The effect of inhibitors on the growth of the entomopoxvirus from Amsacta moorei in Lymantria dispar (gypsy moth) cells.

Within the family of Poxviridae, the entomopoxviruses are the most distant relatives of the more well-known and intensively studied orthopoxviruses (vaccinia and variola). The growth of the entomopoxvirus from Amsacta moorei (AmEPV) has been characterized in cell culture and compared to that of vaccinia virus (VV), the prototypic orthopoxvirus. The overall characteristics of infected cell cultures were generally similar between the two viruses. One striking difference noted was the apparent absence of proteolytic processing of late AmEPV viral proteins, a hallmark of vertebrate poxvirus infections associated with viral morphogenesis. AmEPV, like VV, was found to be sensitive to all the inhibitors of viral infection tested including phosphonoacetic acid, 1-beta-D-arabinofuranosylcytosine, and isatin-beta-thiosemicarbazone (IBT), a compound associated with the rather specific inhibition of vertebrate poxviruses. While both VV and AmEPV are inhibited by IBT, the inhibition of AmEPV, unlike that of VV, is not accompanied by either a breakdown of ribosomal RNA or a global inhibition of late viral protein synthesis. Instead, in the presence of IBT, AmEPV enveloped, immature virions form devoid of a well-differentiated core, which unlike mature virions fail to insert into occlusion bodies.