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Step 1
Use the growth medium, which includes PCR primers, to make billions of copies
of a single gene.
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Genetic vaccines, sometimes called naked-DNA vaccines, are currently being
developed to fight diseases such as AIDS. The goal of these vaccines is to use
a gene from a pathogen to generate an immune response. A gene contains the
instructions to create a protein. With a genetic vaccine, small loops of DNA in
the vaccine invade body cells and incorporate themselves into the cells'
nuclei. Once there, the cells read the instructions and produce the gene's
protein.
Using a technique called PCR, which stands for polymerase chain reaction,
you'll make many copies of a specific gene. The work of
finding the gene and copying sequences of its DNA is done by "primers."
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Step 2
Combine the virus genes with vectors.
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To make your genetic vaccine, you'll use vectors. Vectors are agents that are
able to enter and instruct cells to create proteins based on the vector's DNA
code. In this case, the vectors are loops of double-stranded DNA. You can
exploit the vector's ability to create proteins by splicing a gene from the
virus into a vector. The cell that the vector later invades will then produce
proteins created by the virus.
The vectors and copied genes have been treated with restriction enzymes, which
are agents that cut DNA sequences at known locations. The enzymes have cut open
the round vectors and trimmed the ends of the copied genes.
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Step 3
Add bacteria to the vectors to allow the altered vectors to replicate.
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The ends of the vectors have again come together, but now with a gene spliced
into the loop. You'll need many copies of the vector/gene loop for your genetic
vaccine. These copies can be produced with the help of bacteria.
Vectors are capable of self-replicating when within a bacterial host, as long
as that host is in an environment conducive to growing. After you combine the
vectors and bacteria, the vectors will be shocked into the bacteria.
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Step 4
Use the purifier to separate the altered vectors from the bacteria.
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The final vaccine should include only the vectors, so you'll need to separate
them from the bacteria after enough copies have been produced. This can be done
with a detergent, which ruptures the cell walls of the bacteria and frees the
DNA within.
The relatively large bacterial DNA can then be separated from the smaller DNA
loop that makes up the vector.
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Step 5
Fill the syringe with the altered vectors.
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Upon inoculation, billions of copies of the altered vector will enter the body.
Of these, only 1 percent will work their way into the nuclei of body cells. But
that's enough.
The body's immune system responds to these proteins once they leave the cell.
But more importantly, it also reacts to proteins that are incorporated into the
cells' walls. So in addition to mounting an attack against the free-floating
proteins, the immune system attacks and eliminates cells that have been
colonized by a pathogen. The vaccine, then, works like a live vaccine, but
without the risk. (With a live vaccine, the pathogen can continue to replicate
and destroy cells as it does so.)
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Done
The naked-DNA vaccine is complete.
Select another pathogen.
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Congratulations. You have just produced a naked-DNA HIV
vaccine.
Trials for a genetic vaccine that may protect against AIDS began in 1995. These
vaccines, which contained HIV genes, were given to patients who already were
infected with HIV. A year later, the trials were expanded to test people
without HIV. These trials are still being conducted and have not yet produced
conclusive results.
Human trials for genetic vaccines against herpes, influenza, malaria, and
hepatitis B are also underway.
Note: Although the genetic material of HIV is RNA, the procedure for making the
vaccine is similar.
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