Immunology the Basis of Vaccinology

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Immunology the Basis of Vaccinology
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Behavioral Objectives

• Differentiate between the functions of innate and
  adaptive immune systems.
• Discuss the roles of antigen presenting cells, T
  cells and B cells in immunity
• Classify the different types of vaccines.
• Discuss why infant immunization presents special
  problems

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The immune system

• Innate immunity
• Adaptive immunity

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Purpose of the Immune System

• To prevent infectious diseases
• To cure infectious diseases
• (experiments in nature-boy in the bubble,
  enhanced susceptibility of burn patients and
  patients receiving chemotherapy to infection,
  lack of immunity in naïve populations.)

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Characteristics of the IMMUNE SYSTEM

• Innate immunity
• -1st line of defense
• -provides initial defense against
• infection
• -relatively nonspecific
• -not enhanced by immunization
• -necessary for the establishment
• and enhancement of adaptive
• immunity

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The Role of the Innate Immune System in Adaptive
Immune Responses

• Antigen recognition by professional antigen
  presenting cells dendritic cells,macrophages and
  B cells via PAMPS and TOLL-like recptors
• Antigen processing presentation by MHC class I
  and MHC class II molecules.
• Modulation of the adaptive immune response by
  co-stimulation and cytokine secretion.
• Effector functions induced by components of the
  adaptive immune response

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• Adaptive immunity
• -develops slowly
• -broad activity
• -high degree of specificity
• -enhanced by immunization
• -activity heightened by cross talk with
• the Innate Immune system via cytokines
• ( chemical signals that change the
• behavior of other cell types)

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The adaptive immune system-the target of
vaccination

• Cells Effector function
• B lymphocytes Antibodies
• T lymphocytes Cytokines
• Cytoxicity

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Successful Immunization

• Requires the activation of T B lymphocytes
• T cells have receptors that specifically
  recognize antigenic epitopes presented by MHC
• B cells recognize proteins by receptors that
  specifically bind epitopes in that protein
• Clonal expansion (proliferation)
• Differentation to provide effector functions and
  immunologic memory.

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• T cells
• CD4 cells provide help to
• other cells via cytokines
• CD8 cells are cytotoxic cells
• can also provide help
• B cells
• produce different isotypes of
• antibody which function
• differently depending on Fc
• region

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Principles of Vaccination
Immunity

• Self vs. nonself
• Protection from infectious disease
• Usually indicated by the presence of antibody
• Very specific to a single organism

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Principles of Vaccination
Active Immunity

• Protection produced by the person's own immune
  system
• Usually permanent
• Protection transferred from another person or
  animal
• Temporary protection that wanes with time

Passive Immunity
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Principles of Vaccination
Antigen

• A live or inactivated substance (e.g., protein,
  polysaccharide) capable of producing an immune
  response
• Protein molecules (immuno-globulin) produced by B
  lymphocytes to help eliminate an antigen

Antibody
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Passive Immunity

• Transfer of antibody produced by one human or
  other animal to another
• Temporary protection
• Transplacental most important source in infancy

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Monoclonal Antibody

• Derived from a single type, or clone, of
  antibody-producing cells (B cells)
• Antibody is specific to a single antigen or
  closely related group of antigens
• Used for diagnosis and therapy of certain cancers
  and autoimmune and infectious diseases

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Vaccination

• Active immunity produced by vaccine
• Immunity and immunologic memory similar to
  natural infection but without risk of disease

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Classification of Vaccines

• Live attenuated
• viral
• bacterial
• Inactivated

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Inactivated Vaccines
Whole

• viruses
• bacteria
• protein-based
• toxoid
• subunit
• polysaccharide-based
• pure
• conjugate

Fractional
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• Principles of Vaccination

General Rule
The more similar a vaccine is to the
disease-causing form of the organism, the better
the immune response to the vaccine.
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Live Attenuated Vaccines

• Attenuated (weakened) form of the "wild" virus or
  bacterium
• Must replicate to be effective
• Immune response similar to natural infection
• Usually effective with one dose

except those administered orally
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Live Attenuated Vaccines

• Severe reactions possible
• Interference from circulating antibody
• Fragile must be stored and handled carefully

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Live Attenuated Vaccines

• Viral measles, mumps, rubella,
  varicella/zoster, yellow fever, rotavirus,
  intranasal influenza, rotavirus,
  vaccinia
• Bacterial BCG, oral typhoid

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Inactivated Vaccines

• Cannot replicate
• Generally not as effective as live vaccines
• Less interference from circulating antibody than
  live vaccines
• Generally require 3-5 doses
• Immune response mostly humoral
• Antibody titer may diminish with time

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Inactivated Vaccines
Whole-cell vaccines

• Viral polio, hepatitis A, rabies,
  influenza
• Bacterial pertussis, typhoid cholera,
  plague

not available in the United States
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Inactivated Vaccines
Fractional vaccines

• Subunit hepatitis B, influenza, acellular
  pertussis, human papillomavirus, anthrax
• Toxoid diphtheria, tetanus

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Pure Polysaccharide Vaccines

• Not consistently immunogenic in children younger
  than 2 years of age
• No booster response
• Antibody with less functional activity
• Immunogenicity improved by conjugation

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Polysaccharide Vaccines
Pure polysaccharide

• pneumococcal
• meningococcal
• Salmonella Typhi (Vi)
• Haemophilus influenzae type b
• pneumococcal
• meningococcal

Conjugate polysaccharide
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Problems Associated with Infant Immunization

• Presence of maternal antibody
• complex with vaccine antigens to prevent
  interaction with B cell receptors.
• -Killing live vaccine organisms
• Immaturity of infant immune
• system.

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National Immunization ProgramContact Information

• Telephone 800.CDC.INFO
• Email nipinfo_at_cdc.gov
• Website www.cdc.gov/nip