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D B Boyle

Publications and source records attributed to D B Boyle.

86 records · Page 5Linked to original sources
PubMed1983

Intraerythrocytic development and antigenicity of Plasmodium falciparum and comparison with simian and rodent malaria parasites.

Using sorbitol-synchronised cultures and metabolic labelling with [35S]methionine, the stage specificity of polypeptides synthesised by the intraerythrocytic stages of Plasmodium falciparum was studied. We confirmed that the synthesis of many polypeptides is restricted to defined morphological stages of parasite development, while other polypeptides are synthesised more or less throughout the cycle. The synthesis of at least 6 polypeptides was confined to the period of differentiation of mature trophozoites to schizonts and merozoites. Polypeptides synthesised by a cloned long-term passage isolate were very similar to those of a recently cultured uncloned isolate. Comparison of polypeptides synthesized during differentiation of mature trophozoites to schizonts and merozoites by P. falciparum with those of P. chabaudi and P. knowlesi showed that while P. chabaudi and P. knowlesi synthesised a 250 000 molecular weight polypeptide at this stage the apparently equivalent polypeptide of P. falciparum was of significantly lower molecular weight being 200 000. Using a surface immunoprecipitation technique, it was shown that this 200 000 mol. wt. polypeptide was accessible to antibodies on the surface of erythrocytes infected with mature trophozoites and schizonts. A 150 000 mol. wt. polypeptide was also accessible to antibodies. By comparing polypeptides synthesised during the differentiation of mature trophozoites to schizonts and merozoites with those recovered in the ring stage parasites after schizogony and erythrocyte invasion, it was shown that this 200 000 mol. wt. polypeptide and 140 000 and 120 000 mol. wt. polypeptides were not taken into the erythrocyte by the invading merozoite. The importance of these polypeptides in terms of the parasite biology and in the induction and expression of immunity to malaria is discussed.

Animals↗
PubMed1983

Primary viraemia responses of herons to experimental infection with Murray Valley encephalitis, Kunjin and Japanese encephalitis viruses.

Rufous night herons, Pacific herons, little egrets and intermediate egrets were experimentally infected with Murray Valley encephalitis, Kunjin or Japanese encephalitis viruses. Viraemias of at least one day's duration were detected in all birds except two intermediate egrets inoculated with a very low dose of Kunjin virus and one rufous night heron inoculated with Japanese encephalitis virus. there was usually a viraemia of 3 to 5 days' duration commencing on the first or second day and continuing until day 5 or 6 and rarely until day 7. Maximum titres tended to be higher in young birds, up to 2-5 months of age (10(4)-10(5) mouse LD50/ml), than in older birds more than 8 months of age (10(3)-10(4) mouse LD50/ml). Significant differences in maximum viraemia titres were not observed in the different species or between Murray Valley encephalitis and Kunjin viruses. Japanese encephalitis viraemias were significantly lower, but this was probably due to the high mouse brain passage level of the strain used. The onset of viraemia was earlier in intermediate egrets than in rufous night herons inoculated with similar doses of Murray Valley encephalitis virus, but no difference in the susceptibility to infection was observed. With Kunjin virus there was a significant difference in the susceptibility of intermediate egrets and rufous night herons, with rufous night herons being more susceptible to infection with low doses of virus. This difference in threshold of infection, if it extends to other species with both Kunjin and Murray Valley encephalitis viruses, may, in part, be an explanation for the greater incidence of natural infections observed in rufous night herons compared with other species and orders of water birds.

Animals↗
PubMed1983

Primary antibody responses of herons to experimental infection with Murray Valley encephalitis and Kunjin viruses.

Antibody responses of rufous night herons (Nycticorax caledonicus) and little egrets (Egretta garzetta) following infection with Murray Valley encephalitis and Kunjin viruses were determined. Haemagglutinin-inhibiting antibodies were first detected on day 5 or 6 after inoculation and increased rapidly, reaching maximum titres of 320 to 2560 between 10 and 20 days after inoculation. Titres declined 20-320 between 60 and 120 days after inoculation, then tended to remain stationary. Titres were 2- to 8-fold higher to infecting virus than heterologous virus. Neutralizing antibody development paralleled that of HI antibodies with titres maintained at a higher level for longer periods; however, they did eventually decline to low levels. Following MVE virus infection IgM (19S), HI antibodies were 80-100% of HI antibodies detectable on day 6 or 7 after inoculation and declined rapidly, becoming undetectable by 20 days after inoculation. With Kunjin virus infections, IgM HI antibodies represented 90-100% of HI antibodies detectable on day 6 or 7 after inoculation. Significant levels of IgM HI antibodies were still detectable 20 days after inoculation (5-30% of total HI antibodies) and, in some birds, even at 27 days after inoculation (up to 10%), IgG (7S) HI antibodies were low or undetectable on day 6 or 7 after inoculation, then increased rapidly with rapidly rising HI antibody titres. The specificity of IgM and IgG antibodies and unfractionated sera was determined by testing against Murray Valley encephalitis, Kunjin, Japanese encephalitis and West Nile virus haemagglutinating antigens. It was possible to determine with which virus a bird had been infected from the pattern of cross-reaction with these antigens. These results should provide a rational basis for the interpretation of serological results from naturally infected birds.

Animals↗
PubMed1982

Stage specific protein and nucleic acid synthesis during the asexual cycle of the rodent malaria Plasmodium chabaudi.

