Major Groups of Insect Viruses

Abstract

Insect viruses are heterogeneous and are represented in most of the major viral taxa. Unlike other biological entities, virus classification is non-Linnaean and lacks the subphyla, class, order, and suborder hierarchical divisions. The International Committee on Taxonomy of Viruses (ICTV) has currently placed most known viruses into a hierarchical level of family (suffix - viridae) and in certain cases subfamily ( - virinae) and genus ( - virus). The species, the most important taxon in other living organisms, has been very difficult to apply to viruses. Conventional definitions that describe the species taxa do not apply to these biological macromolecules. A virus species is considered a cluster of virus strains that share common properties distinct from those of other viruses. The ICTV currently accepts the English vernacular name (i.e., poliovirus) as the species. Specialists of the various culture collections assign the hierarchical levels of subspecies, strains, and variants. In many cases, the species of a particular insect virus is named by its respective host. For example, the multiple-embedded nuclear polyhedrosis virus (MNPV) of the alfalfa looper Autographa californica is designated as AcMNPV. In this text, the insect viruses are placed into the major transcriptional virus groups (classes) proposed by Baltimore (1971). Each of these groups possesses a distinctive strategy of replicating and expressing its genetic material in receptive host cells (Table 3–1).