Lecture 22+23: Immunizations Flashcards
Immunization
The process of producing a state of resistance or protection from a pathogenic organism or toxic substance
Passive immunization
Transfer of preformed antibodies to recipient to provide immediate immunological protection
Does passive immunization activate immune system or generate memory response
NO!
What are the two categories or passive immunization
Natural and artificial
What is natural passive immunization
Goal is to protect fetus until its owner immune system is mature
Transfer of maternal antibodies to offspring across the placenta and/or colostrum/milk
What is artificial passive immunization
Goal is to protect an individual from a challenge before their immune system can be activated
Injection with preformed antibodies (ex: antitoxins/antivenins, pooled immune globulin
What is the half life for IgG
21 days
Describe how the transfer of maternal antibodies in utero occurs
IgG crosses the placenta, placental cells internalize serum containing maternal IgG. Neonatal Fc receptors (FcRN) are expressed in internal vesicles and when acidified they can bind material IgG. Transcytosis of maternal IgG and release into fetal circulation
What antibodies are transferred in milk/colostrum
Secretory IgA (and/or IgM) and IgG transferred into milk to newborn (not significant source of IgG)
What antibodies are transferred into the gut
Secretory IgA remains in gut- absence of maternal sIgA alters composition of microbiota
Describe how the transfer and intestinal absorption of maternal antibodies in colostrum and/or milk occurs
Maternal IgG can be absorbed from the GI tracts, neonatal Fc receptors (FcRN) are expressed on surface of enterocytes within the duodenum. Transcytosis of maternal IgG and release into neonatal circulation
Clinical application: Failure of Passive Transfer
Horse and ruminant newborns don’t have any maternal antibody protections so are immunologically naive at birth
Neonates are agammaglobulineimic and are dependent on antibodies absorbed into bloodstream from colostrum
If neonates don’t get adequate colostrum they are are higher risk of infections
How does artificial passive immunization occur
Injection of preformed antibodies from one animal species into another for immediate protection
Serum is collected from animal that has been hyperimmunized with desired antigen
Ig’s are harvest, purified and sometimes cleave Fc region to reduce antigenicity
Injected into patient to provide immediate protection
What are some potential risks to consider for artificial passive immunization
Hypersensitivity reactions as horse antibodies are seen as non-self to dog
May prevent patient from mounting an active immune response to antigens
Clinical application: antitoxins: tetanus (ex of Artificial passive immunization)
Used to prevent and treat tetanus in domestic animals
Tetanus is a potent neurotoxin that inhibits muscle relaxation, antitoxin neutralizes toxin and confers immediate passive immunity for 1-2 weeks
Clinical application: Antivenin (ex: of artificial passive immunization)
Used for treatment of snakebites in domestic animals
What is active immunization
Acquisition or administration of infectious organism, portion of an organism of toxin
Does active immunization produce immunological memoryq
Yes! Immune system in immunized patient is actively developing immune response
What are two categories or active immunization
Natural and artificial
What is active natural immunization
Infection with pathogenic substance
What is artificial active immunization
Vaccination with either preventative or therapeutic vaccines
What type of immunization induces production of antibodies ad development of effector T cells due to exposure of pathogen or vaccination
Active immunization
Repeat exposure ___ antibody titers
Increases
What do vaccination and boosters induce
Class switching, increased antibody titer and increased avidity
Live (infectious) vaccine characteristics
Replicate in host, single dose, less stable, short shelf life, can potentially cause disease, better immunity, no adjuvant required, may revert to virulence, IgG, IgA and cell mediated immune response
Non-living (non-infectious) vaccine characteristics
Can’t cause disease, stable, less robust immunity, often require multiple diseases, requires safe method of inactivation, mainly IgG and little to no cell-mediated immune response
Live virulent vaccines
Relatively rare, high risk of causing disease with live pathogen
What is an example of live virulent vaccine
Orf- used against pustural dermatitis or scabby mouth
Common viral infection of sheep and goats
Can be transmitted to humans
Live attenuated or modified live vaccine
Contain intact, viable organisms but their virulence has been reduced, induce low level infections and replicate but do not induce significant disease or tissue damage in immunocompetent patients
What is one method of attentuation
Repeated culture of pathogen in non-host strain, virus will mutate to be able to grow in non-host cell and then virus no longer grows well in original host cells, used for vaccines
What is the most common type of vaccine in veterinary medicine
Live attenuated and modified live
What are two examples of live attenuated and modified live vaccines
- Bovine coronavirus vaccine- protects calves against enteric disease
- DA2PP, protects dogs against distemper, adenovirus type 2, parainfluenza virus, and parvovirus
