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The process of baculovirus deproteinization.

The localization and function of alkaline protease inside the supervirion capsids (granules, inclusion bodies) of granulosis virus and nuclear polyhedrosis virus have been determined with the help of electron microscopy. It has been shown that deproteinization of baculoviruses proceeds in several steps. The first two stages (the release of virus from supervirion capsids and the release of nucleocapsids from the internal and external coats, were accomplished in the intestine of the insects, while the third stage (the release of nucleic molecules from the nucleocapsids) took place in the nucleoplasm of intestinal epithelial cells.

Animals↗

Semliki Forest virus as an expression vector in insect cell lines.

Studies were undertaken to determine if replication-deficient Semliki Forest virus expression vectors could be successfully used to express foreign gene constructs in insect cell lines. Using green fluorescent protein (GFP) as a marker we recorded infection levels of nearly 100% in the Aedes albopictus cell lines C6/36 and Aa23T, as well as in the Ae. aegypti cell line MOS20. The virus was capable of infecting an Anopheles gambiae cell line MOS55. The amount of GFP protein produced in each cell line was quantified. Northern analysis of viral transcription revealed the presence of novel transcripts in Aa23T, C6/36, and MOS55 cell lines, but not in the BHK or MOS20. The initial characterization of these transcripts is described.

Aedes↗

Cell-free translation of Drosophila C virus RNA: identification of a virus protease activity involved in capsid protein synthesis and further studies on in vitro processing of cricket paralysis virus specified proteins.

Drosophila C virus RNA acted as mRNA in rabbit reticulocyte lysates and directed the synthesis of at least one capsid protein and a number of higher molecular weight proteins. Kinetic analysis by pulse-chase experiments showed that a number of high molecular weight products acted as precursors to the capsid protein(s). Various dilution experiments were performed which showed that the virus specified a protease activity essential for the correct processing of precursors to give the capsid protein(s). A similar result was obtained with Cricket paralysis virus, and mixing experiments showed that the protease activity specified by one virus could perform some of the cleavages resulting in the production of the capsid proteins of the other virus. Some of the cleavages involving the highest molecular weight precursors could not be performed by the protease activity of the other virus. We could find no evidence for intramolecular cleavage of the capsid precursors of either of the viruses.

Animals↗

Interference with polyhedral inclusion body (PIB) production in Trichoplusia ni cells infected with a high passage strain of Autographa californica nuclear polyhedrosis virus (NPV). Brief report.

Trichoplusia ni cells infected with a low passage (LP) strain of Autographa californica nuclear polyhedrosis virus (NPV) produce large numbers of polyhedral inclusion bodies (PIBs). Interference with PIB production occurs when T. ni cells are first inoculated with a high passage (HP) strain and then challenged with the LP strain. PIB production is reduced 100 fold to the level seen with HP virus infection only.

Cell Line↗

Nucleoside triphosphate phosphohydrolase associated with cytoplasmic polyhedrosis virus.

Nucleoside triphosphate phosphohydrolase [EC 3.6.1.15] activity was found to be included in silkworm cytoplasmic polyhedrosis (CP) virus, which synthesizes mRNA carrying the 5'-terminal modification. This enzyme releases orthophosphate from the gamma-position in a nucleoside triphosphate, leaving nucleoside diphosphate. The rate of hydrolysis of ATP is faster than that of any other ribonucleoside triphosphate. Deoxy ATP is hydrolyzed rather faster than ATP. However, polynucleotides carrying triphosphate at the 5'-terminus, that is, 4S RNA which was synthesized by E. coli RNA polymerase [EC 2.7.7.6] using calf thymus DNA as a template, and the phage Q beta RNA (30S), are not effective substrates for this enzyme. Although the CP virion loses the viral genome and one kind of protein component on proteolytic treatment with pronase, the partially degraded virion still retains phosphohydrolase activity. The phosphohydrolase must therefore be associated firmly with the virion. This enzyme does not require the presence of nucleic acid for its function. Phosphohydrolysis of ATP by this enzyme activity represents a first step in the synthesis of the 5'-terminal modified mRNA of CP virus.

Adenosine Triphosphate↗

DNA hybridization assay for detection of gypsy moth nuclear polyhedrosis virus in infected gypsy moth (Lymantria dispar L.) larvae.

Radiolabeled Lymantria dispar nuclear polyhedrosis virus DNA probes were used in a DNA hybridization assay to detect the presence of viral DNA in extracts from infected larvae. Total DNA was extracted from larvae, bound to nitrocellulose filters, and assayed for the presence of viral DNA by two methods: slot-blot vacuum filtration and whole-larval squashes. To test the assays, neonate larvae were fed droplets containing a known concentration of L. dispar nuclear polyhedrosis virus and observed for up to 10 days to determine the percentage of infected larvae. The average percent mortalities were 88.0, 60.7, 26.0, and 5.3% for larvae fed droplets containing 4.0 x 10(4), 1.0 x 10(4), 2.5 x 10(3), and 6.25 x 10(2) polyhedral inclusion bodies (PIBs) per ml, respectively. Other larvae treated with the same virus concentrations were frozen at 2, 4, and 6 days postinoculation and examined by the hybridization techniques. The average percentage of slot blots containing viral DNA equaled 81.0, 58.0, 18.0, and 6.0% for larvae blotted 4 days after treatment with 4.0 x 10(4), 1.0 x 10(4), 2.5 x 10(3), and 6.25 x 10(2) PIBs per ml, respectively, and 89.9, 52.1, 26.6, and 6.0%, respectively at 6 days postinoculation. Thus, the hybridization results were closely correlated with mortality observed in reared larvae. Hybridization of squashes of larvae frozen 4 days after receiving the above virus treatments also produced accurate measures of the incidence of virus infection.

Animals↗

Neutralisation of Trichoplusia ni nuclear polyhedrosis virus with antisera to two forms of the virus.

Two forms of a baculovirus, Trichoplusia ni nuclear polyhedrosis virus, one released at the plasma membrane of cells (cell released virus: CRV) and the other derived from polyhedra (polyhedron derived virus: PDV) occur naturally. Antisera raised against the two forms specifically neutralised the homologous form. The envelope proteins of the two forms were shown to be the major proteins involved in serum neutralisation and to be responsible for the antigenic diversity of the virus forms.

Animals↗