Download 19.Immunoprevention

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
Administration of an antigen (usually as a modified
infectious agent or toxin)
Passive Immunization
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.
2.
3.
4.
5.
6.
7.
8.
9.
Fever
Severe heart disease
Acute transmitted infection
Cancer
Kidney disease
TB infection
Grave’s disease
Diabetes
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)
Primary
Immunization
Age
Type of vaccines
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)
“Booster”
/reimmunization
Age
Type of vaccines
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.
 Conjugated vaccines
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.
 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.
DNA vaccines
Plasmid DNA encoding a protein antigen
from a pathogen can serve as an effective
vaccine inducing both humoral and cellmediated immunity.
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 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?