[1] Fred Hutchinson Canc Res Ctr, Div Clin Res, Gastroenterol Hepatol Sect D2 190, Seattle, WA 98109 USA
[2] Fred Hutchinson Canc Res Ctr, Vaccine & Infect Dis Inst, Seattle, WA 98109 USA
[3] Univ Washington, Dept Med, Seattle, WA USA
[4] Univ Washington, Dept Pediat, Seattle, WA 98195 USA
[5] Univ Washington, Dept Biostat, Seattle, WA 98195 USA