4.45 Flashcards
Two key public health measures have a major effect on lowering the
incidence of infectious disease:
(2)
- Public sanitation
2. Vaccines
- Public sanitation
Potable water supplies, sewage disposal, improvements in housing
- Vaccines
Prevention of infectious diseases by inducing immune responses
Vaccine -
An immunizing agent derived from microorganisms
Vaccines may consist of the following:
3
- Live, attenuated microorganisms
- Killed (irreversibly inactivated) microorganisms
- Products or derivatives of microorganisms
Active immunization -
administration of a vaccine
Passive immunization -
administration of exogenously produced
or preformed antibodies
Passive immunization - postexposure treatment
Injection of purified antibody or antibody-containing serum to provide rapid, temporary
protection or treatment.
Newborns receive natural passive immunization
maternal immunoglobulin that crosses the placenta and is present in breast milk
Uses of passive immunization: (4)
- To prevent disease after a known exposure
- To ameliorate the symptoms of an ongoing disease
- To protect immunodeficient individuals
- To block the action of bacterial toxins and prevent the
diseases they cause
Human Immune Globulins
used against:
(6)
Hepatitis A Hepatitis B Rabies Respiratory Syncytial Virus Varicella zoster Tetanus
Animal Antitoxins
used against:
(2)
Botulism
Diphtheria
Passive immunization
Limitations
(4)
sometimes antiviral antibody titers not high enough
contamination with other infectious agents
need to use early after exposure- often this is not possible
some viruses have a limited extracellular phase- herpesviruses, enteroviruses
Active immunization
Use of vaccines to elicit immune responses (2)
Inactivated, subunit, and killed vaccines Live vaccines (attenuated)
Inactivated, subunit, and killed vaccines
4
No risk of infection
Use large amounts of antigen
Inactivate or kill by chemical treatment (e.g. formalin) or heat
for bacteria, viruses, or bacterial toxins
Purify or synthesize subunits or components of the infectious agent
Inactivated, subunit, and killed vaccines
(3)
— required to boost the immunogenicity of these vaccines
Adjuvants
Alum (aluminum salt)
Modern adjuvants are designed to be or to mimic PAMPs
Adjuvants influence the type of immune response
Adjuvants required to boost the immunogenicity of these vaccines
Modern adjuvants are designed to be or to mimic PAMPs
(3)
bacterial cell wall components
synthetic polymers
bacterial toxins (attenuated)
Active immunization
Some disadvantages
(5)
- Immunity is not usually long-lived (generates a Th2 response that does not elicit
effective immune memory) - Immunity may be humoral and not cell-mediated
- The vaccine does not usually elicit a local IgA response
- Booster shots are required
- Larger doses must be used
Active immunization
Inactivated, subunit, and killed vaccines
Bacterial vaccines (5)
toxoids inactivated (killed) bacteria Vibrio cholera capsule or protein subunits of bacteria Conjugate these because polysaccharides are poor immunogens
toxoids
2
Corynebacterium diphtheriae, Clostridium tetani
capsule or protein subunits of bacteria
Capsular polysaccharide vaccines:
Haemophilus influenzae B
Conjugate these because polysaccharides are poor immunogens
Hib polysasccharide + diphtheria toxoid
Viral vaccines
2
inactivated viruses (polio, hepatitis A, influenza, and rabies) protein subunits of viruses (hepatitis B)
Active immunization
Live vaccines
(5)
Use avirulent or attenuated microorganisms
Immunization resembles the natural infection
Only a single dose usually required
Immunity is generally long-lived
No adjuvant required
Immunization resembles the natural infection
2
host reaction progresses through Th1 and Th2 immune responses
humoral, cellular, and memory immune responses are developed
Active immunization
Live vaccines
Some disadvantages
(3)
- Vaccine microorganism may still be dangerous for immunosuppressed people or
pregnant women, who do not have the immunologic resources to resolve even a
weakened infection - The vaccine microorganism may revert to a virulent form (for viruses)
- The viability of the vaccine must be maintained
Live vaccines
Bacterial vaccines
Calmette-Guerin bacillus (tuberculosis) (3)
attenuated strain of Mycobacterium bovis
not routinely used in United States because vaccinated individuals show false-positive reaction to the tuberculosis test used in this country (PPD test = purified protein derivative test)
Viral vaccines
MMR vaccine
(4)
measles virus (Paramyxovirus family; genus Morbillivirus) mumps virus (Paramyxovirus family; genus Paramyxovirus) rubella virus (Togavirus family; genus Rubivirus) Varicella-zoster virus (also available as part of MMRV vaccine)
correlates of protection =
the host immune responses associated with
disease protection
Vaccines that protect solely or principally by induction of serum antibodies (2)
hepatitis A,
tetanus
Secretory antibodies play a role in protection against infections caused by
agents that must first replicate on mucosal surfaces
Secretory antibodies play a role in protection against infections caused by
agents that must first replicate on mucosal surfaces
ex.
rotavirus
Vaccines for which T-cell responses are essential include (2)
measles, varicella
SARS-CoV-2 vaccines for generating
active immunity
mRNA vaccine encoding the Spike protein
2
Pfizer - BioNTech & Moderna
mRNA enters cells and is translated into parts of Spike
Viral vector vaccine encoding the Spike protein
engineered harmless adenovirus (DNA virus) that infects
cells and then produces parts of Spike
Johnson & Johnson - Janssen
Protein subunit vaccine containing parts of the Spike protein
and adjuvants
Novavax
Treatment for COVID-19 based on passive immunity to SARS-CoV-2
mAb active against original version of SARS CoV-2
received Emergency Use Authorization from the FDA
Monoclonal antibody (mAb)
binds SARS-CoV-2 virions and
“neutralizes” them, which
means it
blocks the virus
from interacting with ACE2
receptors and entering cells
mAb was isolated from a recovered
COVID-19 patient =
a neutralizing
IgG1 mAb directed against the
SARS-CoV-2 spike (S) protein
