[1] NIAID,VIRAL DIS LAB,BETHESDA,MD 20205
[2] HARVARD UNIV,SCH MED,SIDNEY FARBER CANC INST,DEPT HEMATOL ONCOL,BOSTON,MA 02115
[3] HARVARD UNIV,CHILDRENS HOSP,MED CTR,SCH MED,DEPT PEDIAT,BOSTON,MA 02115
[4] HARVARD UNIV,SCH MED,SIDNEY FARBER CANC INST,TUMOR BIOL LAB,BOSTON,MA 02115
[5] HARVARD UNIV,SCH MED,DEPT MICROBIOL & MOLEC GENET,BOSTON,MA 02115
[6] UNIV AUTONOMA MADRID,FAC CIENCIAS,CTR BIOL MOLEC,MADRID 34,SPAIN