Fremont led the initial analysis, which was dedicated to identifying sequences of genetic code that might translate into proteins that could help the virus avoid immune system attacks. He and his colleagues sought such sequences in portions of the virus' accessory genome—areas of its genetic code not commonly found in other viruses.
SARS belongs to a class of viruses known as coronaviruses. Because those viruses typically aren't harmful to humans, researchers suspect a gene in the SARS accessory genome may be providing the virus with most of its pathogenic punch.
Their computerized search highlighted a section of the SARS genetic code that shared several features with immune evasion proteins previously identified in other viruses. Some genetic codes contain sequences of protein-building instructions that the organisms never use, and the researchers had no proof yet that SARS actually made use of the sequence their analysis identified. Geneticists call such sequences of genetic information open reading frames, and the SARS sequence therefore came to be known as open reading frame 7a, or orf7a.
To produce the orf7a protein, research instructor Christopher Nelson, Ph.D., and graduate student Chung Lee, both of the Fremont laboratory, transplanted orf7a into bacteria. When the bacteria made the protein, researchers purified it and used it to determine the three-dimensional structure of orf7a. This purified protein also allowed colleague Michael Diamond, M.D., Ph.D., assistant professor of molecular microbiology, to generate orf7a-specific antibodies.
Andrew Pekosz, Ph.D., assistant professor of molecular microbiology, applied those antibodies to cell cultures infected with the SARS virus, revealing that the virus does produce the orf7a protein.
"We learned that the virus does make the protein, but we also got a big surprise w
Source:Washington University School Of Medicine