The Immune System

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Immunotherapies and Activation Immunotherapies
Points to ponder in this Module

• What are immunotherapies?
• What are activation immunotherapies?
• What are suppression immunotherapies?
• How is the immune system activated during
  vaccination?
• What are the types of vaccines?
• What are the advantages and disadvantages of
  vaccines?
• How is the immune system activated during the
  cancer immunotherapies?
• What are the types of cancer immunotherapies?

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Immunotherapy

• Manipulation of the immune system
• Activation immunotherapies Immunotherapies
  designed to elicit or amplify the immune response
  (vaccination, cancer immunotherapies)
• Suppression immunotherapies Immunotherapies that
  reduce or suppress the immune responses
  (Inhibition of inflammation,
  immuno-suppression during organ transplantations)

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Vaccination

• Activation of the immune system by an exposure to
  antigen that stimulates the adaptive immunity
• Once the adaptive immunity is activated, memory
  cells are formed
• If we are exposed to the same antigen (pathogen)
  in the future, we are protected - immune

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Or in more detail.
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Even 2,500 Years Ago, People Knew Immunity
Worked.

• Greek physicians noticed that people who survived
  smallpox never got it again.
• The insight Becoming infected by certain
  diseases gives immunity.

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Variolation The Earliest Smallpox Vaccines

• The idea of intentionally inoculating healthy
  people to protect them against smallpox dates
  back to China in the sixth century. Chinese
  physicians ground dried scabs from smallpox
  victims and applied the mixture to the noses of
  healthy people.
• In Africa and the Near East, matter taken from
  the smallpox pustulesraised lesions on the skin
  the contain pusof mild cases was inoculated
  through a scratch in an arm or vein. The goal was
  to cause a mild infection of smallpox and
  stimulate an immune response that would give the
  person immunity from the natural infection. This
  process was called variolation.
• Unfortunately, the amount of virus used would
  vary and some would contract smallpox from the
  inoculation and die. Nonetheless, this preventive
  approach became popular in China and South East
  Asia, and probably saved thousands of lives.

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History of Smallpox

• First appeared in Northeastern Africa around
  10,000 BC
• Skin lesions on mummies
• Case fatality, 20-60
• Scars, blindness
• Infants, 80-98 CF

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Vaccination History

• 18th century Jenner used cowpox as a vaccine
  against smallpox
• 19th century Microorganisms causing diseases
  were first isolated, and vaccines started to be
  developed
• 20th century It seemed that thanks to
  vaccination and antibiotics, the problem of
  infectious diseases was solved
• 20th/21st century Emergence of new (viral)
  diseases (AIDS, SARS), against which development
  of effective vaccines is very difficult

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Vaccination first used against smallpox
(variola).
In 1796, Edward Jenner, a doctor in rural
England, showed how inoculation with cowpox virus
offered protection against the related smallpox
virus (variola) with less risks than the earlier
methods using live smallpox virus. Noting that
milkmaids did not generally get smallpox, Jenner
theorized that the blisters which milkmaids
received from cowpox (a disease similar to
smallpox, but much less virulent) protected them
from smallpox. In 1796, Jenner tested his theory
by inoculating a young boy with material from the
cowpox blisters. This produced a fever and some
uneasiness but no great illness. Later, he
exposed the boy to smallpox. Luckily, the boy
survived, and the technique since then has
spread. Vaccinia- mild disease caused by cowpox
? Jenner called this process vaccination. Since
then, number of smallpox cases dramatically
decreased, with the last cases being seen in
1970s.
Edward Jenner
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Elimination of smallpox by vaccination
The last reported case of endemic smallpox
occurred in Somalia (in 1977).
(No need to memorize the dates)

• Stocks of variola virus have been retained in
  two WHO-approved collaborating centers the
  Centers for Disease Control and Prevention (CDC)
  in Atlanta, and the Russian Institute of
  Virology in Novosibirsk.
• There are concerns that not all the smallpox
  preparations developed can be accounted for, and
  that unknown stores of variola virus may exist.

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The End of Smallpox

• 1967
• 10 million cases
• 2 million deaths
• 1972
• Last U.S. vaccination
• Oct. 26, 1977, last case of smallpox
• May 8, 1980, official declaration by WHO -
  Smallpox Eradicated!

