Active and passive immunization Immunity to infectious microorganisms: 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)

Passive immunization Conditions for use of 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

Cautions Anti-isotype or allotype response Anti-isotype or allotype response

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

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

Whole –organism vaccines Attenuated vaccines

Advantages and disadvantages Provide prolonged immune system exposure Provide prolonged immune system exposure Increased immunogenicity Increased immunogenicity Production of memory cells Production of memory cells Single immunization Single immunization Inducing a humoral and cell mediated immunity Inducing a humoral and cell mediated immunity They elicit all the innate and adaptive immune responses They elicit all the innate and adaptive immune responses Live attenuated viral vaccines are usually more effective 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

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

polysaccharide capsule Inability to activate Th cells Inability to activate Th cells May be poorly immunogenic in infants 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)

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 CMI and humoral immunity

Recombinant vector vaccines

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

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

Future of DNA vaccines Malaria,AIDS,influenza and HSV 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. 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.