WASHINGTON -- The Centers for Disease Control and Prevention (CDC) announced today that it has sequenced the genome for the coronavirus believed to be responsible for the global epidemic of severe acute respiratory syndrome (SARS). The CDC sequence is nearly identical to that determined by a Canadian laboratory late last week. The significant difference is that the CDC-determined sequence has 15 additional nucleotides, which provides the important beginning of the sequence, CDC scientists said.
The results came just 12 days after a team of 10 scientists, supported by numerous technicians, began working around the clock to grow cells taken from a throat culture taken from one of the SARS patients in Vero cells (African green monkey kidney cells) in order to reproduce the ribonucleic acid (RNA) of the disease-causing coronavirus. The new sequence has 29,727 nucleotides, which places it well within the typical RNA boundaries for coronaviruses. Members of this viral family tend to have between 29,000 and 31,000 nucleotides.
Identifying the genetic sequence of a new virus is important to efforts to treat or prevent it, said Dr. Julie Gerberding, CDC director. "Research laboratories can use this information to begin to target antiviral drugs, to form the basis for developing vaccines, and to develop diagnostic tests that can lead to early detection."
In sequencing the genome, CDC scientists worked closely with coronavirus experts at academic institutions across the United States. "This is an active, working community of scientific experts who have been contributing their knowledge and expertise throughout this investigation," said William Bellini, PhD, SARS laboratory team coordinator.
The nearly identical findings in the United States and Canada are important because they were derived from different individuals who were infected in different countries. This suggests that the virus probably originated from a common source.
The CDC's analysis of the virus is far from finished, officials emphasized. Because coronaviruses have the ability to mutate rapidly, scientists will compare the sequences from viruses isolated in cell culture to those obtained from diseased tissues taken from SARS patients. "This is essentially a draft. Now we need to see if what we have identified in the laboratory matches what's causing disease in patients," Bellini said.
But the groundbreaking work of isolating the genomic sequence speeds the task of comparison.