Virus Genes 19:3, 251±252, 1999 # 1999 Kluwer Academic Publishers, Boston. Manufactured in The Netherlands.

Book Review

THE INSECT VIRUSES Edited by Lois K. Miller and L. Andrew Ball Publisher: Plenum Press, 1998, New York and London. Volume of the series: The Viruses. Heinz FraenkelConrat and Robert R. Wagner, eds. ISBN 0-306-45881-0 The viruses of vertebrates were the main focus of the research conducted in the last three decades. This research yielded plenty of information that allowed the classi®cation of these viruses into different families, the study of their mode of replication, the mechanisms of infection and interaction with their hosts, etc. In contrast, very little efforts were concentrated on studying the invertebrate counterparts of the mammalian viruses (including the insect viruses) and the result is that our knowledge about them is very little. Thus, even the classi®cation of the insect viruses is not completed as in the case of the Nudiviruses (chapter 3), previously assigned to the Baculoviridae family, and the Ascoviruses (chapter 4). ``The Insect Viruses'' is an attempt to update the information on the viruses that infect insects excluding the baculoviruses, the most investigated insect viruses, that are reviewed in another book of this series. The book starts dealing with the Entomopoxviruses (EPVs) that belong to the Poxviridae family that includes also the Poxviruses of vertebrates. From the very beginning we can distinguish in the EPVs a very particular viral form absent in the vertebrate viruses: occlussion bodies that contain the virions embedded in a paracrystalline matrix, providing protection to the viral particles from environmental stress and improving horizontal transmission. The EPVs share this particular viral phenotype with the Baculoviruses and Cypoviruses (chapter 11). The EPVs are pathogenic to all larval stages of the insect and adult forms, in contrast to the

Baculoviruses that infect only the larval stages. Interesting material is presented on EPV replication, initial studies in the genomic structure and genetic engineering of the 225 kbp DNA of the EPV genome. Also, the ability of these viruses to infect species of Orthoptera, Choleoptera and Diptera, in addition to Lepidoptera makes them appealing for utilization in biological control programs. The invertebrate iridescent viruses (chapter 2) caught the attention of the investigators because of the rainbow color observed in infected invertebrate hosts, due to the presence of paracrystalline viral particles in the host cells. These viruses present circularly permuted and terminal redundant double-stranded DNA genomes varying from 140 to 200 kbp in size. The recent classi®cation of the iridescent viruses of the Iridoviridae family of viruses of vertebrates and invertebrates into the Iridovirus genus and Chloriridovirus genus is discussed. The replication and genomic organization of Iridovirus of insects, such as IV6 of mosquitoes, is compared mainly to the vertebrate type virus of the family FV3 (Frog Virus 3). Pathology, ecology and modest success in insect control are presented as well. Chapter 3 deals with the Nudiviruses, previously classi®ed as non-occluded baculoviruses. These viruses possess the ability to establish latency and persistent infections. The Oryctes virus employed in the past in biological control of the palm tree pest, the beatle O. rhinoceros, is described brie¯y. Also, recent ®ndings on the persistent infection of insect cells by the Hz-1 virus, and the very interesting GSV (Gonadspeci®c virus) of moths, are presented in this chapter. The intriguing huge Ascoviruses (about 400 nm in length), without vertebrate homologues and still unclassi®ed is the subject of chapter 4. These viruses induce cleavage of the host cells into large saclike vesicles through their replication. The data existing on Lepidopteran ascoviruses like SAV (Spodoptera

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ascovirus), TAV (Trichoplusia ni ascovirus) and HAV (Helicoverpa zea ascovirus) and the ichneumonid wasp-associated Diadromus pulchellus ascovirus (DpAV) serve to illustrate the peculiarities of these viruses. Another example of an unusual group of insect viruses is presented in chapter 5, that deals with the Polydnaviruses of segmented circular-DNA genomes. These viruses display an obligate mutualistic association with parasitic Hymenoptera, such as the Campoletis sonorensis polydnavirus (CsPDV), representative member of the Ichnovirus subgroup of Polydnaviruses. This chapter mainly treats the molecular studies of this subgroup and less information is provided about the second subgroup of Polydnaviruses, the Bracoviruses. Expression of different segments of the genomes of Polydnaviruses in different hosts (wasp and parasitized Lepidoptera) is presented. Also, the ability of some of the viral products to immunosuppress the lepidopteran host is discussed allowing the reader to have an initial contact with these unique insect viruses. The insect members of the Parvoviridae family, namely the Densoviruses, is the subject of the next chapter. Though their genome is extremely small (about 6 kbp of single-stranded linear DNA), the information about the replication of these viruses comes mainly from the Junonia coenia, the Galleria mellonella and the Aedes egyptus DNVs. The ability to replicate other DNVs in tissue culture is probably the main obstacle for rapid progress in the study of Densoviruses. Chapter 7 provides detailed structural features of the single-stranded RNA Noda and Tetraviruses. This includes interesting considerations about the architecture required to package the viral genomes exempli®ed by the nodavirus NoV (Nudaurelia capensis o virus), the FHV (Flock house virus) and the BBV (Black beetle virus). Clear and colored illustrations help to clarify the theme. Particle maturation, viral entry and delivery of the viral RNA based on the structural data are presented. Chapters 8 and 9 deal with the biological aspects of Nodaviruses, transmissible from mosquitoes to vertebrates, and Tetraviruses, the only RNA viruses with host range exclusive to insects. The simplicity of the genome of Nodaviruses is emphasized as a good model for the study of translation, replication and encapsidation of viral RNA.

Although no cell line is available to replicate Tetraviruses, the small size of their genome may allow their use in biotechnological approaches, such as in transgenic plants engineered with the Helicoverpa armigera stunt virus (HaSV) or, as versatile particles for RNA delivery (chapter 9). The following chapter covers the picorna-like viruses including a comprehensive table of isolated strains. Representatives of these viruses mentioned in the text are the Drosophila C virus and the Cricket paralysis virus. Replication, host range, natural distribution and ecology of picorna-like viruses are presented as well. The Cypovirus genus of the Reoviridae family of viruses, that comprises the Cytoplasmic polyhedroviruses (CPV), is the subject of chapter 11. The ability of CPVs to generate cytoplasmic crystals that protect the infectivity of the viral particles from hostile environmental conditions facilitates their horizontal transmission. The biochemical characterization of these viruses is described. Some features about viral replication and comparative data on primary structure of polyhedrins are provided. Finally synergism and antagonism between CPV and other pathogens is presented. The book concludes with a chapter on Sindbis virus-based expression vectors, their utilization in expressional studies and in the control of disease transmitted by insect vectors (mosquitoes). The different themes treated in ``The Insect Viruses'' are presented very clearly and this is assisted by photographs and illustrations that facilitate their understanding. It is a good starting point for students and investigators interested in entering this ®eld. In summary, this book brings us the ``state of the art'' on insect viruses. It is a must for insect virologists, that emphasizes the richness of nature, and suggests that novel ®ndings about mechanisms adopted by insect viruses to adapt to their hosts (and the genomic-encoded executors of this mechanisms) are waiting for discovery. Nor Chejanovsky Entomology Department Institute of Plant Protection The Volcani Center, POB 6 Bet Dagan 50250, Israel E-mail: [email protected]