1. Seattle Biomedical Research Institute, Seattle, WA 98109
2. University of Washington, Department of Global Health, Seattle, WA 98109
3. IAVI Neutralizing Antibody Center and Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, CA 92037
4. Laboratory of Molecular Immunology, The Rockefeller University; New York, NY10065
5. Division of Biology, California Institute of Technology, Pasadena, CA 91125