The spheroidin of an entomopoxvirus isolated from the grasshopper Anacridium aegyptium (AaEPV) shares low homology with spheroidins from lepidopteran or coleopteran EPVs.

Based on virion morphology, the current virus taxonomy groups entomopoxviruses (EPVs) (Poxvirus: Entomopoxvirinae) from coleopteran and dipteran hosts in separated genera, wilts it keeps viruses infecting either lepidopteran or orthopteran hosts in the same genus. In contrast to the morphological criteria, the few data available from recent studies at the genetic level have suggested that EPVs infecting different insect orders are phylogenetically distant. In order to elucidate EPVs phylogeny we have cloned and sequence the highly conserved/highly expressed spheroidin gene of Anacridium aegyptium entomopoxvirus (AaEPV). This gene and its promoter is of interest for the development of genetic engineering on EPVs. The spheroidin gene was located in the AaEPV genome by Southern blot and hybridisation with specific degenerated oligonucleotides probes synthesised after partial sequencing of the purified spheroidin protein. A total of 3489 bp were sequenced. This sequence included the coding and promoter region of 969 residues 108. 8 kDa protein identified as spheroidin. AaEPV spheroidin contains 21 cysteine residues (2.2%) and 14 N-glycosylation putative sites distributed along the sequence. The cysteine residues are particularly abundant at the C-terminal end of the protein, with 11 residues in the last 118 aa. Our results confirm that the spheroidin is highly conserved only between EPVs isolated from the same insect order. Polyclonal antibodies raised against AaEPV spherules specifically revealed spheroidin in Western Blots failing to cross-react with MmEPV or AmEPV spheroidins or MmEPV fusolin. Comparison of spheroidins at the aa level demonstrate that AaEPV spheroidin shares only 22.2 and 21.9% identity with the lepidopteran AmEPV and the coleopteran MmEPV spheroidins, respectively, but 82.8% identity with the orthopteran MsEPV spheroidin. Only two highly conserved domains containing the sequence (V/Y)NADTG(C/L) and LFAR(I/A) have been identified in all known spheroidins. The phylogenetic tree constructed according to the CLUSTALX analysis program revealed that EPVs are clearly separated in three groups - lepidopteran, coleopteran and orthopteran - according to the insect order of the virus hosts. In base to our results, the split of the genus Entomopoxvirus B dissociating lepidopteran and orthopteran EPVs into two different genera is suggested.

Protein requirements for assembly of virus-like particles of Junonia coenia densovirus in insect cells.

The coding sequences of four overlapping polypeptides starting at four different in-frame AUG codons and co-terminating at the stop codon of the cap gene of Junonia coenia densovirus (JcDNV) were inserted under the control of the p10 promoter of Autographa californica nucleopolyhedrovirus (AcMNPV) to generate AcMNPV-VP1 (four polypeptides), AcMNPV-VP2 (three polypeptides), AcMNPV-VP3 (two polypeptides), and AcMNPV-VP4 (one polypeptide) recombinant viruses. In all cases, infection of Spodoptera frugiperda cells (Sf9) by each of the four recombinant viruses resulted in the production of virus-like particles (VLPs) 22-25 nm in diameter. The VLPs produced by the three recombinants AcMNPV-VP2, AcMNPV-VP3 and AcMNPV-VP4 were abundant and contained three, two and one polypeptides, respectively. VP4, the shortest polypeptide, thus appears to be sufficient for assembly of VLPs morphologically similar to those formed with two to four polypeptides. The ratio of VPs did not appear to be critical for assembly of the particles. The polypeptide starting at the first AUG immediately downstream from the p10 promoter was always the most abundantly expressed in infected cells, regardless of the construct. In contrast, plaque-purified AcMNPV-VP1 recombinants were unstable and produced less than one-twentieth of the VLPs produced by the others. All VP transcripts started at the TAAG late motif of the p10 promoter and had a poly(A) tail 14 nt downstream of a poly(A) addition signal located 98 nucleotides downstream of the common stop codon. No significant transcription initiation inside the cap sequence of AcMNPV-VP2, AcMNPV-VP3 and AcMNPV-PV4 was observed.

A nonoccluded reovirus of the olive fly, Dacus oleae.

We have isolated paraspherical viral particles, 60 nm in diameter, from adults of the olive fly (Dacus oleae) collected in Greece. The virus actively replicated in midgut epithelial cells and in advanced infections virions accumulated in microvilli. They were released in the gut lumen and were very abundant in fly faeces. The virions exhibited the salient features of reoviruses, with an external shell and an internal core with a tubular subunit protruding at each vertex of the icosahedron. The viral genome consisted of ten segments of double-stranded RNA totalling 23.4 kbp. Based on its overall properties, this virus can be considered as a nonoccluded insect reovirus.

The Melolontha melolontha entomopoxvirus (MmEPV) fusolin is related to the fusolins of lepidopteran EPVs and to the 37K baculovirus glycoprotein.

