The first human antibodies that can neutralize different strains of the virus responsible for outbreaks of severe acute respiratory syndrome (SARS) has been identified by an international research team led by scientists from the National Cancer Institute (NCI) and the National Institute of Allergy and Infectious Diseases (NIAID) and included collaborators from the U.S. Army (USAMRIID), academic institutions in the United States, Switzerland, and Australia.

As explained by Kanta Subbarao, M.D., NIAID, whose laboratory verified the efficacy of the anti-SARS antibodies in animal models:

"This study is important because the viral strain that caused the outbreak in people in 2002 probably no longer exists in nature. What we need to prove for any vaccine, therapeutic, antibody, or drug is that it is effective not only against the strain of SARS virus isolated from people, but also against a variety of animal strains, because animals will be a likely source for re-emergence of the SARS virus."

Dimiter S. Dimitrov, Ph.D., head of the Protein Interaction Group at NCI's Frederick, Md., campus and his colleagues identified two human antibodies that bind to a region on the SARS virus' spike glycoprotein that is called the receptor binding domain (RBD):

• S230.15 - was found in the blood of a patient who had been infected with SARS and later recovered.
• m396 - was taken from a library of human antibodies the researchers developed from the blood of 10 healthy volunteers

Then Dimitrov's team next determined the structure of m396 and its complex with the SARS RBD and showed that the antibody binds to the region on the RBD that allows the virus to attach to host cells.

If the above antibodies were successful in binding to the SARS RBD, they would prevent the virus from attaching to the SARS coronavirus receptor, ACE2, on the outside of human cells, effectively neutralizing it.

Both antibodies potently neutralized samples of the virus from both outbreaks when tested on laboratory cells and samples of the virus taken from wild civets (a cat-like mammal in which strains of the virus were found during the outbreaks) -though with somewhat lower potency.

Find more details from the full report.