[1] NIAID, Immunoregulat Lab, NIH, Bethesda, MD 20892 USA
[2] Johns Hopkins Med Inst, Dept Med, Baltimore, MD 21205 USA
[3] Johns Hopkins Med Inst, Dept Epidemiol, Baltimore, MD 21205 USA
[4] Johns Hopkins Med Inst, Dept Int Hlth, Baltimore, MD 21205 USA
[5] Fred Hutchinson Canc Res Ctr, Div Human Biol, Seattle, WA 98109 USA