SARS may be here to stay
Vaccines
and tracking could benefit from slow mutation of killer
virus genome.
12 May 2003
HELEN R. PILCHER
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Previous
epidemic-causing
viruses have mutated
and died out
naturally. |
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© Corbis |
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The SARS virus may be with us for some time to come.
Its genetic makeup is showing little sign of change, say
researchers. But this may make the spread of the killer
easier to track, and could buy scientists more time to
produce an effective vaccine.
It also means that the virus is unlikely to mutate
into a benign form as did previous epidemic-causing
ones, explains virologist Earl Brown of the University
of Ottawa, Canada. A lethal strain of SIV, an HIV-like
virus that affected chimps, has disappeared this way.
However, the SARS virus only appeared in November
2002, so "it may be too early to draw general
conclusions", says Albert Osterhaus, who is working on
the infectivity of the virus at Erasmus University in
Rotterdam, the Netherlands.
The infective agent behind SARS - the respiratory
condition that has to date infected more than 7,000 and
killed over 500 - is thought to be a new coronavirus.
Normally, coronavirus genomes are highly labile.
Tracking a killer
Edison Liu and his colleagues at the Genome Institute
of Singapore cultured and compared SARS virus samples
taken from Singapore, Canada, Hong Kong, and Guangzhou
and Beijing in China. They found that the majority of
the virus genome has remained unchanged as the infection
has spread.
The handful of genetic modifications that have
occurred as the virus has spread from place to place
over the past five months may help to trace the origin
of infection. SARS viruses from different countries can
have subtly different "molecular signatures", says Liu.
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It may be too
early to draw
general
conclusions
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Albert
Osterhaus
Erasmus
University
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Some of these changes may have occurred in the
laboratory, warns Osterhaus. Before the virus was
analysed, it was grown in monkey cells. The mutations
may have arisen as the virus adapted to its new host. He
suggests that virus taken from or cultured in human
cells should be studied instead.
"There is a great need now for genetic analysis of a
less serious virus," says virologist John Oxford from
the London Queen Mary's School of Medicine. He suggests
that researchers isolate and sequence virus from
patients with only minor symptoms. These data could be
compared against those from lethal strains, to pinpoint
the genes that turn a virus into a killer. These would
offer new targets for drug and vaccine development. |