Last case of Variola, Somalia 1977
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Vaccination
In vaccination, the adaptive immune response is
manipulated in an antigen-specific manner, to
stimulate lymphocyte-mediated protective immunity.

• Viral
• Vaccination
• Bacterial

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Viral vaccination

• The first viral vaccines were made against
  smallpox (since it used to be No. 1 killer) from
  people who had a less severe form of the disease
  (and survived).
• ? These first vaccines were made from a live
  virus ? they often resulted in a death of the
  vaccinated person (1100, which was still much
  more favorable than 13 survival for smallpox).
• Jenners innovation was to use the related
  harmless cowpox virus against smallpox. This
  strategy is not possible for most pathogens,
  since very few pathogens have safe counterparts.
• ? Most viral vaccines used today are composed of
  viruses that have been weakened or killed.

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Vaccination with cowpox virus elicits
neutralizing antibodies that react with antigenic
determinants shared with smallpox virus
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Types of current viral vaccines

• Killed (inactivated) vaccines Prepared by heat
  or formalin treatment or irradiation. Only
  viruses whose nucleic acids can be reliably
  inactivated make suitable killed virus vaccines.
  Examples flu
• Live-attenuated vaccines Prepared from a live
  virus that has mutated so that it has a reduced
  ability to grow in human cells and is no longer
  pathogenic. These vaccines are usually more
  effective than the killed virus vaccines (because
  virus can still replicate, thus mimicking real
  infection). Most viral vaccines used today are
  live attenuated vaccines.
  Examples
  Measles, mumps, rubella (MMR) polio-Sabine
• Subunit vaccines Prepared against surface
  component of the virus, usually using recombinant
  DNA technology.
• Examples hepatitis B virus (HBV)

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Useful vaccines against some viral diseases have
yet to be found

• Vaccines against HIV and SARS have yet to be
  developed.
• In case of HIV, about 20 different HIV vaccines
  are at different stages of development.
• Vaccination against polio or measles was
  facilitated by analysis of protective immune
  responses from people who survived the infection.
  However, in the case of HIV, there is no
  documented case of a person who has recovered
  from acute infection ? mechanisms that terminate
  HIV infection are unknown.
• Another hurdle in development of HIV vaccine is
  the frequent mutation of the HIV virus.

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Types of current bacterial vaccines

1. Killed vaccines
   Examples
   Typhus
2. Live-attenuated vaccines The number of these
   vaccines against bacteria remains small.
   
   Examples Tuberculosis (Bacille Calmette-Guerin
   BCG, used in Europe)
3. Subunit vaccines Prepared against cell wall
   (polysaccharide) components of bacteria.
   
   Examples Meningitis
4. Toxoid vaccines Prepared against toxic proteins
   that are secreted by some bacteria and cause the
   disease. Vaccines against these bacteria are
   prepared by inactivating the toxins the
   inactivated toxins are called toxoids.
   
   Examples diphtheria, tetanus (DPT
   combination vaccine against diphtheria, tetanus
   and pertussis whooping cough)

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Bacille Calmette-Guerin - the current vaccine for
tuberculosis

• The history of BCG is tied to that of smallpox.
  After the success of vaccination in preventing
  smallpox, it was hypothesized that infection with
  bovine tuberculosis (Mycobacterium bovis) might
  protect against infection with human tuberculosis
  (Mycobacterium tuberculosis).
• BCG contains a live attenuated strain of
  Mycobacterium bovis. It was originally isolated
  from a cow with tuberculosis by Calmette and
  Guerin who worked in Paris at the Institute
  Pasteur. This strain was sub-cultured for many
  years.
• BCG was first used as a vaccine in 1921. Since
  then, the vaccine has been widely used in Africa,
  Asia and Europe. Today, it is estimated that more
  than 1 billion people have received BCG.
• BCG immunization causes pain and scarring at the
  site of injection. BCG is very efficacious
  against tuberculosis in the pediatric age group.
  If BCG is accidentally given to an
  immunocompromised patient (e.g., an infant with
  SCID or HIV), it can cause life-threatening
  infection.
• Having had a previous BCG vaccination is a
  frequent cause of a false positive Mantoux test
  (Tuberculin Sensitivity Test or PPD test).

