Took infected matter from a sore on the hand of local milkmaid who had cowpox .
He rubbed it into small incisions on the arm of an 8 year old boy named Edward Phipps.
The boy developed a cowpox sore on his arm.
6 weeks later:
Jenner took some infected matter from a victim of smallpox and rubbed it into incisions made in Phipp’s arm again.
The boy remained healthy!
Jenner produced a vaccine for smallpox .
Louis Pasteur - 1884
Produced a weakened infective material from rabid dogs that was used as a rabies vaccine .
First used on a young boy who had been bitten by a rabid dog.
After a symptom-free incubation period that ranges from 10 days to a year or longer (the average is 30 to 50 days), the patient complains of malaise, loss of appetite, fatigue , headache , and fever . Over half of all patients have pain (sometimes itching) or numbness at the site of exposure. They may complain of insomnia or depression .
Two to 10 days later, signs of nervous system damage appear, hyperactivity and hypersensitivity, disorientation , hallucinations, seizures, and paralysis . Death may be sudden, due to cardiac or respiratory arrest, or follow a period of coma that can last for months with the aid of life-support measures .
Jonas Salk - 1953
Created a polio vaccine .
He actually killed the active form of the virus and used it as a vaccine.
1952 – 57,000 cases of polio.
1957 – virtually no cases.
Albert Sabin - 1960
Treated the polio virus to weaken it.
Produced a longer lasting immunity to polio than the Salk vaccine .
Vaccinations : artificial immunity
1. Inject a dead or weakened form of the virus (called an antigen .)
2. Your body produces antibodies .
3. The antibodies recognize the protein coat of the virus and hold it as it enters the body.
4. Macrophage (a type of white blood cell) surround and digest the virus.
5. You are now immune to this virus.
macrophage engulfs antigen by phagocytosis.
Antigen – A substance that stimulates the production of antibodies.
Antibodies – A substance produced by plasma cells (in the blood) in response to specific antigens. They “hold” the antigen until white blood cells (phagocytes) surround and destroy it.
Vaccines – a commercially produced antigen of a particular disease.
It is not as “strong” as the actual disease itself.
Passive immunity – Babies receive antibodies from their mother.
It is temporary: it usually lasts for only 6-12 months.
Pathogen – an agent that causes disease.
Discovery of a Virus - 1933
Read pages 455-456 in textbook.
Size of a virus
Much smaller than any cell.
Smallest is 17 nm (.000000017 meter) or 17 billionth of a meter! (nm = 10 -9 meter)
The largest is 100 nm (.0000001 nm) or 1 ten millionth of a meter.
Barely visible in an electron microscope.
Composition of a Virus
A strand of nucleic acid (DNA or RNA) surrounded by a protein coat known as a capsid.
It may also have an outer “envelope” that it has taken from a host cell.
It is the shape of the capsid or outer envelope that our immune system recognizes.
Is a virus a living organism?
Living things vs. Virus
Made of cells Not a cell
Metabolism No metabolism
Use energy No cell respiration
Grow/develop No growth or development
Definite life span Life span?
Reproduce Need host cell to reproduce
Respond to stimuli “Inert” (inactive)
Bacteriophage - “bacteria eater”
See page 457 in textbook.
Lytic Cycle – 5 steps
Step 1 – Attachment – Virus attaches to a specific receptor site on a cell.
Step 2 – Penetration – Virus enters the host cell
Step 3 – Replication – Viral DNA and protein is copied.
Step 4 – Assembly - DNA and protein is assembled into a virus.
Step 5 – Release – Viruses rupture the cell membrane and are released to infect other cells.
May trigger a nearby oncogene (cancer causing gene.)
May cause too much of something to be produced.
May cause a severe immune response.
Current Research with gene therapy:
What diseases could be treated with gene therapy? ( From AMA website.)
About 4,000 diseases have been traced to gene disorders. Current and possible candidates for gene therapy include cancer , AIDS , cystic fibrosis , Parkinson’s and Alzheimer’s diseases , amyotrophic lateral sclerosis ( Lou Gehrig's disease ), cardiovascular disease and arthritis .