Vaccines Flashcards
What does it mean when we say a vaccine neutralizes a virus ?
Ab binding to proteins on viral surfaces that would otherwise bind to proteins on host cells makes the virus unable to infect the host cell. It also attracts NK cells for ADCC and activate complement leading to opsonization and recruitment of phagocytes.
What is the concept of A/B toxins ?
Antibody binding to the B subunit of an A/B toxin leads to neutralization of that toxin because it can no longer be internalized by the cell.
Diphteria & Tetanus use this method to infect host cells.
Binding of the B subunit to the outside of the cell allows entry of virus.
What are live-attenuated vaccins ?
A microbe that causes disease is cultured in an environment that selects against pathogenicity. The evolved microbe derived from the disease causing strain has almost all the same epitopes as the pathogenic strain, but isn’t able to cause disease.
Artificial selection ; genetically engineered.
Required the pt to be able to mount a T cell response and/or secrete IgA.
Advantages of live attenuated vaccines ?
Immune response similar to natural infection
Low dose, often only one dose required
Cellular & humoral response
Most effective because :
They replicate (sustained exposure to An)
If they replicate intracellularly, they are presented on MHC I and and you get cellular immunity in addition to humoral immunity.
They replicate at the site of infection, thus producing the right type of response in the right place.
Disadvantages of live-attenuated vaccines :
Severe rx are possible
Dangerous for immuncompromised or pregnant pts
Reversion of virulence is possible
Fragile - must be stroed carefully
What are whole-killed vaccines ?
A microbe that causes disease is killed via heating or chemical trx.
For microbes that cannot be attenuated or with oncogenic potential.
Disadvantages of whole killed/inactivated vaccines ?
E.g. Rabies vaccine
Not as effective as live vaccines
Lack of life-long immunity
generally 3-5 doses required
Immune response moslty humoral
can cause anaphylaxis (frequent exposure with boosters)
Good IgG response, but poor mucosal immunity
What is accelular sub-unit vaccine ?
Particular proteins know to be important for pathogenecity are used in the vaccines.
E.g. RNA vaccines
E.g. Boredtella pertussis in DTaP vaccine
E.g. Hep B v
Are used to avoid complications from whole-killed vaccines.
What are toxoid vacccines ?
An inactivated version of an A/B toxin is used as the basis for the vaccine.
Modified toxin incapable of producing disease = toxoid
Both the tetanus and diphteria component of the DTaP vaccine are examples of toxoids.
What are anticapsular vaccines ?
The CHO capsule made by some bacteria is used in the vaccine. Since CHO are normally poorly immunogenic, it is typically compelxed with a carrier protein.
Some subunit or toxoid vaccines need to be administered with adjuvants. Adjuvants increase immunogenicity by :
Prolongation of An persistance
Enhancement of co-stimulatory signals
Induction of localized inflammation
What is herd immunity ?
Referes to the idea that not everyone needs to be vaccinated to gain protection against a disease, as long as they’re surrounded by people that are surrounded by that disease.
