Vaccines

• What is a vaccine?

  ● Injection of antigens from attenuated (dead or weakened) pathogens

  ● Stimulating formation of memory cells
• Explain how vaccines provide protection to individuals against disease

  1. Specific B cell with complementary receptor binds to antigen

  2. Specific T helper cell binds to APC and stimulates B cell

  3. B lymphocyte divides by mitosis to form clones

  4. Some differentiate into B plasma cells which release antibodies

  5. Some differentiate into B memory cells

  6. On secondary exposure to antigen, B memory cells rapidly divide by mitosis to produce B plasma cells

  7. These release antibodies faster and at a higher concentration
• Explain how vaccines provide protections for populations against disease

  ● Herd immunity- large proportion of population vaccinated, reducing spread of pathogen

  ○ Large proportion of population immune so do not become ill from infection

  ○ Fewer infected people to pass pathogen on / unvaccinated people less likely to come in contact

  with someone with disease
• Describe the differences between active and passive immunity

  Active:

  Initial exposure to antigen eg. vaccine or primary infection

  Memory cells involved

  Antibody produced and secreted by B plasma cells

  Slow; takes longer to develop

  Long term immunity as antibody can be produced in

  response to a specific antigen again

  Passive:

  No exposure to antigen

  No memory cells involved

  Antibody introduced from another organism eg.

  breast milk / across placenta from mother

  Faster acting

  Short term immunity as antibody hydrolysed (endo/exo/dipeptidases)
• Explain the effect of antigen variability on disease and disease prevention

  ● Antigens on pathogens change shape / tertiary structure due to gene mutations (creating new strains)

  ● So no longer immune (from vaccine or prior infection)

  ○ B memory cell receptors cannot bind to / recognise changed antigen on secondary exposure

  ○ Specific antibodies not complementary / cannot bind to changed antigen
• What is a monoclonal antibody?

  ● Antibody produced from genetically identical / cloned B lymphocytes / plasma cells

  ● So have same tertiary structure
• Explain how monoclonal antibodies can be used in medical treatments

  ● Monoclonal antibody has a specific tertiary structure / binding site / variable region

  ● Complementary to receptor / protein / antigen found only on a specific cell type (eg. cancer cell)

  ● Therapeutic drug attached to antibody

  ● Antibody binds to specific cell, forming antigen-antibody complex, delivering drug
• Explain how monoclonal antibodies can be used in medical diagnosis

  ● Monoclonal antibody has a specific tertiary structure / binding site / variable region

  ● Complementary to specific receptor / protein / antigen associated with diagnosis

  ● Dye / stain / fluorescent marker attached to antibody

  ● Antibody binds to receptor / protein / antigen, forming antigen-antibody complex
• Explain the use of antibodies in the ELISA (enzyme-linked immunosorbent assay) test to detect antigens DIRECT ELISA

  1.Attach sample with potential antigens to well

  2 Add complementary monoclonal antibodies with enzymes attached → bind to antigens if present

  3 Wash well → remove unbound antibodies (to prevent false positive)

  4 Add substrate → enzymes create products that cause a colour change (positive result)
• Explain the use of antibodies in the ELISA test to detect antibodies INDIRECT ELISA

  1.Attach specific antigens to well

  2. Add sample with potential antibodies, wash well

  3. Add complementary monoclonal antibodies with enzymes attached → bind to antibodies if present

  4. Wash well → remove unbound antibodies

  5. Add substrate → enzymes create products that

  cause a colour change (positive result)
• Suggest the purpose of a control well in the ELISA test

  ● Compare to test to show only enzyme causes colour change

  ● Compare to test to show all unbound antibodies have been washed away
• Discuss some general ethical issues associated with the use of vaccines and monoclonal antibodies

  ● Pre-clinical testing on / use of animals- potential stress / harm / mistreatment

  ○ But animals not killed & helps produce new drugs to reduce human suffering

  ● Clinical trials on humans- potential harm / side-effects

  ● Vaccines - may continue high risk activities and still develop / pass on pathogen

  ● Use of drug - potentially dangerous side effects
• Suggest some points to consider when evaluating methodology relating to the use of vaccines and monoclonal antibodies

  ● Was the sample size large enough to be representative?

  ● Were participants diverse in terms of age, sex, ethnicity and health status?

  ● Were placebo / control groups used for comparison?

  ● Was the duration of the study long enough to show long-term effects?

  ● Was the trial double-blind (neither doctor / patient knew who was given drug or placebo) to reduce bias?
• What should be considered regarding side effects when evaluating vaccines and monoclonal antibodies?

  The observed side effects and their frequency of occurrence
• Why is it important to use a statistical test when evaluating vaccine data?

  To determine if there is a significant difference between the start and final results
• What does a large standard deviation of final results indicate in vaccine studies?

  It shows that some people did not benefit from the treatment
• What does it mean if the standard deviations of start and final results overlap?

  It may indicate that there is not a significant difference between the two results
• How should the optimum dosage of a vaccine be evaluated?

  By determining if increasing the dose increases effectiveness enough to justify the extra cost
• What cost factors should be considered when evaluating vaccines and monoclonal antibodies?

  The cost of production and distribution