Session 14

• Vaccine

  Inoculation of a weakened or killed form of a pathogen to stimulate the immune system and provide immunity
• Vaccination


  • Works by stimulating the immune system to provide immunity
• Types of vaccines

  • Attenuated whole-agent
  • Inactivated whole-agent
  • Toxoid
  • Subunit
  • Conjugated
  • DNA
• Attenuated whole-agent vaccine


  Weakened microorganisms or viruses that generally provide lifelong immunity
• Inactivated whole-agent vaccine


  Killed bacteria or viruses
• Toxoid vaccine


  Inactivated toxin
• Subunit vaccine


  Antigenic fragments of a microorganism, includes recombinant and acellular vaccines
• Conjugated vaccine


  Combines the desired antigen with a protein that boosts the immune response
• DNA vaccine


  Stimulates humoral and cellular immunity, thermostable, easy to produce, in clinical trials
• Booster immunizations


  Additional doses of a vaccine to maintain immunity
• Adjuvants


  Improve effectiveness of some antigens by increasing availability of antigen in lymph system
• Vaccination strategy for polio


  1. Salk vaccine (inactivated virus) in 1950s

  2. Sabin vaccine (attenuated virus) in 1962

  3. Salk vaccine is safer but no mucosal immunity

  4. Sabin vaccine provides herd immunity
• Principal vaccines used in the US to prevent bacterial diseases


  • DtaP (diphtheria, pertussis, tetanus)
  • Meningococcal meningitis
  • Haemophilus influenzae type b meningitis
  • Pneumococcal conjugate vaccine
• Principal vaccines used in the US to prevent viral diseases

  • Smallpox
  • Poliomyelitis
  • Rabies
  • Hepatitis A
  • Influenza
  • Measles
  • Mumps
  • Rubella
  • Chickenpox
  • Hepatitis B
• Sensitivity


  Percentage of positive samples a test correctly detects
• Specificity


  Percentage of false positive results a test gives
• Monoclonal antibodies (MAbs)


  Single type of antibody directed against one specific epitope, produced by a single B cell clone
• Generation of MAbs


  1. Hybridoma production by fusing a cancerous cell with an antibody-secreting plasma cell

  2. Hybridoma cell culture produces large quantities of the plasma cell's antibodies
• Uses of MAbs


  • Serological identification (tissue and blood typing)
  • Preventing tissue rejection
  • Immunotoxins to treat cancer
  • Measuring serum protein and drug levels
  • Identifying infectious agents
  • Identifying and quantifying hormones
• Developments in new generations of MAbs


  • Chimeric MAbs (66% human)
  • Humanized MAbs (90% human)
  • Fully human antibodies
  • Bacterial, plant and animal systems under investigation to increase production volumes
• Precipitation reactions


  Interaction of soluble antigens with IgG or IgM antibodies
• Precipitin ring test


  Precipitation reactions carried out in a small tube
• Immunodiffusion procedures


  Precipitation reactions carried out in agar gel medium
• Lattice formation


  Optimal proportions of antigens and antibodies leading to precipitation
• Agglutination reactions


  Interaction of particulate antigens and antibodies
• Direct agglutination


  Antigens on a bacterial cell
• Indirect or passive agglutination


  Antigens attached to latex spheres
• Titer

  Concentration of antibodies against a particular antigen
• Seroconversion


  Rising antibody titer from no antibodies to the presence of antibodies
• Neutralization reactions


  Harmful effect of a bacterial exotoxin or virus is eliminated by a specific antibody
• Viral hemagglutination-inhibition tests


  Antibodies prevent viral hemagglutination (agglutination of red blood cells)
• Direct fluorescent-antibody tests


  Identify specific microorganisms
• Indirect fluorescent-antibody (IFA) tests


  Demonstrate the presence of antibodies in serum
• Direct and indirect ELISA tests


  Tests that use enzyme-linked antibodies to detect the presence of antigens or antibodies