title: Polydnavirus-mediated inhibition of lysozyme gene expression and the antibacterial response.
abstract: Parasitism of lepidopteran host larvae by hymenopteran parasitoids impairs the cellular immune response via expression of polydnavirus genes. Encapsulation of parasitoid eggs is thereby prevented. Parasitized insects are susceptible to opportunistic infections, suggesting that additional components of the immune system are affected. Insects normally respond to infection by inducing the synthesis of an array of antibacterial factors, including cecropins and lysozyme via a NFkappaB/lkappaB-like signal transduction pathway. To characterize the effects of PDVs on the antibacterial immune response, plasma antibacterial activities were assayed in H. virescens larvae infected with the C. sonorensis PDV. Plasma lysozyme activity in Heliothis virescens was reduced in parasitized and PDV-infected larvae after immune challenge. To examine the regulation of lysozyme after CsPDV injection, the Heliothis virescens lysozyme cDNA was cloned. In contrast to plasma lysozyme activity, the 1.1 kb lysozyme mRNA was induced in fat body and haemocytes by known elicitors. The data suggest that CsPDV, like some other viruses, regulates host cell gene expression at the level of translation. We propose that the immunodeficiencies caused by CsPDV injection are caused, in part, by the targeted translational inhibition of specific humoral immune response transcripts.
authors.affiliation: Department of Entomology, University of Kentucky, Lexington 40546-0091, USA.
authors.forename: K S
authors.initials: KS
authors.lastname: Shelby
authors.forename: L
authors.initials: L
authors.lastname: Cui
authors.forename: B A
authors.initials: BA
authors.lastname: Webb
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003593:Cytoplasm; D018076:DNA, Complementary; D004790:Enzyme Induction; D005260:Female; D015971:Gene Expression Regulation, Enzymologic; D008837:Micrococcus / Q000276:immunology / Q000502:physiology; D008969:Molecular Sequence Data; D009036:Moths / Q000201:enzymology / Q000276:immunology* / Q000469:parasitology / Q000821:virology; D009113:Muramidase / Q000737:chemistry / Q000235:genetics*; D018071:Polydnaviridae / Q000502:physiology*; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic; D014863:Wasps / Q000502:physiology
chemical_list: D018076:DNA, Complementary; D009113:Muramidase