Immunological characterization of Toscana virus proteins

The genome of Toscana virus (Bunyaviridae family, Phlebovirus genus) consis ts of three single stranded RNA segments (L, M, S), with negative polarity. The L and M segments contain a single ORF in viral complementary sense and the S segment contains two ORFs in "ambisense" orientation. The M segment codes for three proteins in 3'-5' genomic orientation: a 30 kDa non structu ral protein and two 65 kDa glycoproteins, GN, and GC. In this paper we repo rt the expression in E. coli of the S segment ORFs and of three regions of the L ORF. The expressed proteins were used to produce monospecific polyclo nal antibodies in mice. By using these antibodies the N and the NSs protein s were unequivocally assigned to the S viral-complementary and viral-sense ORFs, respectively, and the L protein to the L ORF. We have found that like N and L proteins, NSs protein is associated with the viral nucleocapsids i n mature virions, suggesting its possible involvement in early events of vi ral replication. NSs protein was also found associated with cellular polyso mes. In virus-infected cells the anti-L antibodies recognized proteins shor ter than the full-length L protein, possibly products of L subgenomic segme nts. Interestingly these defective products were not found in mature virion s, suggesting specific mechanisms in virion assembly.