1. Virology Section, Department of Molecular Medicine, Sapienza University, Rome, Italy.
2. Division of Immunology and Allergy, Department of Medicine, Centre Hospitalier Universitaire Vaudois and University of Lausanne, Lausanne, Switzerland.
3. Microbiology Section, Department of Experimental, Diagnostic and Specialty Medicine, School of Medicine, University of Bologna, Bologna, Italy.
4. Department of Clinical Medicine, Sapienza University, Rome, Italy.