/ml on FAVN test in order to be considered ‘test positive’
48
Q

Reasons for vaccine failure:

A
  • The vaccine does not contain appropriate antigens for the strain/serotype of pathogen to which the host is exposed (e.g. Influenza, Leptospirosis)
  • the vaccine has not been stored properly
  • has not been administered properly
49
Q

Reasons for vaccine failure (host factors)

A

-Age
- prior exposure to pathogen (persistent infection ( herpes / retrovirus)
- animal is immunocompromised in some way (chronic disease, concurrent infection, chemotherapy)
- genetically programmed to generate an inappropriate response

50
Q

Reasons for vaccine failure (host factors): Age

A

– Not immunocompetent (<6w YOUNG)
– Interference from MDA (6-12w)
– Immunosenescence (“old age”)

51
Q

Vaccine adverse effects: Feline injection site sarcoma

A
  • Cats vaccinated against FeLV/rabies
  • Annual exposure of the tissues to a mutagenic adjuvant
    – Use a non-adjuvanted vaccine (PureVax FeLV, Merial)
    – Rotate sites of administration
52
Q

Therapeutic vaccines stimulate?

A
  • immune response against tumour antigens: anti-cancer vaccines
  • Human tyrosinase DNA vaccine available for treatment of canine malignant melanoma
53
Q

Some canine vaccines are recommended to be given to puppies at 8 and 10 weeks of age… why?

A

allows early socialization (daycare, parks) …but more vaccine failures

Immunology (10 decks)

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