[1] New York Blood Ctr, Lindsley F Kimball Res Inst, Virol Lab, New York, NY 10021 USA
[2] Univ Calif San Francisco, Dept Microbiol & Immunol, San Francisco, CA 94143 USA
[3] Univ Calif San Francisco, Dept Med, San Francisco, CA 94143 USA
[4] Univ Calif San Francisco, Howard Hughes Med Inst, San Francisco, CA 94143 USA
[5] NYU, Sch Med, Dept Pathol, New York, NY USA