Characterization of the genome of the nucleopolyhedrosis bundle virus pathogenic for Orgyia pseudotsugata

Characterization of the DNA of a Nonoccluded Baculovirus, Hz-1V

The DNA of the nonoccluded baculovirus (Hz-1V) obtained from the IMC-Hz-1 cell line was characterized by physicochemical and restriction endonuclease techniques. Hz-1V DNA isolated from purified virus had buoyant densities of 1.58 and 1.54 g/ml in CsCl-ethidium bromide density gradients, which corresponded to supercoiled and to relaxed circular and linear DNA, respectively. Neutral CsCl equilibrium centrifugation indicated that the Hz-1V DNA had a buoyant density of 1.7024 g/ml, which corresponded to a guanine-plus-cytosine (G+C) content of 43%. Thermal denaturation indicated a high G+C domain(s) in the Hz-1V genomic DNA. The domain(s), which included about 11% of the total genomic DNA, exhibited a T(m) of 97 degrees C. The remaining portion (89%) of the DNA had a T(m) of 86.5 degrees C. The T(m)s corresponded to G+C contents of 42 and 67%, respectively. The mean genetic complexity of Hz-1V DNA determined by DNA reassociation kinetic analysis was found to be 152 x 10(6). A possible rapidly reassociating component comprising approximately 13% of the genome was observed. The mean molecular weights from restriction endonuclease digests were 159 x 10(6) for both HindIII and EcoRI. Genomic heterogeneity was found in both the wild-type Hz-1V stock and in two plaque isolates. Of 12 single-plaque isolates, 3 basic restriction endonuclease DNA fragment patterns were observed. The molecular size estimates from electron microscopic contour lengths of uncloned viral DNA ranged from 70 to 158 megadaltons, and the mode was the 130- to 140-megadalton class.

Characterization of baculovirus p10 synthesis using monoclonal antibodies

A series of monoclonal antibodies were produced against virion proteins of the multicapsid nuclear polyhedrosis virus of Orgyia pseudotsugata (OpMNPV). Four of these antibodies reacted with a protein of 14 kd on Western blots of electrophoretically separated OpMNPV virion proteins. These antibodies were used to identify immunoreactive clones from a lambda gt11 expression library of OpMNPV DNA. By hybridization of insert DNA from the lambda gt11 clones to blots of digests of OpMNPV genomic DNA, and by sequencing the ends of the lambda gt11 inserts, these clones were shown to contain a portion of the p10 gene. The regions containing epitopes recognized by the four monoclonal antibodies were located using fusion proteins made from selected portions of the p10 reading frame in a trpE vector. One of the p10 antibodies was used to characterize p10 synthesis in infected Lymantria dispar cells by using Western blots and immunofluorescent staining. The p10 protein was detected with immunofluorescent microscopy at 14 hr postinfection and by 20 hr it formed intensely staining cytoplasmic structures. On Western blots of infected cells, two forms of p10 (of about 14 and 15 kd) were observed. One of the p10 monoclonal antibodies showed a strong cross-reaction with cytoskeletal structures in uninfected insect cells and rat fibroblasts.

Quantification of two viruses in technical preparations of Orgyia pseudotsugata baculovirus by means of buoyant density centrifugation of viral deoxyribonucleic acid

A reliable method was developed for the quantitative determination of two nuclear polyhcdrosis viruses present in commercially prepared viral insecticides used against Orgyia pseudotsugata. Deoxyribonucleic acids, from nuclear polyhedrosis bundle virus and nuclear polyhedrosis single-rod virus, were separated on CsCl gradients according to their respective buoyant densities, 1.715 and 1.704 g/ml. The proportions of the two viruses were quantified by measuring the relative absorbance at 254 nm of their deoxyribonucleic acid peaks.