Hi all

A very good article about gene therapy.

Quote: "But the use of such new vectors "offers a
great opportunity to maximize the advantages and
minimize the drawbacks of existing delivery systems.""

Robert


http://www.sciencedaily.com/releases/2007/09/070926172158.htm
Source: University of Wisconsin-Madison
Date: September 30, 2007

'Jumping Genes' Could Make For Safer Gene Delivery
System

Science Daily — To move a gene from point A to point
B, scientists and gene therapists have two proven
options: a virus, which can effectively ferry genes of
interest into cells, and a plasmid, an engineered loop
of DNA that can do the same thing, albeit usually only
on a short-term basis.

The catch is that viruses can be infectious and some
types of viruses occasionally land in a target genome
near an oncogene and raise the risk of cancer.
Plasmids don't carry that risk, but they are not
nearly as efficient at reproducing in cells, which is
important when the goal is to integrate an introduced
gene into the targeted cells of the organism or
patient.

Now, however, the advent of new nonviral gene delivery
systems using transposons, or "jumping genes,"
provides a safer alternative than viruses and more
efficient delivery than plasmids, according to a
publication by a University of Wisconsin-Madison
molecular biologist and biological safety expert.

In an article in the current issue (September) of the
journal Applied Biosafety, UW-Madison molecular
biologist and associate biological safety officer
Margy Lambert describes the gene delivery potential of
transposons, stretches of DNA capable of jumping from
one DNA molecule to another.

"Almost any application where you use viral vectors,
you could use this technique," explains Lambert. "You
can do a lot with it, and it is safer. Problems with
viral vectors are extremely rare, but the consequences
can be severe."

Gene therapy, says Lambert, is one area where the new
technology could make a name for itself. At present,
there are an estimated 140 gene therapy trials under
way in the United States. Most are aimed at treating
fatal conditions such as cancer. Many use the less
efficient plasmids as expression vectors, but some
utilize viruses and no gene therapy treatment has been
deemed safe or effective enough to merit Food and Drug
Administration (FDA) approval as a routine therapy.

And sometimes, unanticipated outcomes that belie the
safety of current gene therapy strategies manifest
themselves in tragedy. In July, for example, a
36-year-old Illinois woman died after experimental
gene therapy treatment in which an engineered virus
was injected into her knee to treat rheumatoid
arthritis. The viruses used were engineered to
suppress the immune system only in the knee. In the
case of rheumatoid arthritis, the immune system is out
of whack and is responsible for the painful
inflammation characteristic of the condition. The FDA
has placed the trial on hold while the cause of death
is investigated.

Transposons, or jumping genes, argues Lambert, are a
potentially safer way to go. "You lose the infectivity
component and you minimize the insertional mutagenesis
risk."

Techniques for targeting transposon vectors to regions
of the genome devoid of cancer genes are being
refined. Meanwhile, a key advantage over simple
plasmids is that jumping gene technology is more
effective at achieving stable expression of genes
introduced into animal cells.

To harness jumping genes, researchers use an enzyme to
ferry a desired DNA sequence from one DNA molecule to
another inside a cell. The enzyme can then be turned
off to stop genes from jumping.

Lambert acknowledged there are both technical and
safety issues to be worked out in the development of
transposon vectors before they could be tried in human
therapy. But the use of such new vectors "offers a
great opportunity to maximize the advantages and
minimize the drawbacks of existing delivery systems."

Note: This story has been adapted from material
provided by University of Wisconsin-Madison.



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