3.3 Vaccines and vaccination Flashcards
(53 cards)
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
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)
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
4
Q
Short/ medium term
A
Antibody persists to neutralise pathogen
5
Q
(long term)
A
Memory lymphocytes quick to react
6
Q
What structural antigens are present for neutralizing antibody?
A
Surface expressed (surface spike proteins)
7
Q
Passive immunisation (antibodies);
A
- colostrum antibodies (natural)
- antiserum (artificial)
8
Q
Active immunisation (antigen)
A
-Toxoids
- Modified-live organisms
- Killed organisms
- Subunit antigens
- Recombinant DNA/RNA
9
Q
What do we vaccinate with?
A
- Passive immunisation (antibodies)
- Active immunisation (antigen)
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
11
Q
What age do vaccines begin in puppies?
A
6 weeks
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
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
14
Q
Which immunization is Immediate but short duration of protection
A
Passive immunization
15
Q
Active immunisation:
A
- Vaccinate animal
- Animal makes immune response
- Animal’s own immunity protects against infection
16
Q
Active immunisation (antigen): toxoid
A
Some bacteria (esp Clostridia spp) are pathogenic by virtue of the toxins they produce
17
Q
C. tetani =
A
Tetanus
18
Q
C. botulinum =
A
Botulism “Botox”
19
Q
C. difficile =
A
enterotoxaemia / flesh-eatin’ bug
20
Q
____ effectively prevent the harmful effects of the toxin in the body
A
Neutralizing antibodies
21
Q
Toxoid:
A
Looks similar to toxin but doesn’t have harmful properties
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
Killed (inactivated) vaccines: heat or radiation
Sterilizes organisms
26
Modified live (attenuated) vaccines:
- 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
Attenuation
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
Responsible for attachment ?
Spike protein
29
Subunit vaccines: FeLV
- Leukocell 2 (Zoetis): Purified gp70 envelope protein from virus-infected cells
-Leukogen (Virbac): Recombinant (cloned) p45 envelope protein produced in E. coli
30
Recombinant vaccines identify?
Encoding antigen:
Clone encoding sequence into
- plasmid DNA
- virus vector
31
Recombinant vaccines: When injected into animal, recombinant protein is made in
vivo and stimulates an immune response
32
Recombinant virus vaccine for FeLV
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
Recombinant virus vaccine for Covid-19:
• Coronavirusspikeproteingeneidentified
• Cloned into a simian adenovirus
34
How does the Covid-19 vaccine work?
35
Adjuvants:
- 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
Adjuvants quantitative effect:
Added to killed and subunit vaccines to enhance their immunogenicity and increase antibody response
37
Adjuvants qualitative effect:
Can alter the antibody isotype produced
- IgG / IgA / IgE
Can alter the TH1 : TH2 balance influencing cell- mediated vs antibody-mediated response
38
How do we deliver vaccines ?
- 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
Problem with killed / subunit vaccines?
Single antigen = short antibody response, need another dose for replication
40
MLV / recombinant virus vaccines =
High titre and long plateau phase
41
Vaccine protocols: When vaccinating animals >12 weeks of age
- Killed / subunit vaccines generally require two doses given 2-4 weeks apart.
– MLV / recombinant virus vaccines might only require a single dose.
42
Vaccine protocols: when vaccinating young animals
- 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
When are general boosters given?
one year after primary course
44
When are subsequent boosters given?
Every 1-3 years
– Many modern MLV have a 3 year “duration of immunity”
Ex: rabies DA2PPL
45
What happens if booster is missed?
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
How do we know that the vaccine has worked ?
- 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
Pet Travel Scheme (PETS):
- 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
Reasons for vaccine failure:
- 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
Reasons for vaccine failure (host factors)
-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
Reasons for vaccine failure (host factors): Age
– Not immunocompetent (<6w YOUNG)
– Interference from MDA (6-12w)
– Immunosenescence (“old age”)
51
Vaccine adverse effects: Feline injection site sarcoma
- 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
Therapeutic vaccines stimulate?
- immune response against tumour antigens: anti-cancer vaccines
- Human tyrosinase DNA vaccine available for treatment of canine malignant melanoma
53
Some canine vaccines are recommended to be given to puppies at 8 and 10 weeks of age… why?
allows early socialization (daycare, parks) ...but more vaccine failures
