[1] Univ Modena, Sch Med, Dept Biomed Sci, Sect Gen Pathol, I-41100 Modena, Italy
[2] Univ Modena, Sch Med, Dept Internal Med, Infect Dis Clin, I-41100 Modena, Italy
[3] Univ Roma La Sapienza, Dept Internal Med, Rome, Italy
[4] Ist Super Sanita, I-00161 Rome, Italy
[5] Univ Bergen, Gade Inst, Dept Microbiol & Immunol, Ctr Res Virol, Bergen, Norway
[6] Osaka Univ, Sch Med, Dept Genet, Osaka, Japan
[7] Univ Bologna, Dept Expt Pathol, I-40126 Bologna, Italy
[8] INRCA Ancona, Ancona, Italy