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

SafeEffective 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. Fever2. Severe heart disease3. Acute transmitted infection4. Cancer5. Kidney disease6. TB infection7. Grave’s disease8. Diabetes 9. Immunodeficiency disease

Passive Immunization

Transfer of preformed antibodiesThe protection is transientNo 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)Age Type of vaccines

Primary Immunization

Birth BCG vaccine, Hepatitis B virus vaccine (1 st)

1 month Hepatitis B virus vaccine (2 nd)

2 months Poliovirus vaccine ( 1st)

3 months Poliovirus vaccine ( 2nd), DTP (1st)

4 months Poliovirus vaccine (3rd), DTP (2nd)

5 months DTP (3rd)

6 months Hepatitis B virus vaccine (3rd),Meningococcal polysaccharide vaccine

8 months Measles virus vaccine

1 year Japanese encephalitis vaccine (1st and 2nd)

Planned Immunization Schedule in China (2)

Age Type of vaccines

“Booster” /reimmunization

1.5 years DTP, Measles virus vaccine, poliovirus vaccine, Meningococcal polysaccharide vaccine

2 years Japanese encephalitis vaccine

3 years Japanese encephalitis vaccine

4 years Poliovirus vaccine

5 years DTP, 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.

Salmonellatyphimurium

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

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 questions1. 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?