Lack of infection of vertebrate cells by the densovirus from the maize worm Mythimna loreyi (MlDNV)

Several densoviruses have been used successfully in biological control of pests in the tropics. The densovirus from Mythimna loreyi (MlDNV) could also be an important tool in biological control of important pests. However, safety concerns remain as previous reports suggested that densoviruses may infect and transform L cells (from mouse). In this study, we show using molecular-biology tools that neither L nor other vertebrate cells support replication or transcription of densovirus, either after infection or after transfection. Quantitative PCR indicated no increase of viral DNA due to replication in vertebrate cells, in contrast to that in insect LD652 cells. After transfection, both the NS and VP mRNAs could be detected in LD652 cells but not in L cells. Moreover, the viral genome was excised from the plasmid after transfection of the infectious clone in LD652 cells, indicative of viral NS protein production, in contrast to L cells. The viral genome was able to integrate in the host chromosome of L cells after transfection, but not after infection. However, no viral transcription could be detected after integration.