ASSEMBLY OF AMSACTA-MOOREI ENTOMOPOXVIRUS SPHEROIDIN INTO SPHEROIDS FOLLOWING SYNTHESIS IN INSECT CELLS USING A BACULOVIRUS VECTOR

The gene encoding the major occlusion body protein, spheroidin, of Ams acta moorei entomopoxvirus (AmEPV) was introduced into a baculovirus v ector under control of the polyhedrin gene promoter. A recombinant vir us produced large, ovoid occlusion body-like structures in both Spodop tera frugiperda and Trichoplusia ni cells. These structures resembled the spheroids found in AmEPV-infected Lymantria dispar cells, except t hey were devoid of virus particles and were not surrounded by a membra ne-or envelope-like structure. These results were confirmed by immunof luoresence microscopy and Western blotting using a specific antipeptid e antibody to spheroidin, and suggest that the supramolecular assembly of spheroids is not dependent on other EPV-encoded gene products. Tra nsmission electron microscopy and subcellular fractionation experiment s revealed that the spheroid-like structures were assembled in both th e nucleus and cytoplasm of the recombinant virus-infected cells. This contrasts with the solely cytoplasmic localization found in AmEPV-infe cted cells.