The silicon content of an intact granulosis virus from the salt-marsh caterpillar, Estigmene acrea

Abstract

In this chapter, the European cabbageworm (or large white butterfly), Pieris brassicae, and its granulosis virus (GV) are treated as a model system for the study of a baculovirus and its relationship with its host. An attempt is, therefore, made to bring together as much information as possible that has relevance to this system. This has necessitated frequent use of the results obtained with other hosts and other baculoviruses. For the most part, this approach is productive and seems to be fully justified by the growing evidence of the many points of similarity in the structure and composition of baculoviruses. The virus disease now known as “granulosis,” which occurs only in lepidopterous insects, was first discovered by the Frenchman Paillot in the larvae of Pieris brassicae. He called the disease pseudo-grasserie, since he recognized that the causative agent differed from that known to cause grasserie in the silkworm (Bombyx mori). The term “granulosis,” first proposed by Steinhaus, reflects both the granules observed and the gross appearance of the diseased tissue. However, when Bergold, working with the fir-shoot roller, Choristoneura (Cacoecia) murinana (Hubner), confirmed the suspected viral nature of granulosis disease by electron microscopy, he noted that each “granule” consisted of a capsule-like inclusion body surrounding a rod-shaped virus (virion). He, therefore, called them Viruskapseln, and the disease as Kapselvirus-Kranlcheit. It is now usual to refer to the inclusion body with the contained virion as a “capsule” and to designate the disease “granulosis”. In this chapter, intact virus or capsule means the virion surrounded by the granulin (inclusion body protein), virion, the nucleocapsid and its surrounding envelope (virus or outer membrane), and nucleocapsid, the viral DNA and the protein surrounded by the capsid (inner membrane). Also, granulosis virus (GV) or virus is used as a general term to designate any infective form of the virus (including subviral components); crude virus is the term used for decaying larvae containing virus with considerable quantities of contaminants, such as materials derived from the body of the host and microorganisms.