Induction of a nonoccluded baculovirus persistently infecting Heliothis zea cells by Heliothis armigera and Trichoplusia ni nuclear polyhedrosis viruses

A nonoccluded singly enveloped baculovirus (baculovirus X) persistently infects Heliothis zea (IMC-HZ-1) cells in culture. Singly enveloped nuclear polyhedrosis viruses from H. zea and Heliothis armigera, and multiply enveloped nuclear polyhedrosis viruses from Trichoplusia ni, Spodoptera frugiperda, and Spodoptera littoralis were all found to induce baculovirus X. Experiments are reported which use metabolic inhibitors and inactivated inducing virus to show that it is probable that a structural component of the virus, most likely a protein, is responsible for inducing baculovirus X. The persistent virus is induced to replicate by uv-inactivated virus but not by heat-inactivated inducing virus. The virus is not induced to replicate by a number of metabolic inhibitors in the absence of an inducing virus. Inhibition of transcription and translation prevents the induction of the persistent virus by an inducing virus. Inhibition of DNA replication has no effect on the induction of the virus. This suggests that the persistent virus genome is present in abundance in all cells.

Development and evaluation of methods to detect nucleopolyhedroviruses in larvae of the Douglas-fir tussock moth, Orgyia pseudotsugata (McDunnough)

Various molecular methods are used to detect pathogenic microorganisms and viruses within their hosts, but these methods are rarely validated by direct comparison. Southern hybridization, enzyme-linked immunosorbent assay (ELISA), and a novel DNA extraction/PCR assay were used to detect Orgyia pseudotsugata multiple nucleopolyhedrovirus (OpMNPV) in Douglas-fir tussock moth larvae. PCR was more sensitive than Southern hybridization and ELISA at detecting semipurified virus. ELISA, however, was the most accurate method for detecting virus within larvae, given that Southern hybridization and PCR produced false-negative results (31% and 2.5%, respectively). ELISA may be preferable in some applications because virus infections can be quantified (r(2) = 0.995). These results may be applicable to both applied and academic research that seeks to accurately identify the incidence of viruses and microorganisms that regulate insect populations.

Infectivity and pathogenicity of Baculovirus penaei (BP) in cultured larval and postlarval Pacific white shrimp, Penaeus vannamei, related to the stage of viral development

The infectivity and pathogenicity of the penaeid shrimp virus, Baculovirus penaei (BP), is influenced by the stage of viral development. This study consisted of a preliminary experiment which showed that nonocculuded virus administered per os is infective, followed by two infectivity experiments. In the first phase of each infectivity experiment, mysis stage larvae of Penaeus vannamei were inoculated with BP and samples of infected tissue were collected at various times postinoculation (p.i.). These samples were then used to inoculate either mysis or postlarval stage P. vannamei in the second phase of each experiment. Viral inocula prepared from patently infected tissues consistently produced infections in both mysis and postlarval stage shrimp. Inocula prepared from prepatently infected tissue collected 12-18 h p.i. produced infections in some, but not all replicate cultures, while inocula prepared from tissues collected earlier than 12 h p.i. were not infective. Viral development in mysis stage larvae was substantially delayed and the mortality was significantly lower when the viral inocula were prepared from prepatently compared to patently infected tissues. BP appears to be most pathogenic to larvae that have been exposed to inocula prepared from tissues that had recently developed a high prevalence of patent infections or about 72 h p.i.

Multiplication of a granulosis virus isolated from the potato tuber moth in a new established cell line of Phthorimaea operculella

A newly established cell line was obtained from the culture of embryonic cells of the potato tuber moth Phthorimaea operculella in low temperature conditions (19 degrees C) using modified Grace's medium supplemented with 10% fetal bovine serum. The population doubling time was about 80 h when cells were cultivated at 19 degrees C and 38 h at 27 degrees C. The cell line had a relatively homogeneous population consisting of various sized spherical cells. The cells were cultivated for more than 25 passages. Their polypeptidic profile was different from profiles of other P. operculella cell lines we previously described and from other lepidopteran cells. The new cell line was designated ORS-Pop-95. The complete replication of the potato tuber moth granulosis virus (PTM GV) was obtained in vitro by both viral infection and DNA transfection. PTM GV multiplied at a significant level during several passages of the cell line that was maintained at 19 degrees C. As long as the cells were maintained at 19 degrees C, virus multiplication could also be obtained at the same rate at 27 degrees C. To compare PTM GV multiplied both in vivo and in vitro, we used morphological identification, serological, DNA probe diagnosis and endonuclease digest profile analysis and confirmed the identity of the virus.

