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Title: FLUORESCENT BRIGHTENER INHIBITS APOPTOSIS IN BACULOVIRUS-INFECTED GYPSY MOTH LARVAL MIDGUT CELLS

Author
item Dougherty, Edward
item Narang, Neelam
item Loeb, Marcia
item Lynn, Dwight
item Shapiro, Martin

Submitted to: Biocontrol Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/5/2004
Publication Date: 6/16/2005
Citation: Dougherty, E.M., Narang, N., Loeb, M.J., Lynn, D.E., Shapiro, M. 2005. Fluorescent brightener inhibits apoptosis in baculovirus-infected gypsy moth larval midgut cells. Biocontrol Science and Technology. 16:157-168.

Interpretive Summary: Insects, such as the gypsy moth, are serious pests of forest and agricultural crops. While chemical pesticides can effectively control them, these can have adverse effects on nontarget organisms, including the human population. Biological controls can also be effective and are safer but are also generally more expensive and act more slowly. We have previously shown that fluorescent brighteners, chemicals that are commonly used in laundry detergents, can increase the effectiveness of certain insect viruses as biological control agents. The mode of action of these materials is unknown but increasing our understanding could lead to even better effectiveness of these or similar materials. A cell culture system, also previously developed in this laboratory was used to study the effects of a fluorescent brightener on the infection by an insect virus specific for the gypsy moth. Based on these studies, it appears that fluorescent brighteners inhibit programmed cell death (apoptosis) by infected cells, thus allowing the viruses more time to grow. This, in turn, results in a greater number of pest insects dying. Researchers, at universities, government and commercial laboratories that are involved in developing these viruses as alternatives to chemical pesticides can use this knowledge to determine other materials which might also improve the effectiveness of these and other biological pest controls.

Technical Abstract: Fluorescent brightener significantly lowers the LC50 and LT50 in a variety of nucleopolyhedrovirus-insect host systems. In the gypsy moth, Lymantria dispar (L.), a European NPV strain of virus (LdMNPV) does not replicate in the midgut. However, addition of a fluorescent brightener (Calcofluor M2R) to the virus suspension does result in midgut replication in the gypsy moth larvae. In the current study, we have shown that LdMNPV also does not replicate in a larval midgut primary cell culture system unless a fluorescent brightener (Blankophor P167) is added. Morphological and cellular changes characteristic of apoptotic cell death were noted in infected midgut cells both in vivo and in vitro. In the current studies, we used the TUNEL assay to measure apoptosis in virus infected midgut cell cultures at 24-48 hrs post-infection. A significant decrease in apoptotic midgut cells was noted in the presence of 0.01M brightener. Similar results were recorded in virus-infected larval midguts following ingestion of LdMNPV and brightener. The inhibition of apoptosis and presumptive inhibition of shedding of infected midgut cells in the presence of fluorescent brightener in the insect midgut appeared to promote virus replication and are likely to be partly responsible for enhancement of LdMNPV activity that is observed in gypsy moth larvae.