Complete sequence characterization of the genome of the St Croix River virus, a new orbivirus isolated from cells of Ixodes scapularis

An orbivirus identified as St Croix River virus (SCRV) was isolated from ce lls of Ixodes scapularis ticks, Electron microscopy showed particles with t ypical orbivirus morphology, The SCRV genome was sequenced completely and c ompared to previously characterized orbivirus genomes, Significant identity scores (21-38%) were detected between proteins encoded by segments S1, S2, S4, S5, S6, S8, S9 and S10 of SCRV and those encoded by segments S1, S3, S 4, S5, S6, B7, S9 and S10, respectively, of Bluetongue virus (BTV), the pro totype orbivirus species, The protein encoded by SCRV genome segment 3 (VP3 ) is thought to be the equivalent of VP2 of BTV, Segment 7 encodes a protei n homologous to non-structural protein NS2(ViP) of BTV, Analysis of VP 1(Po l) (segment 1) shows that SCRV is an orbivirus, distantly related to the ot her sequenced species, Blot hybridizations and sequence comparisons of the conserved protein encoded by genome segment 2 (the T2 subcore shell protein ) with previously identified orbiviruses confirm that SCRV is a distinct or bivirus species, unrelated to another tick-borne species, Great Island viru s, The presence of SCRV in cells prepared from tick eggs suggests that tran sovarial transmission of SCRV may occur in ticks.