Establishment of a cell line derived from embryos of the potato tuber moth phthorimaea operculella (Zeller)

A cell line from the main insect pest of potatoes in tropical and subtropical areas, Phthorimaea operculella (Zeller), was obtained from embryoculture. These cells were cultured in Grace's modified medium. The cell line, designated ORS-Pop-93, had a heterogeneous population consisting of spherical and spindle cells with great capacity to adhere and a doubling time of 40 h. They were subcultured for more than 60 passages. Their polypeptidic profile was different from profiles of other lepidopteran cell lines. The cell line supports the multiplication of the Autographa californica nuclear polyhedrosis virus.

Horseradish peroxidase-labelled probes and enhanced chemiluminescence to detect baculoviruses in gypsy moth and eastern spruce budworm larvae

Horseradish peroxidase-labelled whole genomic DNA probes and enhanced chemiluminescence procedures were utilized to detect baculovirus in insect macerates blotted on nylon membranes. Detection levels were similar to those found using 32P-labelled probes; 5 x 10(3) occlusion bodies (OBs), 2 x 10(3) OBs and 4 x 10(4) OBs of Lymantria dispar (L.) nuclear polyhedrosis virus (LdNPV), Choristoneura fumiferana (Clem.) NPV (CfNPV) and C. fumiferana granulosis virus (CfGV) respectively using 10 ng/ml LdNPV DNA probe and 20 ng/ml CfNPV and CfGV probe concentrations. Quantities of purified viral DNA detected were 0.56 ng LdNPV, 0.20 ng CfNPV and 0.10 ng CfGV at similar probe concentrations. Cross reactions were observed between LdNPV DNA probes and CfNPV. Multiple probing of membranes blotted with insect macerates was capable of diagnosing the presence of NPV and GV on membranes. This procedure appears to be useful in the diagnosis of large numbers of insects for several baculoviruses.

Rate of increase of Autographa californica nuclear polyhedrosis virus in Trichoplusia ni larvae determined by DNA:DNA hybridization

The rate of increase and doubling time of the HOB clone of Autographa californica nuclear polyhedrosis virus (AcMNPV-HOB) in neonate Trichoplusia ni larvae was determined by measuring the increase in viral DNA through time following inoculation with average doses of 50 or 17,400 occlusion bodies per larva. Changes in total DNA and viral DNA through time were followed by fluorescence spectroscopy and quantitative slot-blot DNA:DNA hybridization, respectively. Total DNA content (i.e., larval DNA and viral DNA) of larvae infected with the intermediate dose lagged behind that of noninfected larvae 30 hr post-inoculation (p.i), reached a maximum at 51 hr p.i., and stayed constant thereafter. The total DNA content of larvae inoculated with the high dose lagged behind that of the control group from 18 hr p.i. and increased slowly until death of the larvae (ca. 48 hr p.i.). The amount of viral DNA in larvae inoculated with the intermediate dose increased exponentially between 15 and 42 hr p.i., reached a maximum at 48 hr p.i., and stayed constant until 68 hr p.i., by which time most larvae had died. The amount of viral DNA in larvae inoculated with the high dose did not increase exponentially; initially the rate of increase was the same as that for larvae inoculated with the intermediate dose but became progressively lower after 13 hr p.i. Calculations of the rate of increase for AcMNPV-HOB in neonate T. ni larvae inoculated with the intermediate dose and incubated at 29 degrees C resulted in a value of 0.264 hr-1 (doubling time: 2.63 hr).(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies to poliovirus detected by immunoradiometric assay with a monoclonal antibody

An immunoradiometric assay (IRMA) for the assay of antibodies to poliovirus antigens is described. Dilutions of the test sera or whole (finger prick) blood samples were incubated with the Poliovirus antigen bound to a solid phase and the specific antibody was detected by the addition of a mouse anti-human IgG monoclonal antibody (McAb), which was itself revealed by iodinated sheep IgG anti-mouse F(ab). We have shown that this technique is suitable for the estimation of IgG anti-poliovirus antibodies induced in children following polio vaccine. The present study shows that SPRIA provides a simple and inexpensive method for serological studies with poliovirus particularly for use in large-scale surveys.

Growth of nuclear polyhedrosis virus in larvae of the cabbage moth, Mamestra brassicae L

Growth of nuclear polyhedrosis virus (NPV) in 5 larval instars of cabbage moth, Mamestra brassicae, has been quantified using 2 methods. Numbers of polyhedra were estimated by light microscope counts while concentrations of virus protein antigen were estimated using ELISA. Virus growth was rapid initially but slowed during its later stages, although ELISA protein concentrations decreased once a peak had been reached. There was a linear correlation between polyhedral counts and virus protein during the initial growth phase. Maximum polyhedral production ranged from 2 x 107 (first instar) to 3.4 x 109 (fifth instar) and could be correlated directly to increasing larval weight. Using ELisa, virus antigen was detectable at least 24 hours before polyhedra were observed under the light microscope. Productivity ratios ranged from 83,500 in the first instar to 1352 in the fifth instar.

Applied and molecular aspects of insect granulosis viruses

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