Immunology - Vaccines & Vaccination Flashcards
In terms of vaccines, some take advantage of passive transfer of maternal antibodies, anti-serum or venom to give animals short-term, rapid protection.
Explain how a vaccine would exploit MDA & give an example.
Lactovac & Rotavec Corona:
Both contain inactivated
rotavirus, coronavirus & E. Coli
K99 antigen - adjuvanted
In principle, they exploit MDA & passive transfer of immunity; the MOTHER is injected with the antigen but the offspring receive her antibodies through colostrum against these specific viruses and bacteria
Short-term, because MDA really only lasts 8-12 weeks.
In terms of vaccines, some take advantage of passive transfer of maternal antibodies, anti-serum or venom to give animals short-term, rapid protection.
Explain how anti-serum works and give examples.
Anti-serum is the same as Antitoxins (ie., antibodies against toxins produced by bacteria).
The antibodies against bacterial toxins are purified from blood of animal hyper-immunised with the toxoid (inactivated toxin).
Eg. Tetanus Antitoxin
- pure tetanus antibody derived from horses to be used to immunise horses, sheep & dogs against C. tetani infection
- not adjuvanted
- gives immediate protection because it’s an antibody that is tetanus-toxin-specific
In terms of vaccines, some take advantage of passive transfer of maternal antibodies, anti-serum or venom to give animals short-term, rapid protection.
Explain how anti-venom works.
Venom from snake, spider or insect is milked, diluted & injected into horse, sheep or goat, which will produce antibodies against the venom. The antibodies (aka antivenom) is purified from the blood of these animals
As opposed to passive immunisation with antibody, anti-serum or anti-venum, ACTIVE IMMUNISATION involves injecting an animal with attenuated or killed antigen or parts of antigen, or genes of an antigen to stimulate antibody/immune response.
Typically the response takes longer than in passive immunisation with antibody, so there is delayed onset but longer protection. Also, adjuvant is required when the virus is killed or attentuated.
What are six different types of vaccines used in active immunisation?
- Toxoid
- Killed
- Live attenuated (aka Modified Live)
- Subunit
- Recombinant
- DNA
What is Toxoid? Give an example.
Vaccine used in active immunisation.
Pathogenic exotoxins produced by bacteria such as Clostridia spp are inactivated via “chemical modification”, retaining antigenic structure to stimulate neutralising antibodies when injected
Eg. Tetanus Toxoid Concentrated
- used for protection in horse
- not same as Tetanus antitoxin
above, which is used in emergency situations
What is Killed Vaccine?
It’s a vaccine used in active immunisation.
Pathogen has been inactivated chemically (formaldehyde, alkylating agents) or with radiation (sterilisation) so it’s dead & can’t replicate.
- Adjuvanted
- Usually requires at least 2 doses
3-4 weeks apart
Eg. Nobivac FeLV
- inactivated virus obtained by genetic recombination of E.Coli strain
- adjuvanted
What is Attentuated aka Moderated Live Vaccine? How is the virus “moderated”?
Give an example.
MLV is used in active immunisation.
Virus still alive & can replicate, but grows so slowly it that immune system fights it beforehand.
- *Attenuation achieved by:**
- growing virus in lab under unusual conditions (higher or lower temperature or in usual cell line)
- genetic modification: Disrupt virulence genes (cut them out), keep antigenic genes, to make a low-virulence mutant (so far not on the market)
- Low-virulence mutant organisms
- Usually not adjuvanted
Examples:
- *Nobivac Tricat Trio**
- contains live attenuated Feline Calicivirus (FCV), Herpesvirus Type 1 & Feline Panleukopenia virus (FPV)
- not adjuvanted
- *Feline Panleukopenia Virus Vaccine**
- Virus was grown in Snow Leopard kidney cells, adapted to grow here over time until eventually strain of virus evolved that stimulated an immune response in domestic cats without causing disease.
- *Parainfluenza Type 3 Virus Vaccine**
- virus mutant was grown in cell culture at lower temp than its usual environment; now doesn’t cause pneumonia in cattle.
What is subunit vaccine? Give an example.
It’s another vaccine used in active immunisation.
Specific antigen(s) selected from pathogen. Produced either as:
- Purified protein isolated from virus
cultures; or
- Recombinant protein expressed in
bacteria or other vector.
- Synthetic peptide (just makes epitopes)
- Usually adjuvanted
Examples:
- *Leukocell 2**
- purified gp70 envelope protein (subunit) from virus-infected cells usoing purification approach
- *Leukogen**
- recombinant gp45 envelope protein produced in E. Coli using molecular approach
* Both vaccinate against FeLV
What is Recombinant Vaccine? Give an example.
Recombinants are used in active immunisation.
Most advanced. Gene(s) encoding antigen are cloned into viral or bacterial vector. When injected, replication of the recombinant virus generates immune response against recombinant antigen made in vivo.
Example:
Eurifel FeLV
- canarypox (bacterial) vector encoded with FeLV
gp70 protein antigen. As canarypox virus tries to replicate – it can infect mammalian cells but can’t complete its life cycle – it produces FeLV viral proteins necessary to stimulate immune response
What is DNA vaccine? Give an example.
DNA vaccines are made up of a small, circular piece of bacterial DNA (called a plasmid) that has been genetically engineered to produce one or two specific proteins (antigens) from a pathogen. The vaccine DNA is injected into the cells of the body, where the host cells transcribe the DNA to synthesize the pathogen’s proteins. Because these proteins are recognised as foreign, when they are processed by the host cells and displayed on their surface, the immune system is alerted, which then triggers a range of immune responses.
- Less vulnerable to changes in temperature.
Example:
- *West Nile-Innovator DNA**
- against West Nile Virus, for horses (first licensed DNA vaccine )
How are vaccines enhanced by adjuvants?
Usually killed/inactivated & sub-unit (chopped up) vaccines use adjuvants to help enhance their efficacy by acting as a depot of antigen & slowing down the vaccine through the target.
This allows for prolonged exposure of the antigen to the immune system, so many more antibodies will be produced by B-cells (quantitative effect).
Adjuvants can also and help induce class-switching of antibody isotypes from IgG to IgA, for example.
They can also non-selectively trigger the innate immune system via pattern-recognition receptors to influence the adaptive immune system to respond against the antigen component of the vaccine. For example, T-helper cells could be influenced to shift from T-helper Type 2 response (B-cells → antibodies) to T-helper Type 1 (macrophages, phagocytosis, respiratory burst). (qualitative effect)
Explain how different routes of administration of vaccines can influence immune responses.
SQ, IM, Intradermal:
Stimulates good antibody responses, especially IgG (systemic)
Intranasal, oral:
Stimulates good IgA production (mucosal, local)
Give some possible reasons for the failure of vaccines to protect against infection diseases.
Vaccine-related:
1/ Vaccine is expired or not refrigerated/kept at correct temperature
2/ Wrong vaccine / wrong strain of antigen in vaccine
3/ Improperly administered
Animal-related:
1/ Animal genetically predispositioned to resist vaccine
2/ Too young or too old to mount effective immune response
3/ MDA interference
4/ Prior exposure to pathogen
5/ Animal is immunosuppressed already or immunocompromised from illness or concurrent treatment (chemo)
