Active and passive immunizationActive and passive immunization

Immunity to infectious microorganisms:Immunity to infectious microorganisms:

1- Active immunization1- Active immunization

*** natural processes *** natural processes

*** artificial (vaccines) *** artificial (vaccines)

2- Passive immunization2- Passive immunization

*** natural processes (by transfer of maternal Abs *** natural processes (by transfer of maternal Abs across placenta to the fetus or by colostrum and milkacross placenta to the fetus or by colostrum and milk

*** artificial (antisera)*** artificial (antisera)

Passive immunizationPassive immunization

Conditions for use of passive immunizationConditions for use of passive immunization*deficiency in synthesis of Ab*deficiency in synthesis of Ab** exposure or likely exposure to a disease** exposure or likely exposure to a disease*** infection by pathogens*** infection by pathogens(botulism,tetanus,diphtheria,hepatitis,measles, (botulism,tetanus,diphtheria,hepatitis,measles,

rabies and also protection from poisonous rabies and also protection from poisonous snake ,insect bites).snake ,insect bites).

****immediate protection to travelers or health ****immediate protection to travelers or health care workerscare workers

CautionsCautions

Anti-isotype or allotype responseAnti-isotype or allotype response

Success of active immunizationSuccess of active immunization

If the infectious agent does not establish If the infectious agent does not establish latencylatency

Does not undergo any antigenic variationDoes not undergo any antigenic variation Does not interfere with the host immune Does not interfere with the host immune

responseresponse Infectious agent must be limited to human hostInfectious agent must be limited to human host

Designing vaccinesDesigning vaccines

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

Whole –organism vaccinesWhole –organism vaccines

Attenuated vaccinesAttenuated vaccines

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

Whole –organism vaccinesWhole –organism vaccines

inactivated or killedinactivated or killed است **** **** نياز مورد آنها تجويز بار است چند نياز مورد آنها تجويز بار چند

ميكنند ** ** تحريك را هومورال ميكنند ايمني تحريك را هومورال ايمني

وجود عوامل از برخي نشدن فعال غير وجود احتمال عوامل از برخي نشدن فعال غير احتمالدارددارد

polysaccharide capsulepolysaccharide capsule

Inability to activate Th cellsInability to activate Th cells May be poorly immunogenic in infantsMay be poorly immunogenic in infants

Conjugate the antigen to protein carrier to form Conjugate the antigen to protein carrier to form conjugate vaccines:conjugate vaccines:

*Antigen vaccines*Antigen vaccines

Recombinant DNA vaccinesRecombinant DNA vaccines

(Hepatitis B ,HSV,foot and mouth disease virus (Hepatitis B ,HSV,foot and mouth disease virus and papiloma virus)and papiloma virus)

Live viral vector vaccinesLive viral vector vaccines

* The Gene introduce into attenuated virus or * The Gene introduce into attenuated virus or bacteriabacteria

* The attenuated organism as a * The attenuated organism as a vector ,replicating within the host vector ,replicating within the host

* Expressing the gene product of the pathogen.* Expressing the gene product of the pathogen.• CMI and humoral immunityCMI and humoral immunity•

Recombinant vector vaccinesRecombinant vector vaccines

DNA vaccinesDNA vaccines

Plasmid DNA encoding antigenic proteins is Plasmid DNA encoding antigenic proteins is injected directly into the muscle of recipientinjected directly into the muscle of recipient

Muscle and dendritic cells take up the DNA Muscle and dendritic cells take up the DNA and the Ag is expressedand the Ag is expressed

Advantages and disadvantagesAdvantages and disadvantages

Leading to humoral and cellular immunity Leading to humoral and cellular immunity The encoded protein is expressed in its natural formThe encoded protein is expressed in its natural form DNA vaccines cause prolonged expression of the DNA vaccines cause prolonged expression of the

Ag,which generates significant immunilogical Ag,which generates significant immunilogical memory.memory.

Refrigeration is not required,lowers the cost and Refrigeration is not required,lowers the cost and complexity of deliverycomplexity of delivery

The same plasmid vector can be custom tailored to The same plasmid vector can be custom tailored to make a variety of proteins.make a variety of proteins.

Eliciting an innate immune responseEliciting an innate immune response

Future of DNA vaccinesFuture of DNA vaccines

Malaria,AIDS,influenza and HSVMalaria,AIDS,influenza and HSV Future experimental trials of DNA vaccines Future experimental trials of DNA vaccines

will mix genes for antigenic proteins with will mix genes for antigenic proteins with those for cytokines that direct the immune those for cytokines that direct the immune response to the optimum pathway.response to the optimum pathway.