Characterization of Sf9 cell clones with differential susceptibilities to Sf-rhabdovirus X and Sf-rhabdovirus X replication.

Our laboratory previously discovered a novel rhabdovirus in the Spodoptera frugiperda Sf9 insect cell line that was designated as Sf-rhabdovirus. Using limiting dilution, this cell line was found to be a mixed population of cells infected by Sf-rhabdovirus variants containing either the full length X accessory gene with a 3.7 kb internal duplication (designated as Sf-rhabdovirus X) or lacking the duplication and part of the X gene (designated as Sf-rhabdovirus X), and cells that were negative for Sf-rhabdovirus. In this paper, we found that the Sf-rhabdovirus negative cell clones had sub-populations with different susceptibilities to the replication of Sf-rhabdovirus X and X variants: cell clone Sf9-13F12 was more sensitive to replication by both virus variants compared to Sf9-3003; moreover, Sf9-3003 showed more resistance to X replication than to X replication. RNA-Seq analysis indicated significant differentially expressed genes in the Sf9-13F12 and Sf9-3003 cell clones further supporting that distinct sub-populations of virus-negative cells co-exist in the parent Sf9 cell line.