Active and passive immunization

1. Active and passive immunization • Immunity to infectious microorganisms: 1- Active immunization *** natural processes *** artificial (vaccines) 2- Passive immunization *** natural processes (by transfer of maternal Abs across placenta to the fetus or by colostrum and milk *** artificial (antisera)

2. Passive immunization • Conditions for use of passive immunization *deficiency in synthesis of Ab ** exposure or likely exposure to a disease *** infection by pathogens (botulism,tetanus,diphtheria,hepatitis,measles, rabies and also protection from poisonous snake ,insect bites). ****immediate protection to travelers or health care workers

3. Cautions • Anti-isotype or allotype response

4. Success of active immunization • If the infectious agent does not establish latency • Does not undergo any antigenic variation • Does not interfere with the host immune response • Infectious agent must be limited to human host

5. Designing vaccines • Whole –organism vaccines *Attenuated viruses and bacteria ** inactivated or killed • Purified antigen vaccines * polysaccharide capsule ** Toxoid *** Recombinant proteins • DNA vaccines • Recombinant vector vaccines

6. Whole –organism vaccines Attenuated vaccines

7. Advantages and disadvantages • Provide prolonged immune system exposure • Increased immunogenicity • Production of memory cells • Single immunization • Inducing a humoral and cell mediated immunity • They elicit all the innate and adaptive immune responses • Live attenuated viral vaccines are usually more effective *Possibility that they will revert to a virulent form ** complications similar to those seen in the natural disease

8. Whole –organism vaccines • inactivated or killed • **** چند بار تجويز آنها مورد نياز است ** ايمني هومورال را تحريك ميكنند احتمال غير فعال نشدن برخي از عوامل وجود دارد

9. polysaccharide capsule • Inability to activate Th cells • May be poorly immunogenic in infants Conjugate the antigen to protein carrier to form conjugate vaccines: *Antigen vaccines Recombinant DNA vaccines (Hepatitis B ,HSV,foot and mouth disease virus and papiloma virus)

10. Live viral vector vaccines * The Gene introduce into attenuated virus or bacteria * The attenuated organism as a vector ,replicating within the host * Expressing the gene product of the pathogen. • CMI and humoral immunity

11. Recombinant vector vaccines

12. DNA vaccines • Plasmid DNA encoding antigenic proteins is injected directly into the muscle of recipient • Muscle and dendritic cells take up the DNA and the Ag is expressed

13. Advantages and disadvantages • Leading to humoral and cellular immunity • The encoded protein is expressed in its natural form • DNA vaccines cause prolonged expression of the Ag,which generates significant immunilogical memory. • Refrigeration is not required,lowers the cost and complexity of delivery • The same plasmid vector can be custom tailored to make a variety of proteins. • Eliciting an innate immune response

14. Future of DNA vaccines • Malaria,AIDS,influenza and HSV • Future experimental trials of DNA vaccines will mix genes for antigenic proteins with those for cytokines that direct the immune response to the optimum pathway.