[1] KAROLINSKA INST, DEPT IMMUNOL, BOX 60400, S-10401 STOCKHOLM 60, SWEDEN
[2] UNIV ROME, INST INFECT DIS, I-00100 ROME, ITALY
[3] UNIV CHIETI, INST GEN PATHOL, CHIETI, ITALY
[4] UNIV CATTOLICA SACRO CUORE, INST PAEDIAT, I-00168 ROME, ITALY
[5] UNIV ROME, INST PAEDIAT 2, I-00100 ROME, ITALY
[6] NATL CTR BLOOD TRANSFUS, ROME, ITALY