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Role of adjuvants in vaccination

• A prerequisite for a good immune response is a
  state of inflammation.
• During infection, this is initiated by microbial
  products that activate macrophages and recruit
  inflammatory cells.
• In general, immunization with purified proteins
  leads to a poor immune response.
• This response can be enhanced by substances that
  induce inflammation, such as different lipids.
• These substances (that induce local inflammation
  and immune response) are called adjuvants.

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The strongest and most effective adjuvant used in
experimental immunology
The only adjuvants approved for use in humans
22
Are vaccines safe?

• The best vaccines are the live-attenuated
  vaccines, however because of their similarity to
  live pathogens, they can (although rarely) cause
  the disease.
• Example the Sabine polio vaccine that markedly
  reduced the incidence of polio. However, this
  vaccine can cause polio (in 3 people per million)
  ? pressure to develop safer vaccines.
• Today in the U.S., this vaccine is no longer used
  and has been replaced by a killed Inactivated
  Polio Vaccine (IPV).

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Sabine Polio Vaccine illustrates the pluses and
minuses of live vaccines

• Attenuated by a passage in monkey kidney cells
• Eliminated polio
• Associated with an increased risk
  (13,000,000) of developing a real polio
  infection
• Replaced by an Inactivated Polio Vaccine (IPV)
  that has no risks

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Vaccines have yet to be found for many chronic
pathogens

• Vaccines have been developed mainly against acute
  infections that resolve within several weeks
  either by a successful recovery (documenting that
  infection can be cleared by immune system) or by
  the death of the patient.
• Vaccines have yet to be developed against many of
  the chronic diseases that are characterized by
  subversion of the immune system by the pathogen.
  In chronic diseases, there is little evidence
  that immune system can clear the infection ?
  mechanisms terminating the chronic infection are
  unknown (HIV/AIDS).

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HPV Cervical caner
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Figure 12-8
SARS
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Development of vaccines and funding of
health-related research

• Majority of health-related research is federally
  funded by National Institutes of Health (NIH).
• Occurrence and spread of infectious diseases is
  being monitored by the Center for Disease Control
  (CDC in Atlanta).
• Vaccine development is funded by the National
  Institute of Allergy and Immunology Diseases
  (NIAID) of NIH, and by biotech companies (Merck,
  Pfizer).
• All vaccines have to be approved by the federal
  Food and Drug Administration (FDA).

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Cancer Immunotherapy

• Can immune stimulators combat cancer?
• Which forms of immunotherapy can be used?
• Is vaccination effective against established
  tumors?

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During oncogenesis, some of the antigens on the
cancer cell surface change ( tumor antigens).
Some of these tumor antigens are shed from the
cancer cells. These shed antigens prompt action
from cytotoxic T cells, NK cells, and
macrophages.
According to the theory of immune surveillance,
patrolling cells of the immune system provide
continuous surveillance, catching and eliminating
cells that undergo malignant transformation.
Tumors develop when this immune surveillance
breaks down or is overwhelmed.
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Immune responses to tumors
Ab / ADCC / cytokine attack
Th
B
Th cells stimulate other T/B cells
APC recruits T cells able to recognize tumor
antigens
CTL recognize and destroy other tumor cells
T
T
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Cancer therapies

• Surgery
• Chemotherapy
• Radiation therapy
• Immunotherapy
• Types of immunotherapies include
• Cancer vaccines (active specific immunotherapies)
  
• Monoclonal antibody therapy (passive specific
  immunotherapies)
• Nonspecific immunotherapies (cytokines)

Classical New, emerging
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Immunotherapies

