occlusionderived

Occlusion-derived (often written as occlusion-derived virus or ODV) is a term used in virology to describe one form of virion produced by members of the Baculoviridae family. Baculoviruses generate two distinct virion types during infection: occlusion-derived virions (ODVs) and budded virions (BVs). ODVs are embedded within protein matrices known as occlusion bodies, which protect the virions in the environment and facilitate transmission between insect hosts.

ODVs are responsible for oral infection of insects. After an insect larva ingests occlusion bodies, the alkaline conditions of the gut dissolve the protein matrix and release ODVs. The virions then infect midgut epithelial cells, initiating the narrow, localized infection that can lead to systemic spread via budded virions. This dual-virion strategy enables both environmental persistence and efficient systemic infection within the host.

Structurally, ODVs are enveloped nucleocapsids with a distinct envelope that carries specific proteins required for oral infectivity. The occlusion bodies themselves are typically composed of polyhedrin in nucleopolyhedroviruses (NPVs) or granulin in granuloviruses (GVs). Per os infectivity factors (PIFs) embedded in the ODV envelope are essential for initiating infection in the gut.

Ecologically and practically, baculoviruses and their ODVs are used as biological control agents against pest insects. The environmental stability of occlusion bodies supports field deployment, while the host specificity of many baculoviruses helps minimize non-target effects.

See also: Baculoviridae, occlusion bodies, polyhedrin, granulovirus, per os infectivity factors.