[1] KAROLINSKA INST,DEPT IMMUNOL,S-10401 STOCKHOLM 60,SWEDEN
[2] KAROLINSKA INST,DEPT VIROL,S-10401 STOCKHOLM 60,SWEDEN
[3] UNITA SOCIO SANIT LOCALE 751,MILAN,ITALY
[4] UNIV ROME TOR VERGATA,DEPT PAEDIAT,ROME,ITALY
[5] NATL BACTERIOL LAB,DEPT VIROL,S-10521 STOCKHOLM,SWEDEN
[6] UNIV MILAN,DEPT PAEDIAT 1,I-20122 MILAN,ITALY
[7] UNIV MILAN,DEPT PAEDIA 4,I-20122 MILAN,ITALY
[8] UNIV MILAN,DIV NEONATOL OBSTET & GYNECOL MANGIAGALLI,I-20122 MILAN,ITALY