Jean-Claude Veyrunes

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.

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.

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.

Pathogenicity of diatraea saccharalis densovirus to host insets and characterization of its viral genome

Pathogenicity of the Diatraea saccharalis densovirus (DsDNV) was tested on its host larvae. The results showed that up to 4 days after inoculation, no larvae mortality was observed and the infected larvae started to exhibit the infection symptoms from the fourth day. After 5 days of infection, the cumulative mortality of infected larvae increased significantly and reached 60% after 12 days and 100% after 21 days of infection, whereas that of the control group was only 10% and 20%, respectively, after same periods of infection, suggesting that the high mortality of infected larvae groups was due to the high pathogenicity of DsDNV. The size of the DsDNA was determined by Electron microscopy visualization of viral DNA molecules and gel electrophoresis of both native and endonuclease digested DNA fragments. The total length of the native DsDNA was about 5.95 kb. The DsDNV DNA was digested with 16 restriction enzymes and a restriction map of those enzymes was constructed with 41 restriction sites. Comparison of the restriction map of the DsDNV genome with those of the genomes of Junonia coenia densovirus (JcDNV) and Galleria mellonella densovirus (GmDNV) indicated that the three densovirus genomes were found to share many identical restriction sites. Thus, most of the restriction sites of the following endonucleases Bam H I, Hha I, Xba I, Cla I, Asp 700, Spe I, Nco I and Bcl I, were found to be conserved among the three densovirus genomes. Symmetrical cleavage sites mapped at the both ends of the genome suggested the presence of inverted terminal repeats (ITRs) whose size was estimated to be about 500 bp. The similar genome size, almost identical restriction sites and presence of an ITR of about 500 bp for these three densoviruses suggested that they belong to the same group of ambisense densoviruses.

A symptomless «Drosophila X virus from haploid Drosophila cell lines and from fœtal calf serum: A further indication of the exogenous origin of this virus

Summary A virus morphologically similar to « Drosophila X virus (DXV) was obtained from haploid cell lines and from serum added to the culture medium. This virus (DXV 2 ) did not induce the usual symptoms of DXV on Drosophila, i.e. sensitivity to CO 2 and early mortality. DXV 2 has been compared to the classical virus (DXV 1 ). They are serologically identical and their RNA has two segments with the same electrophoretic mobility. DXV 2 is thus a non-pathogenic DXV mutant. The similarity of the DXV from cell lines and from corresponding calf serum shows that cellular infections come from the serum.

Étude d'un virus isolé d'une population naturelle de Culicoides sp. (Diptera: Ceratopogonidae)

Summary A virus was isolated from a natural population of larvae of Culicoides sp. The viral particles were naked, icosahedral, with an electron microscopic diameter of 54 nm. They banded at a density of 1.32 in CsCl. The genome consisted of two pieces of dsRNA with molecular weights of 2.5 and 2.6×106 daltons. The proteins were resolved into six polypeptides by polyacrylamide gel electrophoresis. According to these characteristics, this Culicoides virus is akin to infectious pancreatic necrosis virus, infectious bursal disease virus, Drosophila X virus, tellina virus and ostrea virus. In this group, the Culicoides virus and the Drosophila X virus are closely related.