Chap 17 – BYU – Flashcards
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| Active immunization |
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| administration of a vaccine so that the patient actively mounts a protective immune response |
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| Passive immunization |
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| individual acquires immunity through the transfer of antibodies formed by an immune individual or animal |
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| History of Immunization |
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| • The Chinese noticed that children who recovered from smallpox did not contract the disease a second time • They infected young children with material from a smallpox scab to induce immunity in these children, a process known as variolation • The use of variolation spread to England and America but was eventually stopped due to the risk of death • Edward Jenner found that protection against smallpox could be induced by inoculation with material from an individual infected with cowpox, a similar but much milder disease |
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| History of Immunization |
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| • Since the Latin word for cow is vacca, this process was called vaccination, and the inoculum was termed a vaccine • Louis Pasteur developed a vaccine against Pasteurella multocida • Practice of transferring protective antibodies was developed when it was discovered that vaccines protected through the action of antibodies |
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| Vaccine Types |
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| • 3 general types of vaccines – Attenuated live – Inactivated (killed), whole or subunit – Toxoid |
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| Attenuated Vaccines |
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| • Also called modified live vaccines • Uses pathogens that are living but have reduced virulence so they don’t cause disease • Attenuation is the process of reducing virulence – Viruses often attenuated by raising them in tissue culture cells for which they aren’t adapted until they lose the ability to produce disease – Bacteria can be made avirulent by culturing under unusual conditions (BCG) or through genetic manipulation |
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| Attenuated Vaccines |
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| • Can result in mild infections but no disease in normal individual • Contain replicating microbes that can stimulate a strong immune response due to fact that it is an actual infection • Viral vaccines trigger a cell-mediated immune response dominated by TH1 and cytotoxic T cells • Vaccinated individuals can infect those around them, providing herd immunity |
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| Problems with Attenuated Vaccines |
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| • Attenuated microbes may retain enough virulence to cause disease, especially in immunosuppressed individuals • Pregnant women should not receive live vaccines due to the risk of the modified pathogen crossing the placenta • Modified viruses may occasionally revert to wild type or mutate to a virulent form |
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| Inactivated Vaccines |
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| • Can be either whole agent vaccines produced with deactivated but whole microbes, or subunit vaccines produced with antigenic fragments of microbes • Both types are safer than live vaccines since they cannot replicate or mutate to a virulent form • When microbes are killed, one must not alter the antigens responsible for stimulating protective immunity • Formaldehyde is commonly used to inactivate microbes by cross-linking their proteins and nucleic acids • Usually recognized as exogenous antigens and stimulate a TH2 response that promotes antibody-mediated immunity |
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| Problems with Inactivated Vaccines |
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| • Do not stimulate herd immunity • Whole agent vaccines may stimulate an inflammatory response due to nonantigenic portions of the microbe • Weak immunogenicity, since the microbes don’t reproduce and are cleared before they stimulate a strong immune response |
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| Problems with Inactivated Vaccines |
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| • Administration in high or multiple doses, or the incorporation of an adjuvant, can make the vaccine more effective – Adjuvants are substances that increase the immunogenicity of the vaccine – Adjuvants may also stimulate local inflammation – High and multiple vaccine doses may produce allergic reactions |
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| Some Common Adjuvants Toxoid Vaccines |
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| • Chemically or thermally modified toxins used to stimulate active immunity • Useful for some bacterial diseases • Stimulate antibody-mediated immunity • Require multiple doses because they don’t replicate in the host and are cleared quickly |
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| Adult Immunization Schedule Modern Vaccine Technology |
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| • Research attempts to make vaccines that are more effective, cheaper, and safer • A variety of recombinant DNA techniques can be used to make improved vaccines |
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| Vaccine Safety |
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| • Problems associated with vaccination – Mild toxicity is the most common problem • Especially seen with whole agent vaccines that contain adjuvants • May cause pain at the injection site and in rare cases can cause general malaise or fever high enough to induce seizures – Anaphylactic shock • Is an allergic reaction that may develop to a component of the vaccine |
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| Vaccine Safety 2 |
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| – Residual virulence • Attenuated viruses occasionally cause disease in healthy children or adults – Allegations that certain vaccines against childhood diseases cause or trigger autism, diabetes, and asthma • Research has not substantiated these allegations |
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| Passive Immunity |
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| • Administration of preformed antibodies to a patient • Used when protection against a recent infection or an ongoing disease is needed quickly • Immunologists remove the serum from human or animal donors that have been infected with the disease or immunized against it • Serum used for passive immunizations is called antiserum |
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| Limitations of Antisera |
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| • Contain antibodies against many different antigens not just the ones of interest • Repeated injections of antisera collected from a different species can trigger allergic reactions • Antisera may be contaminated with viral pathogens • Antibodies of antisera are degraded relatively quickly • Some of these limitations have been overcome through the development of hybridomas and monoclonal antibodies |
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| Immune Testing |
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| • Serology = study and diagnostic use of antigen-antibody interactions in blood serum • Use immunological processes in two general diagnostic ways – Use known antibodies to detect antigens associated with an infectious agent – Use antigens to detect specific antibodies in a patient’s blood to determine exposure to a specific pathogen • Test chosen based on the suspected diagnosis, cost to perform the test, and the speed with which a result can be obtained |
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| Immune Testing |
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| • Numerous types of serologic test – Precipitation tests – Agglutination tests – Neutralization tests – Labeled antibody tests |
