Lecture 34: Vaccines and Microbial Diseases

Edward Jenner

credited with cowpox vaccination

- cowpox vaccination also prevented smallpox

Scheme for Classifying Specific Immunities

natural and artificial

- both have active and passive branches

Natural Immunity

acquired from normal life experience of a human

- active: getting sick and recovering; develops your own immune response

- passive: acquiring antibodies from natural source (breast milk)

Artificial Immunity

produced purposefully through medical procedures

- active: vaccines

- passive: plasma transfer either to assist someone’s immune system or generate a monochrome antibody in the lab

Vaccines Target…

activate B and T cells

- B cells will make antibodies to neutralize live virus

- T cells will lyse virally infected cells

- MHC I activates CD8 T cell

- MHC II activates CD4 helper T cell

Vaccination Goals

expose someone to material that is antigenic but not pathogenic

- stimulate the immune system to protect against future exposure to virulent pathogen

- has to have low level of adverse side effects, protect against pathogen, T and B cell memory, not require numerous boosters, inexpensive

Killed or Inactivated Pathogen Vaccine

the organism does not multiply

- influenza, polio

Live Attenuated Pathogen Vaccine

weakened organism that is passed through cells that they don’t typically infect

- alive but with lowered virulence

- ensures antigens are presented on MHC class I

- MMR (measles, mumps, rubella)

Acellular or Subunit (Toxoid) Vaccine

antigenic portion of the toxin

- tetanus, diphtheria, HPV

Recombinant Vaccine

removal of gene and leaves just antigens for the vaccine

- efficacy of vaccine is time dependent

- Hep B series, Hib

Phases of Vaccine Safety

three phases

- vaccines will only be licensed and produced if they are safe and effective

Vaccine Safety Phase 1

small number of individuals (20-100) that volunteer for vaccine

- takes about six months to a year to complete

- looks at side effects, metabolism, immune system response

Vaccine Safety Phase 2

100-500 volunteers

- assesses safety, if it works, how much is needed, side effects

- six months to one year to complete

Vaccine Safety Phase 3

hundreds to thousands of volunteers

- safety, side effects, immune response

COVID Vaccine Strategy

RNA delivery in a vesicle is translated

- protein is translated in a way where some is released to activate B cells while others are targeted to the proteosome where they activate T cells and others are released for phagocytosis and allow MHC II  

Biosafety Level (BSL) 1

general personal protection, teaching labs, non-pathogenic microbes

BSL-2

biosafety cabinets, gloves, splash guards, human samples and pathogenic organisms

- ex. HIV, hepatitis, organisms not transmitted by inhalation

BSL-3

characteristics are same as BSL-2 but it can cause lethal infections via aerosolized route

- ex. SARS, flu, tuberculosis, anthrax

BSL-4

deadly pathogens for which there is no vaccine, high level of transmission, or mortality

- only 13 in the US

- ex. smallpox, ebola, lassa, marburg

Foodborne Disease

ingestion of contaminated food is common source of gastrointestinal disease

- leading source is produce followed by meat and poultry (meat and poultry lead to more deaths)

- can cause infections or intoxications

Foodborne Intoxication

illness is due to a toxin, not the organism itself

- organisms get killed by cooking but they can produce enterotoxins

- cannot be treated with antibiotics

- ex. S. aureus and C. botulinum

Foodborne Infection

microorganisms are ingested with food and colonize the GI tract

- onset takes longer; due to bacterial growth in GI tract

- can be treated with antibiotics

Listeriosis

typically in deli meats but has also been seen in cantaloupe, hummus, ice cream, cheese  

- in healthy adults: one day incubation period and two days of symptoms; It can cause intracellular infections and cross into the placenta in pregnant women