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Biomedical subjects

L J Harrison

Publications and source records attributed to L J Harrison.

At least 55 records · Page 3Linked to original sources
PubMed1989

Antigens of parasitic helminths in diagnosis, protection and pathology.

A thorough study of parasitic helminth antigens is a pre-requisite for control programmes based on accurate immunochemical diagnosis, protection by vaccination and perhaps immune modulation to diminish pathological sequelae. Studies should be directed at the identification of those stage- or age-specific surface, secreted and somatic antigens which are involved in the host-parasite interactions responsible for immunity and/or pathology. Current methods of diagnosis of parasitic infections often fail to detect low-level patent infections, which incurs the risk of having a reservoir capable of perpetuating infections. There is, then, an urgent requirement for accurate immunochemical diagnosis, to be used in association with, and for the evaluation of, drug treatment and vector elimination, in parasite control programmes. Given the high sensitivity of current immunoassay technology, the only bar to establishing the necessary immunological tests is the choice of suitably specific antigen/antibody systems. Assays designed to detect parasite products or antigens are a major priority, as they indicate current infection, whereas those which detect antibody only indicate exposure to infection, which may or may not be current. Surface and secreted antigens are the most likely targets for protective immune responses and thus form a logical focus for vaccine design. The cestodes, which present such strong evidence for immunity following natural infection, are likely to yield effective vaccines by modern procedures. Certain antigens must, however, stimulate the humoral and/or cellular responses which are responsible for the undesirable immunopathological consequences of many helminthic diseases. The nematodes and trematodes furnish some extreme examples of such pathology. The ultimate objective in identifying these particular antigens is to utilize them in the appropriate down-regulation of the immune response responsible for such pathology. As an illustration, we have presented an interesting correlation between one particular clinical condition of onchocerciasis (Sowda) and the serological response, defined both in terms of the parasite antigens and an immunoglobulin class-restricted antibody response. Finally, the complexity of these parasite systems and the host response to the parasite should not be underestimated. Modern analytical techniques allow their detailed analysis in terms of the humoral antibody responses and afford the possibility of the future development of control and disease management procedures tailored to each individual host-parasite system. However, novel systems are required to complete the analysis of the cellular components of the immune response to parasite antigens, and functional studies are needed to determine the role that these parasite antigens play in the complex interaction between parasite and host.

Animals↗
PubMed1989

Specific detection of circulating surface/secreted glycoproteins of viable cysticerci in Taenia saginata cysticercosis.

A mouse monoclonal antibody (MoAb), reactive with a repetitive carbohydrate epitope on lentil-lectin adherent glycoproteins present on the surface and in the secretions of Taenia saginata cysticerci, was used in the construction of a diagnostic ELISA assay to detect these glycoproteins in the serum of T. saginata infected cattle. The MoAb was used as the trapping layer and subsequently bound glycoprotein was revealed using the same MoAb and biotinylated peroxidase-streptavidin complex as the developing system. The assay was suitably specific. Exceptionally low background values were obtained with sera from animals with a range of commonly occurring tropical parasitic infections, including Taenia hydatigena, Echinococcus granulosus and Fasciola gigantica. The minimal detection level was approximately 200 live cysticerci in cattle. Parasite derived glycoprotein could be detected in serum from about 4-5 weeks post-infection onwards and was associated with a current infection, as drug treatment of infected cattle to kill the cysticerci resulted in the disappearance of these components from the circulation, while the titre of anti-parasite antibody remained high. The same assay also detected Taenia solium cysticercosis in humans.

Animals↗
PubMed1989

Taenia saginata and Taenia solium: reciprocal models.

Taenia solium and Taenia saginata are of such close taxonomic relationship that each can be regarded as a model for the other. In these particular species the only available hosts are either humans or large domesticated animals. This has imposed severe safety and/or economic restrictions on the extent of the experimental work which could be attempted. Furthermore, there is a limit to the relevance of work with less closely related species such as Taenia ovis, Taenia taeniaeformis and Taenia pisiformis with their differing host species, larval forms and locations within the intermediate host tissue. However, the application of both monoclonal antibody based and modern molecular biological techniques to the T. solium and T. saginata systems does much to overcome or circumvent some of the problems. Thus advances made in the analysis, diagnosis or immuno-prophylaxis of one of these species are at least potentially both of direct and immediate or indirect benefit to the work on the other species.

