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 orwater 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”

T4 Bacteriophage

Viruses

Is it Alive?• NO!

– 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