Gene Mutation May Explain SARS

SARS Genetically Targeted?

October 1, 2003

WASHINGTON (Reuters) -- A genetic susceptibility may explain why SARS raged last year in Southeast Asia and nowhere else in the world outside of Toronto, Taiwanese researchers reported this week.

They found a certain variant in an immune system gene called human leukocyte antigen, or HLA, made patients in Taiwan much more likely to develop life-threatening symptoms of SARS.

The gene variant is common in people of southern Chinese descent, the team at Mackay Memorial Hospital in Taipei reported.

Their finding, published in an online journal, BMC Medical Genetics, must be confirmed by independent researchers. But the Taiwanese team said the genetics could explain the puzzling distribution of SARS last year.

"After the outbreak of SARS coronavirus infection in the Guangdong Province of China, it was surprising to observe that the spreading of the disease was mostly confined among southern Asian populations (the Hong Kong people, Vietnamese, Singaporeans and Taiwanese)," they wrote.

The head of infectious diseases at the U.S. Centers for Disease Control and Prevention, Dr. James Hughes, said genetic susceptibility was one area his agency was investigating.

"It is conceivable that people of a certain genetic disposition have a susceptibility to or risk of complications," Hughes said in an interview.

Severe Acute Respiratory Syndrome first arose in Guangdong last November. It spread to Hong Kong, Taiwan, Vietnam, Beijing and Singapore, carried by infected airline passengers.

SARS eventually was suspected of affecting 8,098 people and killing 774, according to the World Health Organization's latest figures.

The flu-like disease is caused by a virus from a family known as coronaviruses. They cause diseases in livestock and some cases of the common cold in people.

The SARS coronavirus is unique genetically but similar versions have been found in animals sold in Chinese food markets.

Marie Lin, Chun-Hsiung Huang and colleagues examined the HLA gene in 37 cases of probable SARS, 28 fever patients excluded later as probable SARS, and 101 non-infected health care workers who were exposed or possibly exposed to SARS coronavirus.

"An additional control set of 190 normal healthy unrelated Taiwanese was also used in the analysis," they wrote in their report.

They found that patients with severe cases of SARS were likely to have a version of the HLA gene called HLA-B 4601.

Seasonal

They noted that no indigenous Taiwanese, who make up about 1.5 percent of the population, ever developed SARS. HLA-B 4601 is not seen among indigenous Taiwanese, they noted.

"Interestingly, (HLA-B 4601) is also seldom seen in European populations," they added.

Dr. Frederick Hayden, an expert on influenza and SARS at the University of Virginia, said it would take a large, carefully designed study to confirm the findings.

"It certainly warrants study," he said.

Researchers at a SARS meeting in Washington said they still do not know if the respiratory disease will re-emerge this year, but believe it may because other coronaviruses are known to have seasonal patterns.

"We probably will face SARS again," Hughes told the conference.

http://www.cnn.com/2003/WORLD/asiapcf/southeast/10/01/sars.gene.reut/index.html