Active and passive immunization

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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

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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

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Whole organism vaccines

• inactivated or killed
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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
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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

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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

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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.