1. Department of Biomedical Sciences and BiotechnologiesUniversity of CagliariCagliariItaly
2. Present address: Department of SurgicalMicrosurgical and Medical SciencesUniversity of SassariSassariItaly
3. 2nd Division of MedicineAzienda Ospedaliera BrotzuCagliariItaly
4. Department of Biomedical SciencesUniversity of SassariSassariItaly
5. Department of Medical Sciences “Mario Aresu”University of CagliariCagliariItaly
6. Present address: Hepatic Pathogenesis SectionLaboratory of Infectious DiseasesNational Institute of Allergy and Infectious DiseasesNational Institutes of HealthBethesdaMDUSA