ISG15 and infection: To investigate whether sandfly viruses can inhibit IFN-signaling, we tested the induction of several ISGs following infection with sandfly fever virus Naples (SFNV) or Sicily (SFSV) and stimulation with IFN, including interferon-stimulated gene 15 (ISG15), myxovirus-resistance A (Mx1), and oligoadenylate synthetase 1 (OAS1, Figure 1A).