1. Department of Medical Microbiology and Immunology “Prof. Elisey Yanev, MD”, Medical University–Plovdiv, Plovdiv, Bulgaria
2. Research Institute, Medical University–Plovdiv, Plovdiv, Bulgaria
3. Laboratory of Clinical Immunology, University Hospital “St. George”, Plovdiv, Bulgaria
4. Department of Epidemiology and Disaster Medicine, Faculty of Public Health, Medical University–Plovdiv, Plovdiv, Bulgaria