No evidence of productive replication of two insect rhabdoviruses in mammalian cell lines.

Bombyx mori taastrup virus (BmTV) and Spodoptera frugiperda rhabdovirus (SfRV) persistently infect insect cell lines used in baculovirus expression vector systems. To assess their biosafety, eight mammalian cell lines were inoculated with conditioned medium containing both viruses. Viral RNA levels declined rapidly, with no evidence of productive replication; an independent 3-day experiment likewise showed significant decreases in three representative mammalian cell lines. No recoverable infectious BmTV was detected in culture supernatants from selected mammalian cell lines at 14 days postinoculation. Transient viral RNA persistence and increased metabolic activity in two cell lines suggest possible cell type-specific responses to virus exposure.