The parasitic wasp Microplitis demolitor lays its egg into the hemocoel of a Lepidopteran larva, where the egg hatches and the larva develops and matures at the expense of the host. To evade the immune system of the host, the wasp has incorporated a polydnavirus, Microplitis demolitor Bracovirus (MdBV), which it inserts along with the egg into the hemocoel. The virus infects primarily hemocytes and fatbody cells, which then express viral gene products that are essential to the wasp's evasion of the phagocytic and encapsulation response mounted by the host. Among the viral proteins expressed are a family of proteins with homology to inhibitors of kappa-B binding Rel proteins (IkBs) from insects and mammals. My research involves testing the hypothesis that these proteins act to suppress the host immune system by competing with endogenous IkBs for binding of Rel protein transcription factors, thereby inhibiting the upregulation of immune factors that might be involved in clearing the parasite. I am also going to test the hypothesis that the 12 IkB like proteins have differential binding affinities for different Rel dimer combinations using recombinant viral proteins and well characterized Drosophila melanogaster Rel proteins. We hope to use this system as a tool to dissect and characterize the intricate immune responses regulated by Rel protein transcription factors.

My graduate studies involved determining how the insect cuticle morphs from a soft, pliable hydrophilic structure to a rigid, hard, hydrophobic exoskeleton; a process termed cuticle sclerotization. Cuticular proteins and chitin are secreted by the underlying epithelial cells and make up the bulk of the cuticle. Cuticle sclerotization, or tanning, occurs when N-acylcatecholamines in the cuticle are oxidized to electrophilic quinones and quinone methides by phenoloxidases. The quinones then undergo Michael addition by nucleophilic side chains of cuticular proteins, forming covalent attachment of cuticular protein to N-acylcatecholamine (a process termed catecholation). It is then hypothesized that the bound catechols are re-oxidized by phenoloxidases, which allows another nucleophilic addition of a different macromolecular entity (probably a cuticular protein or chitin). This process is thought to continue until most of the components of the cuticle are covalently cross-linked into a supra-molecular structure via the N-acylcatecholamines. This process, put forward by Pryor in 1940, is termed the quinone tanning hypothesis. To test this hypothesis we developed a simplified in vitro sclerotization model, involving recombinant cuticular proteins from Manduca sexta , the phenoloxidase laccase (both commercially available fungal laccase and recombinant laccase 1 from M. sexta ), and the N-acylcatecholamines N-beta-alanyldopamine and N-acetyldopamine. In this model we have demonstrated that the cuticular proteins become covalently cross-linked upon the oxidation of the N-acylcatecholamines with laccase, and are in the process of determining which residues of the protein are involved in covalently bonding the catecholamines and/or other residues in adjacent proteins.