A person who survived SARS developed an antibody that researchers call S309 in a new study published in Nature magazine (via LiveScience). The study was conducted by doctors from the University of Washington, Pasteur Institute in France, Università della Svizzera Italiana, Switzerland, and Vir Biotechnology. If Vir sounds familiar, that’s because it’s one of the US companies that’s currently looking to develop monoclonal antibodies for COVID-19.

The S309 antibody, found in the blood of that person, showed a strong ability to bind to the novel coronavirus’s spike protein, which is the key virus component of both SARS and SARS-CoV-2 that allows these two viruses to attach themselves to cells and invade them. Without this process, the virus can’t enter the cell to replicate itself, and a patient wouldn’t get COVID-19 even after contracting the virus.

Lab experiments show that S309 can bind itself to the spike protein, but testing on humans will be required to see whether the antibody is effective and safe. S309 is just one of the 25 SARS monoclonal antibodies found in blood from the patient, including samples taken in 2004 and 2013.