Protein composition of the Diachasmimorpha longicaudata entomopoxvirus (DlEPV) extracellular mature virion

DlEPV is a symbiotic entomopoxvirus of the Diachasmimorpha longicaudata parasitic wasp (Braconidae) that inhibits the encapsulation response by hemocytes of their larval host Anastrepha suspensa (Diptera: Tephritidae). In our ongoing effort to identify and characterize the DlEPV virion proteins, Edman degradation and HPLC-MS/MS analyses of proteins were conducted using sucrose-purified DlEPV virions fractionated by SDS-PAGE. The resulting peptides, identified (=/>95 % probability) by the Mascot and Scaffold programs, were used to blast the non-redundant ncbi and our existing DlEPV partial genomic databases. Homologs of >10 poxvirus proteins were identified. These included the major core proteins P4a and P4b and enzymatic proteins such as the nucleoside triphosphate phosphohydrolase (NPH) I and II and poly(A) polymerase catalytic large subunit (PAP-L). Mouse polyclonal anti-DlEPV sera (pAb) used to probe western blots of hemocyte proteins from hosts at different times (hours) post parasitism (hpp), revealed that the P4 core proteins were the first to be detected 12-24 hpp. Transmission electron microscopy also revealed that at 12-24 hpp, infecting virions attached to and coalesced with hemocyte membranes via long membranous spikes and their cores were released into the cytoplasm. Confocal immunofluorescence microscopy using the pAb and a Zenon-labeled goat anti-mouse second antibody, detected the virions at the periphery of the hemocyte cytoplasm within 72 hpp. Sequence alignment of the P4 and other structural proteins with their chordopoxvirus and entomopoxvirus homologs revealed 30-40 % and 40-55% amino acid identities, respectively. The effect of viral membrane proteins on host hemocyte behavior is currently under investigation in our laboratory.