• Cancer vaccines (Active Specific Immunotherapy)
• Contain cancer cells, parts of the cancer cells,
  or pure tumor-associated antigens (antigens
  expressed only on tumor cells but not on healthy
  cells).
• Induce production of tumor-specific antibodies
  and stimulate killer CD8 T cells to attack the
  cancer cells.
• So far used only in clinical trials not approved
  for general use.
• Monoclonal Antibody Therapy (Passive Specific
  Immunotherapy)
• Monoclonal antibody therapy is a passive
  immunotherapy because the antibodies against the
  tumor-associated antigens are produced outside
  the body (in the lab) rather than by the immune
  system. This type of therapy can be effective
  even if the immune system is weakened.
• Approved for treatment of certain cancers (breast
  cancer, leukemias).
• Nonspecific Immunotherapies (Cytokines)
• Stimulate the immune system in a very general
  way.
• Interleukin-2 (IL-2) Stimulates the ability of
  NK cells to kill the cancer cells. Used to treat
  melanomas and kidney cancers.
• Interferons Slow the growth of cancer cells
  stimulate the cancer killing ability of NK cells.
  Used to treat leukemias, lymphomas and melanoma.

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Passive immunotherapy

• Administration of monoclonal antibodies, which
  target either tumor-specific or over-expressed
  antigens.
• Kills tumor cells in several ways

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Immunotherapy
Radioisotope
Herceptin
Growth factor
Herceptin blocks receptor
Antibody
Antigen
Breast cancer cell
Lymphoma cell
Lymphoma cell destroyed
Growth slows
A new approach to cancer therapy uses antibodies
that have been specially made to recognize
specific cancers. When coupled with natural
toxins, drugs, or radioactive substances, the
antibodies seek out their target cancer cells and
deliver their lethal load.
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Antibody-based immunotherapy
Name Malignancy Target
Rituxan B cell lymphoma CD20
Herceptin Breast, lymphoma Her-2/neu
Campath B-CLL CD52
Erbitux Colo-rectal EGFR
Avastin Colo-rectal VEGF
Name Malignancy Target
Mylotarg AML CD33 (calicheamicin)
Bexxar B cell lymphoma CD20 (131In / 90Y)
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Active immunotherapies

• Cytokines- IL-2 / IFNs / TNFa
• Vaccination strategies- single peptide multi
  ple peptides HSP complexes
  whole tumor cells
• Cell-based therapies - tumor-specific
  CTL tumor-derived APC DC priming

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HPV Antibodies (Vaccines) Prevent Infection and
Cervical Cancer

• Human papillomavirus (HPV) is the most common
  sexually transmitted virus in the United States.
  At least 70 percent of sexually active persons
  will be infected with HPV at some time in their
  lives. HPV infects both men and women.
• Over 99 percent of cervical cancer cases are
  linked to long-term infections with high-risk
  HPV.
• The vaccination protects a person from future
  infection by the high-risk HPV
• After the vaccination, if an exposure occurs,
  the vaccinated persons antibodies against the
  HPV opsonize the virus and prevent it from
  attachment to the host epithelial cells..

Papillomavirus
Antibodies
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Humanized monoclonal antibodies
0

• Use of mouse monoclonal antibodies for
  immunotherapy in humans is limited by immune
  responses in humans against the foreign mouse
  antibody proteins.
• Complementarity determining regions (CDR) of
  mouse monoclonal antibodies can be grafted onto
  the framework of a human immunoglobulin.
  Recombinant antibodies are less immunogenic and
  induce less allergic reactions.

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Dendritic cell therapy

• Dendritic cells are key components of the
  adaptive immune response
• APC function with ability to direct IR
  (activation/tolerance)
• Present in peripheral blood as circulating
  subtypes (lt0.4 TWC)

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Dendritic cell sources for therapy
Copland et al (2005) Cancer Immunol. Immunother.
54297
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DC-based therapy
Currently in Phase II and Phase III trials for
melanoma, prostatic carcinoma and lymphoma.
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Cancer Immunotherapy Dendritic Cells That
Attack Cancer
By modifying dendritic cells, researchers are
able to activate T cells that attack the cancer
cells. Because a tumor antigen alone is not
enough to result in a strong immune response,
cytokines are first fused to a tumor antigen with
the hope that this will send a strong antigenic
signal. Next, the patient's dendritic cells are
isolated and grown in the incubator to let them
take up this fused cytokine-tumor antigen. This
enables the dendritic cells to mature and
eventually display the same tumor antigens as
appear on the patient's cancer cells. When these
special mature dendritic cells are given back to
the patient, they present their newly acquired
tumor antigens to the T cells that can respond
and attack the patient's cancer cells.
Dendrion FDA approval for prostate cancer
treatment