Lectures 17 & 18 - Vaccines

Vaccines

innocuous preparation made from pathogen that is used for vaccination. They provide immunity against infection of that pathogen. Vaccines can be injected, inhaled, or ingested.

Lack of new vaccines against some diseases

Pathogens are constantly changing, very expensive, and many legal and political issues.

Ancient perspectives of vaccine discovery

Observation of lifelong immunity after contracting small pox or plague by, China, India, Greece, Egypt. Materials from dried smallpox pustules inoculated into arm of healthy person to induce immunity. Process was called “variolation”. Effective for about 99 out of 100 people.

Cowpox virus

No affect to humans, but similar enough to provide immunity against smallpox. Immunity first discovered in milkmaids. Cowpox vesicle vaccine become the first vaccine in London, ~Late 1700s.

1st immunological experiment by Louis Pasteur

Live Bacillus anthracis given to one sheep live and another after heating and chemically inactivated to 2nd sheep. 2nd sheep lives and gains immunity.

Active immunization

vaccination with antigen, live or killed. Host develops protection of pathogen in next infection

Passive immunization

Administration of pre-formed antibodies prophylactically or to treat active infections (rabies, snake bites, etc)

Pasteur Rabies vaccine

Administered to 9 year old Joseph Meister in 1885. Rabies virus is very poor at replicating in the human body. This was an active immunization.

Herd Immunity

Unvaccinated in vaccinated population. The individual remains protected as long as he remains in a vaccinated population. He becomes vulnerable after leaving that population.

Whooping cough

DTP(Whole killed BAC) vaccine decreases incidents of whooping cough. DTP vaccine rumors about neurological damage. DTP production stops. DTaP(Toxoid and proteins) produced in the 90s. Partially immune population. Numbers have still not reached the low numbers that DTP created.

D & T

Detoxified forms of bacterial toxins. Soluble proteins.

P

whole killed B. pertussis – complex mixture of components some of which are toxic. 20% of infants experienced side effects ranging from mild discomfort to convulsions. The convulsions were subsequently found to not be caused by the whole killed bacteria.

aP

the toxoid form of pertussis toxin, plus a surface antigen (adhesin)

Booster Shots

Needed because some molecules are not long lived in the body. The body needs another dose to keep immunity.

Polysaccharide vaccines

effective for adults, but not for stimulating the immune system in children. Composed of polysaccharide antigens of encapsulated bacteria.

Conjugate Vaccines: Hib vaccine

targets Haemophilus influenzae type b. Doesn’t produce toxin and coats itself in polysaccharide capsule which prevents C3b from binding. This vaccine triggers production of Ab that bind to capsular polysaccharides, allowing for phagocytosis and opsonization.

Conjugate vaccines:

refers to a vaccine where the bacterial antigen is coupled with a non-specific protein molecule to induce a T cell response. B cell is activated and differentiates into plasma and memory cells.

Synthetic Vaccines

First you need to know where the body 1st encounters pathogen and where it goes after. Know what virulence factors are present.

Effectiveness of vaccines & safety considerations

The vaccine must induce the right immunity, be stable during storage (cold, preservatives), and have sufficient immunogenicity

Adjuvant

refers to a substance that non-specifically enhances the immune response to an antigen

Alum

aluminum hydroxide gel. thought to promote slow release of antigen, but now thought to enhance antigen uptake by DCs and other APCs. good for TH2 but poor for TH1

Passive Immunization

preformed antibodies administered to individual. Artificially by human pooled serum, or naturally from mother to newborn. Artificial passive immunization can be life saving but will not allow for the development of memory cells.