Infectivity and mode of action of Baculoviruses

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Abstract
The genus Baculovirus contains three subgroups of viral types: (1) nuclear polyhedrosis viruses (NPVs), (2) granulosis viruses (GVs), and (3) nonoccluded baculoviruses. While little information is available for viruses from the third subgroup, several aspects of the infectivity and mode of action of NPVs and GVs have been studied. The most common route of entry of a virus into an insect host is per os, and both virus types enter midgut cells (primary site of infection) by membrane fusion. However, two distinct mechanisms of virus uncoating occur among the baculoviruses: NPVs uncoat within the nucleus, whereas GVs uncoat at the nuclear pore complex. Baculoviruses of subgroup 3 appear to uncoat by either mechanism. In addition to replicating within the nucleus, NPV inoculum virus may pass through the intestinal epithelium immediately after ingestion, thereby establishing a systemic infection of the hemocoel prior to virus replication in midgut cells. The GVs do not appear to pass through midgut cells as rapidly as NPVs and in general, the developmental cycle of GVs is longer than that of NPVs. NPVs have been grown in cell culture while GVs have not.