[1] Charles Univ, Dept Pediat Oncol, Hosp Motol, Fac Med 2, CR-15006 Prague 5, Czech Republic
[2] Charles Univ, Fac Med 2, Inst Med Microbiol, Prague, Czech Republic
[3] Univ British Columbia, Dept Paediat, Vancouver, BC, Canada
[4] Texas Childrens Hosp, Baylor Coll Med, Texas Childrens Canc Ctr, Houston, TX 77030 USA
[5] Texas Childrens Hosp, Baylor Coll Med, Serv Hematol, Houston, TX 77030 USA