MECHANISMS OF DEVELOPMENTAL RESISTANCE TO BACULOVIRUS IN GYPSY MOTH (LYMANTRIA DISPAR)

Open Access
- Author:
- McNeil, James Robert
- Graduate Program:
- Entomology
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- October 02, 2008
- Committee Members:
- Kelli Hoover, Dissertation Advisor/Co-Advisor
Kelli Hoover, Committee Chair/Co-Chair
Diana Lynn Cox Foster, Committee Member
Consuelo M De Moraes, Committee Member
Frederick Eugene Gildow Jr., Committee Member - Keywords:
- immunity
hemocyte
developmental resistance
baculovirus
gypsy moth
pathogenesis - Abstract:
- Developmental resistance of lepidopteran larvae to mortal baculovirus infection is a welldocumented phenomenon. Viral susceptibility decreases as the insect ages within an instar and between instars. It is usually attributed to midgut-based barriers to infection, but developmental resistance within the fourth instar of the gypsy moth, Lymantria dispar, to the baculovirus Lymantria dispar multiple nucleocapsid nucleopolyhedrovirus (LdMNPV) involves both midgut and systemic components, making it an ideal model system for studying anti-viral responses in insect hosts. Investigations of LdMNPV pathogenesis using a construct genetically engineered with a lacZ reporter gene showed that mid-instar, resistant-aged larvae blocked or eliminated initial viral infections in the midgut more effectively than newly molted, susceptible-aged larvae. Systemic infections in resistant-aged larvae were either prevented from spreading by encapsulating infected tissue or eliminated entirely, possibly through apoptosis. Hemocytes were not resistant to infection and did not impede LdMNPV development. Further studies determined that immunosuppression of L. dispar larvae with a polydnavirus increased LdMNPV mortality, but did not eliminate developmental resistance. However, resistant-aged larvae were able to target immune responses more effectively than susceptible-aged larvae, and this difference reduced viral spread in vivo. These studies further expand our knowledge of the mechanisms of developmental resistance in lepidopteran/baculovirus systems and lay the groundwork for further studies of the mechanisms of anti-viral defenses in insect systems.