Chapter 18 Practical Applications of Immunology
Vaccine History • Variolation: Inoculation of smallpox into skin (18th century) • Vaccination: Inoculation of cowpox into skin • Herd immunity results when most of a population is immune to a disease.
Jenner • On 14th May 1796, Edward Jennerused cowpox-infected material obtained from the hand of Sarah Nemes, a milkmaid from his home village of Berkley in Gloucestershire to successfully vaccinate 8 year old James Phipps. On 1st July 1796, Jenner challenged the boy by deliberately inoculating him with material from a real case of smallpox.He did not become infected!
How Vaccines work • Trigger your own immune response • Artificially acquired active immunity • Virus, Bacterial or Toxins • Attenuated - no longer virulent • Inactivated or Killed - formalin, phenol or heat destroyed
Types of Vaccines • Attenuated whole agent vaccines: • Live, attenuated (weakened) microbes - virus or bacteria • Long term immunity • May back mutate to virulent strain (rare) • Inactivated (killed) vaccines: • Killed by formalin, phenol or heat • Toxoids • Not as long lasting • Safe • Subunit vaccine: • Uses fragments from virus or bacteria • Produced by recombinant methods Recombinvac • Safe • Clean • Conjugated vaccines: • Bind to larger particle or protein to enhance antigenicity
Principal Vaccines Used in the United States to Prevent Bacterial Diseases in Humans • DTaP - Trivalent (three in one) • Diphtheria: Purified diphtheria toxoid • Pertussis: Acellular fragments of B. pertussis • Tetanus: Purified tetanus toxoid • Meningococcal meningitis: Purified polysaccharide from N. meningitidis • Haemophilus influenzae type b meningitis: Polysaccharides conjugated with protein • Pneumococcal conjugate vaccine: S. pneumoniae antigens conjugated with protein
Principal Vaccines Used in the United States to Prevent Viral Diseases in Humans • Smallpox: Live vaccinia virus • Poliomyelitis: Inactivated virus • Rabies: Inactivated virus • Hepatitis A: Inactivated virus • Influenza: Inactivated or attenuated virus • Measles: Attenuated virus • Mumps: Attenuated virus • Rubella: Attenuated virus • Chickenpox: Attenuated virus • Hepatitis B: Antigenic fragments (recombinant vaccine)
Other Diagnostic applications: Serological Tests Diagnostic Immunological tests: • Direct tests detect antigens (from patient sample) • Indirect tests detect antibodies (in patient's serum)
Diagnostic Immunology: Precipitation Reactions Precipitation Reactions: • Involve soluble antigens with antibodies • Precipitin Ring test Figure 18.3
Agglutination Reactions • Involve particulate antigens and antibodies • Antigens may be: • On a cell (direct agglutination) • Attached to latex spheres (indirect or passive agglutination) Figure 18.4
Hemagglutination • Hemagglutination involves agglutination of RBCs. Figure 18.7
Neutralization Reactions • Antibodies help eliminate the harmful effect of a virus or exotoxin • Viral hemagglutination inhibition tests for the presence of antibodies in a patients serum by the antibodies' ability to prevent viruses from agglutinating RBCs. Figure 18.8b
Antibody Titer • Is the concentration of antibodies against a particular antigen Figure 18.5
Complement Fixation Figure 18.9.1
Complement Fixation Figure 18.9.2
Fluorescent Antibody Techniques (Direct) Figure 18.10a
Fluorescent Antibody Techniques (Indirect) Figure 18.10b
Enzyme-Linked Immunosorbent Assay(Direct ELISA) Figure 18.12a
Enzyme-Linked Immunosorbent Assay (Indirect ELISA) Figure 18.12b
Serological Tests Figure 18.13
Serological Tests: Summary • Precipitation: Soluble antigens • Agglutination: Particulate antigens • Hemagglutination: Agglutination of RBCs • Neutralization (inhibition): Inactivates toxin or virus • Fluorescent-antibody technique: Antibodies linked to fluorescent dye • Complement fixation: RBCs are indicator • ELISA: Enzyme linked to antibody amplifies results for easier visibility and more sensitivity.