What is an example of a vaccine that provides cross-protection
DA2PP provides protection against CAV-2 but also CAV-1 which is infectious canine hepatitis/blue eye
Which vaccine type may have deletions or modifications of key virulence factors
Live attenuated or modified live
What is aujesky’s disease
Suid herpesvirus infection; neurological and respiratory signs, fetal abortion
What important components does aujesky’s disease (pseudorabies) vaccine contain
Vaccine strain has a genetic deletion of thymidine kinase (TK) or glycoprotein E (gE)- both genes are important in viral invasion and replication
What are DIVA vaccines
Attenuation that makes a vaccine strain antigenically different from natural occurring pathogen allows for differentiation between infected vs vaccinated animal s
Aka: marker vaccine
What is an example of DIVA/marker vaccines
Infectious bovine rhinotrachetitis (IBR)- gene deletion of surface glycoprotein E (GpE or gE) in vaccine strain
What would indicate that a cow was naturally infected with IBR
Serological detection of anti-GpE antibodies
What are inactivated and killed vaccines
Intact, killed organism, pathogens are dead so they are unable to replicate in host, no risk of causing disease
Organism should have minimal changes to antigen structure
No risk of reversion back to virulent strain
What are two methods of inactivation of organisms
Chemical and low energetic electron radiation
What is chemical inactivation
Mix live virus with B-PL or formalin—> virus structure is intact but chemically intact
What happens to a virus exposed to low energetic electron irradiation
Intact antigens but destroyed nuclei acids
What are some examples of killed/inactivated vaccines
IBR, rabies, equine west Nile
Killed vaccines are often less _____ and only stimulate an antibody response
Immunogenic
What do killed/inactivated vaccines often require to maximize effectiveness of immune response to vaccine components
Adjuvant
What is an adjuvant
Substances that promote persistence in the tissues and/or enhance the immunogenicity of an antigen, added to vaccines to augment the immune response
How do adjuvants augment the immune response
Increase persistence of antigen, PRR activation, enhanced antigen uptake, increased antigen presentation to T cells, recruitment of immune cells
How does a depot adjuvant work
Slow removal of antigen—> prolonged immune response
How do particulate adjuvants work
Enhanced antigen presentation—> enhanced cytokine production by APCs—> enhanced Th cell response—-> enhanced cell-mediated immunity
How do immunostimulatory adjuvants work
Stimulate TLR’s—> enhance s=cytokine production by APCs—> enhance Th cell responses—> enhanced antibody production
What are toxoid vaccines
Modified toxins so that toxoid retains antigenicity but toxic moiety has been altered so no longer toxic
Ex: tetanus toxin
What are subunit vaccines
Contain parts/portions of an organism
What is an example of a subunit vaccine
Streptococcus equi (strangles) vaccine- concentrated purified M protein from bacterium, also contains adjuvant aluminum hyroxide
What are the three main types of recombinant vaccines
Make DNA vaccines, recombinant subunit vaccines and vectored vaccines
How do recombinant vaccines work
Identify gene of interest, clone gene and insert gene into construct
What is the goal of recombinant vaccines
Induce both humoral and cell-mediated immunity to antigens
Naked (Plasmid) DNA vaccines
Contain genetically engineered DNA, insertion of immunogenic gene into a plasmid expression vector, transform into bacteria and replicate, APC’s take up DNA and then synthesize pathogenic protein to activate both B and T cells
What are some examples of naked plasmid DNA vaccine
Melanoma for dogs (oncept)
West Nile for horses (d/c)
What are recombinant subunit vaccines
Recombinant plasmid DNA is engineered and inserted into a host organism for culture (typically bacterial host
Host cells synthesize recombinant proteins of interest
What are some examples of recombinant subunit vaccines
Recombinant Lyme disease vaccine- OspA protein
Chimeric recombinant Lyme disease vaccine- OspA and chimeric OspC protein
What are vectored vaccines
Consist of a live, non-pathogenic or attenuated organism (vector) genetically engineered to contain a gene from a pathogen
Infects cell but can’t cause disease
Infected cells synthesize the pathogens antigens to trigger immune response
What is an example of vectored vaccines
recombinant FeLV vaccine- canarypox vector encoding FeLV p27 antigen
What are the 10 commandments of vaccination
- Not every animal requires a vaccine
- There are core and non-core vaccines
- Vaccines should be administered to as many animals as possible within a herd or population
- Young animals require special considerations since maternally derived antibodies can interfere
- Animals should be vaccinated as infrequently as is possible or required- know duration of immunity
- Vaccines should not be administered to pregnant animals unless specifically recommended
- Generally, vaccines should not be administered to sick or immunosuppressed animals
- Veterinarians in consultation with clients should decide which vaccines are appropriate
- Always read and understand vaccine data sheet
- Detailed records should be kept of vaccines administered
What are the most likely adverse events associated with vaccines
Errors, normal toxicity, hypersensitivity, neurological reactions and foreign body reactions