The asexual, intraerythrocytic stage of Plasmodium chabaudi develops synchronously in CBA mice. This in vivo synchrony has been exploited in in vitro pulse-labelling experiments to investigate the stage specificity of macromolecular synthesis by malaria parasites. Groups of mice were infected on day 0 with P. chabaudi and on day 3, individual mice were killed at three hour intervals, and the parasitised blood labelled in vitro for 2 h with radioactive precursors of protein or nucleic acid synthesis. By taking 11 samples covering one and one-third parasite division cycles, it was shown that the synthesis of many parasite polypeptides was restricted to defined morphological stages of parasite development. Other polypeptides were synthesised more or less continuously during the growth cycle. The synthesis of at least 6 polypeptides was confined to schizont or merozoite differentiation. RNA synthesis was shown to increase in rate steadily during parasite growth and to fall sharply during merozoite invasion. Approximately 40% of DNA synthesis was shown to occur during trophozoite growth, but the majority (60%) was confined to a short 4-6 h period at or just before schizogony.

Animals↗
PubMed1982

Identification of a schizont- and species-specific surface glycoprotein on erythrocytes infected with rodent malarias.

Erythrocytes infected with mature trophozoites of Plasmodium chabaudi and reticulocytes infected with P. berghei were labelled metabolically in vitro with [35S]methionine. The labelled cells were incubated with normal and immune serum and washed to remove unbound antibody. Solubilisation of the antibody-coated cells in detergent was followed by co-precipitation of antibody/antigen complexes and analysis of the immunoprecipitates by SDS-PAGE and fluorography. One major parasite polypeptide of 250 000 daltons was found to be exposed to antibody in both species. A labelled band of the same molecular weight could be identified by immunoprecipitation and SDS-PAGE analysis of P. chabaudi-infected cells that had been surface-labelled with periodate/NaB3H4. This molecule also incorporated [3H]glucosamine in short term cultures of mature parasitised erythrocytes. The results suggest that a 250 000 dalton glycoprotein which is synthesised only by late trophozoites or schizonts is exposed either on the surface of the infected erythrocyte, the surface of the merozoite, or both. Furthermore, the exposed portion of the molecule was not immunologically cross-reactive in the two Plasmodium species, but some cross reaction was detectable in total parasite lysates. The significance of these findings to protective immunity is discussed.

Animals↗
PubMed1982

Monoclonal antibodies that protect in vivo against Plasmodium chabaudi recognize a 250,000-dalton parasite polypeptide.

Twenty monoclonal antibodies have been prepared to the erythrocytes from CBA/Ca mice infected with the rodent malaria Plasmodium chabaudi. By immunofluorescence, 15 of these antibodies recognized parasite antigens expressed only during the development of mature trophozoites to schizonts and merozoites, 2 recognized parasite antigens that were expressed throughout most of the intraerythrocytic cycle, and 3 recognized the membranes of all infected and uninfected erythrocytes. By immunoprecipitation of [35S]methionine-labeled, parasitized erythrocytes, parasite antigens recognized by all of the antiparasite antibodies were characterized. Eleven precipitated a 250,000-dalton parasite polypeptide which was synthesized and expressed late in the intraerythrocytic cell cycle and which appeared to be the major coat protein of the merozoites. In passive protection experiments, transfer of hyperimmune serum before infection with the parasite resulted in a delay in the rise of parasitemia, reduction in peak parasitemias, and a delay in the clearance of the parasitemia. Two monoclonal antibodies to the 250,000-dalton polypeptide had a similar but not as marked effect on parasitemia when given as a single dose before infection. When mixed and administered throughout the course of infection, their effects were greater. They had no influence on the course of Plasmodium berghei KSP11 parasitemia. Monoclonal antibodies to other parasite antigens and normal erythrocyte antigens failed to have a significant and reproducible effect on P. chabaudi parasitemia. The results suggest that this 250,000-dalton malaria parasite antigen may be important in the induction and expression of antibody-mediated immunity to malaria.

Animals↗
PubMed1976

Avian adenoviruses isolated from poultry in Queensland.

Adenoviruses isolated from Queensland poultry flocks with respiratory disease and/or egg production problems have been serotyped by comparison with Japanese and Irish types. Two serological types were recognized among 14 isolates examined; 4 were type 112 (Celo type) and the remaining 10 type 506. Isolates B1363 and B4015 were further characterized by immunodiffusion. Both isolates were shown to contain the avian adenovirus group antigen and B1363 also shared a second (type) antigen with Celo (Phelps) strain. Immuno-electron microscopy revealed the presence of adenovirus group antigen and freedom from contamination with other viruses.

Adenoviridae↗
PubMedDate not supplied

Recovery of immunodeficient mice from a vaccinia virus/IL-2 recombinant infection.

Vaccinia virus recombinants that express cloned genes encoding antigens of unrelated infectious agents, such as hepatitis B virus and human immunodeficiency virus (HIV), provide a new approach to the development of live vaccines. Although there is evidence that genetically engineered vaccinia viruses have reduced pathogenicity a major obstacle to their use as vaccines is that severe complications can occur after vaccination, especially in immunodeficient individuals. We describe here a recombinant vaccinia virus expressing murine interleukin-2 (IL-2) and show that athymic nude mice infected with the recombinant virus resolve the virus infection rapidly whereas mice infected with control virus develop a progressive vaccinal disease. By incorporating the gene for IL-2 in live virus vaccines it may be possible to prevent the severe complications that arise in recipients with an impaired immune system.

Animals↗
PubMedDate not supplied

Gelatin encapsulated nitrogen microbubbles as ultrasonic contrast agents.

Gelatin encapsulated nitrogen microbubbles were effective ultrasonic contrast agents in in vitro phantom and in vivo rabbit V2 carcinoma studies. Intra-arterial injection of 80-micrometer gelatin encapsulated nitrogen microbubbles appeared to improve tumor visualization by rim enhancement, which persisted for several minutes.

Aerosols↗