Animals↗
PubMed1988

Excreted/secreted products of developing Taenia saginata metacestodes.

Excretions and secretions (ES) and somatic components of 4, 8, 12 and 16-week-old Taenia saginata metacestodes were biosynthetically radio-isotope labelled by incubating the larvae in the presence of [35S]methionine. Despite their small size, 4-week-old metacestodes produced as much isotope-labelled ES/parasite as older metacestodes, indicating a proportionately greater metabolic activity of the parasite at this age. In situ the 4-week-old metacestodes were surrounded by a marked granulomatous cellular infiltrate which had largely resolved around 8-week-old metacestodes. Examination of the isotope-labelled ES by SDS-PAGE revealed distinct age-specific components from 4- and 12-week-old metacestodes and other ES components which were produced by all the ages of metacestodes examined. In comparison the labelled somatic components were conserved. Antigenic characterization of the ES by immunoprecipitation against a panel of clinically defined bovine sera combined with SDS-PAGE analysis, identified some highly immunogenic parasite products and others which did not elicit an antibody response demonstrable by immunoprecipitation. These components are of interest in relation to the host/parasite relationship, to the construction of diagnostic assays for the detection of T. saginata cysticercosis, and to the immunity that cattle develop against this parasite.

Animals↗
PubMed1986

Variations in Echinococcus granulosus of bovine origin identified by enzyme electrophoresis.

Hydatid cysts of bovine, equine, porcine, ovine, caprine and human origin and also from gerbils used to passage cysts of human origin were obtained from various geographical locations. Extracts from these cysts were compared for the electrophoretic forms of glucose phosphate isomerase. Equine and porcine cyst extracts had identical zymogram patterns. These differed markedly from the zymogram patterns of cysts of ovine, caprine and human origin which appeared identical to the ovine strain. In contrast both types of zymogram patterns were found in extracts from cysts obtained from cattle. This variation seemed to be associated with both geographical location and the fertility of the cysts.

Animals↗
PubMed1986

Passive protection against Taenia saginata infection in cattle by a mouse monoclonal antibody reactive with the surface of the invasive oncosphere.

The surface, excretory/secretory and intracellular compartments of Taenia saginata oncospheres were analysed by a combination of immunochemical techniques and by the use of selected hybridoma antibodies. The surface proteins of the oncospheres were directly iodinated by the lactoperoxidase technique and the intracellular and excretory/secretory components were labelled biosynthetically by culture in vitro with 35S-methionine. Analysis of radiolabelled proteins by SDS-PAGE revealed a restricted number of components in all of these three compartments. Mouse derived monoclonal antibodies directed against the oncospheral stage of this parasite demonstrated both stage specific and common determinants on the surfaces of the oncospheres and the metacestodes. One monoclonal (IgM) antibody, reactive with the oncosphere surface, which had a half life of 4.1 days when injected into calves, conferred protection against oral infection with T. saginata eggs. A monoclonal antibody reactive with a major secreted component did not confer passive protection.

Animals↗
PubMed1986

Immunoglobulin class responses to Taenia taeniaeformis in susceptible and resistant mice.

The immunoglobulin class response of two inbred strains of mice, C57BL/6 and C3H/He, to infection and challenge with Taenia taeniaeformis larvae was compared using the enzyme-linked immunosorbent assay and gel electrophoresis followed by immunoelectrotransfer blot (Western blotting) techniques. The C57BL/6 mice, which are relatively resistant to infection, had a more restricted humoral response than the more susceptible, C3H/He mice. C3H/He mice produced a wider range of immunoglobulin classes, in particular IgA and IgG3, to those antigens recognized by both strains of mice. In addition they produced antibodies to a wider range of antigens. The production of these additional antibodies by the susceptible strain raises the possibility that some of the antibodies may have specificities which interfere, or block the action of potentially protective antibodies. Antibodies, mainly of the IgG1, IgG2a and IgG2b classes, to antigens of approximately less than 21,000, 21,000-23,000, 30,000 and 60,000 mol. wt, present both in the oncosphere and the metacestode extracts, were found in serum from previously infected and resistant mice of both strains. These antigens may be important in stimulating protective concomitant immunity.

Animals↗
PubMed1986

Serum antibody levels to Taenia saginata in cattle grazed on Scottish pastures.

