[1] La Jolla Inst Immunol, Div Vaccine Discovery, San Diego, CA 92037 USA
[2] Univ Minnesota, Sch Med, Dept Microbiol & Immunol, Minneapolis, MN 55455 USA
[3] US FDA, Div Bacterial Parasit & Allergen Prod, Ctr Biol Evaluat & Res, Silver Spring, MD USA
[4] Univ Calif San Diego, Sch Med, San Diego, CA 92103 USA