Immunology 19 - Immunology 19 Vaccination Vaccines can be...

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Immunology 19- Vaccination Vaccines can be based on attenuated pathogens or material from killed organisms 1. Attenuated organisms with reduced pathogenicity, which would stimulate protective immunity but not cause disease 2. Development of vaccines based on killed organisms and subsequently on purified components of the organisms that would be effective as live whole organisms; vaccines based on the conjugation of purified antigens Most vaccines are given to children within the first year of life (measles, mumps, rubella, chickenpox and influenza given between ages of 1-2 yrs) For many pathogens, natural infection does not seem to generate protective immunity, and infections become chronic or recurrent; antibodies are insufficient to prevent reinfecction and to eliminate the pathogen; cell mediated immunity seems to be more important in limiting these pathogens but is insufficient to provide full immunity (malaria, tuberculosis, HIV) More rational approach to vaccines: based on a detailed molecular understanding of microbial pathogenecity, analysis of the protective host response to pathogenic organisms, and an understanding of the regulation of the immune system to generate effective T and B lymphocyte responses Most effective vaccines generate antibodies that prevent the damage caused by toxins or that neutralize the pathogen and stop infection Many effective vaccines currently work by inducing Ab’s against the pathogen; for many pathogens, including extracellular organisms and viruses, Ab’s can provide protective immunity Tetanus/dipheria: pre-existing Ab against the exotoxin is necessary to provide defense against these diseases Antibodies can protect by preventing secondary infection (certain viral infections)= neutralization ; ability of an AB to neutralize a pathogen depends on affinity, isotype, complement and activity of phagocytic cells; ex polio Usually antibodies produced by infection or vaccination are able to neutralize the virus Immune responses to infectious agents usually involve Ab directed at multiple epitopes, and only some of these Abs (if any) confer protection; the particular T cell epitopes recognized can also affect the nature of the response Linked recognition: antigen specific B and T cells provide mutually activating signals, leading to affinity maturation and isotype switching that may be required for neutralizaiton; requires that an appropriate peptide epitope for T cells is presented by the B cells, and the T cell epitope typically must be contained within the region of protein epitope recognized by the B cell Effective vaccines must induce long lasting protection while being safe and inexpensive 1. Must provoke effective immunity 2. Must be safe; must not cause illness or death 3. Must be able to produce protective immunity in a very high proportion of the people whom it is given 3. Must generate long lived immunological response (esp. Imp. in poor countries);
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Immunology 19 - Immunology 19 Vaccination Vaccines can be...

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