Summary auto-generated
This study demonstrates that a laboratory culture of Mamestra brassicae (cabbage moth) insects harbors a persistent, low-level infection with a baculovirus closely resembling M. brassicae multiple nucleocapsid nucleopolyhedrovirus (MbMNPV). Although conventional virus detection methods failed to identify infectious particles in the laboratory-cultured insects (MbLC), feeding virus-free wild-stock insects (MbWS) with MbLC fat-body cells resulted in overt MbMNPV infection and death. The researchers found polyhedrin-specific mRNA in MbLC fat-body cells using RT-PCR, and demonstrated the presence of viral transcriptional factors capable of activating baculovirus early, late, and very-late gene promoters. Additionally, cell lines derived from MbLC fat-body tissue induced MbMNPV infection when fed to MbWS larvae, with viral DNA characterized by restriction analysis confirming genuine MbMNPV infection. These findings provide indirect evidence that the latent MbMNPV persists as a low-level chronic infection rather than as dormant integrated or episomal DNA, with continuous but minimal expression of viral genes and production of infectious particles.
Key findings
- A laboratory culture of M. brassicae insects contains a persistent, low-level MbMNPV infection detectable only through sensitive techniques like RT-PCR, not conventional virus extraction methods
- Fat-body cells from infected insects express polyhedrin mRNA and viral transcriptional factors capable of activating early, late, and very-late baculovirus gene promoters
- Cell lines established from infected fat-body tissue retain infectious MbMNPV particles capable of causing overt infection in virus-free insects when fed orally
- The persistent infection differs from latent viral states maintained as integrated or episomal DNA, suggesting continuous low-level viral protein expression occurs within infected cells
- Virus sequences and gene expression are localized to fat-body tissue and detected throughout the insect life cycle (egg, larval, pupal, and adult stages)
This summary was generated automatically from the article PDF and is not part of the original publication. Refer to the PDF for the authoritative text.
Abstract
A laboratory culture of Mamestra brassicae insects (MbLC) harbours a latent or occult baculovirus that resembles M. brassicae multiple nucleocapsid nucleopolyhedrovirus (MbMNPV). Although conventional extraction techniques have failed to detect the presence of virus in MbLC, control virus-free insects (MbWS) died of an MbMNPV-like infection after being fed MbLC fat-body cells. This suggested that the MbLC cells harboured infectious MbMNPV, albeit at low levels. We have also demonstrated that fat-body cells from MbLC, but not from MbWS, contain mRNA specific for the polyhedrin gene and transcriptional factors that are capable of activating baculovirus late and very late gene promoters linked to a reporter gene encoding chloramphenicol acetyltransferase. Our data provide indirect evidence that the latent MbMNPV in the MbLC insects is maintained as a persistent infection, with the expression of viral genes at a low level.