Vaccination Strategies Flashcards
2 types of vaccines
- killed (inactivated): diptheria-tetanus-pertussis
- live (attenuated): yellow fever
Vaccine
A preparation of living or inactivated pathogens used as an antigen
Vaccination
Administration of a living or inactivated pathogen to induce an immune response
Protective immunity
Vaccine induced effectors (antibodies) prevent re-infection
- long-lived plasma cells in the bone marrow to maintain antibody levels in the bloodstream to neutralize the pathogen at the site of pathogen invasion
Immunological memory
Vaccine-induced memory lymphocytes will not prevent re-infection, but can prevent disease or reduce severity of disease
- vaccine-induced memory lymphocytes circulate thru secondary lymphoid tissues
What determines longevity of plasma cells?
- differs with vaccines/antigens
- with apoptosis, antibody levels drop below level of protection, require boosters or a second infection will be established
Memory lymphocytes are exported from ____
Germinal center
- rapidly reactivated to proliferate to provide protection and high levels in the bloodstream
- requires a sufficient incubation period
Example of inactivated vaccine
- diptheria: inactivated toxin from corynebacterium diptheriae
- tetanus: inactivated toxin from clostridium tetani
- pertussis: surface protein antigen and the toxin from bordetella pertussis
Characteristics of killed vaccines
- killed vaccines generally result in an antibody response
- very poor inducer of cytotoxic T cells
How many doses of a primary, killed vaccine are required?
Multiple doses
- germinal centers are short-lived with killed vaccines (antigen is non-replicating so only a few lymph nodes are engaged)
Adjuvant
Substances that enhance the immunogenicity of antigens
- aluminum hydroxide is common adjuvant in human vaccines
- maintains a deposit of antigen at the site of injection
- slow release of aluminum particles with antigen = uptake by macrophages and immature DCs
Correlates of protection
Vaccine-induced immune responses that protect against disease
- antibodies must be present at the time of exposure to the pathogen
Vaccine boosters DTP
Required every 10 years
- duration of effectors (antibody): D = 19 yrs, T = 11 yrs, P = 10 yrs
Killed vaccines are handled as ____
Extracellular pathogen
- do NOT induce cytotoxic T cells
Germinal centers of live vaccines
Germinal centers persist with replicating live vaccines
- adjuvant not required
Live vaccine correlate of protection
Antibodies must be present at the time of exposure to the pathogen
YF-17D
Induces DC maturation and cross-presentation
Characteristics of live vaccines
Live vaccines can mimic a natural infection resulting in polyvalent immunity
- neutralizing antibody
- CD4+ helper T cell
- CD8+ cytotoxic T cells
Why do some vaccines need a booster?
For diseases in which antibody levels strongly correlate with protection
- decision for a booster is based on the persistence of antibodies and the incubation period of the disease (pace of pathogenesis)
Persistence of antibodies
- long lived plasma cells can have a finite lifespan (are not maintained after some vaccinations and require boosters)
- memory B cells are maintained for decades after most vaccinations and natural infections
Seronegative
Absence of specific antibody
Are seronegative individuals protected from Corynebacterium diptheriae toxin?
If they have missed their boosters, then they become seronegative
- strictly dependent on memory cells since receptors are lost
- memory response requires 3-5 days to kick in
- diptheria pace of pathogenesis occurs in 2-5 days
= seronegative individuals are NOT protected (memory response is longer than the incubation period)
Are seronegative individuals protected from hepatitis B virus?
In viral diseases, the pace of pathogenesis is generally slow
- boosters are not recommended
- if you become seronegative, then you will be protected due to long 45 day incubation period
