Applications of Immune
Responses
Chapter 17
Smallpox virus (or plague bacteria
[Yersina pestis])Smallpox
has killed more
people than any other infectious
disease
In the first half of the 1900s,
smallpox was killing 4 million
people worldwide each year
In 1958, the Soviet Union proposed
the global eradication of smallpox
by using a concerted vaccination
program
Smallpox infects only humans,
thus it could be eradicated
The program was started in the
late 1960s
Representation of the Effects of
Smallpox Vaccination
17.1 Principles of Immunizations
Vaccines safely elicit an adaptive (T cell and
B cell) immune response to pathogenic
microbes
In the process, they stimulate:
High-affinity antibodies
Class switching of antibodies (e.g., IgG, IgA)
Memory T cells and B cells
There are two types of vaccines
Inactivated (all bacteria and some viruses)
Attenuated-live (some viruses)
17.1 Principles of Immunizations
17.1 Principles of Immunizations
17.2 Vaccine and Immunization
Attenuation Procedures
Use of a similar virus that is non-
pathogenic
Vaccinia virus for smallpox
Relies upon cross-reactive immunity
Serial passage of pathogenic virus in cell
culture or embyronated eggs
Since cells and eggs have no immune
system, mutant viruses arise that lose
virulence
These viruses often retain their antigenic
determinants and thus elicit strong
17.2 Vaccine and Immunization
Procedures
Inactivation
Formalin (37% formaldehyde)
Cross-links proteins and nucleic acids
Used for toxoid (inactivated toxin)
vaccines, such as tetanus
β-propiolactone (BPL)
Nucleic acid mutagen
Breaks down rapidly
After 24 hours, virtually none exists in a
vaccine preparation
17.2 Vaccine and Immunization
Procedures
Inactivated vaccines
Whole-agent: entire microbe is in the vaccine
(inactivated poliovirus)
Toxoid: No cells, just their toxin(s) (tetanus)
Protein subunit vaccine: Only antigenic
subunits (acellular pertussis, hepatitis B)
Polysaccharide conjugate vaccines
By conjugating (covalently-linking) polysaccharide
antigens to proteins, the antigen becomes T-dependent
Haemophilus influenzae type b (Hib) and Streptococcus
pneumonia
Requires an adjuvant (e.g aluminum
hydroxide) to stimulate the innate immune
response
17.2 Vaccine and Immunization
Procedures
Advantages/Disadvantages of Attenuation
Advantages Disadvantages
Stronger antibody response More expensive
Perishable (live viruses);
Requires fewer boosters
requires refrigeration
Pathogenic revertants
Longer memory
(rare)
Stimulates MHC I
Possible contamination with
processing (cytotoxic T
other viruses
cells)
More closely resembles
natural infection
17.2 Vaccine and Immunization
Procedures
Advantages/Disadvantages of Inactivation
Advantages Disadvantages
Less Expensive Weaker antibody response
Stable (room temp storage) Requires mre boosters
No chance of infection Shorter memory
Contaminating viruses will Does not stimulate MHC I
also be inactivated processing (no Tc cells)
Does not resemble natural
infection
17.2 Vaccine and Immunization
Procedures
The importance of routine immunization in
children
Prior to the use of routine immunization,
thousands of children died or were disabled
by infectious diseases in the U. S.
Globally, measles still kills 700,000 people,
mostly children, per year
By immunizing, the incidence of the disease,
and consequently the microbe, decrease
substantially
For each infectious disease, a target vaccine
coverage rate is needed to reduce the
incidence of disease to nearly zero
For measles, this rate is 95%
17.2 Vaccine and Immunization
Procedures
Vaccine side effects
Risk
The risk of vaccination is not zero
But the risk of not vaccinating is far
greater
Those who do not immunize their children
take advantage of those who do assume the
risks
Vaccines and autism spectrum disorders
Large-scale population studies have shown
that the incidence of autism spectrum
disorders in vaccinated and unvaccinated
17.2 Vaccine and Immunization
Procedures
Japan’s experience with pertussis (whooping
cough)
1972: Mandatory vaccination at 3 months reduces the
incidence of pertussis to fewer than 300 cases per year
1973-74: Two children die shortly after vaccination
1974: Politicians change the first vaccination age to 2
years (instead of 3 months)
1979: Japan reports more than 13,000 cases of
pertussis with 41 deaths. Some surviving have
permanent neurological damage (which is what
pertussis toxins do)
1980: Japan returns to their previous vaccine schedule
and within a few years the incidence of pertussis
returns to 1972 levels
17.3 Principles of
Immunologic Testing
Antibodies are generated in response to
infection
The presence of antibodies in the blood
(serum) to a pathogen are highly suggestive
of infection
Detection of IgM indicates recent infection
Detection of IgG indicates recent or distant
infection
The study of blood antibodies is serology
17.3 Principles of
Immunologic Testing
Blood collection
Collect blood without anticoagulants
Allow to stand at room temp 30 min for
clot formation, then at 4° C for 1 hour for
contraction
Centrifuge the blood to separate clot from
serum
Aspirate the serum into a new tube
Dilute for testing (usually 1:20 for IgM or
1:100 for IgG testing)
17.3 Principles of
Immunologic Testing
Serological tests
Agglutination (e.g. influenza typing)
Precipitation
Immunofluorescence
Enzyme-linked immunosorbant assay
(ELISA)
Western blot
17.5 Using Labeled Antibodies to
Detect Antigen-Antibody Interactions
ELISA
Antigen: Coat known protein antigen to a solid-surface
Polyvinyl chloride (PVC) is commonly used because it
has a high affinity for proteins
Serum sample: Add patient’s serum and incubate 1 hour
If antibodies to the antigen are present, they will bind to
the antigen coated on the plate
Detection antibody: Wash with saline, then add an
enzyme-conjugated anti-human IgG antibody
If the patient has antibodies, they will be bound by the
detection antibody
Substrate: Wash with saline, then add substrate that turns
color in the presence of the enzyme