http://www.washingtonpost.com/ac2/wp-dyn/A17363-2003Apr22?language=printer
Virus Is Mutating Rapidly, Genetic Sequencing in China Indicates
By John Pomfret
Washington Post Foreign Service
Wednesday, April 23, 2003; Page A26
BEIJING, April 22 -- Chinese scientists have deciphered the genetic code of
a
number of samples of the SARS virus and say their research could provide
important clues as to whether the microbe will weaken or increase in
severity
over time.
Yang Huanming, one of China's best-known geneticists, said the work has
shown
significant differences between virus samples from patients in Guangzhou and
in Beijing, indicating that the virus is mutating rapidly.
Yang's Beijing Genomics Institute has sequenced SARS, severe acute
respiratory
syndrome, in a joint project with the Institute of Microbiology and
Epidemiology of the Academy of Military Medical Sciences. He said samples
already sequenced in the United States and Canada were similar to the
Guangzhou samples because the American and Canadian samples came from people
who caught the disease in southern China. But when researchers did
sequencing
of samples collected in Beijing, about 1,200 miles to the north, they
detected
significant differences from the southern strain.
"We don't have evidence that these structural differences are related to the
intensity of the disease," Yang said in an interview at the institute,
located
on the outskirts of Beijing, "but that possibility can't be excluded."
The SARS virus belongs to a family of viruses known as coronaviruses, which
are prone to mutations. So it is not surprising that the virus has developed
changes in its genetic makeup, according to other scientists. The key
question
is whether the changes affect the virus in any meaningful way, such as
making
it more or less likely to spread or more or less likely to cause severe
disease. Most mutations in viruses have little effect on how the disease
manifests in humans.
"These mutations may cause the virus to become more virulent, or
alternatively
the mutations may cause the virus to become less virulent," said Michael
Lai,
a coronavirus expert at the University of Southern California. "It will take
more analysis to know."
The mutations were seen in all five of the viruses' known functional genes,
with most of them occurring in the gene that carries the instructions for
the
distinctive spikes that jut from the outside of the virus, according to Siqi
Liu, associate director at the Beijing Genomics Institute, part of the
Chinese
Academy of Sciences.
The only way to determine whether the mutations are changing how the virus
behaves is by seeing whether patients or animals infected with the virus
with
the mutations are getting sicker or are more infectious, Lai said.
"If you see all the patients have more severe disease, then this would
suggest
this mutation has some effect," Lai said.
Drafts of the sequences have been posted on a public Web site for other
scientists to review, officials said.
The Chinese institute began sequencing samples on April 15, three days after
Canadian researchers successfully sequenced another sample of SARS.
Researchers sequenced tissue samples from the lungs of two deceased
patients,
one in Guangzhou and one in Beijing; a mix of samples from the liver and
lymph
gland of another Beijing patient; and samples from nasal and throat cultures
of several SARS patients in Beijing.
Yang and other institute scientists hypothesized that the vast differences
in
the intensity of the disease from patient to patient may be explained by
mutations within the virus. Some patients with SARS have been dubbed "poison
kings" by the Chinese because of their tendency to infect scores of people.
Some scientists have discounted this theory, however, saying steps taken to
protect against infection are the determining factor.
Wang Jian, one of Yang's colleagues, said the mutations also might explain
why
the virus seems to lose strength over time. "It can go in both directions,"
he
said. "It can become less virulent or more poisonous."
Yang said his institute would soon be sequencing samples from Inner Mongolia
and other parts of China where SARS is currently spreading.
Staff writer Rob Stein in Washington contributed to this report.
© 2003 The Washington Post Company
________________________________
Henry L Niman, PhD
Department of Bioengineering
Shriners' Burn Center
51 Blossom Street, Room 422
Boston, MA 02114 USA
[email protected]
617.877.0987 Mobile
412.968.0431 Home
412.968.0432 FAX
--
The silver-list is a moderated forum for discussion of colloidal silver.
Instructions for unsubscribing may be found at: http://silverlist.org
To post, address your message to: [email protected]
Silver-list archive: http://escribe.com/health/thesilverlist/index.html
List maintainer: Mike Devour <[email protected]>
