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Step 1
Use the tissue culture to grow new viruses.
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You are about to create a live-attenuated vaccine,
which means that you need to alter a
pathogen—in this case a measles virus—so
that it will still invade cells in the body and use
those cells to make many copies of itself, just as
would any other live virus. The altered virus must
be similar enough to the original measles virus to
stimulate an immune response, but not so similar
that it brings on the disease itself.
To create a new strain of the virus, you'll need to
let it grow in a tissue culture.
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Step 2
Fill the syringe with a strain of the virus that has
desirable characteristics.
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The tissue culture is an artificial growth medium
for the virus. You will intentionally make the
environment of the culture different than that of
the natural human environment. For this vaccine,
you'll keep the culture at a lower temperature.
Over time, the virus will evolve into strains that
grow better in the lower temperature. Strains that
grow especially well in this cooler environment are
selected and allowed to evolve into new strains.
These strains are more likely to have a difficult
time growing in the warmer environment of the human
body. After many generations, a strain is selected
that grows slow enough in humans to allow the immune
system to eliminate it before it spreads.
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Done
The measles vaccine is complete.
Select another pathogen.
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Congratulations. You have just produced a
live-attenuated measles vaccine.
Like the smallpox vaccine, the virus within the
vaccine will invade body cells, multiply within the
cells, then spread to other body cells. The virus
used in the measles vaccine today took almost ten
years to create. The starting stock for the virus
originated from a virus living in a child in 1954.
Live-attenuated vaccines are also used to protect
the body against mumps, rubella, polio, and yellow
fever.
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