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Pathogens & Immunity
• Text Chapter 6- 7- 8
What is a pathogen
• Anything that causes harm to your body
– Bacteria, virus, protista and fungi are all
kingdoms that contain common pathogenic
organisms
– Animals (mosquitos, tapeworms) and plants
(poison ivy, poison oak) are larger
pathogenic organisms
Pathogenic Fungus
Animal pathogens
Roundworms, heartworm &
tapeworms
Transmission of pathogens
• Contaminated food, water
• Bodily fluids via unprotected sex, sharing of needles
during drug use
• Mother to unborn child
•
• Airborne
– Attach to dust or
water droplets
Vectors
• Mosquitoes
– West Nile Virus, Malaria
• Houseflies, tse tse fly (African Sleeping
Sickness)
• Ticks – Lyme disease (bacteria)
• Animals - Rabies (virus)
How do they work?
• Transmitted or vectored by a number of
ways…
• Propagated
• Spread person to person
• Common source
• All get sick from one source point, i.e.
contaminated water
How to stop a pathogen…
• Prevent entry to body
– Good hygiene, insect repellent, boil water,
throughly cook food, do not engage in risky
behaviors
• Promote a rapid immune response
– Healthy lifestyle – diet, sleep, exercise
• Medicines
– Anitibiotics, antivirals, fungicides
• Vaccines
– Teach your immune system to recognize
invaders
The immune response
• Antigen
– nametags for all cells and cell-like
organisms
• Host
– the organism or cell that is under attack;
has a particular receptor site for antigens
• Antibody
– a protein made by the body to prevent
attachment of pathogen to host cell
vaccine
• A little bit of virus (weakened or dead)
that “teaches” your body to make
antibodies
• Your body remembers how to fight
pathogens by “memory B cells”
Viruses
T4 Bacteriophage
• NO!
Is it Alive?
– Do not perform the 6 characteristics of
life
• 1. cells
• 2. organization
• 3. energy use
• 4. homeostasis
• 5. growth & development
• 6. reproduction
Influenza
Virus
What is a Virus?
• Obligate intracellular parasite
– Piece of DNA or RNA covered with a capsid
• Protein “coat”
Classification of Viruses
• No Kingdom!
• classify based on the
host they invade
– Plants, animals, bacteria
• Genetic material
– DNA or RNA
– RNA viruses are called
retrovirus
• morphology
Viral Shapes
How do Viruses work? Must have
host
Lytic or virulent cycle
•
1. Finds specific host – antigen “name tags”
matches a host “docking station”
2. Injects its nucleic acid into host
cell
3. Host cell becomes a viral “factory” to make new
viruses
4. Host cell bursts  releases viruses, kills host
Lysogenic or Temperate Cycle
• Some viruses enter host and become
dormant
– Inactive
• Can become activated by another virus
– Example – cold sore viruses made
active by common cold
Beneficial Virus?!
• Control of other diseases
• Useful in Genetic Engineering as a
vector of new DNA
– Gene therapy to cure genetic disorders
– Ie. Cystic fibrosis
Effects of Viruses
• Harmful pathogenic
HIV – AIDS Pandemic
• Human Immunodeficiency Virus
– Causes Auto Immune Disorder Syndrome
(AIDS)
– Spread through blood, semen, vaginal
fluid, and breast milk
– Attacks immune system – Helper T
cells, which controls the rest of your
immune system
Spread of HIV
25
million
dead to
date
Control of
HIV
• Education!
• Protection
– Vaccines
– Interferon
• Keep it dormant – control trauma, stress
• Boost immune system