Immunoprevention

Definition By using immunological agents to construct, improve or inhibit immune response, people can prevent some diseases.

 Artificial immunization (active and passive)  Development of new vaccines  Application of vaccines

Active Immunization Passive Immunization Administration of an antigen (usually as a modified infectious agent or toxin) Administration of antibody, or antibody-contained serum for passive protection of the host

Acquisitions of active and passive immunity

 Active Immunization  Elicit protective immunity: Ab, cellular responses  Elicit immunologic memory  Methods: natural infection, vaccines

Principles of active Immunization

Basic features of vaccine Safe Effective Practical

Types of vaccines 1.Attenuated organisms (Measles) 2.Inactivated organisms (Hepatitis A vaccine) 3.Toxoid (Diphtheria, Tetanus)

Whole organisms

Some conditions should not use active immunization 1. Fever 2. Severe heart disease 3. Acute transmitted infection 4. Cancer 5. Kidney disease 6. TB infection 7. Grave’s disease 8. Diabetes 9. Immunodeficiency disease

 Passive Immunization Transfer of preformed antibodies The protection is transient No memory response

There are some conditions that warrant the use of passive immunization  Deficiency of antibody synthesis  Exposure or likely exposure to a disease that will cause complications  Infection by pathogens whose effects may be ameliorated by antibody

Weakness of passive immunization 1.Isotypic determinants of the foreign antibody (IgE production) 2.Formation of immune complex (IgG, IgM) 3.Anti-allotype responses

 Planned Immunization Childhood immunizations have already been a part of routine health care.

Planned Immunization Schedule in China (1) AgeType of vaccines Primary Immunization BirthBCG vaccine, Hepatitis B virus vaccine (1 st ) 1 monthHepatitis B virus vaccine (2 nd ) 2 months Poliovirus vaccine ( 1 st ) 3 monthsPoliovirus vaccine ( 2 nd ), DTP (1 st ) 4 monthsPoliovirus vaccine (3 rd ), DTP (2 nd ) 5 monthsDTP (3 rd ) 6 monthsHepatitis B virus vaccine (3 rd ), Meningococcal polysaccharide vaccine 8 monthsMeasles virus vaccine 1 yearJapanese encephalitis vaccine (1 st and 2 nd )

Planned Immunization Schedule in China (2) AgeType of vaccines “Booster” /reimmunization 1.5 yearsDTP, Measles virus vaccine, poliovirus vaccine, Meningococcal polysaccharide vaccine 2 yearsJapanese encephalitis vaccine 3 yearsJapanese encephalitis vaccine 4 yearsPoliovirus vaccine 5 yearsDTP, Measles virus vaccine, BCG vaccine, Japanese encephalitis vaccine

 Development of new vaccines Subunit vaccines Conjugate vaccines Synthetic peptide vaccines Recombinant vector vaccines Gene-engineering vaccines DNA vaccines Transgenic plant vaccines

Subunit vaccines The current vaccine for Streptococcus pneumoniae, which causes pneumococcal pneumonia, consists of 23 antigenically different capsular polysaccharides. The vaccine induces formation of opsonizing antibodies and is now on the list of vaccines recommended for all infants. The vaccine for Neisseria meningitidis, a common cause of bacterial meningitis, also consists of purified capsular polysaccharides. One limitation of polysaccharide vaccines is their inability to activate Th cells.

Involve Th cells directly in the response to a polysaccharide antigen conjugate the antigen to some sort of protein carrier. For example, the vaccine for Haemophilus influenzae type b (Hib), the major cause of bacterial meningitis in children less than 5 years of age, consists of type b capsular polysaccharide covalently linked to a protein carrier, tetanus toxoid. Conjugated vaccines

Synthetic peptide vaccines The use of synthetic peptides as vaccines has not progressed as originally projected. Peptides are not as immunogenic as proteins, and it is difficult to elicit both humoral and cellular immunity to them

Multivalent Vaccines

Recombinant vector vaccines Genes that encode major antigens of specially virulent pathogens can be introduced into attenuated viruses or bacteria. The attenuated organism serves as a vector, replicating within the host and expressing the gene product of the pathogen. Salmonella typhimurium

Recombinant adenovirus for tumor

Genetic engineering vaccines Theoretically, the gene encoding any immunogenic protein can be cloned and expressed in bacterial, yeast, or mammalian cells using recombinant DNA technology. This vaccine was developed by cloning the gene for the major surface antigen of hepatitis B virus (HBsAg) and expressing it in yeast cells.

Plasmid DNA encoding a protein antigen from a pathogen can serve as an effective vaccine inducing both humoral and cell- mediated immunity. DNA vaccines

DNA vaccines induce humoral and cellular immunity

Transgenic plant vaccines

 Application of vaccines 1. Prevention of infectious disease 2. Prevention of tumor 3. Others (Prevention of conception, treatment of drug dependency)

Review questions 1. What are the advantages and disadvantages of using attenuated organisms as vaccines? 2. A young girl who had never been immunized to tetanus stepped on a rusty nail and got a deep puncture wound. The doctor cleaned out the wound and gave the child an injection of tetanus antitoxin. a. Why was antitoxin given instead of a booster shot of tetanus toxoid? b. If the girl receives no further treatment and steps on a rusty nail again 3 years later, will she be immune to tetanus?