The serum antibody levels to Taenia saginata of three groups of cattle were assessed by an enzyme-linked immunosorbent assay (ELISA). The first group of cattle were from four farms which had a confirmed T saginata cysticercosis outbreak, all of which had cattle classed as infected by ELISA. The second group were from four farms where sewage sludge had been applied to pasture subsequently grazed by the cattle. One of these farms had cattle classed as infected by ELISA. The control cattle, which were all classed as uninfected by ELISA, came from five farms whose pasture had not been treated with sewage sludge. In a wider survey, involving sera from 47 additional farms, the majority could not be distinguished from the control farms in the earlier survey. However, samples from three of the farms had a similar number of positives to two of the known infected farms in the initial survey. Since the ELISA assay may indicate infected herds, farms such as these warrant further investigation.

Animal Feed↗
PubMed1985

Attempted infection of calves with Taenia crocutae cysticerci and their subsequent serological response.

The susceptibility of naive cattle to infection with cysticerci of Taenia crocutae was tested using three six- to nine-month-old Ayrshire bull calves, previously unexposed to infection with taeniid eggs. One calf was given 10,000 T crocutae eggs orally, another 5000 hatched unactivated oncospheres orally and the third 5000 hatched and activated oncospheres by intravenous injection. None of the calves contained viable cysticerci at post mortem examination 15 to 17 weeks later. All three calves contained small numbers of lesions in the liver and lesions were also present in the lungs of the calf which received oncospheres intravenously. All the calves developed an antibody response which was most pronounced in the calf given hatched unactivated oncospheres orally.

Animals↗
PubMed1984

Variation in 'target' antigens between appropriate and inappropriate hosts of Taenia saginata metacestodes.

The antibody response of the appropriate hosts (cattle) to Taenia saginata larvae was compared with that of an inappropriate host (Balb/c mice) using gel electrophoresis followed by immunoelectrotransfer blot techniques (Western blotting). Three groups of cattle were included, those known to be resistant to challenge infection because of repeated oral challenge with T. saginata eggs over a 1-year period, a previously infected but known susceptible group and a group of uninfected controls. Serum from the mice and the two groups of infected cattle contained antibodies recognizing different 'target' antigens, some of which may be related to host resistance. The potential value of the technique of Western blotting in dissecting the humoral response of a particular host species to parasitic infection and in the identification of those antigens suitable for the production of effective vaccines is discussed.

Animals↗
PubMed1984

Absorption of cysticerci in cattle after treatment of taenia saginata cysticercosis with praziquantel.

Two groups of calves aged 10 to 15 weeks were orally infected with either 6000 or 30,000 Taenia saginata eggs. Three to four months later they were treated with praziquantel, three doses of 50 mg kg-1 on three consecutive days. All the cysticerci were killed by the drug and most were absorbed by between six and nine months after treatment. From then on there was little further absorption and residual calcified cysts were still found in the carcases up to 24 months after drug treatment. These residual calcified cysts were particularly common in the heart muscles and would probably have been detected at meat inspection.

Animals↗
PubMed1981

A comparison of the enzyme linked immunosorbent assay and the indirect haemagglutination technique applied to sera from cattle experimentally infected with Taenia saginata (Goeze, 1782).

The serological response of 6 calves to experimental oral infection with between 60,000 and 100,000 Taenia saginata eggs at 3-12 months of age was monitored by the enzyme-linked immunosorbent assay (ELISA) and the tanned cell indirect haemagglutination technique (IDH). A serum antibody response was detected by both techniques by 2-3 weeks post infection, rising to a plateau about 4-6 weeks post infection. The serum antibody levels began to decline by about 30 weeks post infection. Two uninfected control cattle gave negative reactions. In addition, the serological response of 5 calves which had received a dose of 10,000 T. saginata eggs at 2-3 days of age and then weekly serial doses of 500 eggs for 12 months thereafter, was compared with a similar group of 5 calves, which had received the single infection of 10,000 eggs at 2-3 days of age only. Calves in both groups developed an antibody response detectable by the ELISA technique whereas those in a group of 5 control calves did not show such a response. When studied individually however there was marked variation in the serum antibody levels of these young cattle, as although some calves gave a relatively strong serological response, others hardly varied from the controls.

Animals↗