Cypovirus

Cypoviruses (aka cytoplasmic polyhedrosis virus; CPV) are a genus of viruses in the Reoviridae family. The virions have an icosahedral structure typical of other reoviruses and are 55-69 nm in diameter. The genome is composed of 10 segments of double-stranded RNA. The virions are embedded in a protein matrix to form the structures referred to as polyhedra or occlusion bodies.

Cypoviruses have only been isolated from insects. Morphologically, these viruses have much in common with the much more widely studied nucleopolyhedroviruses (NPV), a genus of arthropod viruses in the Baculovirus family. However, CPV have a RNA genome and replicate in the cytoplasm of the infected cells while NPV have a DNA genome and replicate in the nucleus.

Pathogenesis
Infection occurs when a susceptible insect consumes the polyhedra, usually as a contaminant on the insect’s food (in most cases, foliage of a plant). The polyhedra dissolve in the digestive tract of the insect, releasing the virus particles that penetrate the gut epithelial cells. Replication of the virus is often confined to these cells and the progeny virus, in the form of new polyhedra are excreted in the insect feces, thus contaminating more foliage resulting in the spread of the disease to additional insects. The progression of the disease can be rather slow, but the virus infection is normally fatal