Host Range and Population Survey of Spodoptera frugiperda Rhabdovirus

Abstract

The Sf9 and Sf21 cell lines derived from ovarian tissues of the wide-host-range phytophagous lepidopteranSpodoptera frugiperdaare widely used for research and commercial-scale production of recombinant proteins. These cell lines are chronically infected with a rhabdovirus (Sf-RV) that does not cause any overt cytopathic effects. We demonstrate that wild populations ofS. frugiperdain the eastern United States and Caribbean are infected with genetically diverse strains of Sf-RV and that this virus is also capable of infecting cells ofSpodoptera exigua,Heliothis subflexa, andBombyx mori. Feeding studies demonstrated the ability ofS. frugiperdalarvae to deposit Sf-RV onto human-consumed vegetables during feeding. Although no evidence for replication in two species of plant cells was detected, subcellular localization studies demonstrated that the Sf-RV nucleocapsid was targeted to plasmodesmata, while two forms of the accessory protein were differentiated on the basis of their ability to localize to nuclei. Collectively, the results from this study suggest that environmental exposure of humans to Sf-RV is likely to be commonplace and frequent, but its inability to replicate in plant or human cells suggests that there is no substantial risk to human health.IMPORTANCEInsect-derived cell lines are widely used commercially for the production of vaccines and protein-based pharmaceuticals. After decades of safe and beneficial use, it was a surprise to the biotechnology industry to discover an endemic rhabdovirus in Sf9 cells. This discovery was made possible only by the substantial advancements in DNA sequencing technologies. Given the public health concerns associated with many rhabdovirus species, several initiatives were undertaken to establish thatSpodoptera frugiperdarhabdovirus (Sf-RV) does not pose a threat to humans. Such actions include the generation of cell lines that have been cleared of Sf-RV. Given that Sf9 is derived from a moth whose larvae feed on human-edible foods, we explored the prevalence of Sf-RV in its wild and lab-grown populations, as well as its ability to be deposited on food items during feeding. Collectively, our data suggest that there is no overt risk from exposure to Sf-RV.

Knockout of Dicer-2 in the Sf9 cell line enhances the replication of Spodoptera frugiperda rhabdovirus and conditionally increases baculovirus replication

“…Furthermore, an analysis of a dataset of deep-sequenced small RNAs bound to Ago2 in BmN cells [35] revealed abundant 20 nt reads mapping to the genome of SfRV in both polarities [58]. Since the BmN cell line, another lepidopteran cell line used for baculovirus expression, has also been reported to be persistently infected with SfRV [59], the presence of siRNA reads corresponding to the SfRV genome also suggests that SfRV RNA is targeted by endogenous Dicer-2 in this cell line. These observations provide indirect support to the hypothesis that SfRV RNA is targeted by Dicer-2 in Sf9 cells.…”

Advances in Control Strategies against Spodoptera frugiperda. A Review

“…The symptoms are loss of appetite, lethargy, body sagging, softening of the integument, and a tendency to turn off color. Some viruses studied against S. frugiperda are Rhabdovirus (Sf-RV) [61]; granulovirus (SfGV ARG) type 1, 2, and 3 [62,63]; ascovirus (SfAV-1a) [64]; ichnovirus (HdIV) [65]; and the most studied, nucleopolyhedrovirus (SfMNPV) [55,66]. Undoubtedly, this strategy has shown high efficiency in the control of S. frugiperda in in vitro evaluations.…”

Viruses of the Fall Armyworm Spodoptera frugiperda: A Review with Prospects for Biological Control

“…Sf-rhabdovirus was found permanently infecting Sf9 cells and the virus sequence was also detected in a parental Sf cell line, Sf21 [53]. In addition, Sfrhabdovirus is infectious to the High Five cell line from the noctuid Trichoplusia ni and the SL2 cell line from D. melanogaster but is not infectious to human cell lines [53,84]. Subsequently, two lepidopteran-associated new sigma-like viruses were discovered from RNAseq data [85].…”

“…Subsequently, two lepidopteran-associated new sigma-like viruses were discovered from RNAseq data [85]. More recently, the presence of genetically diverse isolates of Sf-rhabdoviruses was identified in naturally occurring adult S. frugiperda populations [84]. Nonetheless, no study has so far demonstrated the presence of the rhabdoviruses in any of the larval stages of FAW.…”