[1] Emory Univ, Emory Vaccine Ctr, Atlanta, GA 30322 USA
[2] Univ Washington, Howard Hughes Med Inst, Seattle, WA 98195 USA
[3] Univ Penn, Abramson Family Canc Res Inst, Philadelphia, PA 19104 USA
[4] Univ Penn, Dept Med, Philadelphia, PA 19104 USA
[5] Univ Cambridge, Dept Med, Med Res Council Ctr, Wellcome Trust Immunol Unit, Cambridge CB2 2QH, England