Transcript Chapter 17
Chapter 17 Applications of Immune Responses A Glimpse in History • Chinese writings from the Sung Dynasty (AD 960-1280) indicate a process called variolation, where small crusts of smallpox pustules were inhaled or placed in a scratch of the skin. • The resulting disease was mild, but permanent immunity developed. • Variolation was common in China and the Middle East as long as 1000 years ago, but did not get popular in Europe until 1719. • Yet, due to high costs, it was not used commonly. In 1796, Edward Jenner and others worked together to spread the practice of variolation. Pasteur later changes the term to vaccination to describe any type of protective innoculation. Immunization • The process of inducing immunity to protect against disease. • Immunization has had the biggest impact on human health of any medical procedure. 17.1 principles of immunization • Naturally acquired immunity is the acquisition of adaptive immunity from normal events, such as exposure to an infectious agent. • Artificially acquired immunity is the result of immunization, where the immune system responds to the injection. Active immunity – result of an immune system response in an individual upon exposure to antigen. Passive immunity – occurs naturally during pregnancy. The mothers IgG antibodies cross the placenta to protect the fetus. ◦ These protect the baby in the first six months of life ◦ IgA is also found in breast milk and protects the digestive tract. ◦ Unfortunately, this immunity does not form memory. 17.2 Vaccines and Immunization Procedures • A vaccine is a preparation of a pathogen or its products used to induce active immunity. • Vaccines protect the individual as well as a population by preventing spread of the disease – The phenomenon of herd immunity occurs when a portion of the population is immune to a disease, Attenuated Vaccines • A weakened form of the pathogen that is generally unable to cause disease. • The strain replicates in the recipient causing an infection with a mild or undetectable disease that usually results in long term immunity. • Include the vaccinations for measles, mumps, rubella, yellow fever, and polio. • Attenuated vaccines have several advantages over inactivated ones: – A single dose of attenuated vaccine is usually enough to cause long-lasting immunity. – It can also spread from the immunized person to their contacts, thus inadvertently giving them immunity. • There are few disadvantages of these vaccines: – They can possibly cause disease in immunosuppressed patients and can revert or mutate to becoming pathogenic again. – They require refrigeration to keep them active Inactivated vaccines • A pathogen that is unable to replicate, but retains the immunogenicity of the infectious agent or toxin. • They cannot cause infection or revert to the pathogenic form, so they do not cause as magnified of an immune response. • To compensate for the low effective dose, many boosters may be needed. Inactivated whole agent vaccines Contain killed microorganisms or inactivated viruses. Vaccines are made by treating the infectious agent with a chemical that does not significantly change the contagion. Such treatments leave the agent immunogenic, but not able to reproduce. Vaccines include those against cholera, influenza, rabies, and the Salk Polio vaccine Toxoids • Inactivated toxins used to protect against diseases due to toxins produced by invading bacteria. • The toxins are treated to destroy the toxic part of the molecule while maintaining the antigenic sites. • Vaccines of this type include those for diphtheria and tetanus. Protein Subunit vaccines • Composed of key protein antigens or antigenic fragments of the infectious agent rather than the whole cell or virus. • They can only be developed after research reveals which component of the microbe causes the immune response. • Killed vaccines are known for causing side effects that can include pain, tenderness at the injection site, fever, and occasionally convulsions. • A subunit vaccine does not cause these side effects. • Examples of this type include the hepatitis B vaccine and the acellular pertussis vaccine. Polysaccharide vaccines Composed of the polysaccharides that make up the capsule of certain organisms. Conjugate vaccines intentionally convert polysaccharides into T dependent antigens by linking the polysaccharides to proteins. Examples include the Haemophilus influenza type b (which has nearly eliminated meningitis in children) and a vaccine for Streptococcus pneumonia. • Many inactivated viruses include adjuvant, which is a substance that enhances the immune response to antigens. The importance of routine immunizations for children • Before vaccinations, children died of common childhood diseases; those who did not die could be permanently disabled. • One reason some children are not vaccinated is because their parents refuse to have them treated due to rare instances where the vaccine causes harm. • While there is always risk associated with any medical procedure, the risks of vaccines are very low; and the benefits of vaccines far outweigh the risks. Current Progress in immunization • Due to a better understanding of immunity, great progress is being made. • An understanding of the immune response can lead to the development of more effective vaccines. • New types of vaccines are being studied: peptide vaccines, edible vaccines, and DNA based vaccines are all being studied. • Peptide are made of antigenic peptides from disease-causing organisms. They are heat stable and do not contain materials that cause unwanted side effects • Edible vaccines are created by transferring genes encoding the antigens of an organism into a plant. – If produced, they could be grown in many parts of the world, therefore eliminating problems of storage and transport. • DNA based vaccines are segments of naked DNA from infectious agents that can be directly introduced into muscles. – The host tissues expresses the DNA briefly, producing microbial agents encoded by the DNA which causes an immune response. Vaccine Descriptions: HEPB: PROTECTS AGAINST HEPATITIS B DTAP: A COMBINED VACCINE THAT PROTECTS AGAINST DIPHTHERIA, TETANUS, AND PERTUSSIS (WHOOPING COUGH) HIB: PROTECTS AGAINST HAEMOPHILUS INFLUENZAE TYPE B PCV: PROTECTS AGAINST PNEUMOCOCCAL DISEASE POLIO: PROTECTS AGAINST POLIO, THE VACCINE IS ALSO KNOWN AS IPV RV: PROTECTS AGAINST INFECTIONS CAUSED BY ROTAVIRUS INFLUENZA: PROTECTS AGAINST INFLUENZA (FLU) MMR: PROTECTS AGAINST MEASLES, MUMPS, AND RUBELLA (GERMAN MEASLES) VARICELLA: PROTECTS AGAINST VARICELLA, ALSO KNOWN AS CHICKENPOX HEPA: PROTECTS AGAINST HEPATITIS A Works Cited • Nester, Anderson, Roberts and Nester. Microbiology: A Human Perspective. • Tortora, Funke, and Case. Microbiology: An Introduction. • http://www.cdc.gov/vaccines/parents/rec-izbabies.html