1. Laboratorio di Microbiologia Molecolare e Biotecnologia (LA.M.M.B.), Dipartimento di Biotecnologie Mediche, Università di Siena, 53100 Siena, Italy.
2. Sclavo Vaccines Association, 53100 Siena, Italy.
3. Department of Microbiology and Immunology, Institute of Biomedicine, Sahlgrenska Academy, University of Gothenburg, Medicinaregatan 7A, Gothenburg, Sweden.
4. Department of Infectious Diseases, Leiden University Medical Center, Leiden, Netherlands.
5. Center for Vaccinology, Geneva University Hospitals and University of Geneva, 1211 Geneva, Switzerland.