Vaccines

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Author:
mfawcett
ID:
190763
Filename:
Vaccines
Updated:
2012-12-28 09:06:33
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vaccine vaccines bod pathology
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Description:
End of 'viruses' lecture series, on vaccines.
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  1. 5 types of public health control measures
    • quarantine/isolation/slaughter eg with smallpox, rabies
    • surveillance: notifiable diseases eg influenza, measles, rabies, AIDS. Allows swift action eg vaccination/anti-viral drugs
    • sanitary engineering/food hygiene regulations: polio and Hep A spread by faeco-oral route
    • vector control: eg yellow fever spread by mosquitoes
    • screening of blood and blood products: Hep B and C, HIV
  2. what virus causes smallpox?
    Variola
  3. 2 strains of variola, mortality difference
    • variola major: 30-40% mortality
    • variola minor aka alastrim: 1% mortality
  4. visual difference between smallpox and chickenpox
    smallpox more centrifugal (pustules more abundant on face than trunk)
  5. first measure for controlling smallpox
    variolation: injection of pus under skin
  6. what is ring vaccination?
    Vaccinating people in close contact with the disease to prevent it spreading
  7. Why is variola virus still under testing? (2)
    • developing a safer vaccine
    • drugs that prevent smallpox because of the fear of bioterrorism
  8. 6 reasons why smallpox eradication was possible
    • acute disease
    • no animal reservoir
    • easily diagnosed
    • WHO determination
    • good vaccine: potent at single dose, low cost, abundant, heat stable, easy to administer, induced both cellular and humoural immunity
    • no antigenic variation
  9. what is the only other infectious disease to have been eradicated?
    Rinderpest, by vaccination
  10. What did Pasteur produce vaccines for in 1885? (2) how?
    • Anthrax and rabies
    • drying spinal cord of rabbits with rabies so that infectivity had pretty much gone but virus antigen remained
  11. How is rabies vaccine produced now?
    • Grown in cell culture
    • treated with B-propriolactone to inactivate virus infectivity
  12. How did Theiler produce a vaccine for yellow fever?
    Passing virus multiple times: retained infectivity but had lost virulence - 1st live attenuated vaccine
  13. How are influenza vaccines produced now?
    Grown in eggs, purifying HA and NA and using these with an adjuvant: a subunit vaccine
  14. How were the 2 types of polio vaccines created?
    • Salk: purification, chemical inactivation, injection
    • Sabin: serial passage - live attenuated
  15. What was the first genetically engineered vaccine? How was it made?
    Hep B: expressing Hep B surface antigen (HBsAg) in yeast, purifying, and injecting with adjuvant
  16. 3 types of vaccine
    • live
    • dead
    • passive
  17. 2 types of live vaccines, with examples. Pros and cons.
    • Attenuated mutants of wild type (yellow fever, MMR, Sabin polio)
    • live related: vaccinia for smallpox, turkey herpes virus for Marek's disease (chicken tumours)
    • Pros: cellular and humoural immunity, self replicating (cheaper), long lived
    • Cons: can mutate to become virulent, may be dangerous in immunocompromised hosts
  18. 2 types of dead vaccines, with examples. Pros and cons.
    • Purified and inactivated whole virus preparations (Salk polio)
    • subunit vaccines from whole vaccine/genetically engineered parts (influenza, HBV, HPV)
    • pros: safe
    • cons: multiple injection, only antibody responses (not cellular)
  19. describe passive immunisation
    • administration of antibodies (human monoclonal)
    • eg after exposure to rabies or HBV as neonate
    • pros: immediate protection
    • cons: serum sickness (formerly), short lived
  20. 4 new approaches to vaccine development
    • rational attenuation: specific modification/deletion f a virus gene that confers virulence eg thymidine kinase deletion in pseudorabies virus
    • vector-mediated sub-unit delivery: rabies glycoprotein gene into vaccina virus for foxes
    • virus-like particles: eg HPV 16 and 18 vaccine is made of only capsid, with no genome
    • nucleic acid immunisation: prime-boost. Inject DNA encoding the desired antigen under a strong promoter. Boost with a live virus vector expressing the same antigen.
  21. what is the main challenge with antiviral chemotherapy? How is this dealt with?
    • Specificity: viral things not human
    • target nucleic acid polymerases, proteases, influenza NA, HIV integrase
  22. Describe AZT
    • azidothymidine
    • made into dNTP form by cellular kinases
    • incorporated into DNA by reverse transcriptase
    • chain terminator (no 3' hydroxyl)
  23. Describe ACV
    • Acyclovir
    • made into dNTP by HSV thymidine kinase
    • chain terminator
  24. 4 types of antiviral chemotherapy
    • AZT
    • ACV
    • protease inhibitors (for cleaving gag and pol of HIV
    • Tamiflu (Oseltamivir phosphate): analogue of sialic acid, inhibits NA. Agglutination happens.
  25. 4 useful things about viruses
    • studying cell biology and immunology
    • gene therapy
    • vaccine development
    • cancer therapy (oncolytic viruses)

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