Hajime Mori and Peter Metcalf
from: Insect Virology (Edited by: Sassan Asgari and Karyn N. Johnson). Caister Academic Press, U.K. (2010)
Cypovirus are members of the Reoviridae family of segmented dsRNA genome viruses which are unique amongst Reoviridae because the infectious forms of the virus are polyhedra, crystalline occlusion bodies containing thousands of virus particles that form in the cytoplasm of infected cells. Polyhedra are micron-size infectious protein crystals which function to protect the virus particles within the crystals from hostile environmental conditions. Polyhedra are stable, only dissolving at pH > 10.5 in the larval midgut, allowing virus particles released from ingested polyhedra to infect the epithelia. Here we briefly review current knowledge of cypovirus and summarize structures of both the virus particle and of polyhedra. The two structures provide a framework for understanding both the formation and stability of polyhedra, and the molecular events that cause virus particles to be incorporated into polyhedra in the cytoplasm of infected cells. This information has been exploited to develop a general method to stabilize proteins by incorporating them into modified polyhedra. We describe these modified polyhedra or 'nano-containers', which have a variety of applications, including the development of stabilized growth factors for cell-culture. Finally we discuss evidence for the possible evolution of cypovirus from members of plant Reoviridae read more ...