Nucleotide variability of Toscana virus M segment in strains isolated from clinical cases

Toscana virus (TOSV), a member of the Bunyaviridae family, is an important etiologic agent of neurologic infection transmissible to humans by bites of the Phlebotomus spp. In consideration of the variations in the antigenic properties of Bunyaviruses and their potential genetic variability, we analysed a large region (2500 nt) of the Toscana virus M segment coding for the non-structural protein (NSm) and the GN and GC glycoproteins in several strains isolated from patients with meningitis from 1998 to 2004 in the region of Tuscany in Italy. The sequences were compared with the reference strain of Toscana virus isolated from phlebotomus (ISS Phl. 3) and revealed some changes in amino acids, particularly in the GC protein, that are probably involved in recognition and binding to the cell receptor. The analyses were aimed at identifying the amino acid changes commonly to all of the clinical isolates potentially related to TOSV virulence.