Vaccines Flashcards
4 features of ideal vaccines
- Induce immunity in most individuals
- Give long-lived immunity
- Not be toxic or induce illness
- Shouldn’t require boosters
Vaccination definition
Deliberately giving an antigen so as to elicit an immune response
Immunization definition
Providing the body with specific defenses against an antigen
Passive immunization features
Transferring antibodies from one individual to another for protection
Immediate and doesn’t elicit memory response
Active immunization features
Vaccination: administer antigen to elicit an adaptive immune response
Formation of memory cells: prolonged protection
Live vaccines
Contain attenuated organism (limited virulence)
Cause infection, but not disease
Induces TH1 and TH2 responses
How attenuation is achieved
Growing organism in vitro until it loses virulence
Mutate virulence gene
Delete virulence gene
Disadvantages to live vaccines
Cannot be used with immunocompromised individuals
Not very stable
Can revert to virulence
Killed/inactivated vaccines
Killing virus/bacteria, but preserving antigenic integrity
Disadvantages to killed/inactivated vaccines
Mostly induce antibodies only
Require large amounts of antigen (organism doesn’t multiply)
Protection is shorter term- boosters are needed
Advantages of killed/inactivated vaccines
More stable storage
Unlikely to cause disease in immunosuppressed individuals
Subunit vaccines
Contain defined proteins from an infectious agent rather than the whole organism
Disadvantage of subunit vaccines
Only stimulates immunity against a single protein- may not impart full protection
Must choose carefully which antigen to target
Toxoid vaccines
Type of subunit vaccine
Used with pathogens in which a secreted toxin is the cause of disease (ex- tetanus)
Toxin is inactivated
Recombinant vector vaccine
Type of subunit vaccine
Inserting gene for pathogenic antigen into harmless vector (live organism that doesn’t cause disease)
Vector produces protein
Conjugate vaccine
Type of subunit vaccine
Covalently linking “poor” antigen to carrier that is immunogenic
DNA vaccine
Type of subunit vaccine
Plasmid carries genetic information of antigen
Injection into muscle cells results in temporary production of encoded protein
Disadvantage of DNA vaccine
Potential for DNA incorporation into cellular genome
Are DNA and recombinant vector vaccines currently in use?
No- still in clinical testing stage
Relationship between vaccine safety and efficacy
Safety is inversely proportional to efficacy
Subunit vaccines are more effective than live-attenuated vaccines, but live-attenuated vaccines are safer than subunit vaccines
Adjuvants
Substances that enhance immunogenicity of antigen
3 ways in which adjuvants work
Convert soluble proteins into particulate material
Stimulate cytokine production by APCs
Slowly release antigen to maintain antigen half life
Benefits of adjuvants
Improved immediate responses to antigen Fewer boosters needed Overcome immunosuppression Target antigens to APCs Activate APCs Improved response to targets with low antigenicity
ISCOM vaccines
Type of adjuvant
Immunostimulating complex: delivers antigen to cytoplasm by forming micelle that fuses with cell
Reasons why vaccines can fail
Interference with maternal antibodies Senescence Improper application of vaccine Physiologic state of recipient Host genetics Antigenic variation in pathogen strain Extremely virulent pathogen strain encountered Insufficient time to mount immune response Poor technique
Advantage of injection
Ease of anatomic site access
Disadvantages of injection
Cost of needles
Capture of animal
Artificial route of entry for most pathogens
Primarily induce IgG responses
2 ways that allergy shots work
- Exposes allergen to immune system in a way that favors IgG production over IgE
- Inducing T regulatory cells that inhibit allergen-specific B and T cells