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| Precipitation Tests |
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| • One of the easiest of serological tests • Based on the idea that soluble antigens and antibody mixed in the proper proportion form large macromolecular complexes called precipitates |
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| Antigen and Antibody Proportions |
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| • Correct proportions are important to create precipitation • Insure optimal antibody and antigen concentrations using 2 techniques: – Immunodiffusion – Immunelectrophoresis |
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| Radial Immunodiffusion |
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| • Commonly used to measure the concentrations of specific antibodies or immunoglobulins in a person’s serum • Produce anti-antibodies by injecting human antibodies (of 1 class) into an individual of another species where they will be antigenic and cause production of antibodies directed against the human antibodies • The human antibodies are the “antigen” in the test, and the anti-antibody is the antibody |
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| Immunelectrophoresis |
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| • Improves the resolution of an immunodiffusion test • Can resolve more than 30 distinct antigens at once • Commonly used to demonstrate the absence of a normal antigen or to detect the presence of excessive amounts of an antigen |
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| Agglutination Tests |
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| • Agglutination occurs due to the cross-linking of antibodies with particulate antigens • Agglutination is the clumping of insoluble particles, whereas precipitation involves the aggregation of soluble molecules • These reactions are easy to see and interpret with the unaided eye • Hemagglutination, the agglutination of red blood cells, can be used to determine blood type |
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| Neutralization Tests |
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| • Based on the concept that antibodies can neutralize biological activity of many pathogens and their toxins • 2 Neutralization tests: – Viral neutralization – Viral hemagglutination inhibition test |
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| Viral Neutralization |
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| • Viruses introduced into appropriate cell cultures will invade and kill the cells, a phenomenon called cytopathic effect • The ability of a virus to kill culture cells is neutralized when the virus is first mixed with antibodies against it • Absence of cytopathic effect indicates the presence of antibodies against the virus • Test is sensitive and specific enough to identify whether an individual has been exposed to a particular virus or viral strain |
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| Viral Hemagglutination Inhibition Test |
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| • Useful for viruses that aren’t cytopathic • Test based on viral hemagglutination, the ability of some viral surface proteins to clump red blood cells • Serum from an individual will stop viral hemagglutination if the serum contains antibodies against the specific virus • Commonly used to detect antibodies against influenza, measles, and mumps viruses |
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| Labeled Antibody Test |
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| • Use antibody molecules that are linked to some molecular “label” that enables them to be easily detected • Used to detect either antigens or antibodies • 3 examples – Fluorescent antibody tests – ELISA – Western blot test |
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| Fluorescent Antibody Test |
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| • Uses fluorescent dyes as labels • Fluorescein is the most important dye used in these tests – Chemically linked to an antibody without affecting antibody’s ability to bind antigen – Glows bright green when exposed to fluorescent light • Fluorescein-labeled antibodies used in 2 types of tests – Direct fluorescent antibody test – Indirect fluorescent antibody tests |
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| Direct Fluorescent Antibody Tests |
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| • Identifies the presence of antigen in tissue – Tissue sample flooded with labeled antibody – Antibody and antigen are allowed to bind for a short period – Unbound antibody washed from the preparation – Results observed under a fluorescent microscope • Used to identify small numbers of bacteria in patient tissues • Not a quantitative test- the amount of fluorescence observed is not directly related to the amount of antigen present |
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| Indirect Fluorescent Antibody Tests |
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| • Similar to direct test, except 2 antibodies are used; the first is unlabeled and detects antigen of interest; the second is labeled and detects the first antibody • Advantage is that the same labeled anti-antibody can be used in many different detection tests |
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| Indirect Fluorescent Antibody Tests |
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| • Similar to direct test, except 2 antibodies are used; the first is unlabeled and detects antigen of interest; the second is labeled and detects the first antibody • Advantage is that the same labeled anti-antibody can be used in many different detection tests |
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| ELISA |
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| • Stands for Enzyme-Linked Immunosorbent Assay • Uses an enzyme as the label – Reaction of the enzyme with its substrate produces a colored product indicative of antibody presence • Most common form of ELISA is used to detect the presence of antibodies in serum |
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| Antibody Sandwich ELISA |
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| • Modification of the ELISA technique • Commonly used to detect antigen • Antigen being tested for is “sandwiched” between two antibody molecules |
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| Advantages of The ELISA |
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| • Can detect either antibody or antigen • Can quantify amounts of antigen or antibody • Easy to perform, inexpensive, and can test many samples quickly • Plates coated with antigen and gelatin can be stored for later testing • Very sensitive |
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| Western Blot Test |
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| • Technique for detecting antibodies against multiple antigens in a complex mixture • Can detect more types of antibodies and are less subject to misinterpretation than other tests |
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| Recent Developments in Immune Testing |
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| • Development of simple immunoassays that give results in minutes • Generally not quantitative but are useful in determining a preliminary diagnosis • Most common are the immunofiltration and immunochromotography assays – Immunofiltration • Rapid ELISA that uses antibodies bound to membrane filters rather than polystyrene plates • Membrane filters have a large surface area making the assay quicker to complete |
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| Recent Developments in Immune Testing 2 |
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| – Immunochromatography • Very rapid and easy to read ELISAs • Antigen solution flows through a porous strip where it encounters antibody labeled with either pink colloidal gold or blue colloidal selenium • Antigen-Antibody immune complexes flow through a region and encounter antibody against them, resulting in a visible pink or blue line • Used in pregnancy testing to detect human chorionic gonadotropin (HCG) |