We have cloned and sequenced a 1.7-kbp DNA fragment of the MmEPV genome encompassing the major polypeptide of the spindle-shaped inclusions gene termed fusolin. The sequence contained a single open reading frame of 1203 nt capable of coding for a polypeptide of 45.8 kDa. The 13 N-terminal amino acid (aa) residues were hydrophobic and could act as a signal peptide. The aa sequence also contained 13 cysteine residues very likely involved in paracrystal formation. This sequence showed significant homologies with the fusolins of two lepidopteran EPVs, the Choristoneura biennis EPV (CbEPV) and the Heliothis armigera EPV, and also with the 37K glycoproteins of Autographa californica and Orgyia pseudotsugata baculoviruses. No homology was found between the MmEPV fusolin and the 100K MmEPV spherulin, nor with the 110K polypeptide of the CbEPV and Amsacta moorei EPV spheroidins. These data were confirmed by Western blot analysis. Transfection of vaccinia-infected mammalian cells with a plasmid encompassing the fusolin sequence plus the upstream regulatory region resulted in transient expression of the gene. This indicated that the vaccinia transcription machinery is able to transcribe the fusolin gene. The fusolin was also expressed in insect cells via a recombinant baculovirus.

Cloning and sequencing of the spherulin gene, the occlusion body major polypeptide of the Melolontha melolontha entomopoxvirus (MmEPV).

In the late stage of infection, virions of the Melolontha melolontha entomopoxvirus (MmEPV) are occluded into cytoplasmic paracrysalline proteinaceous occlusion bodies designated spherules (A. Amargier, C. Vago, G. Meynadier, 1964, Mikroskopie 19, 309-315). We have cloned and sequenced a 4-kpb DNA fragment of the MmEPV genome encompassing the spherule major protein gene named spherulin. The spherulin gene contains an open reading frame able to code for a 942-amino-acid (aa) polypeptide (MW 109 kDa), consistent with a size above 100 kDa determined by SDS-PAGE for purified spherulin. The MmEPV spherulin showed more than 40% as homology with the Amsacta moorei EPV (AmEPV) spheroidin and shared homologies with the partially sequenced Choristoneura biennis EPV (CbEPV) spheroidin, indicating that this biologically important polypeptide is well conserved among EPVs infecting phylogenetically as distant groups of insects as lepidoptera and coleoptera. Western blot analyses confirmed the relationships between the three polypeptides. In contrast, no homology was detected between the MmEPV spherulin and EPV fusolins or vertebrate poxvirus A-type inclusion proteins. The 45 bases upstream from the ATG initiation codon of spherulin shared 60% homology with the vaccinia virus late promoters including the highly conserved TAAATG consensus sequence. Furthermore, the 5' extremity of the spherulin mRNA consisted of a poly(A) tract of about 20 nucleotides just upstream from the AUG translational initiation codon. These are characteristic features of vertebrate poxvirus late mRNAs suggesting similar modalities of gene expression for vertebrate and insect poxvirus genomes.

Restriction maps and sequence homologies of two densovirus genomes.

The genomes of Junonia coenia densonucleosis virus (JcDNV) and Galleria mellonella densonucleosis virus (GmDNV) were analysed by restriction endonuclease analysis and Southern blot hybridization. A total of 37 and 33 restriction sites were mapped on JcDNV and GmDNV DNA, respectively. BglI, HaeII and BstEII were site-specific for JcDNV DNA, and BglII and ClaI for GmDNV DNA. The two genomes had nearly identical maps for several restriction endonucleases and Southern blot hybridization using a total genomic JcDNV probe indicated extensive DNA sequence homologies spanning the entire length of the two genomes. Symmetrical cleavage sites, mapping at the extremities of both genomes, confirmed the presence of inverted terminal repeats of at least 420 to 440 bases in length.

Drosophila S virus is a member of the Reoviridae family.

The S character of Drosophila simulans, the absence or malformation or both of bristles and other cuticular structures, was described by Comendador (Drosophila Inf. Serv. 55:26-28, 1980). Its characteristics (maternal transmission, low pathogenicity, and sensitivity to temperature) suggested the existence of a virus as the causative agent. Indeed, reoviruslike particles were found in subcuticular cells of S individuals, and its association with S phenotypic expression was shown. This virus was called Drosophila S virus (DSV) (C. Louis, M. López-Ferber, N. Plus, G. Kuhl, and S. Baker, J. Virol. 62:1266-1270, 1988). We report here the purification and analysis of some properties of DSV particles, the morphology (spherical, 60 nm in diameter with an electron dense central core and less dense shell) and genome composition (double-stranded RNA divided into segments), which classify DSV as a new member of the family Reoviridae.

[Discovery and purification of a virus in gland hyperplasia of insects. Study of Merodon equistris F. (Diptera, Syrphidae)]. / Mise en évidence et purification d'un virus dans la prolifération monstrueuse glandulaire d'Insectes. Etude sur Merodon equestris F. (Diptè4re, Syrphidae).

ADNA virus was purified from the salivary gland affected by a large proliferation in the Diptera Merodon equestris. Structure, nucleic acid as well as development and intracellular cycle of the virus have been characterized.

A comparison of buoyant density and polypeptides of Drosophila P, C and A viruses.

On the basis of their buoyant densities in CsCl and their capsid polypeptides, three viruses isolated from Drosophila spp. which were originally described as serotypes, are now classified as distinct viruses. The biochemical properties of each virus suggest that it has several key features in common with the mammalian picornaviruses.

[Ultrastructure, development and nucleic acid of the S virus from the decapod crustacea Macropipus depurator L]. / Ultrastructre, développement et acide nucléique du virus S du crustacé décapode Macropipus depurator L.

The "S" crabe virus recently isolated from Macropipus depurator (Decapoda) has been purified and its nucleic acid has been recognized as a DNA. The visualization of the structure and of several phases of the cycle of the virus permits to situate this virus near the Bunyavirus and Paramyxovirus groups.