[1] Univ Calif San Francisco, Dept Pediat, Div Infect Dis, San Francisco, CA 94143 USA
[2] Univ British Columbia, Dept Biochem & Mol Biol, Vancouver, BC V5Z 1M9, Canada
[3] Univ British Columbia, Ctr Blood Res, Vancouver, BC V5Z 1M9, Canada
[4] Univ Calif San Francisco, San Francisco Gen Hosp, Dept Med, Div Infect Dis, San Francisco, CA USA