Institute for Cancer Research, Fox Chase Cancer Center, Philadelphia, PA, United States of America.|The Scripps Research Institute, La Jolla, CA, United States of America.|The Scripps Research Institute, La Jolla, CA, United States of America.|Department of Biochemistry, University of Washington, Seattle, WA, United States of America.|The Scripps Research Institute, La Jolla, CA, United States of America.|IAVI Neutralizing Antibody Center at TSRI, La Jolla, CA, United States of America.|The Scripps Research Institute, La Jolla, CA, United States of America.|Institute for Cancer Research, Fox Chase Cancer Center, Philadelphia, PA, United States of America.