Novel Toscana Virus Reverse Genetics System Establishes NSs as an Antagonist of Type I Interferon Responses

Viruses. 2020 Apr 4;12(4):400. doi: 10.3390/v12040400.


The sand fly-borne Toscana virus (TOSV) is the major cause of human meningoencephalitis in the Mediterranean basin during the summer season. In this work, we have developed a T7 RNA polymerase-driven reverse genetics system to recover infectious particles of a lineage B strain of TOSV. The viral protein pattern and growth properties of the rescued virus (rTOSV) were found to be similar to those of the corresponding wild-type (wt) virus. Using this system, we genetically engineered a TOSV mutant lacking expression of the non-structural protein NSs (rTOSVɸNSs). Unlike rTOSV and the wt virus, rTOSVɸNSs was unable to (i) suppress interferon (IFN)-b messenger RNA induction; and (ii) grow efficiently in cells producing IFN-b. Together, our results highlight the importance of NSs for TOSV in evading the IFN response and provide a comprehensive toolbox to investigate the TOSV life cycle in mammalian and insect host cells, including several novel polyclonal antibodies.

Keywords: Arbovirus; Bunyavirales; Phenuiviridae; Phlebovirus; Toscana virus; interferon; neglected diseases; reverse genetics; sand fly fever.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • A549 Cells
  • Animals
  • Antibodies, Viral / immunology
  • Cell Line
  • Chlorocebus aethiops
  • Cricetinae
  • DNA-Directed RNA Polymerases / genetics
  • Genome, Viral
  • Humans
  • Insecta
  • Interferon-beta / antagonists & inhibitors*
  • Interferon-beta / immunology
  • Kidney / cytology
  • Mutation
  • Reverse Genetics*
  • Sandfly fever Naples virus / genetics*
  • Sandfly fever Naples virus / immunology
  • Vero Cells
  • Viral Nonstructural Proteins / genetics*
  • Viral Nonstructural Proteins / immunology*
  • Viral Proteins / genetics


  • Antibodies, Viral
  • Viral Nonstructural Proteins
  • Viral Proteins
  • Interferon-beta
  • bacteriophage T7 RNA polymerase
  • DNA-Directed RNA Polymerases