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M D Summers

Publications and source records attributed to M D Summers.

12 recordsLinked to original sources
PubMed1992

Sequence, genomic organization of the EcoRI-A fragment of Autographa californica nuclear polyhedrosis virus, and identification of a viral-encoded protein resembling the outer capsid protein VP8 of rotavirus.

We present the sequence and genomic organization of the EcoRI-A fragment of the Autographa californica multicapsid nuclear polyhedrosis virus, which represents 11% of the AcMNPV genome. Fifteen putative open reading frames and their respective amino acid sequences are described. One open reading frame is similar to the VP8 protein of rotavirus.

Amino Acid Sequence↗
PubMed1990

Use of early baculovirus promoters for continuous expression and efficient processing of foreign gene products in stably transformed lepidopteran cells.

Baculoviruses are currently used as vectors for the transient high-level expression of foreign gene products in insect cells. In this study, we demonstrate that baculoviruses can also be made to continuously express a foreign gene product by using the promoter from IE1, an immediate early viral gene, to produce stably-transformed insect cells. This approach gave levels of foreign gene expression lower than those usually obtained with the lytic baculovirus expression vector system. Expression, however, was continuous and stable, and a complex human glycoprotein (tissue plasminogen activator) was processed more efficiently. We conclude that stable transformation is a feasible approach for baculovirus-mediated foreign gene expression in lepidopteran cells, particularly for products that are relatively poorly-expressed and/or processed in lytically infected cells.

Animals↗
PubMed1979

Autographa californica nuclear polyhedrosis virus structural proteins compared from in vivo and in vitro sources.

Polyhedrin obtained from Autographa californica nuclear polyhedrosis virus (AcMNPV) was apparently not modified in terms of primary structure after passage through alternate host systems, both in vivo and in vitro, as investigated by two-dimensional, high-voltage electrophoresis of tryptic digests of this protein as well as amino acid analysis. N-terminal analyses were conducted using an improved technique which showed proline to be the N-terminal amino acid. In addition, passage of enveloped nucleocapsids through alternate hosts as studied by SDS-PAGE showed the polypeptide compositions to be very similar.

Amino Acids↗
PubMed1978

Immunoperoxidase detection of baculovirus antigens in insect cells.

The sequence of events in the infection of TN-368-10 and TN-368-13 cells by Autographa californica nuclear polyhedrosis virus (AcMNPV) was investigated by using the indirect immunoperoxidase technique. Antisera raised against enveloped nucleocapsids detected homologous antigens at 6 to 8 h post infection which was about 2 h before the appearance of both intracellular and extracellular infectious virus. Similar tests using polyhedrin antiserum showed that polyhedrin is first synthesized at 12 h post infection, 2 to 4 h after the appearance of infectious nonoccluded virus. The immunoperoxidase technique was also applied to four other invertebrate cell lines after inoculation with AcMNPV. The most significant result was that 90% of AcMNPV-inoculated Bombyx mori 5 cells produced enveloped nucleocapsid antigens and infectious virus but only 1% or less of the cells produced polyhedrin. This disparity emphasizes the need for assays for NPV infection that are independent of polyhedron production.

Antigens, Viral↗
PubMed1976

Comparison of biophysical and morphological properties of occluded and extracellular nonoccluded baculovirus from in vivo and in vitro host systems.

Electron microscopic examination and buoyant density profiles of nonoccluded Rachiplusia ou and Autographa californica nuclear polyhedrosis viruses purified from both infectious insect hemolymph and cell culture medium revealed that the viruses are enveloped, single nucleocapsids. The envelopes exhibited variation in the amount and degree of fit with regard to the nucleocapsids. This was determined by: (i) electron microscopic observations of virus budding from the surface of infected cells; (ii) electron microscopic observations of negatively stained preparations of pelleted, highly purified, nonoccluded enveloped particles; and (iii) the resolution and density distributions of nonoccluded virus in sucrose gradients after centrifugation to equilibrium; all were compared with virus extracted from polyhedra. Peplomers, ovserved on the surface of enveloped nucleocapsids of nonoccluded virus, are not associated with polyhedra-derived virus. Density gradient analysis indicated that virus from insect hemolymph and culture medium exhibited similar densities of approximately 1.17 to 1.18 g/ml. This is significantly different from the buoyant density of an alkali-liberated, enveloped single nucleocapsid (1.20 g/ml). Results of this study show that the nonoccluded forms of two nuclear polyhedrosis viruses from two different sources, hemolymph and cell culture, are similar with regard to several morphological and biophysical characteristics but are quite different from the alkali-liberated, polyhedra-derived form of the virus.

