[1] UNIV MILAN, SAN RAFFAELE INST, I-20122 MILAN, ITALY
[2] UNIV GENEVA, HOP CANTONAL, DIV INFECT DIS, CH-1211 GENEVA 4, SWITZERLAND
[3] UNIV FERRARA, INST GEN PATHOL, I-44100 FERRARA, ITALY
[4] CNR, CTR BIOMEMBRANES, I-35100 PADUA, ITALY
[5] UNIV TEXAS, MED BRANCH, DEPT PHYSIOL & BIOPHYS, GALVESTON, TX 77550 USA