interference
is an “old antiviral strategy” used by plants, worms
and other lower species. Small interfering RNA, or siRNA, degrades
messenger RNA.
Messenger RNA is a substance that acts as an intermediary between
the genes of a cell, hidden deep inside its central core, and the
proteins that the cell eventually manufactures for various purposes.
They are like signals travelling between the cell’s ‘head
office’ and its manufacturing plant.
In a cell infected by a virus, or one that has turned cancerous,
the ‘head office’ has been taken over by an invading
force; commands are issued that direct the formation of new viruses
rather than useful proteins, or command the cell to divide when
it should not.
Small interfering RNA molecules garble these messages so that the
harmful ones do not get through.
Researchers have discovered that RNA interference can also work
in the cells of mammals. It has huge potential because it is extremely
specific - it is capable of garbling ‘abnormal’ instructions
but allowing normal ones to get through - and is very powerful:
in test-tube studies, it induced 100 per cent suppression of viral
and cancer-proliferation commands.
Dr Lieberman said: “We thought it would be a good idea to
harness it to combat viral infection, in particular HIV.”
Drs Moiz Kitabwalla and Ruth Ruprecht of the Dana-Farber Cancer
Institute in Boston said: “there is a definite need for new
strategies to target HIV, since more and more people are infected
with drug-resistant strains.”
However, their report “RNA Interference - A New Weapon Against
HIV and Beyond” says that many obstacles need to be overcome
before the strategy can be clinically used.
Getting siRNA into cells is an inefficient process, and making sure
it remains stable inside cells will be another challenge. Strategies
for inducing cells to make their own siRNA are being studied.
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