Animals↗
PubMed1976

Occluded and nonoccluded nuclear polyhedrosis virus grown in Trichoplusia ni: comparative neutralization comparative infectivity, and in vitro growth studies.

Nuclear polyhedrosis virus infections of lepidopteran cells often result in the production of both occluded and nonoccluded virus. The characterization of these two different forms has been the subject of several papers. We have divided the nonoccluded virus (NOV) category further into plasma membrane-budded non-occluded virus (PMB-NOV), intracellular NOV, and hemolymph-derived NOV, and have done additional studies investigating the differences between these nonoccluded forms and the alkali-liberated forms from occlusions of the nuclear polyhedrosis viruses of Autographa californica and Rachiplusa ou. The methods used to discern differences and similarities among the forms were serological, biochemical, and visual, all related to their biological acitivity. Neutralization studies revealed that alkali-liberated virus and PMB-NOV had both similar and different antigens. Antisera raised against alkali-liberated virus from occlusions neutralized the alkali-liberated form of the virus, but did not neutralize the intracellular or extracellular nonoccluded forms. Antisera raised against the TN-368-13 PMB-NOV, however, neutralized the alkali-liberated forms as well as all forms of the NOV. Adsorption of this antisera with alkali-liberated virus did not diminish the neutralization titer against the nonoccluded forms, thus confirming the antigenic differences between the alkali-liberated and nonoccluded forms of the virus. Physical-infectious particle ratio calculations indicated that the PMB-NOV of Autographa californica are about 1,900-fold more infectious than the single-nucleocapsid-per-envelope alkali-liberated particles and about 1,700-fold more infectious than the multiple-nucleocapsid-per-envelope particles, as assayed in vitro. In addition, a study of viral growth kinetics monitored concurrently with the appearance of polyhedra showed that PMB-NOV production is shut down with the onset of polyhedron formation.

Animals↗
PubMed1975

Trichoplusia ni granulosis virus granulin: a phenol-soluble, phosphorylated protein.

Trichoplusia ni granulosis virus granulin consists of one major polypeptide component with an estimated molecular weight of 28,000. The protein is phenol soluble, phosphorylated, and acidic. A protease activated by alkaline conditions is also associated with solubilized granulin preparations. If not properly inactivated, the protease will introduce extensive artifact into the protein giving rise to ambiguous and incorrect results as analyzed by SDS-polyacrylamide gel electrophoresis and peptide mapping. Procedures are documented for enzyme inactivation and the preparation of granulin in highly purified form for characterization.

Amino Acids↗
PubMed1975

Nuclear polyhedrosis virus detection: relative capabilities of clones developed from Trichoplusia ni ovarian cell line TN-368 to serve as indicator cells in a plaque assay.

Cloned cell lines from the established Trichoplusia ni line TN-368 appear to differ from one another in their relative capabilities to serve as plaque assay indicator cell lines for Autographa californica nuclear polyhedrosis virus. Although there seems to be little correlation between their relative generation times and their efficiency in supporting plaque formation as indicator cell lines, there does seem to be a relationship within a given line between its capability to serve as an indicator and its phase of growth as a population; i.e., lag, logarithmic, or stationary. Both the parent line and clone 10 were more efficient indicators when they were in the logarithmic phase of growth than when in either the lag or stationary phases. Also, there appears to be a rough correlation between the capability of a given clone to serve as an indicator and the rate at which polyhedra first appear in the nuclei of the infected cells, with the best indicators producing polyhedra first. Increased incubation time has no effect on equalizing the plaque assay results for the less efficient clones. It was observed, also, that those clones that are the least efficient as plaque assay indicators produce the most external PFU per cell.

Cell Line↗
PubMedDate not supplied

Comparative studies of baculovirus granulins and polyhedrins.

Granulins and polyhedrins from five baculoviruses exhibit similar chemical and physical properties. Although similarities are demonstrated, it has been shown that each of the proteins is different and apparently specific to a given virus. The granulins and polyhedrins exhibit a major polypeptide component of an estimated molecular weight of 28,000. Alkaline protease activity has been detected in each preparation. N-terminal analyses reflect differences between granulins and polyhedrins studied: granulosis virus = Asx, and nuclear polyhedrosis virus = Glx. Two-dimensional high-voltage electrophoresis of highly purified granulin and polyhedrin preparations reveals relatedness as well as differences among the proteins as assessed by electrophoretic migration patterns.

Amino Acids↗