Roberta T. Hess

Neutralization of budded Autographa californica NPV by a monoclonal antibody: Identification of the target antigen

Abstract A neutralizing monoclonal antibody of the budded phenotype of Autographa californica nuclear polyhedrons virus did not react with the occluded form of the virus as determined by neutralization, ELISA, and indirect immunoperoxidase staining. The antibody did react with the surface of infected cells in the prepolyhedra stage of cytopathic effect, the period of active virus budding. Immunoelectron microscopy indicated the antigen(s) reactive with the neutralizing antibody was present all around the viral envelope, but was more highly concentrated at the end with peplomers. Four proteins were immunoprecipitated from solubilized, radiolabeled budded virus preparations with the monoclonal antibody. The major protein had a molecular weight of approximately 64,000, while the other three were approximately 127,000, 59,000, and 49,000. All four proteins could be labeled with N-acetyl-d-[1-3H]glucosamine. This glycosylation reaction could be inhibited by tunicamycin.

Characteristics of the Specific Bacterium Associated With Heterorhabditis Bacteriophora (Heterorhabditidae: Rhabditida)

The infective stage juveniles of Heterorhabditis bacteriophora Poinar (Heterorhabditidae: Rhabditida) carry a specific bacterium in the lumen of their pharynx and intestine. The bacterial cells are large, motile, peritrichously flagellated, gram negative, non-sporeforming rods. They are released by the infective-stage juveniles after they reach the hemolymph of susceptible insects. Additional cultural and biological characteristics of the specific bacterium are presented.

Ultrastructure of 40-Million-Year-Old Insect Tissue

Examination of the ultrastructure of preserved tissue in the abdomen of a fossil fly (Mycetophilidae: Diptera) entombed in Baltic amber revealed recognizable cell organelles. Structures that corresponded to muscle fibers, nuclei, ribosomes, lipid droplets, endoplasmic reticulum, and mitochondria were identified with the transmission electron microscope. Preservation was attributed to inert dehydration as well as the presence of compounds in the original sap which functioned as natural fixatives. This evidence of cell organelles in fossilized soft tissues represent an extreme form of mummification since Baltic amber is considered to have formed about 40 million years ago.

Microorganisms associated with the spider mite predator Metaseiulus (= Typhlodromus) occidentalis: Electron microscope observations☆

Abstract Two morphologically distinct forms of microorganisms were observed with the electron microscope in the tissues of the phytoseiid mite Metaseiulus (= Typhlodromus) occidentalis . The forms were distinguished on the basis of cell wall structure and cytoplasmic inclusions. One microorganism, designated type A, was observed in all mites examined. The second microorganism, type B, was observed in approximately two-thirds of the mites examined. If present, type B microorganisms occurred in all ovaries and egges, suggesting that transovarial transmission may take place. In some mites large numbers of type B microorganisms were observed within Malpighian tubule lumens and in a rectal plug. Whether this population was primarily or secondarily associated with a pathology is discussed.

Evidence for microfilament involvement in budded Autographa californica nuclear polyhedrosis virus production.

Autographa californica nuclear polyhedrosis virus (AcNPV) is a large, double-stranded DNA virus that infects lepidopteran insects. In the course of infection two different forms of the virus are produced; one that serves to spread the infection from insect to insect and another that spreads the infection within the insect from cell to cell. The latter form matures by budding from the plasma membrane of infected cells. We have found that cytochalasins B and D prevent the production of infectious budded AcNPV, not by inhibiting budding but by inhibiting the synthesis of complete virions. In the presence of cytochalasins B and D, particles lacking nucleocapsids bud from the plasma membrane of AcNPV infected cells, implicating microfilaments in the synthesis, transport and/or assembly of critical virus components.

The fine structure of the epicuticular particles of Enchytraesus fragmentosus

Epicuticular particles occurring on the surface of axenically grown Enchytraesus fragmentosus Bell are described and their origin is demonstrated to be from microvilli. Enzymatic digestion by RNase, DNase, trypsin, and pepsin indicates that the epicuticular particles are not viral in nature as previously suggested. The function of the epicuticular particles is suggested to be to aid in the stability of the mucoid coat of the worm.

