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Understanding Immunology: from Phagocytes to Vaccine Types

Explore the complex world of immunology from how phagocytes engulf bacteria to different vaccine types combating viruses. Learn about B cells, antibodies, CD4 and CD8 cells, and types of vaccines for various pathogens.

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Understanding Immunology: from Phagocytes to Vaccine Types

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  1. Phagocyte phagocyte moves towards the bacterium engulfs it digests it

  2. B cells B Cell Receptor Naïve B cell

  3. B cells and antibodies B cell attaches to antigen cloning of daughter cells daughter cells produce antibodies Antibodies neutralise antibodies phagocyte consumes an antibody coated virus

  4. Cytotoxic CD8 cells CD8 cells can recognise markers on the outside of infected cells CD8 destroys infected cell which stops cell from producing more virus or bacteria

  5. Antigen presenting cells These cells can engulf invading organisms Antigens presented to CD4 cells The foreign organism is broken up into smaller pieces

  6. CD4 cell

  7. Analogy for the immune system

  8. Naïve and Memory B cells • Naïve B cell • Once activated it divides many times making two types of clones • The plasma cell which makes and releases large amounts of the appropriate antibody • The memory B cell which can live for years • Memory B cells • The existence of memory B cells means that the body can respond much more quickly

  9. CD4 and CD8 • Cluster of Differentiation • Molecules on the surface of the cells that help the T cell attach to the antigen • CD4 cells • Th1 (humoral response) Th2 (cell mediated response) Th0 (??) • CD8 cells • Cytotoxic lymphocytes (CTL) • CD45RA – Naïve cells • CD45RO – Memory cells

  10. Viral Load CD4 Count Levels in the Blood Set Point Below the limit of the test Seroconversion Asymptomatic Symptomatic CD4 count viral load over time

  11. HIV virion Fatty (lipid bilayer) membrane Glycoprotein gp120 Protein p18 Reverse transcriptase enzyme Protein p24

  12. Vaccine - Ideal characteristics • Prevent transmission by mucosa & injecting • Excellent safety profile • Single dose administration • Offers protection for a long time • Low cost • Stability and ease of administration • Works against a wide range of different strains

  13. Immune system responses • Humoral response • Based on antibodies and the B cells that produce them • Cell-mediated response • Based on cytotoxic CD8 cells • Mucosal immunity • The above but concentrated in the mucosal membranes where most transmission occurs • Current trend • is to aim to stimulate a sufficient HIV-specific CTL response to control or prevent HIV infection

  14. Types of vaccine • Live attenuated vaccines • Defective or weakened form of the virus • Previous example original smallpox vaccine, vaccinia • Research in monkeys indicates may slowly lead to immune disease • Inactivated or 'killed' vaccines • Recombinant sub-unit envelope vaccines • Recombinant vectored vaccines • DNA vaccines and replicons • Combination vaccines or ‘prime and boost’

  15. Types of vaccine • Live attenuated vaccines • Inactivated or 'killed' vaccines • Second classic technique (e.g. Dr Jonas Salk in creating the world's first successful polio vaccine) • No-one has yet claimed any significant success • Maybe difficult to distinguish between vaccine immune response and infection • Recombinant sub-unit envelope vaccines • Recombinant vectored vaccines • DNA vaccines and replicons • Combination vaccines or ‘prime and boost’

  16. Types of vaccine • Live attenuated vaccines • Inactivated or 'killed' vaccines • Recombinant sub-unit envelope vaccines • Seek to stimulate antibodies to HIV by mimicking proteins on the surface of HIV (e.g. gp120) • Initial research was strain-specific and produced poor antibody responses • Recently more hope • Recombinant vectored vaccines • DNA vaccines and replicons • Combination vaccines or ‘prime and boost’

  17. Types of vaccine • Live attenuated vaccines • Inactivated or 'killed' vaccines • Recombinant sub-unit envelope vaccines • Recombinant vectored vaccines • incorporate harmless bits of HIV into established vaccines • ALVAC series of vaccines are canarypox based vaccines • Vaccine strains of adenovirus • recombinant rabies virus vaccines • DNA vaccines and replicons • Combination vaccines or ‘prime and boost’

  18. Types of vaccine • Live attenuated vaccines • Inactivated or 'killed' vaccines • Recombinant sub-unit envelope vaccines • Recombinant vectored vaccines • DNA vaccines and replicons • involve HIV genetic sequences which, once injected, induce expression of HIV antigens by human cells. • In the case of replicons, these sequences are wrapped in the outer coat of an unrelated virus. • Combination vaccines or ‘prime and boost’

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