Temporal events in the invasion of the codling moth, Cydia pomonella, by a granulosis virus: an electron microscope study

Abstract The replication cycle of the granulosis virus of Cydia pomonella, the codling moth, was studied at the cellular and tissue level. Membranelike complexes were observed forming within the remnants of the nucleolus in the cytoplasm of infected cells. Differences in cell polarity relative to the sites of virus entry assembly and budding as well as differences in the temporal aspects of replication were observed between midgut, fat body, and epidermal cells. The progressive spread of virus throughout larval tissues was studied at 24, 32, 48, 56, and 72 hr postinfection. The basal lamina seemed to be an effective barrier for the release of budded progeny virus into the hemocoel and large numbers of budded virus were produced.

Alternate pathway of entry of budded autographa californica nuclear polyhedrosis virus fusion at the plasma membrane

Recently we reported that the budded phenotype of Autographa californica nuclear polyhedrosis virus (AeNPV BV) functionally entered IPLB-SF-21 cells by adsorptive endocytosis and that neutralizing monoclonal antibody AcV1 acted by preventing AcNPV BV from using this entry pathway (L. E. Volkman and P. A. Goldsmith (1985), Virology 143, 185-195). Not all infectivity could be neutralized by AcV1, however, and in the study reported herein we investigated the nature of the particles responsible for this residual infectivity, and obtained evidence for an alternate entry pathway for both AcNPV BV and AcV1 treated BV. Residual infectivity was shown to be due to AcV1 linked AcNPV BV and not aberrant particles lacking the AcV1-reactive BV epitope. We obtained evidence that entry by fusion at the plasma membrane, but not phagocytosis, appeared to be an additional, functionally less efficient entry pathway. Fusion was indicated by the detection of viral envelope antigen in the host cell plasma membrane by immunoelectron microscopy. Fusion occurred even at 4 degrees , which was unexpected and highly unusual. Treatment of cells with cytochalasin B inhibited phagocytosis but did not reduce BV infectivity.

Site of action of a synergistic factor of a granulosis virus of the armyworm, Pseudaletia unipuncta

Abstract A synergistic factor (SF), which is present in the capsule matrix protein of a granulosis virus of the armyworm, Pseudaletia unipuncta , enhances baculovirus infection in armyworm larvae. The site of action of the SF was investigated. The oral inoculation of SF did not enhance the infectious hemolymph virions which had been inoculated into the hemocoel. The SF also did not enhance the infection of purified enveloped virions when both virus and SF were inoculated into the hemocoel, but enhancement occurred when they were inoculated orally. Thus, the activity of the SF was confined to the midgut lumen. Observations with ferritin-conjugated antibody indicated that the site of action of SF was the cell membrane of the microvillus. There were more ferritin particles attached to midgut cell membranes of larvae inoculated orally with SF than to those of control larvae inoculated with buffer.

Post-larval mortality of the endoparasitic isopod castrator Portunion conformis (Epicaridea: Entoniscidae) in the shore crab, Hemigrapsus oregonensis , with a description of the host response

The shore crabs, Hemigrapsus oregonensis and H. nudus , sometimes kill the female endoparasitic entoniscid isopod, Portunion conformis , a parasitic castrator. Studies of host populations from Baja California, Mexico to Vancouver Island, Canada, show that the incidence of parasitized hosts with dead parasites and the percentage of the parasite population found dead vary markedly with locality but only occasionally with season. Both higher incidences of hosts with dead P. conformis and higher proportions of the total parasite population found dead are associated with (1) high prevalence of parasitism, (2) female hosts and (3) large hosts. Within a host, the proportion of the parasites that are dead is not related to the degree of multiple infection. Typically, either all or none of the parasites in a multiple infection are dead. Supernumerary juvenile parasites do not suffer differential mortality. The developmental stage of the female parasite does not seem to influence the likelihood of death. The presence of dead parasites may not confer an acquired immunity to re-infection. These features suggest that parasite death is typically the result of activation of a successful host defensive process rather than indicative of a defect on the part of the parasites. Parasitized female hosts can regain their reproductive capabilities following death of the parasite. Post-parasitic broods are smaller than normal. Reproductive recovery is presumed to provide the selective pressure favouring evolution of a lethal host response. The host-produced sheath surrounding female parasites is a haemocytic response. Sheaths enclosing dead parasites are thicker and more electron dense than those containing healthy parasites. The sheath of a healthy P. conformis may actually protect the parasite from a more intense host response.